-\input texinfo
-@c %**start of header
+\input texinfo @c -*-texinfo-*-
+@comment %**start of header
@setfilename tar.info
-@settitle GNU tar
+@include version.texi
+@settitle GNU tar @value{VERSION}
+@setchapternewpage odd
+
@finalout
+
@smallbook
@c %**end of header
-@c ======================================================================
-@c This document has three levels of rendition: PUBLISH, DISTRIB or PROOF,
-@c as decided by @set symbols. The PUBLISH rendition does not show
-@c notes or marks asking for revision. Most users will prefer having more
-@c information, even if this information is not fully revised for adequacy,
-@c so DISTRIB is the default for tar distributions. The PROOF rendition
-@c show all marks to the point of ugliness, but is nevertheless useful to
-@c those working on the manual itself.
-@c ======================================================================
-
-@ifclear PUBLISH
-@ifclear DISTRIB
-@ifclear PROOF
-@set DISTRIB
-@end ifclear
-@end ifclear
-@end ifclear
-
-@ifset PUBLISH
-@set RENDITION The book, version
-@end ifset
-
-@ifset DISTRIB
-@set RENDITION FTP release, version
-@end ifset
-
-@ifset PROOF
-@set RENDITION Proof reading version
-@end ifset
-
-@c ---------------------------------------------------------------------
-@c The @FIXME's, @UNREVISED and @c comments are part Fran@,{c}ois's work
-@c plan. These annotations are somewhat precious to him; he asks that I
-@c do not alter them inconsiderately. Much work is needed for GNU tar
-@c internals (the sources, the programs themselves). Revising the
-@c adequacy of the manual while revising the sources, and cleaning them
-@c both at the same time, seems to him like a good way to proceed.
-@c ---------------------------------------------------------------------
-
-@c Output marks for nodes needing revision, but not in PUBLISH rendition.
-
-@macro UNREVISED
-@ifclear PUBLISH
-@quotation
-@emph{(This message will disappear, once this node revised.)}
-@end quotation
-@end ifclear
-@end macro
-
-@c Output various FIXME information only in PROOF rendition.
-
-@macro FIXME{string}
-@allow-recursion
-@quote-arg
-@ifset PROOF
-@strong{<FIXME>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-ref{string}
-@quote-arg
-@ifset PROOF
-@strong{<REF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-pxref{string}
-@quote-arg
-@ifset PROOF
-@strong{<PXREF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-xref{string}
-@quote-arg
-@ifset PROOF
-@strong{<XREF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@c @macro option{entry}
-@c @quote-arg
-@c @opindex{--\entry\}
-@c @value{\entry\}
-@c @end macro
-
-@set op-absolute-names @kbd{--absolute-names} (@kbd{-P})
-@set ref-absolute-names @ref{absolute}
-@set xref-absolute-names @xref{absolute}
-@set pxref-absolute-names @pxref{absolute}
-
-@set op-after-date @kbd{--after-date=@var{date}} (@kbd{--newer=@var{date}}, @kbd{-N @var{date}})
-@set ref-after-date @ref{after}
-@set xref-after-date @xref{after}
-@set pxref-after-date @pxref{after}
-
-@set op-append @kbd{--append} (@kbd{-r})
-@set ref-append @ref{add}
-@set xref-append @xref{add}
-@set pxref-append @pxref{add}
-
-@set op-atime-preserve @kbd{--atime-preserve}
-@set ref-atime-preserve @ref{Attributes}
-@set xref-atime-preserve @xref{Attributes}
-@set pxref-atime-preserve @pxref{Attributes}
-
-@set op-backup @kbd{--backup}
-@set ref-backup @ref{Backup options}
-@set xref-backup @xref{Backup options}
-@set pxref-backup @pxref{Backup options}
-
-@set op-block-number @kbd{--block-number} (@kbd{-R})
-@set ref-block-number @ref{verbose}
-@set xref-block-number @xref{verbose}
-@set pxref-block-number @pxref{verbose}
-
-@set op-blocking-factor @kbd{--blocking-factor=@var{512-size}} (@kbd{-b @var{512-size}})
-@set ref-blocking-factor @ref{Blocking Factor}
-@set xref-blocking-factor @xref{Blocking Factor}
-@set pxref-blocking-factor @pxref{Blocking Factor}
-
-@set op-bzip2 @kbd{--bzip2} (@kbd{-y})
-@set ref-bzip2 @ref{gzip}
-@set xref-bzip2 @xref{gzip}
-@set pxref-bzip2 @pxref{gzip}
-
-@set op-checkpoint @kbd{--checkpoint}
-@set ref-checkpoint @ref{verbose}
-@set xref-checkpoint @xref{verbose}
-@set pxref-checkpoint @pxref{verbose}
-
-@set op-compare @kbd{--compare} (@kbd{--diff}, @kbd{-d})
-@set ref-compare @ref{compare}
-@set xref-compare @xref{compare}
-@set pxref-compare @pxref{compare}
-
-@set op-compress @kbd{--compress} (@kbd{--uncompress}, @kbd{-Z})
-@set ref-compress @ref{gzip}
-@set xref-compress @xref{gzip}
-@set pxref-compress @pxref{gzip}
-
-@set op-concatenate @kbd{--concatenate} (@kbd{--catenate}, @kbd{-A})
-@set ref-concatenate @ref{concatenate}
-@set xref-concatenate @xref{concatenate}
-@set pxref-concatenate @pxref{concatenate}
-
-@set op-create @kbd{--create} (@kbd{-c})
-@set ref-create @ref{create}
-@set xref-create @xref{create}
-@set pxref-create @pxref{create}
-
-@set op-delete @kbd{--delete}
-@set ref-delete @ref{delete}
-@set xref-delete @xref{delete}
-@set pxref-delete @pxref{delete}
-
-@set op-dereference @kbd{--dereference} (@kbd{-h})
-@set ref-dereference @ref{dereference}
-@set xref-dereference @xref{dereference}
-@set pxref-dereference @pxref{dereference}
-
-@set op-directory @kbd{--directory=@var{directory}} (@kbd{-C @var{directory}})
-@set ref-directory @ref{directory}
-@set xref-directory @xref{directory}
-@set pxref-directory @pxref{directory}
-
-@set op-exclude @kbd{--exclude=@var{pattern}}
-@set ref-exclude @ref{exclude}
-@set xref-exclude @xref{exclude}
-@set pxref-exclude @pxref{exclude}
-
-@set op-exclude-from @kbd{--exclude-from=@var{file-of-patterns}} (@kbd{-X @var{file-of-patterns}})
-@set ref-exclude-from @ref{exclude}
-@set xref-exclude-from @xref{exclude}
-@set pxref-exclude-from @pxref{exclude}
-
-@set op-extract @kbd{--extract} (@kbd{--get}, @kbd{-x})
-@set ref-extract @ref{extract}
-@set xref-extract @xref{extract}
-@set pxref-extract @pxref{extract}
-
-@set op-file @kbd{--file=@var{archive-name}} (@kbd{-f @var{archive-name}})
-@set ref-file @ref{file}
-@set xref-file @xref{file}
-@set pxref-file @pxref{file}
-
-@set op-files-from @kbd{--files-from=@var{file-of-names}} (@kbd{-T @var{file-of-names}})
-@set ref-files-from @ref{files}
-@set xref-files-from @xref{files}
-@set pxref-files-from @pxref{files}
-
-@set op-force-local @kbd{--force-local}
-@set ref-force-local @ref{file}
-@set xref-force-local @xref{file}
-@set pxref-force-local @pxref{file}
-
-@set op-group @kbd{--group=@var{group}}
-@set ref-group @ref{Option Summary}
-@set xref-group @xref{Option Summary}
-@set pxref-group @pxref{Option Summary}
-
-@set op-gzip @kbd{--gzip} (@kbd{--gunzip}, @kbd{--ungzip}, @kbd{-z})
-@set ref-gzip @ref{gzip}
-@set xref-gzip @xref{gzip}
-@set pxref-gzip @pxref{gzip}
-
-@set op-help @kbd{--help}
-@set ref-help @ref{help}
-@set xref-help @xref{help}
-@set pxref-help @pxref{help}
-
-@set op-ignore-failed-read @kbd{--ignore-failed-read}
-@set ref-ignore-failed-read @ref{Reading}
-@set xref-ignore-failed-read @xref{Reading}
-@set pxref-ignore-failed-read @pxref{Reading}
-
-@set op-ignore-zeros @kbd{--ignore-zeros} (@kbd{-i})
-@set ref-ignore-zeros @ref{Reading}
-@set xref-ignore-zeros @xref{Reading}
-@set pxref-ignore-zeros @pxref{Reading}
-
-@set op-incremental @kbd{--incremental} (@kbd{-G})
-@set ref-incremental @ref{Inc Dumps}
-@set xref-incremental @xref{Inc Dumps}
-@set pxref-incremental @pxref{Inc Dumps}
-
-@set op-info-script @kbd{--info-script=@var{script-name}} (@kbd{--new-volume-script=@var{script-name}}, @kbd{-F @var{script-name}})
-@set ref-info-script @ref{Multi-Volume Archives}
-@set xref-info-script @xref{Multi-Volume Archives}
-@set pxref-info-script @pxref{Multi-Volume Archives}
-
-@set op-interactive @kbd{--interactive} (@kbd{-w})
-@set ref-interactive @ref{interactive}
-@set xref-interactive @xref{interactive}
-@set pxref-interactive @pxref{interactive}
-
-@set op-keep-old-files @kbd{--keep-old-files} (@kbd{-k})
-@set ref-keep-old-files @ref{Writing}
-@set xref-keep-old-files @xref{Writing}
-@set pxref-keep-old-files @pxref{Writing}
-
-@set op-label @kbd{--label=@var{archive-label}} (@kbd{-V @var{archive-label}})
-@set ref-label @ref{label}
-@set xref-label @xref{label}
-@set pxref-label @pxref{label}
-
-@set op-list @kbd{--list} (@kbd{-t})
-@set ref-list @ref{list}
-@set xref-list @xref{list}
-@set pxref-list @pxref{list}
-
-@set op-listed-incremental @kbd{--listed-incremental=@var{snapshot-file}} (@kbd{-g @var{snapshot-file}})
-@set ref-listed-incremental @ref{Inc Dumps}
-@set xref-listed-incremental @xref{Inc Dumps}
-@set pxref-listed-incremental @pxref{Inc Dumps}
-
-@set op-mode @kbd{--mode=@var{permissions}}
-@set ref-mode @ref{Option Summary}
-@set xref-mode @xref{Option Summary}
-@set pxref-mode @pxref{Option Summary}
-
-@set op-multi-volume @kbd{--multi-volume} (@kbd{-M})
-@set ref-multi-volume @ref{Multi-Volume Archives}
-@set xref-multi-volume @xref{Multi-Volume Archives}
-@set pxref-multi-volume @pxref{Multi-Volume Archives}
-
-@set op-newer-mtime @kbd{--newer-mtime=@var{date}}
-@set ref-newer-mtime @ref{after}
-@set xref-newer-mtime @xref{after}
-@set pxref-newer-mtime @pxref{after}
-
-@set op-no-recursion @kbd{--no-recursion}
-@set ref-no-recursion @ref{recurse}
-@set xref-no-recursion @xref{recurse}
-@set pxref-no-recursion @pxref{recurse}
-
-@set op-null @kbd{--null}
-@set ref-null @ref{files}
-@set xref-null @xref{files}
-@set pxref-null @pxref{files}
-
-@set op-numeric-owner @kbd{--numeric-owner}
-@set ref-numeric-owner @ref{Attributes}
-@set xref-numeric-owner @xref{Attributes}
-@set pxref-numeric-owner @pxref{Attributes}
-
-@set op-old-archive @kbd{--old-archive} (@kbd{-o})
-@set ref-old-archive @ref{old}
-@set xref-old-archive @xref{old}
-@set pxref-old-archive @pxref{old}
-
-@set op-one-file-system @kbd{--one-file-system} (@kbd{-l})
-@set ref-one-file-system @ref{one}
-@set xref-one-file-system @xref{one}
-@set pxref-one-file-system @pxref{one}
-
-@set op-owner @kbd{--owner=@var{user}}
-@set ref-owner @ref{Option Summary}
-@set xref-owner @xref{Option Summary}
-@set pxref-owner @pxref{Option Summary}
-
-@set op-posix @kbd{--posix}
-@set ref-posix @ref{posix}
-@set xref-posix @xref{posix}
-@set pxref-posix @pxref{posix}
-
-@set op-preserve @kbd{--preserve}
-@set ref-preserve @ref{Attributes}
-@set xref-preserve @xref{Attributes}
-@set pxref-preserve @pxref{Attributes}
-
-@set op-record-size @kbd{--record-size=@var{size}}
-@set ref-record-size @ref{Blocking}
-@set xref-record-size @xref{Blocking}
-@set pxref-record-size @pxref{Blocking}
-
-@set op-recursive-unlink @kbd{--recursive-unlink}
-@set ref-recursive-unlink @ref{Writing}
-@set xref-recursive-unlink @xref{Writing}
-@set pxref-recursive-unlink @pxref{Writing}
-
-@set op-read-full-records @kbd{--read-full-records} (@kbd{-B})
-@set ref-read-full-records @ref{Blocking}
-@set xref-read-full-records @xref{Blocking}
-@set pxref-read-full-records @pxref{Blocking}
-@c FIXME: or should it be Reading, or Blocking Factor
-
-@set op-remove-files @kbd{--remove-files}
-@set ref-remove-files @ref{Writing}
-@set xref-remove-files @xref{Writing}
-@set pxref-remove-files @pxref{Writing}
-
-@set op-rsh-command @kbd{rsh-command=@var{command}}
-
-@set op-same-order @kbd{--same-order} (@kbd{--preserve-order}, @kbd{-s})
-@set ref-same-order @ref{Scarce}
-@set xref-same-order @xref{Scarce}
-@set pxref-same-order @pxref{Scarce}
-@c FIXME: or should it be Reading, or Attributes?
-
-@set op-same-owner @kbd{--same-owner}
-@set ref-same-owner @ref{Attributes}
-@set xref-same-owner @xref{Attributes}
-@set pxref-same-owner @pxref{Attributes}
-
-@set op-same-permissions @kbd{--same-permissions} (@kbd{--preserve-permissions}, @kbd{-p})
-@set ref-same-permissions @ref{Attributes}
-@set xref-same-permissions @xref{Attributes}
-@set pxref-same-permissions @pxref{Attributes}
-@c FIXME: or should it be Writing?
-
-@set op-show-omitted-dirs @kbd{--show-omitted-dirs}
-@set ref-show-omitted-dirs @ref{verbose}
-@set xref-show-omitted-dirs @xref{verbose}
-@set pxref-show-omitted-dirs @pxref{verbose}
-
-@set op-sparse @kbd{--sparse} (@kbd{-S})
-@set ref-sparse @ref{sparse}
-@set xref-sparse @xref{sparse}
-@set pxref-sparse @pxref{sparse}
-
-@set op-starting-file @kbd{--starting-file=@var{name}} (@kbd{-K @var{name}})
-@set ref-starting-file @ref{Scarce}
-@set xref-starting-file @xref{Scarce}
-@set pxref-starting-file @pxref{Scarce}
-
-@set op-suffix @kbd{--suffix=@var{suffix}}
-@set ref-suffix @ref{Backup options}
-@set xref-suffix @xref{Backup options}
-@set pxref-suffix @pxref{Backup options}
-
-@set op-tape-length @kbd{--tape-length=@var{1024-size}} (@kbd{-L @var{1024-size}})
-@set ref-tape-length @ref{Using Multiple Tapes}
-@set xref-tape-length @xref{Using Multiple Tapes}
-@set pxref-tape-length @pxref{Using Multiple Tapes}
-
-@set op-to-stdout @kbd{--to-stdout} (@kbd{-O})
-@set ref-to-stdout @ref{Writing}
-@set xref-to-stdout @xref{Writing}
-@set pxref-to-stdout @pxref{Writing}
-
-@set op-totals @kbd{--totals}
-@set ref-totals @ref{verbose}
-@set xref-totals @xref{verbose}
-@set pxref-totals @pxref{verbose}
-
-@set op-touch @kbd{--touch} (@kbd{-m})
-@set ref-touch @ref{Writing}
-@set xref-touch @xref{Writing}
-@set pxref-touch @pxref{Writing}
-
-@set op-unlink-first @kbd{--unlink-first} (@kbd{-U})
-@set ref-unlink-first @ref{Writing}
-@set xref-unlink-first @xref{Writing}
-@set pxref-unlink-first @pxref{Writing}
-
-@set op-update @kbd{--update} (@kbd{-u})
-@set ref-update @ref{update}
-@set xref-update @xref{update}
-@set pxref-update @pxref{update}
-
-@set op-use-compress-prog @kbd{--use-compress-prog=@var{program}}
-@set ref-use-compress-prog @ref{gzip}
-@set xref-use-compress-prog @xref{gzip}
-@set pxref-use-compress-prog @pxref{gzip}
-
-@set op-verbose @kbd{--verbose} (@kbd{-v})
-@set ref-verbose @ref{verbose}
-@set xref-verbose @xref{verbose}
-@set pxref-verbose @pxref{verbose}
-
-@set op-verify @kbd{--verify} (@kbd{-W})
-@set ref-verify @ref{verify}
-@set xref-verify @xref{verify}
-@set pxref-verify @pxref{verify}
-
-@set op-version @kbd{--version}
-@set ref-version @ref{help}
-@set xref-version @xref{help}
-@set pxref-version @pxref{help}
-
-@set op-version-control @kbd{--version-control=@var{method}}
-@set ref-version-control @ref{Backup options}
-@set xref-version-control @xref{Backup options}
-@set pxref-version-control @pxref{Backup options}
-
-@set op-volno-file @kbd{--volno-file=@var{file-of-number}}
-@set ref-volno-file @ref{Using Multiple Tapes}
-@set xref-volno-file @xref{Using Multiple Tapes}
-@set pxref-volno-file @pxref{Using Multiple Tapes}
-
-@include version.texi
+@include rendition.texi
+@include value.texi
@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp
@syncodeindex vr cp
@defindex op
-@syncodeindex op cp
-@ifinfo
-@format
-START-INFO-DIR-ENTRY
-* tar: (tar). Making tape (or disk) archives.
-END-INFO-DIR-ENTRY
-@end format
-@end ifinfo
+@copying
-@ifinfo
-This file documents GNU @code{tar}, a utility used to store, backup, and
-transport files.
-
-Copyright 1992, 1994, 1995, 1996, 1997, 1999 Free Software Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
-
-@ignore
-Permission is granted to process this file through TeX and print the
-results, provided the printed document carries copying permission
-notice identical to this one except for the removal of this paragraph
-(this paragraph not being relevant to the printed manual).
-
-@end ignore
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Foundation.
-@end ifinfo
+This manual is for @acronym{GNU} @command{tar} (version
+@value{VERSION}, @value{UPDATED}), which creates and extracts files
+from archives.
-@setchapternewpage odd
+Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
+2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+
+@quotation
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being "GNU General Public License", with the
+Front-Cover Texts being ``A GNU Manual,'' and with the Back-Cover Texts
+as in (a) below. A copy of the license is included in the section
+entitled "GNU Free Documentation License".
+
+(a) The FSF's Back-Cover Text is: ``You are free to copy and modify
+this GNU Manual. Buying copies from GNU Press supports the FSF in
+developing GNU and promoting software freedom.''
+@end quotation
+@end copying
+
+@dircategory Archiving
+@direntry
+* Tar: (tar). Making tape (or disk) archives.
+@end direntry
-@shorttitlepage GNU @code{tar}
+@dircategory Individual utilities
+@direntry
+* tar: (tar)tar invocation. Invoking @GNUTAR{}.
+@end direntry
+
+@shorttitlepage @acronym{GNU} @command{tar}
@titlepage
-@title GNU tar: an archiver tool
+@title @acronym{GNU} tar: an archiver tool
@subtitle @value{RENDITION} @value{VERSION}, @value{UPDATED}
-@author Melissa Weisshaus, Jay Fenlason,
-@author Thomas Bushnell, n/BSG, Amy Gorin
-@c he said to remove it: Fran@,{c}ois Pinard
-@c i'm thinking about how the author page *should* look. -mew 2may96
+@author John Gilmore, Jay Fenlason et al.
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999 Free Software
-Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
-
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Foundation.
+@insertcopying
@end titlepage
-@ifinfo
+@ifnottex
+@node Top
+@top @acronym{GNU} tar: an archiver tool
-This file documents GNU @code{tar}, which is a utility used to store,
-backup, and transport files. @code{tar} is a tape (or disk) archiver.
-This manual documents the release @value{VERSION}.
+@insertcopying
-@end ifinfo
+@cindex file archival
+@cindex archiving files
+
+The first part of this master menu lists the major nodes in this Info
+document. The rest of the menu lists all the lower level nodes.
+@end ifnottex
-@node Top, Introduction, (dir), (dir)
+@c The master menu, created with texinfo-master-menu, goes here.
+@c (However, getdate.texi's menu is interpolated by hand.)
@menu
* Introduction::
* Date input formats::
* Formats::
* Media::
+
+Appendices
+
+* Changes::
+* Configuring Help Summary::
+* Genfile::
+* Snapshot Files::
+* Free Software Needs Free Documentation::
+* Copying This Manual::
+* Index of Command Line Options::
* Index::
+@detailmenu
--- The Detailed Node Listing ---
Introduction
* Book Contents:: What this Book Contains
* Definitions:: Some Definitions
-* What tar Does:: What @code{tar} Does
-* Naming tar Archives:: How @code{tar} Archives are Named
-* posix compliance::
-* Authors:: GNU @code{tar} Authors
+* What tar Does:: What @command{tar} Does
+* Naming tar Archives:: How @command{tar} Archives are Named
+* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
-Tutorial Introduction to @code{tar}
+Tutorial Introduction to @command{tar}
* assumptions::
* stylistic conventions::
-* basic tar options:: Basic @code{tar} Operations and Options
+* basic tar options:: Basic @command{tar} Operations and Options
* frequent operations::
* Two Frequent Options::
* create:: How to Create Archives
* extract dir::
* failing commands::
-Invoking GNU @code{tar}
+Invoking @GNUTAR{}
* Synopsis::
* using tar options::
* Styles::
* All Options::
* help::
+* defaults::
* verbose::
* interactive::
* Old Options:: Old Option Style
* Mixing:: Mixing Option Styles
-All @code{tar} Options
+All @command{tar} Options
* Operation Summary::
* Option Summary::
* Short Option Summary::
-GNU @code{tar} Operations
+@GNUTAR{} Operations
* Basic tar::
* Advanced tar::
+* create options::
* extract options::
* backup::
* Applications::
* looking ahead::
-Advanced GNU @code{tar} Operations
+Advanced @GNUTAR{} Operations
* Operations::
-* current state::
* append::
* update::
* concatenate::
* delete::
* compare::
-How to Add Files to Existing Archives: @code{--append}
+How to Add Files to Existing Archives: @option{--append}
* appending files:: Appending Files to an Archive
* multiple::
* how to update::
-Options Used by @code{--extract}
+Options Used by @option{--create}
+
+* Ignore Failed Read::
+
+Options Used by @option{--extract}
* Reading:: Options to Help Read Archives
-* Writing:: Changing How @code{tar} Writes Files
+* Writing:: Changing How @command{tar} Writes Files
* Scarce:: Coping with Scarce Resources
Options to Help Read Archives
* read full records::
* Ignore Zeros::
-* Ignore Failed Read::
-Changing How @code{tar} Writes Files
+Changing How @command{tar} Writes Files
-* Prevention Overwriting::
+* Dealing with Old Files::
+* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::
-Options to Prevent Overwriting Files
-
-* Keep Old Files::
-* Unlink First::
-* Recursive Unlink::
-
Coping with Scarce Resources
* Starting File::
Performing Backups and Restoring Files
-* Full Dumps:: Using @code{tar} to Perform Full Dumps
-* Inc Dumps:: Using @code{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Full Dumps:: Using @command{tar} to Perform Full Dumps
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
Setting Parameters for Backups and Restoration
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-Choosing Files and Names for @code{tar}
+Choosing Files and Names for @command{tar}
* file:: Choosing the Archive's Name
* Selecting Archive Members::
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
Reading Names from a File
Excluding Some Files
+* controlling pattern-matching with exclude::
* problems with exclude::
-Crossing Filesystem Boundaries
+Crossing File System Boundaries
* directory:: Changing Directory
* absolute:: Absolute File Names
Date input formats
-* General date syntax:: Common rules.
-* Calendar date item:: 19 Dec 1994.
-* Time of day item:: 9:20pm.
-* Timezone item:: EST, DST, BST, UCT, AHST, ...
-* Day of week item:: Monday and others.
-* Relative item in date strings:: next tuesday, 2 years ago.
-* Pure numbers in date strings:: 19931219, 1440.
-* Authors of getdate:: Bellovin, Salz, Berets, et al.
+* General date syntax:: Common rules.
+* Calendar date items:: 19 Dec 1994.
+* Time of day items:: 9:20pm.
+* Time zone items:: @sc{est}, @sc{pdt}, @sc{gmt}, ...
+* Day of week items:: Monday and others.
+* Relative items in date strings:: next tuesday, 2 years ago.
+* Pure numbers in date strings:: 19931219, 1440.
+* Seconds since the Epoch:: @@1078100502.
+* Authors of get_date:: Bellovin, Eggert, Salz, Berets, et al.
Controlling the Archive Format
-* Portability:: Making @code{tar} Archives More Portable
+* Portability:: Making @command{tar} Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
-* Extensions:: GNU Extensions to the Archive Format
-* cpio:: Comparison of @code{tar} and @code{cpio}
+* Extensions:: @acronym{GNU} Extensions to the Archive Format
+* cpio:: Comparison of @command{tar} and @command{cpio}
-Making @code{tar} Archives More Portable
+Making @command{tar} Archives More Portable
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: POSIX archives
+* posix:: @acronym{POSIX} archives
* Checksumming:: Checksumming Problems
+* Large or Negative Values:: Large files, negative time stamps, etc.
Using Less Space through Compression
Many Archives on One Tape
* Tape Positioning:: Tape Positions and Tape Marks
-* mt:: The @code{mt} Utility
+* mt:: The @command{mt} Utility
Using Multiple Tapes
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
+
+GNU tar internals and development
+
+* Genfile::
+* Snapshot Files::
+
+Copying This Manual
+
+* Free Software Needs Free Documentation::
+* GNU Free Documentation License:: License for copying this manual
+
+@end detailmenu
@end menu
-@node Introduction, Tutorial, Top, Top
+@node Introduction
@chapter Introduction
-Welcome to the GNU @code{tar} manual. GNU @code{tar} is used to create
-and manipulate files (@dfn{archives}) which are actually collections of
+@GNUTAR{} creates
+and manipulates @dfn{archives} which are actually collections of
many other files; the program provides users with an organized and
systematic method for controlling a large amount of data.
+The name ``tar'' originally came from the phrase ``Tape ARchive'', but
+archives need not (and these days, typically do not) reside on tapes.
@menu
* Book Contents:: What this Book Contains
* Definitions:: Some Definitions
-* What tar Does:: What @code{tar} Does
-* Naming tar Archives:: How @code{tar} Archives are Named
-* posix compliance::
-* Authors:: GNU @code{tar} Authors
+* What tar Does:: What @command{tar} Does
+* Naming tar Archives:: How @command{tar} Archives are Named
+* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
@end menu
-@node Book Contents, Definitions, Introduction, Introduction
-@ifinfo
-@heading What this Book Contains
-@end ifinfo
+@node Book Contents
+@section What this Book Contains
The first part of this chapter introduces you to various terms that will
-recur throughout the book. It also tells you who has worked on GNU
-@code{tar} and its documentation, and where you should send bug reports
+recur throughout the book. It also tells you who has worked on @GNUTAR{}
+and its documentation, and where you should send bug reports
or comments.
The second chapter is a tutorial (@pxref{Tutorial}) which provides a
-gentle introduction for people who are new to using @code{tar}. It is
+gentle introduction for people who are new to using @command{tar}. It is
meant to be self contained, not requiring any reading from subsequent
chapters to make sense. It moves from topic to topic in a logical,
progressive order, building on information already explained.
Although the tutorial is paced and structured to allow beginners to
-learn how to use @code{tar}, it is not intended solely for beginners.
+learn how to use @command{tar}, it is not intended solely for beginners.
The tutorial explains how to use the three most frequently used
operations (@samp{create}, @samp{list}, and @samp{extract}) as well as
two frequently used options (@samp{file} and @samp{verbose}). The other
concepts of using a Unix-type operating system; @pxref{Tutorial}.)
The third chapter presents the remaining five operations, and
-information about using @code{tar} options and option syntax.
+information about using @command{tar} options and option syntax.
-@FIXME{this sounds more like a GNU Project Manuals Concept [tm] more
+@FIXME{this sounds more like a @acronym{GNU} Project Manuals Concept [tm] more
than the reality. should think about whether this makes sense to say
here, or not.} The other chapters are meant to be used as a
reference. Each chapter presents everything that needs to be said
about a specific topic.
-One of the chapters (@pxref{Date input formats}) exists in its entirety
-in other GNU manuals, and is mostly self-contained. In addition, one
-section of this manual (@pxref{Standard}) contains a big quote which is
-taken directly from @code{tar} sources.
+One of the chapters (@pxref{Date input formats}) exists in its
+entirety in other @acronym{GNU} manuals, and is mostly self-contained.
+In addition, one section of this manual (@pxref{Standard}) contains a
+big quote which is taken directly from @command{tar} sources.
-In general, we give both the long and short (abbreviated) option names
+In general, we give both long and short (abbreviated) option names
at least once in each section where the relevant option is covered, so
that novice readers will become familiar with both styles. (A few
options have no short versions, and the relevant sections will
indicate this.)
-@node Definitions, What tar Does, Book Contents, Introduction
+@node Definitions
@section Some Definitions
@cindex archive
@cindex tar archive
-The @code{tar} program is used to create and manipulate @code{tar}
+The @command{tar} program is used to create and manipulate @command{tar}
archives. An @dfn{archive} is a single file which contains the contents
of many files, while still identifying the names of the files, their
owner(s), and so forth. (In addition, archives record access
-permissions, user and group, size in bytes, and last modification time.
+permissions, user and group, size in bytes, and data modification time.
Some archives also record the file names in each archived directory, as
-well as other file and directory information.) You can use @code{tar}
+well as other file and directory information.) You can use @command{tar}
to @dfn{create} a new archive in a specified directory.
@cindex member
@cindex member name
The files inside an archive are called @dfn{members}. Within this
manual, we use the term @dfn{file} to refer only to files accessible in
-the normal ways (by @code{ls}, @code{cat}, and so forth), and the term
+the normal ways (by @command{ls}, @command{cat}, and so forth), and the term
@dfn{member} to refer only to the members of an archive. Similarly, a
-@dfn{file name} is the name of a file, as it resides in the filesystem,
+@dfn{file name} is the name of a file, as it resides in the file system,
and a @dfn{member name} is the name of an archive member within the
archive.
@cindex extraction
@cindex unpacking
The term @dfn{extraction} refers to the process of copying an archive
-member (or multiple members) into a file in the filesystem. Extracting
+member (or multiple members) into a file in the file system. Extracting
all the members of an archive is often called @dfn{extracting the
archive}. The term @dfn{unpack} can also be used to refer to the
extraction of many or all the members of an archive. Extracting an
the archive. You may also @dfn{list} the members in a given archive
(this is often thought of as ``printing'' them to the standard output,
or the command line), or @dfn{append} members to a pre-existing archive.
-All of these operations can be peformed using @code{tar}.
+All of these operations can be performed using @command{tar}.
-@node What tar Does, Naming tar Archives, Definitions, Introduction
-@section What @code{tar} Does
+@node What tar Does
+@section What @command{tar} Does
@cindex tar
-The @code{tar} program provides the ability to create @code{tar}
+The @command{tar} program provides the ability to create @command{tar}
archives, as well as various other kinds of manipulation. For example,
-you can use @code{tar} on previously created archives to extract files,
+you can use @command{tar} on previously created archives to extract files,
to store additional files, or to update or list files which were already
stored.
-Initially, @code{tar} archives were used to store files conveniently on
-magnetic tape. The name @samp{tar} comes from this use; it stands for
-@code{t}ape @code{ar}chiver. Despite the utility's name, @code{tar} can
+Initially, @command{tar} archives were used to store files conveniently on
+magnetic tape. The name @command{tar} comes from this use; it stands for
+@code{t}ape @code{ar}chiver. Despite the utility's name, @command{tar} can
direct its output to available devices, files, or other programs (using
-pipes). @code{tar} may even access remote devices or files (as archives).
+pipes). @command{tar} may even access remote devices or files (as archives).
@FIXME{the following table entries need a bit of work..}
-You can use @code{tar} archives in many ways. We want to stress a few
+You can use @command{tar} archives in many ways. We want to stress a few
of them: storage, backup, and transportation.
@table @asis
@item Storage
-Often, @code{tar} archives are used to store related files for
-convenient file transfer over a network. For example, the GNU Project
-distributes its software bundled into @code{tar} archives, so that
-all the files relating to a particular program (or set of related
-programs) can be transferred as a single unit.
+Often, @command{tar} archives are used to store related files for
+convenient file transfer over a network. For example, the
+@acronym{GNU} Project distributes its software bundled into
+@command{tar} archives, so that all the files relating to a particular
+program (or set of related programs) can be transferred as a single
+unit.
A magnetic tape can store several files in sequence. However, the tape
has no names for these files; it only knows their relative position on
the tape. One way to store several files on one tape and retain their
-names is by creating a @code{tar} archive. Even when the basic transfer
+names is by creating a @command{tar} archive. Even when the basic transfer
mechanism can keep track of names, as FTP can, the nuisance of handling
-multiple files, directories, and multiple links makes @code{tar}
+multiple files, directories, and multiple links makes @command{tar}
archives useful.
Archive files are also used for long-term storage. You can think of
this as transportation from the present into the future. (It is a
science-fiction idiom that you can move through time as well as in
-space; the idea here is that @code{tar} can be used to move archives in
+space; the idea here is that @command{tar} can be used to move archives in
all dimensions, even time!)
@item Backup
-Because the archive created by @code{tar} is capable of preserving file
-information and directory structure, @code{tar} is commonly used for
-performing full and incremental backups of disks. A backup puts a
-collection of files (possibly pertaining to many users and
-projects) together on a disk or a tape. This guards against accidental
-destruction of the information in those files. GNU @code{tar} has
-special features that allow it to be used to make incremental and full
-dumps of all the files in a filesystem.
+Because the archive created by @command{tar} is capable of preserving
+file information and directory structure, @command{tar} is commonly
+used for performing full and incremental backups of disks. A backup
+puts a collection of files (possibly pertaining to many users and
+projects) together on a disk or a tape. This guards against
+accidental destruction of the information in those files.
+@GNUTAR{} has special features that allow it to be
+used to make incremental and full dumps of all the files in a
+file system.
@item Transportation
You can create an archive on one system, transfer it to another system,
files from one system to another.
@end table
-@node Naming tar Archives, posix compliance, What tar Does, Introduction
-@section How @code{tar} Archives are Named
+@node Naming tar Archives
+@section How @command{tar} Archives are Named
-Conventionally, @code{tar} archives are given names ending with
-@samp{.tar}. This is not necessary for @code{tar} to operate properly,
+Conventionally, @command{tar} archives are given names ending with
+@samp{.tar}. This is not necessary for @command{tar} to operate properly,
but this manual follows that convention in order to accustom readers to
it and to make examples more clear.
@cindex tar file
@cindex entry
@cindex tar entry
-Often, people refer to @code{tar} archives as ``@code{tar} files,'' and
+Often, people refer to @command{tar} archives as ``@command{tar} files,'' and
archive members as ``files'' or ``entries''. For people familiar with
-the operation of @code{tar}, this causes no difficulty. However, in
+the operation of @command{tar}, this causes no difficulty. However, in
this manual, we consistently refer to ``archives'' and ``archive
-members'' to make learning to use @code{tar} easier for novice users.
+members'' to make learning to use @command{tar} easier for novice users.
-@node posix compliance, Authors, Naming tar Archives, Introduction
-@section POSIX Compliance
+@node Authors
+@section @GNUTAR{} Authors
-@noindent
-@FIXME{must ask franc,ois about this. dan hagerty thinks this might
-be an issue, but we're not really sure at this time. dan just tried a
-test case of mixing up options' orders while the variable was set, and
-there was no problem...}
-
-We make some of our recommendations throughout this book for one
-reason in addition to what we think of as ``good sense''. The main
-additional reason for a recommendation is to be compliant with the
-POSIX standards. If you set the shell environment variable
-@code{POSIXLY_CORRECT}, GNU @code{tar} will force you to adhere to
-these standards. Therefore, if this variable is set and you violate
-one of the POSIX standards in the way you phrase a command, for
-example, GNU @code{tar} will not allow the command and will signal an
-error message. You would then have to reorder the options or rephrase
-the command to comply with the POSIX standards.
-
-There is a chance in the future that, if you set this environment
-variable, your archives will be forced to comply with POSIX standards,
-also. No GNU @code{tar} extensions will be allowed.
-
-@node Authors, Reports, posix compliance, Introduction
-@section GNU @code{tar} Authors
-
-GNU @code{tar} was originally written by John Gilmore, and modified by
-many people. The GNU enhancements were written by Jay Fenlason, then
-Joy Kendall, and the whole package has been further maintained by
-Thomas Bushnell, n/BSG, and finally Fran@,{c}ois Pinard, with
-the help of numerous and kind users.
-
-We wish to stress that @code{tar} is a collective work, and owes much to
+@GNUTAR{} was originally written by John Gilmore,
+and modified by many people. The @acronym{GNU} enhancements were
+written by Jay Fenlason, then Joy Kendall, and the whole package has
+been further maintained by Thomas Bushnell, n/BSG, Fran@,{c}ois
+Pinard, Paul Eggert, and finally Sergey Poznyakoff with the help of
+numerous and kind users.
+
+We wish to stress that @command{tar} is a collective work, and owes much to
all those people who reported problems, offered solutions and other
insights, or shared their thoughts and suggestions. An impressive, yet
partial list of those contributors can be found in the @file{THANKS}
-file from the GNU @code{tar} distribution.
+file from the @GNUTAR{} distribution.
@FIXME{i want all of these names mentioned, Absolutely. BUT, i'm not
sure i want to spell out the history in this detail, at least not for
@FIXME{History is more important, and surely more interesting, than
actual names. Quoting names without history would be meaningless. FP}
-Jay Fenlason put together a draft of a GNU @code{tar} manual,
-borrowing notes from the original man page from John Gilmore. This
-draft has been distributed in @code{tar} versions 1.04 (or even
-before?) @FIXME{huh? IMO, either we know or we don't; the
-parenthetical is confusing.} through 1.10, then withdrawn in version
-1.11. Thomas Bushnell, n/BSG and Amy Gorin worked on a tutorial and
-manual for GNU @code{tar}. Fran@,{c}ois Pinard put version 1.11.8
-of the manual together by taking information from all these sources
-and merging them. Melissa Weisshaus finally edited and redesigned the
-book to create version 1.12. @FIXME{update version number as
-necessary; i'm being optimistic!} @FIXME{Someone [maybe karl berry?
-maybe bob chassell? maybe melissa? maybe julie sussman?] needs to
-properly index the thing.}
+Jay Fenlason put together a draft of a @GNUTAR{}
+manual, borrowing notes from the original man page from John Gilmore.
+This was withdrawn in version 1.11. Thomas Bushnell, n/BSG and Amy
+Gorin worked on a tutorial and manual for @GNUTAR{}.
+Fran@,{c}ois Pinard put version 1.11.8 of the manual together by
+taking information from all these sources and merging them. Melissa
+Weisshaus finally edited and redesigned the book to create version
+1.12. @FIXME{update version number as necessary; i'm being
+optimistic!} @FIXME{Someone [maybe karl berry? maybe bob chassell?
+maybe melissa? maybe julie sussman?] needs to properly index the
+thing.}
For version 1.12, Daniel Hagerty contributed a great deal of technical
consulting. In particular, he is the primary author of @ref{Backups}.
-@node Reports, , Authors, Introduction
+In July, 2003 @GNUTAR{} was put on CVS at savannah.gnu.org
+(see @url{http://savannah.gnu.org/projects/tar}), and
+active development and maintenance work has started
+again. Currently @GNUTAR{} is being maintained by Paul Eggert, Sergey
+Poznyakoff and Jeff Bailey.
+
+Support for @acronym{POSIX} archives was added by Sergey Poznyakoff.
+
+@node Reports
@section Reporting bugs or suggestions
@cindex bug reports
If you find problems or have suggestions about this program or manual,
please report them to @file{bug-tar@@gnu.org}.
-@node Tutorial, tar invocation, Introduction, Top
-@chapter Tutorial Introduction to @code{tar}
+When reporting a bug, please be sure to include as much detail as
+possible, in order to reproduce it. @FIXME{Be more specific, I'd
+like to make this node as detailed as 'Bug reporting' node in Emacs
+manual}.
-This chapter guides you through some basic examples of three @code{tar}
-operations: @samp{--create}, @samp{--list}, and @samp{--extract}. If
-you already know how to use some other version of @code{tar}, then you
+@node Tutorial
+@chapter Tutorial Introduction to @command{tar}
+
+This chapter guides you through some basic examples of three @command{tar}
+operations: @option{--create}, @option{--list}, and @option{--extract}. If
+you already know how to use some other version of @command{tar}, then you
may not need to read this chapter. This chapter omits most complicated
-details about how @code{tar} works.
+details about how @command{tar} works.
@menu
* assumptions::
* stylistic conventions::
-* basic tar options:: Basic @code{tar} Operations and Options
+* basic tar options:: Basic @command{tar} Operations and Options
* frequent operations::
* Two Frequent Options::
* create:: How to Create Archives
* going further::
@end menu
-@node assumptions, stylistic conventions, Tutorial, Tutorial
-@ifinfo
-@heading Assumptions this Tutorial Makes
-@end ifinfo
+@node assumptions
+@section Assumptions this Tutorial Makes
-This chapter is paced to allow beginners to learn about @code{tar}
+This chapter is paced to allow beginners to learn about @command{tar}
slowly. At the same time, we will try to cover all the basic aspects of
these three operations. In order to accomplish both of these tasks, we
have made certain assumptions about your knowledge before reading this
use some basic utilities. For example, you should know how to create,
list, copy, rename, edit, and delete files and directories; how to
change between directories; and how to figure out where you are in the
-filesystem. You should have some basic understanding of directory
+file system. You should have some basic understanding of directory
structure and how files are named according to which directory they are
in. You should understand concepts such as standard output and standard
-input, what various definitions of the term ``argument'' mean, the
-differences between relative and absolute path names, and @FIXME{what
-else?}.
+input, what various definitions of the term ``argument'' mean, and the
+differences between relative and absolute path names. @FIXME{and what
+else?}
@item
This manual assumes that you are working from your own home directory
(unless we state otherwise). In this tutorial, you will create a
-directory to practice @code{tar} commands in. When we show path names,
+directory to practice @command{tar} commands in. When we show path names,
we will assume that those paths are relative to your home directory.
For example, my home directory path is @file{/home/fsf/melissa}. All of
my examples are in a subdirectory of the directory named by that path
Additionally, working with tapes is much more complicated than working
with hard disks. For these reasons, the tutorial does not cover working
with tape drives. @xref{Media}, for complete information on using
-@code{tar} archives with tape drives.
+@command{tar} archives with tape drives.
@FIXME{this is a cop out. need to add some simple tape drive info.}
@end itemize
-@node stylistic conventions, basic tar options, assumptions, Tutorial
-@ifinfo
-@heading Stylistic Conventions
-@end ifinfo
+@node stylistic conventions
+@section Stylistic Conventions
In the examples, @samp{$} represents a typical shell prompt. It
precedes lines you should type; to make this more clear, those lines are
shown in @kbd{this font}, as opposed to lines which represent the
computer's response; those lines are shown in @code{this font}, or
-sometimes @samp{like this}. When we have lines which are too long to be
-displayed in any other way, we will show them like this:
-
-@smallexample
-This is an example of a line which would otherwise not fit in this space.
-@end smallexample
+sometimes @samp{like this}.
-@FIXME{how often do we use smallexample?}
+@c When we have lines which are too long to be
+@c displayed in any other way, we will show them like this:
-@node basic tar options, frequent operations, stylistic conventions, Tutorial
-@section Basic @code{tar} Operations and Options
+@node basic tar options
+@section Basic @command{tar} Operations and Options
-@code{tar} can take a wide variety of arguments which specify and define
+@command{tar} can take a wide variety of arguments which specify and define
the actions it will have on the particular set of files or the archive.
-The main types of arguments to @code{tar} fall into one of two classes:
+The main types of arguments to @command{tar} fall into one of two classes:
operations, and options.
Some arguments fall into a class called @dfn{operations}; exactly one of
-these is both allowed and required for any instance of using @code{tar};
+these is both allowed and required for any instance of using @command{tar};
you may @emph{not} specify more than one. People sometimes speak of
@dfn{operating modes}. You are in a particular operating mode when you
have specified the operation which specifies it; there are eight
The other arguments fall into the class known as @dfn{options}. You are
not required to specify any options, and you are allowed to specify more
-than one at a time (depending on the way you are using @code{tar} at
+than one at a time (depending on the way you are using @command{tar} at
that time). Some options are used so frequently, and are so useful for
helping you type commands more carefully that they are effectively
``required''. We will discuss them in this chapter.
-You can write most of the @code{tar} operations and options in any of
-three forms: long (mnemonic) form, short form, and old style. Some of
-the operations and options have no short or ``old'' forms; however, the
-operations and options which we will cover in this tutorial have
+You can write most of the @command{tar} operations and options in any
+of three forms: long (mnemonic) form, short form, and old style. Some
+of the operations and options have no short or ``old'' forms; however,
+the operations and options which we will cover in this tutorial have
corresponding abbreviations. @FIXME{make sure this is still the case,
-at the end} We will indicate those abbreviations appropriately to get
+at the end}We will indicate those abbreviations appropriately to get
you used to seeing them. (Note that the ``old style'' option forms
-exist in GNU @code{tar} for compatibility with Unix @code{tar}. We
-present a full discussion of this way of writing options and operations
-appears in @ref{Old Options}, and we discuss the other two styles of
-writing options in @ref{Mnemonic Options} and @ref{Short Options}.)
+exist in @GNUTAR{} for compatibility with Unix
+@command{tar}. In this book we present a full discussion of this way
+of writing options and operations (@pxref{Old Options}), and we discuss
+the other two styles of writing options (@xref{Mnemonic Options}, and
+@pxref{Short Options}).
In the examples and in the text of this tutorial, we usually use the
long forms of operations and options; but the ``short'' forms produce
-the same result and can make typing long @code{tar} commands easier.
+the same result and can make typing long @command{tar} commands easier.
For example, instead of typing
-@example
+@smallexample
@kbd{tar --create --verbose --file=afiles.tar apple angst aspic}
-@end example
+@end smallexample
@noindent
you can type
-@example
+@smallexample
@kbd{tar -c -v -f afiles.tar apple angst aspic}
-@end example
+@end smallexample
@noindent
or even
-@example
+@smallexample
@kbd{tar -cvf afiles.tar apple angst aspic}
-@end example
+@end smallexample
@noindent
For more information on option syntax, see @ref{Advanced tar}. In
The term, ``option'', can be confusing at times, since ``operations''
are often lumped in with the actual, @emph{optional} ``options'' in certain
general class statements. For example, we just talked about ``short and
-long forms of options and operations''. However, experienced @code{tar}
+long forms of options and operations''. However, experienced @command{tar}
users often refer to these by shorthand terms such as, ``short and long
options''. This term assumes that the ``operations'' are included, also.
Context will help you determine which definition of ``options'' to use.
Similarly, the term ``command'' can be confusing, as it is often used in
-two different ways. People sometimes refer to @code{tar} ``commands''.
-A @code{tar} @dfn{command} is the entire command line of user input
-which tells @code{tar} what to do --- including the operation, options,
+two different ways. People sometimes refer to @command{tar} ``commands''.
+A @command{tar} @dfn{command} is the entire command line of user input
+which tells @command{tar} what to do --- including the operation, options,
and any arguments (file names, pipes, other commands, etc). However,
-you will also sometimes hear the term ``the @code{tar} command''. When
+you will also sometimes hear the term ``the @command{tar} command''. When
the word ``command'' is used specifically like this, a person is usually
-referring to the @code{tar} @emph{operation}, not the whole line.
+referring to the @command{tar} @emph{operation}, not the whole line.
Again, use context to figure out which of the meanings the speaker
intends.
-@node frequent operations, Two Frequent Options, basic tar options, Tutorial
+@node frequent operations
@section The Three Most Frequently Used Operations
Here are the three most frequently used operations (both short and long
this chapter will cover how to use these operations in detail. We will
present the rest of the operations in the next chapter.
-@table @kbd
+@table @option
@item --create
@itemx -c
-Create a new @code{tar} archive.
+Create a new @command{tar} archive.
@item --list
@itemx -t
List the contents of an archive.
Extract one or more members from an archive.
@end table
-@node Two Frequent Options, create, frequent operations, Tutorial
+@node Two Frequent Options
@section Two Frequently Used Options
-To understand how to run @code{tar} in the three operating modes listed
+To understand how to run @command{tar} in the three operating modes listed
previously, you also need to understand how to use two of the options to
-@code{tar}: @samp{--file} (which takes an archive file as an argument)
-and @samp{--verbose}. (You are usually not @emph{required} to specify
-either of these options when you run @code{tar}, but they can be very
+@command{tar}: @option{--file} (which takes an archive file as an argument)
+and @option{--verbose}. (You are usually not @emph{required} to specify
+either of these options when you run @command{tar}, but they can be very
useful in making things more clear and helping you avoid errors.)
@menu
* help tutorial::
@end menu
-@node file tutorial, verbose tutorial, Two Frequent Options, Two Frequent Options
-@unnumberedsubsec The @samp{--file} Option
+@node file tutorial
+@unnumberedsubsec The @option{--file} Option
-@table @kbd
+@table @option
+@opindex file, tutorial
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Specify the name of an archive file.
@end table
-You can specify an argument for the @value{op-file} option whenever you
-use @code{tar}; this option determines the name of the archive file
-that @code{tar} will work on.
-
-If you don't specify this argument, then @code{tar} will use a
-default, usually some physical tape drive attached to your machine.
-If there is no tape drive attached, or the default is not meaningful,
-then @code{tar} will print an error message. The error message might
-look roughly like one of the following:
+You can specify an argument for the @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option whenever you
+use @command{tar}; this option determines the name of the archive file
+that @command{tar} will work on.
+
+@vrindex TAPE
+If you don't specify this argument, then @command{tar} will examine
+the environment variable @env{TAPE}. If it is set, its value will be
+used as the archive name. Otherwise, @command{tar} will use the
+default archive, determined at the compile time. Usually it is
+standard output or some physical tape drive attached to your machine
+(you can verify what the default is by running @kbd{tar
+--show-defaults}, @pxref{defaults}). If there is no tape drive
+attached, or the default is not meaningful, then @command{tar} will
+print an error message. The error message might look roughly like one
+of the following:
-@example
+@smallexample
tar: can't open /dev/rmt8 : No such device or address
tar: can't open /dev/rsmt0 : I/O error
-@end example
+@end smallexample
@noindent
-To avoid confusion, we recommend that you always specfiy an archive file
-name by using @value{op-file} when writing your @code{tar} commands.
-For more information on using the @value{op-file} option, see
+To avoid confusion, we recommend that you always specify an archive file
+name by using @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) when writing your @command{tar} commands.
+For more information on using the @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option, see
@ref{file}.
-@node verbose tutorial, help tutorial, file tutorial, Two Frequent Options
-@unnumberedsubsec The @samp{--verbose} Option
+@node verbose tutorial
+@unnumberedsubsec The @option{--verbose} Option
-@table @kbd
+@table @option
+@opindex verbose, introduced
@item --verbose
@itemx -v
-Show the files being worked on as @code{tar} is running.
+Show the files being worked on as @command{tar} is running.
@end table
-@value{op-verbose} shows details about the results of running
-@code{tar}. This can be especially useful when the results might not be
-obvious. For example, if you want to see the progress of @code{tar} as
-it writes files into the archive, you can use the @samp{--verbose}
+@option{--verbose} (@option{-v}) shows details about the results of running
+@command{tar}. This can be especially useful when the results might not be
+obvious. For example, if you want to see the progress of @command{tar} as
+it writes files into the archive, you can use the @option{--verbose}
option. In the beginning, you may find it useful to use
-@samp{--verbose} at all times; when you are more accustomed to
-@code{tar}, you will likely want to use it at certain times but not at
-others. We will use @samp{--verbose} at times to help make something
+@option{--verbose} at all times; when you are more accustomed to
+@command{tar}, you will likely want to use it at certain times but not at
+others. We will use @option{--verbose} at times to help make something
clear, and we will give many examples both using and not using
-@samp{--verbose} to show the differences.
+@option{--verbose} to show the differences.
-Sometimes, a single instance of @samp{--verbose} on the command line
+Sometimes, a single instance of @option{--verbose} on the command line
will show a full, @samp{ls} style listing of an archive or files,
-giving sizes, owners, and similar information. Other times,
-@samp{--verbose} will only show files or members that the particular
+giving sizes, owners, and similar information. @FIXME{Describe the
+exact output format, e.g., how hard links are displayed.}
+Other times, @option{--verbose} will only show files or members that the particular
operation is operating on at the time. In the latter case, you can
-use @samp{--verbose} twice in a command to get a listing such as that
+use @option{--verbose} twice in a command to get a listing such as that
in the former case. For example, instead of saying
-@example
+@smallexample
@kbd{tar -cvf afiles.tar apple angst aspic}
-@end example
+@end smallexample
@noindent
above, you might say
-@example
+@smallexample
@kbd{tar -cvvf afiles.tar apple angst aspic}
-@end example
+@end smallexample
@noindent
This works equally well using short or long forms of options. Using
long forms, you would simply write out the mnemonic form of the option
twice, like this:
-@example
+@smallexample
$ @kbd{tar --create --verbose --verbose @dots{}}
-@end example
+@end smallexample
@noindent
Note that you must double the hyphens properly each time.
-Later in the tutorial, we will give examples using @w{@samp{--verbose
+Later in the tutorial, we will give examples using @w{@option{--verbose
--verbose}}.
-@node help tutorial, , verbose tutorial, Two Frequent Options
-@unnumberedsubsec Getting Help: Using the @code{--help} Option
+@node help tutorial
+@unnumberedsubsec Getting Help: Using the @option{--help} Option
-@table @kbd
+@table @option
+@opindex help
@item --help
-The @samp{--help} option to @code{tar} prints out a very brief list of
+The @option{--help} option to @command{tar} prints out a very brief list of
all operations and option available for the current version of
-@code{tar} available on your system.
+@command{tar} available on your system.
@end table
-@node create, list, Two Frequent Options, Tutorial
+@node create
@section How to Create Archives
@UNREVISED
-One of the basic operations of @code{tar} is @value{op-create}, which
-you use to create a @code{tar} archive. We will explain
-@samp{--create} first because, in order to learn about the other
+@cindex Creation of the archive
+@cindex Archive, creation of
+One of the basic operations of @command{tar} is @option{--create} (@option{-c}), which
+you use to create a @command{tar} archive. We will explain
+@option{--create} first because, in order to learn about the other
operations, you will find it useful to have an archive available to
practice on.
@file{blues}, @file{folk}, and @file{jazz}. The archive is called
@file{collection.tar}.
-This section will proceed slowly, detailing how to use @samp{--create}
+This section will proceed slowly, detailing how to use @option{--create}
in @code{verbose} mode, and showing examples using both short and long
forms. In the rest of the tutorial, and in the examples in the next
chapter, we will proceed at a slightly quicker pace. This section
moves more slowly to allow beginning users to understand how
-@code{tar} works.
+@command{tar} works.
@menu
* prepare for examples::
* create dir::
@end menu
-@node prepare for examples, Creating the archive, create, create
+@node prepare for examples
@subsection Preparing a Practice Directory for Examples
To follow along with this and future examples, create a new directory
and be of different lengths. Our examples assume that @file{practice}
is a subdirectory of your home directory.
-Now @code{cd} to the directory named @file{practice}; @file{practice}
+Now @command{cd} to the directory named @file{practice}; @file{practice}
is now your @dfn{working directory}. (@emph{Please note}: Although
the full path name of this directory is
@file{/@var{homedir}/practice}, in our examples we will refer to
this directory as @file{practice}; the @var{homedir} is presumed.
In general, you should check that the files to be archived exist where
-you think they do (in the working directory) by running @code{ls}.
+you think they do (in the working directory) by running @command{ls}.
Because you just created the directory and the files and have changed to
that directory, you probably don't need to do that this time.
It is very important to make sure there isn't already a file in the
working directory with the archive name you intend to use (in this case,
@samp{collection.tar}), or that you don't care about its contents.
-Whenever you use @samp{create}, @code{tar} will erase the current
-contents of the file named by @value{op-file} if it exists. @code{tar}
-will not tell you if you are about to overwrite a file unless you
-specify an option which does this @FIXME{xref to the node for
---backup!}. To add files to an existing archive, you need to use a
-different option, such as @value{op-append}; see @ref{append} for
-information on how to do this.
-
-@node Creating the archive, create verbose, prepare for examples, create
+Whenever you use @samp{create}, @command{tar} will erase the current
+contents of the file named by @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) if it exists. @command{tar}
+will not tell you if you are about to overwrite an archive unless you
+specify an option which does this (@pxref{backup}, for the
+information on how to do so). To add files to an existing archive,
+you need to use a different option, such as @option{--append} (@option{-r}); see
+@ref{append} for information on how to do this.
+
+@node Creating the archive
@subsection Creating the Archive
+@opindex create, introduced
To place the files @file{blues}, @file{folk}, and @file{jazz} into an
archive named @file{collection.tar}, use the following command:
-@example
+@smallexample
$ @kbd{tar --create --file=collection.tar blues folk jazz}
-@end example
+@end smallexample
The order of the arguments is not very important, @emph{when using long
option forms}. You could also say:
-@example
+@smallexample
$ @kbd{tar blues --create folk --file=collection.tar jazz}
-@end example
+@end smallexample
@noindent
However, you can see that this order is harder to understand; this is
why we will list the arguments in the order that makes the commands
easiest to understand (and we encourage you to do the same when you use
-@code{tar}, to avoid errors).
+@command{tar}, to avoid errors).
Note that the part of the command which says,
-@w{@kbd{--file=collection.tar}} is considered to be @emph{one} argument.
+@w{@option{--file=collection.tar}} is considered to be @emph{one} argument.
If you substituted any other string of characters for
-@kbd{`collection.tar'}, then that string would become the name of the
+@kbd{collection.tar}, then that string would become the name of the
archive file you create.
The order of the options becomes more important when you begin to use
into the habit of typing options in the order that makes inherent sense.
@xref{short create}, for more information on this.
-In this example, you type the command as shown above: @samp{--create}
+In this example, you type the command as shown above: @option{--create}
is the operation which creates the new archive
-(@file{collection.tar}), and @samp{--file} is the option which lets
+(@file{collection.tar}), and @option{--file} is the option which lets
you give it the name you chose. The files, @file{blues}, @file{folk},
and @file{jazz}, are now members of the archive, @file{collection.tar}
-(they are @dfn{file name arguments} to the @samp{--create} operation)
-@FIXME{xref here to the discussion of file name args?}. Now that they
-are are in the archive, they are called @emph{archive members}, not
-files @FIXME{xref to definitions?}.
+(they are @dfn{file name arguments} to the @option{--create} operation).
+@FIXME{xref here to the discussion of file name args?}Now that they are
+in the archive, they are called @emph{archive members}, not files.
+(@pxref{Definitions,members}).
-When you create an archive, you @emph{must} specify which files you want
-placed in the archive. If you do not specify any archive members, GNU
-@code{tar} will complain.
+When you create an archive, you @emph{must} specify which files you
+want placed in the archive. If you do not specify any archive
+members, @GNUTAR{} will complain.
-If you now list the contents of the working directory (@kbd{ls}), you will
+If you now list the contents of the working directory (@command{ls}), you will
find the archive file listed as well as the files you saw previously:
-@example
+@smallexample
blues folk jazz collection.tar
-@end example
+@end smallexample
@noindent
Creating the archive @samp{collection.tar} did not destroy the copies of
the files in the directory.
-Keep in mind that if you don't indicate an operation, @code{tar} will not
-run and will prompt you for one. If you don't name any files, @code{tar}
+Keep in mind that if you don't indicate an operation, @command{tar} will not
+run and will prompt you for one. If you don't name any files, @command{tar}
will complain. You must have write access to the working directory,
or else you will not be able to create an archive in that directory.
-@emph{Caution}: Do not attempt to use @value{op-create} to add files to
+@emph{Caution}: Do not attempt to use @option{--create} (@option{-c}) to add files to
an existing archive; it will delete the archive and write a new one.
-Use @value{op-append} instead. @xref{append}.
+Use @option{--append} (@option{-r}) instead. @xref{append}.
-@node create verbose, short create, Creating the archive, create
-@subsection Running @samp{--create} with @samp{--verbose}
+@node create verbose
+@subsection Running @option{--create} with @option{--verbose}
-If you include the @value{op-verbose} option on the command line,
-@code{tar} will list the files it is acting on as it is working. In
+@opindex create, using with @option{--verbose}
+@opindex verbose, using with @option{--create}
+If you include the @option{--verbose} (@option{-v}) option on the command line,
+@command{tar} will list the files it is acting on as it is working. In
verbose mode, the @code{create} example above would appear as:
-@example
+@smallexample
$ @kbd{tar --create --verbose --file=collection.tar blues folk jazz}
blues
folk
jazz
-@end example
+@end smallexample
This example is just like the example we showed which did not use
-@samp{--verbose}, except that @code{tar} generated the remaining lines
+@option{--verbose}, except that @command{tar} generated the remaining lines
@iftex
(note the different font styles).
@end iftex
@end ifinfo
In the rest of the examples in this chapter, we will frequently use
-@code{verbose} mode so we can show actions or @code{tar} responses that
+@code{verbose} mode so we can show actions or @command{tar} responses that
you would otherwise not see, and which are important for you to
understand.
-@node short create, create dir, create verbose, create
+@node short create
@subsection Short Forms with @samp{create}
-As we said before, the @value{op-create} operation is one of the most
-basic uses of @code{tar}, and you will use it countless times.
+As we said before, the @option{--create} (@option{-c}) operation is one of the most
+basic uses of @command{tar}, and you will use it countless times.
Eventually, you will probably want to use abbreviated (or ``short'')
forms of options. A full discussion of the three different forms that
options can take appears in @ref{Styles}; for now, here is what the
-previous example (including the @value{op-verbose} option) looks like
+previous example (including the @option{--verbose} (@option{-v}) option) looks like
using short option forms:
-@example
+@smallexample
$ @kbd{tar -cvf collection.tar blues folk jazz}
blues
folk
jazz
-@end example
+@end smallexample
@noindent
As you can see, the system responds the same no matter whether you use
forms. For example, suppose you attempted the above example in the
following way:
-@example
+@smallexample
$ @kbd{tar -cfv collection.tar blues folk jazz}
-@end example
+@end smallexample
@noindent
-In this case, @code{tar} will make an archive file called @file{v},
+In this case, @command{tar} will make an archive file called @file{v},
containing the files @file{blues}, @file{folk}, and @file{jazz}, because
-the @samp{v} is the closest ``file name'' to the @samp{-f} option, and
-is thus taken to be the chosen archive file name. @code{tar} will try
+the @samp{v} is the closest ``file name'' to the @option{-f} option, and
+is thus taken to be the chosen archive file name. @command{tar} will try
to add a file called @file{collection.tar} to the @file{v} archive file;
-if the file @file{collection.tar} did not already exist, @code{tar} will
+if the file @file{collection.tar} did not already exist, @command{tar} will
report an error indicating that this file does not exist. If the file
@file{collection.tar} does already exist (e.g., from a previous command
-you may have run), then @code{tar} will add this file to the archive.
-Because the @samp{-v} option did not get registered, @code{tar} will not
+you may have run), then @command{tar} will add this file to the archive.
+Because the @option{-v} option did not get registered, @command{tar} will not
run under @samp{verbose} mode, and will not report its progress.
The end result is that you may be quite confused about what happened,
This example,
-@example
+@smallexample
$ @kbd{tar blues --create folk --file=collection.tar jazz}
-@end example
+@end smallexample
@noindent
is confusing as it is. When shown using short forms, however, it
becomes much more so:
-@example
+@smallexample
$ @kbd{tar blues -c folk -f collection.tar jazz}
-@end example
+@end smallexample
@noindent
It would be very easy to put the wrong string of characters
-immediately following the @samp{-f}, but doing that could sacrifice
+immediately following the @option{-f}, but doing that could sacrifice
valuable data.
For this reason, we recommend that you pay very careful attention to
especially when using short option forms. Not having the option name
written out mnemonically can affect how well you remember which option
does what, and therefore where different names have to be placed.
-(Placing options in an unusual order can also cause @code{tar} to
-report an error if you have set the shell environment variable,
-@code{POSIXLY_CORRECT}; @pxref{posix compliance} for more information
-on this.)
-@node create dir, , short create, create
+@node create dir
@subsection Archiving Directories
@cindex Archiving Directories
@cindex Directories, Archiving
You can archive a directory by specifying its directory name as a
-file name argument to @code{tar}. The files in the directory will be
+file name argument to @command{tar}. The files in the directory will be
archived relative to the working directory, and the directory will be
re-created along with its contents when the archive is extracted.
have followed the previous instructions in this tutorial, you should
type:
-@example
+@smallexample
$ @kbd{cd ..}
$
-@end example
+@end smallexample
@noindent
This will put you into the directory which contains @file{practice},
-i.e. your home directory. Once in the superior directory, you can
+i.e., your home directory. Once in the superior directory, you can
specify the subdirectory, @file{practice}, as a file name argument. To
store @file{practice} in the new archive file @file{music.tar}, type:
-@example
+@smallexample
$ @kbd{tar --create --verbose --file=music.tar practice}
-@end example
+@end smallexample
@noindent
-@code{tar} should output:
+@command{tar} should output:
-@example
+@smallexample
practice/
practice/blues
practice/folk
practice/jazz
practice/collection.tar
-@end example
+@end smallexample
Note that the archive thus created is not in the subdirectory
@file{practice}, but rather in the current working directory---the
-directory from which @code{tar} was invoked. Before trying to archive a
+directory from which @command{tar} was invoked. Before trying to archive a
directory from its superior directory, you should make sure you have
write access to the superior directory itself, not only the directory
-you are trying archive with @code{tar}. For example, you will probably
+you are trying archive with @command{tar}. For example, you will probably
not be able to store your home directory in an archive by invoking
-@code{tar} from the root directory; @value{xref-absolute-names}. (Note
+@command{tar} from the root directory; @xref{absolute}. (Note
also that @file{collection.tar}, the original archive file, has itself
-been archived. @code{tar} will accept any file as a file to be
+been archived. @command{tar} will accept any file as a file to be
archived, regardless of its content. When @file{music.tar} is
extracted, the archive file @file{collection.tar} will be re-written
into the file system).
-If you give @code{tar} a command such as
+If you give @command{tar} a command such as
-@example
+@smallexample
$ @kbd{tar --create --file=foo.tar .}
-@end example
+@end smallexample
@noindent
-@code{tar} will report @samp{tar: foo.tar is the archive; not dumped}.
-This happens because @code{tar} creates the archive @file{foo.tar} in
-the current directory before putting any files into it. Then, when
-@code{tar} attempts to add all the files in the directory @file{.} to
-the archive, it notices that the file @file{foo.tar} is the same as the
-archive, and skips it. (It makes no sense to put an archive into
-itself.) GNU @code{tar} will continue in this case, and create the
-archive normally, except for the exclusion of that one file.
-(@emph{Please note:} Other versions of @code{tar} are not so clever;
-they will enter an infinite loop when this happens, so you should not
-depend on this behavior unless you are certain you are running GNU
-@code{tar}. @FIXME{bob doesn't like this sentence, since he does it
-all the time, and we've been doing it in the editing passes for this
-manual: In general, make sure that the archive is not inside a
-directory being dumped.})
-
-@node list, extract, create, Tutorial
+@command{tar} will report @samp{tar: ./foo.tar is the archive; not
+dumped}. This happens because @command{tar} creates the archive
+@file{foo.tar} in the current directory before putting any files into
+it. Then, when @command{tar} attempts to add all the files in the
+directory @file{.} to the archive, it notices that the file
+@file{./foo.tar} is the same as the archive @file{foo.tar}, and skips
+it. (It makes no sense to put an archive into itself.) @GNUTAR{}
+will continue in this case, and create the archive
+normally, except for the exclusion of that one file. (@emph{Please
+note:} Other versions of @command{tar} are not so clever; they will
+enter an infinite loop when this happens, so you should not depend on
+this behavior unless you are certain you are running @GNUTAR{}.)
+ @FIXME{bob doesn't like this sentence, since he does
+it all the time, and we've been doing it in the editing passes for
+this manual: In general, make sure that the archive is not inside a
+directory being dumped.}
+
+@node list
@section How to List Archives
+@opindex list
Frequently, you will find yourself wanting to determine exactly what a
-particular archive contains. You can use the @value{op-list} operation
+particular archive contains. You can use the @option{--list} (@option{-t}) operation
to get the member names as they currently appear in the archive, as well
as various attributes of the files at the time they were archived. For
example, you can examine the archive @file{collection.tar} that you
created in the last section with the command,
-@example
+@smallexample
$ @kbd{tar --list --file=collection.tar}
-@end example
+@end smallexample
@noindent
-The output of @code{tar} would then be:
+The output of @command{tar} would then be:
-@example
+@smallexample
blues
folk
jazz
-@end example
+@end smallexample
@FIXME{we hope this will change. if it doesn't, need to show the
creation of bfiles somewhere above!!! : }
@noindent
The archive @file{bfiles.tar} would list as follows:
-@example
+@smallexample
./birds
baboon
./box
-@end example
+@end smallexample
@noindent
-Be sure to use a @value{op-file} option just as with @value{op-create}
+Be sure to use a @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option just as with @option{--create} (@option{-c})
to specify the name of the archive.
-If you use the @value{op-verbose} option with @samp{--list}, then
-@code{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
+@opindex list, using with @option{--verbose}
+@opindex verbose, using with @option{--list}
+If you use the @option{--verbose} (@option{-v}) option with @option{--list}, then
+@command{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
showing owner, file size, and so forth.
-If you had used @value{op-verbose} mode, the example above would look
+If you had used @option{--verbose} (@option{-v}) mode, the example above would look
like:
-@example
+@smallexample
$ @kbd{tar --list --verbose --file=collection.tar folk}
--rw-rw-rw- myself user 62 1990-05-23 10:55 folk
-@end example
+-rw-r--r-- myself user 62 1990-05-23 10:55 folk
+@end smallexample
+
+@cindex listing member and file names
+@anchor{listing member and file names}
+It is important to notice that the output of @kbd{tar --list
+--verbose} does not necessarily match that produced by @kbd{tar
+--create --verbose} while creating the archive. It is because
+@GNUTAR{}, unless told explicitly not to do so, removes some directory
+prefixes from file names before storing them in the archive
+(@xref{absolute}, for more information). In other
+words, in verbose mode @GNUTAR{} shows @dfn{file names} when creating
+an archive and @dfn{member names} when listing it. Consider this
+example:
+
+@smallexample
+@group
+$ @kbd{tar cfv archive /etc/mail}
+tar: Removing leading `/' from member names
+/etc/mail/
+/etc/mail/sendmail.cf
+/etc/mail/aliases
+$ @kbd{tar tf archive}
+etc/mail/
+etc/mail/sendmail.cf
+etc/mail/aliases
+@end group
+@end smallexample
+
+@opindex show-stored-names
+ This default behavior can sometimes be inconvenient. You can force
+@GNUTAR{} show member names when creating archive by supplying
+@option{--show-stored-names} option.
+
+@table @option
+@item --show-stored-names
+Print member (as opposed to @emph{file}) names when creating the archive.
+@end table
-@cindex File name arguments, using @code{--list} with
-@cindex @code{--list} with file name arguments
+@cindex File name arguments, using @option{--list} with
+@opindex list, using with file name arguments
You can specify one or more individual member names as arguments when
-using @samp{list}. In this case, @code{tar} will only list the
+using @samp{list}. In this case, @command{tar} will only list the
names of members you identify. For example, @w{@kbd{tar --list
--file=afiles.tar apple}} would only print @file{apple}.
@FIXME{we hope the relevant aspects of this will change:}Because
-@code{tar} preserves paths, file names must be specified as they appear
+@command{tar} preserves paths, file names must be specified as they appear
in the archive (ie., relative to the directory from which the archive
was created). Therefore, it is essential when specifying member names
-to @code{tar} that you give the exact member names. For example,
+to @command{tar} that you give the exact member names. For example,
@w{@kbd{tar --list --file=bfiles birds}} would produce an error message
something like @samp{tar: birds: Not found in archive}, because there is
no member named @file{birds}, only one named @file{./birds}. While the
with @file{folk}, because @file{folk} is in the archive file
@file{collection.tar}. If you are not sure of the exact file name, try
listing all the files in the archive and searching for the one you
-expect to find; remember that if you use @samp{--list} with no file
-names as arguments, @code{tar} will print the names of all the members
+expect to find; remember that if you use @option{--list} with no file
+names as arguments, @command{tar} will print the names of all the members
stored in the specified archive.
@menu
* list dir::
@end menu
-@node list dir, , list, list
+@node list dir
@unnumberedsubsec Listing the Contents of a Stored Directory
-@UNREVISED
-
-@FIXME{i changed the order of these nodes around and haven't had a
-chance to play around with this node's example, yet. i have to play
-with it and see what it actually does for my own satisfaction, even if
-what it says *is* correct..}
To get information about the contents of an archived directory,
use the directory name as a file name argument in conjunction with
-@value{op-list}. To find out file attributes, include the
-@value{op-verbose} option.
+@option{--list} (@option{-t}). To find out file attributes, include the
+@option{--verbose} (@option{-v}) option.
For example, to find out about files in the directory @file{practice}, in
the archive file @file{music.tar}, type:
-@example
+@smallexample
$ @kbd{tar --list --verbose --file=music.tar practice}
-@end example
+@end smallexample
-@code{tar} responds:
+@command{tar} responds:
-@example
+@smallexample
drwxrwxrwx myself user 0 1990-05-31 21:49 practice/
--rw-rw-rw- myself user 42 1990-05-21 13:29 practice/blues
--rw-rw-rw- myself user 62 1990-05-23 10:55 practice/folk
--rw-rw-rw- myself user 40 1990-05-21 13:30 practice/jazz
--rw-rw-rw- myself user 10240 1990-05-31 21:49 practice/collection.tar
-@end example
+-rw-r--r-- myself user 42 1990-05-21 13:29 practice/blues
+-rw-r--r-- myself user 62 1990-05-23 10:55 practice/folk
+-rw-r--r-- myself user 40 1990-05-21 13:30 practice/jazz
+-rw-r--r-- myself user 10240 1990-05-31 21:49 practice/collection.tar
+@end smallexample
-When you use a directory name as a file name argument, @code{tar} acts on
+When you use a directory name as a file name argument, @command{tar} acts on
all the files (including sub-directories) in that directory.
-@node extract, going further, list, Tutorial
+@node extract
@section How to Extract Members from an Archive
@UNREVISED
@cindex Extraction
@cindex Retrieving files from an archive
@cindex Resurrecting files from an archive
+@opindex extract
Creating an archive is only half the job---there is no point in storing
files in an archive if you can't retrieve them. The act of retrieving
members from an archive so they can be used and manipulated as
unarchived files again is called @dfn{extraction}. To extract files
-from an archive, use the @value{op-extract} operation. As with
-@value{op-create}, specify the name of the archive with @value{op-file}.
-Extracting an archive does not modify the archive in any way; you can
-extract it multiple times if you want or need to.
+from an archive, use the @option{--extract} (@option{--get} or
+@option{-x}) operation. As with @option{--create}, specify the name
+of the archive with @option{--file} (@option{-f}) option. Extracting
+an archive does not modify the archive in any way; you can extract it
+multiple times if you want or need to.
-Using @samp{--extract}, you can extract an entire archive, or specific
+Using @option{--extract}, you can extract an entire archive, or specific
files. The files can be directories containing other files, or not. As
-with @value{op-create} and @value{op-list}, you may use the short or the
+with @option{--create} (@option{-c}) and @option{--list} (@option{-t}), you may use the short or the
long form of the operation without affecting the performance.
@menu
* extracting archives::
* extracting files::
* extract dir::
+* extracting untrusted archives::
* failing commands::
@end menu
-@node extracting archives, extracting files, extract, extract
+@node extracting archives
@subsection Extracting an Entire Archive
To extract an entire archive, specify the archive file name only, with
no individual file names as arguments. For example,
-@example
+@smallexample
$ @kbd{tar -xvf collection.tar}
-@end example
+@end smallexample
@noindent
produces this:
-@example
--rw-rw-rw- me user 28 1996-10-18 16:31 jazz
--rw-rw-rw- me user 21 1996-09-23 16:44 blues
--rw-rw-rw- me user 20 1996-09-23 16:44 folk
-@end example
+@smallexample
+-rw-r--r-- me user 28 1996-10-18 16:31 jazz
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+-rw-r--r-- me user 20 1996-09-23 16:44 folk
+@end smallexample
-@node extracting files, extract dir, extracting archives, extract
+@node extracting files
@subsection Extracting Specific Files
To extract specific archive members, give their exact member names as
-arguments, as printed by @value{op-list}. If you had mistakenly deleted
+arguments, as printed by @option{--list} (@option{-t}). If you had mistakenly deleted
one of the files you had placed in the archive @file{collection.tar}
earlier (say, @file{blues}), you can extract it from the archive without
-changing the archive's structure. It will be identical to the original
-file @file{blues} that you deleted. @FIXME{check this; will the times,
-permissions, owner, etc be the same, also?}
+changing the archive's structure. Its contents will be identical to the
+original file @file{blues} that you deleted.
First, make sure you are in the @file{practice} directory, and list the
files in the directory. Now, delete the file, @samp{blues}, and list
You can now extract the member @file{blues} from the archive file
@file{collection.tar} like this:
-@example
+@smallexample
$ @kbd{tar --extract --file=collection.tar blues}
-@end example
+@end smallexample
@noindent
If you list the files in the directory again, you will see that the file
-@file{blues} has been restored, with its original permissions, creation
-times, and owner. @FIXME{This is only accidentally true, but not in
+@file{blues} has been restored, with its original permissions, data modification
+times, and owner.@FIXME{This is only accidentally true, but not in
general. In most cases, one has to be root for restoring the owner, and
use a special option for restoring permissions. Here, it just happens
that the restoring user is also the owner of the archived members, and
you may have made before deleting the file from the file system,
however, will @emph{not} have been made to the archive member.) The
archive file, @samp{collection.tar}, is the same as it was before you
-extracted @samp{blues}. You can confirm this by running @code{tar} with
-@value{op-list}.
+extracted @samp{blues}. You can confirm this by running @command{tar} with
+@option{--list} (@option{-t}).
@FIXME{we hope this will change:}Remember that as with other operations,
specifying the exact member name is important. @w{@kbd{tar --extract
--file=bfiles.tar birds}} will fail, because there is no member named
@file{birds}. To extract the member named @file{./birds}, you must
specify @w{@kbd{tar --extract --file=bfiles.tar ./birds}}. To find the
-exact member names of the members of an archive, use @value{op-list}
+exact member names of the members of an archive, use @option{--list} (@option{-t})
(@pxref{list}).
-If you give the @value{op-verbose} option, then @value{op-extract} will
-print the names of the archive members as it extracts them.
+You can extract a file to standard output by combining the above options
+with the @option{--to-stdout} (@option{-O}) option (@pxref{Writing to Standard
+Output}).
+
+If you give the @option{--verbose} option, then @option{--extract}
+will print the names of the archive members as it extracts them.
-@node extract dir, failing commands, extracting files, extract
+@node extract dir
@subsection Extracting Files that are Directories
Extracting directories which are members of an archive is similar to
the working directory, then files in the extracted directory will be
placed into the directory of the same name. Likewise, if there are
files in the pre-existing directory with the same names as the members
-which you extract, the files from the extracted archive will overwrite
+which you extract, the files from the extracted archive will replace
the files already in the working directory (and possible
subdirectories). This will happen regardless of whether or not the
-files in the working directory were more recent than those extracted.
+files in the working directory were more recent than those extracted
+(there exist, however, special options that alter this behavior
+@pxref{Writing}).
However, if a file was stored with a directory name as part of its file
name, and that directory does not exist under the working directory when
-the file is extracted, @code{tar} will create the directory.
+the file is extracted, @command{tar} will create the directory.
-We can demonstrate how to use @samp{--extract} to extract a directory
+We can demonstrate how to use @option{--extract} to extract a directory
file with an example. Change to the @file{practice} directory if you
weren't there, and remove the files @file{folk} and @file{jazz}. Then,
go back to the parent directory and extract the archive
@file{music.tar}. To extract only the files you deleted, use the
following command:
-@example
+@smallexample
$ @kbd{tar -xvf music.tar practice/folk practice/jazz}
-@end example
+practice/folk
+practice/jazz
+@end smallexample
+
+@noindent
+If you were to specify two @option{--verbose} (@option{-v}) options, @command{tar}
+would have displayed more detail about the extracted files, as shown
+in the example below:
-@FIXME{need to show tar's response; used verbose above. also, here's a
-good place to demonstrate the -v -v thing. have to write that up
-(should be trivial, but i'm too tired!).}
+@smallexample
+$ @kbd{tar -xvvf music.tar practice/folk practice/jazz}
+-rw-r--r-- me user 28 1996-10-18 16:31 practice/jazz
+-rw-r--r-- me user 20 1996-09-23 16:44 practice/folk
+@end smallexample
@noindent
Because you created the directory with @file{practice} as part of the
@FIXME{IMPORTANT! show the final structure, here. figure out what it
will be.}
-@node failing commands, , extract dir, extract
+@node extracting untrusted archives
+@subsection Extracting Archives from Untrusted Sources
+
+Extracting files from archives can overwrite files that already exist.
+If you receive an archive from an untrusted source, you should make a
+new directory and extract into that directory, so that you don't have
+to worry about the extraction overwriting one of your existing files.
+For example, if @file{untrusted.tar} came from somewhere else on the
+Internet, and you don't necessarily trust its contents, you can
+extract it as follows:
+
+@smallexample
+$ @kbd{mkdir newdir}
+$ @kbd{cd newdir}
+$ @kbd{tar -xvf ../untrusted.tar}
+@end smallexample
+
+It is also a good practice to examine contents of the archive
+before extracting it, using @option{--list} (@option{-t}) option, possibly combined
+with @option{--verbose} (@option{-v}).
+
+@node failing commands
@subsection Commands That Will Fail
Here are some sample commands you might try which will not work, and why
If you try to use this command,
-@example
+@smallexample
$ @kbd{tar -xvf music.tar folk jazz}
-@end example
+@end smallexample
@noindent
you will get the following response:
-@example
+@smallexample
tar: folk: Not found in archive
tar: jazz: Not found in archive
$
-@end example
+@end smallexample
@noindent
This is because these files were not originally @emph{in} the parent
directory @file{..}, where the archive is located; they were in the
@file{practice} directory, and their file names reflect this:
-@example
+@smallexample
$ @kbd{tar -tvf music.tar}
practice/folk
practice/jazz
practice/rock
-@end example
+@end smallexample
@FIXME{make sure the above works when going through the examples in
order...}
@noindent
Likewise, if you try to use this command,
-@example
+@smallexample
$ @kbd{tar -tvf music.tar folk jazz}
-@end example
+@end smallexample
@noindent
you would get a similar response. Members with those names are not in the
@FIXME{more examples, here? hag thinks it's a good idea.}
-@node going further, , extract, Tutorial
+@node going further
@section Going Further Ahead in this Manual
@FIXME{need to write up a node here about the things that are going to
be in the rest of the manual.}
-@node tar invocation, operations, Tutorial, Top
-@chapter Invoking GNU @code{tar}
+@node tar invocation
+@chapter Invoking @GNUTAR{}
@UNREVISED
-This chapter is about how one invokes the GNU @code{tar} command, from
-the command synopsis (@pxref{Synopsis}). There are numerous options,
-and many styles for writing them. One mandatory option specifies
-the operation @code{tar} should perform (@pxref{Operation Summary}),
-other options are meant to detail how this operation should be performed
-(@pxref{Option Summary}). Non-option arguments are not always interpreted
-the same way, depending on what the operation is.
+This chapter is about how one invokes the @GNUTAR{}
+command, from the command synopsis (@pxref{Synopsis}). There are
+numerous options, and many styles for writing them. One mandatory
+option specifies the operation @command{tar} should perform
+(@pxref{Operation Summary}), other options are meant to detail how
+this operation should be performed (@pxref{Option Summary}).
+Non-option arguments are not always interpreted the same way,
+depending on what the operation is.
You will find in this chapter everything about option styles and rules for
writing them (@pxref{Styles}). On the other hand, operations and options
are fully described elsewhere, in other chapters. Here, you will find
only synthetic descriptions for operations and options, together with
-pointers to other parts of the @code{tar} manual.
+pointers to other parts of the @command{tar} manual.
Some options are so special they are fully described right in this
chapter. They have the effect of inhibiting the normal operation of
-@code{tar} or else, they globally alter the amount of feedback the user
-receives about what is going on. These are the @value{op-help} and
-@value{op-version} (@pxref{help}), @value{op-verbose} (@pxref{verbose})
-and @value{op-interactive} options (@pxref{interactive}).
+@command{tar} or else, they globally alter the amount of feedback the user
+receives about what is going on. These are the @option{--help} and
+@option{--version} (@pxref{help}), @option{--verbose} (@pxref{verbose})
+and @option{--interactive} options (@pxref{interactive}).
@menu
* Synopsis::
* Styles::
* All Options::
* help::
+* defaults::
* verbose::
* interactive::
@end menu
-@node Synopsis, using tar options, tar invocation, tar invocation
-@section General Synopsis of @code{tar}
+@node Synopsis
+@section General Synopsis of @command{tar}
-The GNU @code{tar} program is invoked as either one of:
+The @GNUTAR{} program is invoked as either one of:
-@example
+@smallexample
@kbd{tar @var{option}@dots{} [@var{name}]@dots{}}
@kbd{tar @var{letter}@dots{} [@var{argument}]@dots{} [@var{option}]@dots{} [@var{name}]@dots{}}
-@end example
+@end smallexample
The second form is for when old options are being used.
-You can use @code{tar} to store files in an archive, to extract them from
+You can use @command{tar} to store files in an archive, to extract them from
an archive, and to do other types of archive manipulation. The primary
-argument to @code{tar}, which is called the @dfn{operation}, specifies
-which action to take. The other arguments to @code{tar} are either
-@dfn{options}, which change the way @code{tar} performs an operation,
+argument to @command{tar}, which is called the @dfn{operation}, specifies
+which action to take. The other arguments to @command{tar} are either
+@dfn{options}, which change the way @command{tar} performs an operation,
or file names or archive members, which specify the files or members
-@code{tar} is to act on.
+@command{tar} is to act on.
You can actually type in arguments in any order, even if in this manual
the options always precede the other arguments, to make examples easier
to understand. Further, the option stating the main operation mode
-(the @code{tar} main command) is usually given first.
+(the @command{tar} main command) is usually given first.
Each @var{name} in the synopsis above is interpreted as an archive member
-name when the main command is one of @value{op-compare}, @value{op-delete},
-@value{op-extract}, @value{op-list} or @value{op-update}. When naming
-archive members, you must give the exact name of the member in the
-archive, as it is printed by @value{op-list}. For @value{op-append}
-and @value{op-create}, these @var{name} arguments specify the names
-of either files or directory hierarchies to place in the archive.
+name when the main command is one of @option{--compare}
+(@option{--diff}, @option{-d}), @option{--delete}, @option{--extract}
+(@option{--get}, @option{-x}), @option{--list} (@option{-t}) or
+@option{--update} (@option{-u}). When naming archive members, you
+must give the exact name of the member in the archive, as it is
+printed by @option{--list}. For @option{--append} (@option{-r}) and
+@option{--create} (@option{-c}), these @var{name} arguments specify
+the names of either files or directory hierarchies to place in the archive.
These files or hierarchies should already exist in the file system,
-prior to the execution of the @code{tar} command.
+prior to the execution of the @command{tar} command.
-@code{tar} interprets relative file names as being relative to the
-working directory. @code{tar} will make all file names relative
+@command{tar} interprets relative file names as being relative to the
+working directory. @command{tar} will make all file names relative
(by removing leading slashes when archiving or restoring files),
-unless you specify otherwise (using the @value{op-absolute-names}
-option). @value{xref-absolute-names}, for more information about
-@value{op-absolute-names}.
+unless you specify otherwise (using the @option{--absolute-names}
+option). @xref{absolute}, for more information about
+@option{--absolute-names}.
If you give the name of a directory as either a file name or a member
-name, then @code{tar} acts recursively on all the files and directories
+name, then @command{tar} acts recursively on all the files and directories
beneath that directory. For example, the name @file{/} identifies all
-the files in the filesystem to @code{tar}.
+the files in the file system to @command{tar}.
The distinction between file names and archive member names is especially
important when shell globbing is used, and sometimes a source of confusion
for newcomers. @xref{Wildcards}, for more information about globbing.
The problem is that shells may only glob using existing files in the
-file system. Only @code{tar} itself may glob on archive members, so when
-needed, you must ensure that wildcard characters reach @code{tar} without
+file system. Only @command{tar} itself may glob on archive members, so when
+needed, you must ensure that wildcard characters reach @command{tar} without
being interpreted by the shell first. Using a backslash before @samp{*}
or @samp{?}, or putting the whole argument between quotes, is usually
sufficient for this.
Even if @var{name}s are often specified on the command line, they
can also be read from a text file in the file system, using the
-@value{op-files-from} option.
+@option{--files-from=@var{file-of-names}} (@option{-T @var{file-of-names}}) option.
-If you don't use any file name arguments, @value{op-append},
-@value{op-delete} and @value{op-concatenate} will do nothing, while
-@value{op-create} will usually yield a diagnostic and inhibit @code{tar}
-execution. The other operations of @code{tar} (@value{op-list},
-@value{op-extract}, @value{op-compare}, and @value{op-update}) will act
-on the entire contents of the archive.
+If you don't use any file name arguments, @option{--append} (@option{-r}),
+@option{--delete} and @option{--concatenate} (@option{--catenate},
+@option{-A}) will do nothing, while @option{--create} (@option{-c})
+will usually yield a diagnostic and inhibit @command{tar} execution.
+The other operations of @command{tar} (@option{--list},
+@option{--extract}, @option{--compare}, and @option{--update})
+will act on the entire contents of the archive.
@cindex exit status
@cindex return status
-Besides successful exits, GNU @code{tar} may fail for many reasons.
-Some reasons correspond to bad usage, that is, when the @code{tar}
-command is improperly written.
-Errors may be encountered later, while encountering an error
-processing the archive or the files. Some errors are recoverable,
-in which case the failure is delayed until @code{tar} has completed
-all its work. Some errors are such that it would not meaningful,
-or at least risky, to continue processing: @code{tar} then aborts
-processing immediately. All abnormal exits, whether immediate or
-delayed, should always be clearly diagnosed on @code{stderr}, after
-a line stating the nature of the error.
-
-GNU @code{tar} returns only a few exit statuses. I'm really
+Besides successful exits, @GNUTAR{} may fail for
+many reasons. Some reasons correspond to bad usage, that is, when the
+@command{tar} command is improperly written. Errors may be
+encountered later, while encountering an error processing the archive
+or the files. Some errors are recoverable, in which case the failure
+is delayed until @command{tar} has completed all its work. Some
+errors are such that it would not meaningful, or at least risky, to
+continue processing: @command{tar} then aborts processing immediately.
+All abnormal exits, whether immediate or delayed, should always be
+clearly diagnosed on @code{stderr}, after a line stating the nature of
+the error.
+
+@GNUTAR{} returns only a few exit statuses. I'm really
aiming simplicity in that area, for now. If you are not using the
-@value{op-compare} option, zero means that everything went well, besides
-maybe innocuous warnings. Nonzero means that something went wrong.
-Right now, as of today, ``nonzero'' is almost always 2, except for
-remote operations, where it may be 128.
-
-@node using tar options, Styles, Synopsis, tar invocation
-@section Using @code{tar} Options
-
-GNU @code{tar} has a total of eight operating modes which allow you to
-perform a variety of tasks. You are required to choose one operating
-mode each time you employ the @code{tar} program by specifying one, and
-only one operation as an argument to the @code{tar} command (two lists
-of four operations each may be found at @ref{frequent operations} and
-@ref{Operations}). Depending on circumstances, you may also wish to
-customize how the chosen operating mode behaves. For example, you may
-wish to change the way the output looks, or the format of the files that
-you wish to archive may require you to do something special in order to
-make the archive look right.
-
-You can customize and control @code{tar}'s performance by running
-@code{tar} with one or more options (such as @value{op-verbose}, which
-we used in the tutorial). As we said in the tutorial, @dfn{options} are
-arguments to @code{tar} which are (as their name suggests) optional.
-Depending on the operating mode, you may specify one or more options.
-Different options will have different effects, but in general they all
-change details of the operation, such as archive format, archive name,
-or level of user interaction. Some options make sense with all
-operating modes, while others are meaningful only with particular modes.
-You will likely use some options frequently, while you will only use
-others infrequently, or not at all. (A full list of options is
-available in @pxref{All Options}.)
-
-Note that @code{tar} options are case sensitive. For example, the
-options @samp{-T} and @samp{-t} are different; the first requires an
+@option{--compare} @option{--diff}, @option{-d}) option, zero means
+that everything went well, besides maybe innocuous warnings. Nonzero
+means that something went wrong. Right now, as of today, ``nonzero''
+is almost always 2, except for remote operations, where it may be
+128.
+
+@node using tar options
+@section Using @command{tar} Options
+
+@GNUTAR{} has a total of eight operating modes which
+allow you to perform a variety of tasks. You are required to choose
+one operating mode each time you employ the @command{tar} program by
+specifying one, and only one operation as an argument to the
+@command{tar} command (two lists of four operations each may be found
+at @ref{frequent operations} and @ref{Operations}). Depending on
+circumstances, you may also wish to customize how the chosen operating
+mode behaves. For example, you may wish to change the way the output
+looks, or the format of the files that you wish to archive may require
+you to do something special in order to make the archive look right.
+
+You can customize and control @command{tar}'s performance by running
+@command{tar} with one or more options (such as @option{--verbose}
+(@option{-v}), which we used in the tutorial). As we said in the
+tutorial, @dfn{options} are arguments to @command{tar} which are (as
+their name suggests) optional. Depending on the operating mode, you
+may specify one or more options. Different options will have different
+effects, but in general they all change details of the operation, such
+as archive format, archive name, or level of user interaction. Some
+options make sense with all operating modes, while others are
+meaningful only with particular modes. You will likely use some
+options frequently, while you will only use others infrequently, or
+not at all. (A full list of options is available in @pxref{All Options}.)
+
+@vrindex TAR_OPTIONS, environment variable
+@anchor{TAR_OPTIONS}
+The @env{TAR_OPTIONS} environment variable specifies default options to
+be placed in front of any explicit options. For example, if
+@code{TAR_OPTIONS} is @samp{-v --unlink-first}, @command{tar} behaves as
+if the two options @option{-v} and @option{--unlink-first} had been
+specified before any explicit options. Option specifications are
+separated by whitespace. A backslash escapes the next character, so it
+can be used to specify an option containing whitespace or a backslash.
+
+Note that @command{tar} options are case sensitive. For example, the
+options @option{-T} and @option{-t} are different; the first requires an
argument for stating the name of a file providing a list of @var{name}s,
while the second does not require an argument and is another way to
-write @value{op-list}.
+write @option{--list} (@option{-t}).
In addition to the eight operations, there are many options to
-@code{tar}, and three different styles for writing both: long (mnemonic)
+@command{tar}, and three different styles for writing both: long (mnemonic)
form, short form, and old style. These styles are discussed below.
Both the options and the operations can be written in any of these three
styles.
@FIXME{menu at end of this node. need to think of an actual outline
-for this chapter; probably do that after stuff from chap. 4 is
+for this chapter; probably do that after stuff from chapter 4 is
incorporated.}
-@node Styles, All Options, using tar options, tar invocation
+@node Styles
@section The Three Option Styles
There are three styles for writing operations and options to the command
-line invoking @code{tar}. The different styles were developed at
-different times during the history of @code{tar}. These styles will be
+line invoking @command{tar}. The different styles were developed at
+different times during the history of @command{tar}. These styles will be
presented below, from the most recent to the oldest.
-Some options must take an argument. (For example, @value{op-file} takes
-the name of an archive file as an argument. If you do not supply an
-archive file name, @code{tar} will use a default, but this can be
-confusing; thus, we recommend that you always supply a specific archive
-file name.) Where you @emph{place} the arguments generally depends on
-which style of options you choose. We will detail specific information
-relevant to each option style in the sections on the different option
-styles, below. The differences are subtle, yet can often be very
-important; incorrect option placement can cause you to overwrite a
-number of important files. We urge you to note these differences, and
-only use the option style(s) which makes the most sense to you until you
-feel comfortable with the others.
-
-@FIXME{hag to write a brief paragraph on the option(s) which can
-optionally take an argument}
+Some options must take an argument. (For example, @option{--file}
+(@option{-f})) takes the name of an archive file as an argument. If
+you do not supply an archive file name, @command{tar} will use a
+default, but this can be confusing; thus, we recommend that you always
+supply a specific archive file name.) Where you @emph{place} the
+arguments generally depends on which style of options you choose. We
+will detail specific information relevant to each option style in the
+sections on the different option styles, below. The differences are
+subtle, yet can often be very important; incorrect option placement
+can cause you to overwrite a number of important files. We urge you
+to note these differences, and only use the option style(s) which
+makes the most sense to you until you feel comfortable with the others.
+
+Some options @emph{may} take an argument (currently, there are
+two such options: @option{--backup} and @option{--occurrence}). Such
+options may have at most long and short forms, they do not have old style
+equivalent. The rules for specifying an argument for such options
+are stricter than those for specifying mandatory arguments. Please,
+pay special attention to them.
@menu
* Mnemonic Options:: Mnemonic Option Style
* Mixing:: Mixing Option Styles
@end menu
-@node Mnemonic Options, Short Options, Styles, Styles
+@node Mnemonic Options
@subsection Mnemonic Option Style
-@FIXME{have to decide whether or ot to replace other occurrences of
+@FIXME{have to decide whether or not to replace other occurrences of
"mnemonic" with "long", or *ugh* vice versa.}
Each option has at least one long (or mnemonic) name starting with two
-dashes in a row, e.g. @samp{list}. The long names are more clear than
+dashes in a row, e.g., @option{--list}. The long names are more clear than
their corresponding short or old names. It sometimes happens that a
single mnemonic option has many different different names which are
-synonymous, such as @samp{--compare} and @samp{--diff}. In addition,
+synonymous, such as @option{--compare} and @option{--diff}. In addition,
long option names can be given unique abbreviations. For example,
-@samp{--cre} can be used in place of @samp{--create} because there is no
+@option{--cre} can be used in place of @option{--create} because there is no
other mnemonic option which begins with @samp{cre}. (One way to find
this out is by trying it and seeing what happens; if a particular
-abbreviation could represent more than one option, @code{tar} will tell
+abbreviation could represent more than one option, @command{tar} will tell
you that that abbreviation is ambiguous and you'll know that that
abbreviation won't work. You may also choose to run @samp{tar --help}
-to see a list of options. Be aware that if you run @code{tar} with a
+to see a list of options. Be aware that if you run @command{tar} with a
unique abbreviation for the long name of an option you didn't want to
-use, you are stuck; @code{tar} will perform the command as ordered.)
+use, you are stuck; @command{tar} will perform the command as ordered.)
Mnemonic options are meant to be obvious and easy to remember, and their
meanings are generally easier to discern than those of their
corresponding short options (see below). For example:
-@example
+@smallexample
$ @kbd{tar --create --verbose --blocking-factor=20 --file=/dev/rmt0}
-@end example
+@end smallexample
@noindent
gives a fairly good set of hints about what the command does, even
-for those not fully acquainted with @code{tar}.
+for those not fully acquainted with @command{tar}.
Mnemonic options which require arguments take those arguments
-immediately following the option name; they are introduced by an equal
-sign. For example, the @samp{--file} option (which tells the name
-of the @code{tar} archive) is given a file such as @file{archive.tar}
-as argument by using the notation @samp{--file=archive.tar} for the
-mnemonic option.
-
-@node Short Options, Old Options, Mnemonic Options, Styles
+immediately following the option name. There are two ways of
+specifying a mandatory argument. It can be separated from the
+option name either by an equal sign, or by any amount of
+white space characters. For example, the @option{--file} option (which
+tells the name of the @command{tar} archive) is given a file such as
+@file{archive.tar} as argument by using any of the following notations:
+@option{--file=archive.tar} or @option{--file archive.tar}.
+
+In contrast, optional arguments must always be introduced using
+an equal sign. For example, the @option{--backup} option takes
+an optional argument specifying backup type. It must be used
+as @option{--backup=@var{backup-type}}.
+
+@node Short Options
@subsection Short Option Style
Most options also have a short option name. Short options start with
-a single dash, and are followed by a single character, e.g. @samp{-t}
-(which is equivalent to @samp{--list}). The forms are absolutely
+a single dash, and are followed by a single character, e.g., @option{-t}
+(which is equivalent to @option{--list}). The forms are absolutely
identical in function; they are interchangeable.
The short option names are faster to type than long option names.
Short options which require arguments take their arguments immediately
following the option, usually separated by white space. It is also
possible to stick the argument right after the short option name, using
-no intervening space. For example, you might write @w{@samp{-f
-archive.tar}} or @samp{-farchive.tar} instead of using
-@samp{--file=archive.tar}. Both @samp{--file=@var{archive-name}} and
-@w{@samp{-f @var{archive-name}}} denote the option which indicates a
+no intervening space. For example, you might write @w{@option{-f
+archive.tar}} or @option{-farchive.tar} instead of using
+@option{--file=archive.tar}. Both @option{--file=@var{archive-name}} and
+@w{@option{-f @var{archive-name}}} denote the option which indicates a
specific archive, here named @file{archive.tar}.
+Short options which take optional arguments take their arguments
+immediately following the option letter, @emph{without any intervening
+white space characters}.
+
Short options' letters may be clumped together, but you are not
-required to do this (as compared to old options; see below). When short
-options are clumped as a set, use one (single) dash for them all, e.g.
-@w{@samp{@code{tar} -cvf}}. Only the last option in such a set is allowed
-to have an argument@footnote{Clustering many options, the last of which
-has an argument, is a rather opaque way to write options. Some wonder if
-GNU @code{getopt} should not even be made helpful enough for considering
-such usages as invalid.}.
+required to do this (as compared to old options; see below). When
+short options are clumped as a set, use one (single) dash for them
+all, e.g., @w{@samp{@command{tar} -cvf}}. Only the last option in
+such a set is allowed to have an argument@footnote{Clustering many
+options, the last of which has an argument, is a rather opaque way to
+write options. Some wonder if @acronym{GNU} @code{getopt} should not
+even be made helpful enough for considering such usages as invalid.}.
When the options are separated, the argument for each option which requires
an argument directly follows that option, as is usual for Unix programs.
For example:
-@example
+@smallexample
$ @kbd{tar -c -v -b 20 -f /dev/rmt0}
-@end example
+@end smallexample
If you reorder short options' locations, be sure to move any arguments
that belong to them. If you do not move the arguments properly, you may
end up overwriting files.
-@node Old Options, Mixing, Short Options, Styles
+@node Old Options
@subsection Old Option Style
@UNREVISED
with a dash, you are announcing the short option style instead of the
old option style; short options are decoded differently.}. This set
of letters must be the first to appear on the command line, after the
-@code{tar} program name and some whitespace; old options cannot appear
+@command{tar} program name and some white space; old options cannot appear
anywhere else. The letter of an old option is exactly the same letter as
the corresponding short option. For example, the old option @samp{t} is
-the same as the short option @samp{-t}, and consequently, the same as the
-mnemonic option @samp{--list}. So for example, the command @w{@samp{tar
-cv}} specifies the option @samp{-v} in addition to the operation @samp{-c}.
+the same as the short option @option{-t}, and consequently, the same as the
+mnemonic option @option{--list}. So for example, the command @w{@samp{tar
+cv}} specifies the option @option{-v} in addition to the operation @option{-c}.
@FIXME{bob suggests having an uglier example. :-) }
Thus, the example given previously could also be written in the old
style as follows:
-@example
+@smallexample
$ @kbd{tar cvbf 20 /dev/rmt0}
-@end example
+@end smallexample
@noindent
-Here, @samp{20} is the argument of @samp{-b} and @samp{/dev/rmt0} is
-the argument of @samp{-f}.
+Here, @samp{20} is the argument of @option{-b} and @samp{/dev/rmt0} is
+the argument of @option{-f}.
On the other hand, this old style syntax makes it difficult to match
option letters with their corresponding arguments, and is often
confusing. In the command @w{@samp{tar cvbf 20 /dev/rmt0}}, for example,
-@samp{20} is the argument for @samp{-b}, @samp{/dev/rmt0} is the
-argument for @samp{-f}, and @samp{-v} does not have a corresponding
+@samp{20} is the argument for @option{-b}, @samp{/dev/rmt0} is the
+argument for @option{-f}, and @option{-v} does not have a corresponding
argument. Even using short options like in @w{@samp{tar -c -v -b 20 -f
/dev/rmt0}} is clearer, putting all arguments next to the option they
pertain to.
If you want to reorder the letters in the old option argument, be
sure to reorder any corresponding argument appropriately.
-This old way of writing @code{tar} options can surprise even experienced
+This old way of writing @command{tar} options can surprise even experienced
users. For example, the two commands:
-@example
+@smallexample
@kbd{tar cfz archive.tar.gz file}
@kbd{tar -cfz archive.tar.gz file}
-@end example
+@end smallexample
@noindent
are quite different. The first example uses @file{archive.tar.gz} as
the value for option @samp{f} and recognizes the option @samp{z}. The
second example, however, uses @file{z} as the value for option
-@samp{f}---probably not what was intended.
+@samp{f} --- probably not what was intended.
-Old options are kept for compatibility with old versions of @code{tar}.
+Old options are kept for compatibility with old versions of @command{tar}.
This second example could be corrected in many ways, among which the
following are equivalent:
-@example
+@smallexample
@kbd{tar -czf archive.tar.gz file}
@kbd{tar -cf archive.tar.gz -z file}
@kbd{tar cf archive.tar.gz -z file}
-@end example
+@end smallexample
@FIXME{still could explain this better; it's redundant:}
@cindex option syntax, traditional
-As far as we know, all @code{tar} programs, GNU and non-GNU, support
-old options. GNU @code{tar} supports them not only for historical
-reasons, but also because many people are used to them. For
-compatibility with Unix @code{tar}, the first argument is always
-treated as containing command and option letters even if it doesn't
-start with @samp{-}. Thus, @samp{tar c} is equivalent to @w{@samp{tar
--c}:} both of them specify the @value{op-create} command to create an
-archive.
-
-@node Mixing, , Old Options, Styles
+As far as we know, all @command{tar} programs, @acronym{GNU} and
+non-@acronym{GNU}, support old options. @GNUTAR{}
+supports them not only for historical reasons, but also because many
+people are used to them. For compatibility with Unix @command{tar},
+the first argument is always treated as containing command and option
+letters even if it doesn't start with @samp{-}. Thus, @samp{tar c} is
+equivalent to @w{@samp{tar -c}:} both of them specify the
+@option{--create} (@option{-c}) command to create an archive.
+
+@node Mixing
@subsection Mixing Option Styles
-All three styles may be intermixed in a single @code{tar} command, so
-long as the rules for each style are fully respected@footnote{Before GNU
-@code{tar} version 1.11.6, a bug prevented intermixing old style options
-with mnemonic options in some cases.}. Old style options and either of the
-modern styles of options may be mixed within a single @code{tar} command.
-However, old style options must be introduced as the first arguments only,
+All three styles may be intermixed in a single @command{tar} command,
+so long as the rules for each style are fully
+respected@footnote{Before @GNUTAR{} version 1.11.6,
+a bug prevented intermixing old style options with mnemonic options in
+some cases.}. Old style options and either of the modern styles of
+options may be mixed within a single @command{tar} command. However,
+old style options must be introduced as the first arguments only,
following the rule for old options (old options must appear directly
-after the @code{tar} command and some whitespace). Modern options may
-be given only after all arguments to the old options have been collected.
-If this rule is not respected, a modern option might be falsely interpreted
-as the value of the argument to one of the old style options.
+after the @command{tar} command and some white space). Modern options
+may be given only after all arguments to the old options have been
+collected. If this rule is not respected, a modern option might be
+falsely interpreted as the value of the argument to one of the old
+style options.
For example, all the following commands are wholly equivalent, and
illustrate the many combinations and orderings of option styles.
-@example
+@smallexample
@kbd{tar --create --file=archive.tar}
@kbd{tar --create -f archive.tar}
@kbd{tar --create -farchive.tar}
@kbd{tar f archive.tar --create}
@kbd{tar f archive.tar -c}
@kbd{tar fc archive.tar}
-@end example
+@end smallexample
On the other hand, the following commands are @emph{not} equivalent to
the previous set:
-@example
+@smallexample
@kbd{tar -f -c archive.tar}
@kbd{tar -fc archive.tar}
@kbd{tar -fcarchive.tar}
@kbd{tar -farchive.tarc}
@kbd{tar cfarchive.tar}
-@end example
+@end smallexample
@noindent
These last examples mean something completely different from what the
user intended (judging based on the example in the previous set which
uses long options, whose intent is therefore very clear). The first
-four specify that the @code{tar} archive would be a file named
-@samp{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
+four specify that the @command{tar} archive would be a file named
+@option{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
respectively. The first two examples also specify a single non-option,
@var{name} argument having the value @samp{archive.tar}. The last
example contains only old style option letters (repeating option
@samp{h}, or @samp{i}), with no argument value. @FIXME{not sure i liked
the first sentence of this paragraph..}
-@node All Options, help, Styles, tar invocation
-@section All @code{tar} Options
+@node All Options
+@section All @command{tar} Options
The coming manual sections contain an alphabetical listing of all
-@code{tar} operations and options, with brief descriptions and cross
+@command{tar} operations and options, with brief descriptions and cross
references to more in-depth explanations in the body of the manual.
They also contain an alphabetically arranged table of the short option
forms with their corresponding long option. You can use this table as
-a reference for deciphering @code{tar} commands in scripts.
+a reference for deciphering @command{tar} commands in scripts.
@menu
* Operation Summary::
* Short Option Summary::
@end menu
-@node Operation Summary, Option Summary, All Options, All Options
+@node Operation Summary
@subsection Operations
-@table @kbd
+@table @option
+@opindex append, summary
@item --append
@itemx -r
Appends files to the end of the archive. @xref{append}.
+@opindex catenate, summary
@item --catenate
@itemx -A
-Same as @samp{--concatenate}. @xref{concatenate}.
+Same as @option{--concatenate}. @xref{concatenate}.
+@opindex compare, summary
@item --compare
@itemx -d
system, and reports differences in file size, mode, owner,
modification date and contents. @xref{compare}.
+@opindex concatenate, summary
@item --concatenate
@itemx -A
-Appends other @code{tar} archives to the end of the archive.
+Appends other @command{tar} archives to the end of the archive.
@xref{concatenate}.
+@opindex create, summary
@item --create
@itemx -c
-Creates a new @code{tar} archive. @xref{create}.
+Creates a new @command{tar} archive. @xref{create}.
+@opindex delete, summary
@item --delete
Deletes members from the archive. Don't try this on a archive on a
tape! @xref{delete}.
+@opindex diff, summary
@item --diff
@itemx -d
-Same @samp{--compare}. @xref{compare}.
+Same @option{--compare}. @xref{compare}.
+@opindex extract, summary
@item --extract
@itemx -x
Extracts members from the archive into the file system. @xref{extract}.
+@opindex get, summary
@item --get
@itemx -x
-Same as @samp{--extract}. @xref{extract}.
+Same as @option{--extract}. @xref{extract}.
+@opindex list, summary
@item --list
@itemx -t
Lists the members in an archive. @xref{list}.
+@opindex update, summary
@item --update
@itemx -u
-@FIXME{It was: A combination of the @samp{--compare} and @samp{--append} operations.
-This is not true and rather misleading, as @value{op-compare}
-does a lot more than @value{op-update} for ensuring files are identical.}
-Adds files to the end of the archive, but only if they are newer than
-their counterparts already in the archive, or if they do not already
-exist in the archive.
+@FIXME{It was: A combination of the @option{--compare} and
+@option{--append} operations. This is not true and rather misleading,
+as @option{--compare} (@option{--diff}, @option{-d}) does a lot more than @option{--update} (@option{-u}) for
+ensuring files are identical.} Adds files to the end of the archive,
+but only if they are newer than their counterparts already in the
+archive, or if they do not already exist in the archive.
@xref{update}.
@end table
-@node Option Summary, Short Option Summary, Operation Summary, All Options
-@subsection @code{tar} Options
+@node Option Summary
+@subsection @command{tar} Options
-@table @kbd
+@table @option
+@opindex absolute-names, summary
@item --absolute-names
@itemx -P
-Normally when creating an archive, @code{tar} strips an initial @samp{/} from
-member names. This option disables that behavior. @FIXME-xref{}.
+Normally when creating an archive, @command{tar} strips an initial
+@samp{/} from member names. This option disables that behavior.
+@xref{absolute}.
+@opindex after-date, summary
@item --after-date
-(See @samp{--newer}; @FIXME-pxref{}.)
-
-@item --atime-preserve
+(See @option{--newer}, @pxref{after})
-Tells @code{tar} to preserve the access time field in a file's inode when
-dumping it. @FIXME-xref{}.
+@opindex anchored, summary
+@item --anchored
+An exclude pattern must match an initial subsequence of the name's components.
+@xref{controlling pattern-matching with exclude}.
+@opindex atime-preserve, summary
+@item --atime-preserve
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+
+Attempt to preserve the access time of files when reading them. This
+option currently is effective only on files that you own, unless you
+have superuser privileges.
+
+@option{--atime-preserve=replace} remembers the access time of a file
+before reading it, and then restores the access time afterwards. This
+may cause problems if other programs are reading the file at the same
+time, as the times of their accesses will be lost. On most platforms
+restoring the access time also requires @command{tar} to restore the
+data modification time too, so this option may also cause problems if
+other programs are writing the file at the same time. (Tar attempts
+to detect this situation, but cannot do so reliably due to race
+conditions.) Worse, on most platforms restoring the access time also
+updates the status change time, which means that this option is
+incompatible with incremental backups.
+
+@option{--atime-preserve=system} avoids changing time stamps on files,
+without interfering with time stamp updates
+caused by other programs, so it works better with incremental backups.
+However, it requires a special @code{O_NOATIME} option from the
+underlying operating and file system implementation, and it also requires
+that searching directories does not update their access times. As of
+this writing (November 2005) this works only with Linux, and only with
+Linux kernels 2.6.8 and later. Worse, there is currently no reliable
+way to know whether this feature actually works. Sometimes
+@command{tar} knows that it does not work, and if you use
+@option{--atime-preserve=system} then @command{tar} complains and
+exits right away. But other times @command{tar} might think that the
+option works when it actually does not.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@option{--atime-preserve=replace}, but this may change in the future
+as support for @option{--atime-preserve=system} improves.
+
+If your operating system does not support
+@option{--atime-preserve=system}, you might be able to preserve access
+times reliably by by using the @command{mount} command. For example,
+you can mount the file system read-only, or access the file system via
+a read-only loopback mount, or use the @samp{noatime} mount option
+available on some systems. However, mounting typically requires
+superuser privileges and can be a pain to manage.
+
+@opindex backup, summary
@item --backup=@var{backup-type}
-Rather than deleting files from the file system, @code{tar} will back them up
-using simple or numbered backups, depending upon @var{backup-type}.
-@FIXME-xref{}.
+Rather than deleting files from the file system, @command{tar} will
+back them up using simple or numbered backups, depending upon
+@var{backup-type}. @xref{backup}.
+@opindex block-number, summary
@item --block-number
@itemx -R
-With this option present, @code{tar} prints error messages for read errors
-with the block number in the archive file. @FIXME-xref{}.
+With this option present, @command{tar} prints error messages for read errors
+with the block number in the archive file. @xref{block-number}.
+@opindex blocking-factor, summary
@item --blocking-factor=@var{blocking}
@itemx -b @var{blocking}
-Sets the blocking factor @code{tar} uses to @var{blocking} x 512 bytes per
-record. @FIXME-xref{}.
+Sets the blocking factor @command{tar} uses to @var{blocking} x 512 bytes per
+record. @xref{Blocking Factor}.
+@opindex bzip2, summary
@item --bzip2
-@itemx -y
+@itemx -j
-This option tells @code{tar} to read or write archives through @code{bzip2}.
-@FIXME-xref{}.
+This option tells @command{tar} to read or write archives through
+@code{bzip2}. @xref{gzip}.
+@opindex checkpoint, summary
@item --checkpoint
-This option directs @code{tar} to print periodic checkpoint messages as it
+This option directs @command{tar} to print periodic checkpoint messages as it
reads through the archive. Its intended for when you want a visual
-indication that @code{tar} is still running, but don't want to see
-@samp{--verbose} output. @FIXME-xref{}.
+indication that @command{tar} is still running, but don't want to see
+@option{--verbose} output. @FIXME-xref{}
+
+@opindex check-links, summary
+@item --check-links
+@itemx -l
+If this option was given, @command{tar} will check the number of links
+dumped for each processed file. If this number does not match the
+total number of hard links for the file, a warning message will be
+output.
+
+Future versions will take @option{-l} as a short version of
+@option{--check-links}. However, current release still retains the old
+semantics for @option{-l}.
+@xref{Changes}, for more information.
+
+@opindex compress, summary
+@opindex uncompress, summary
@item --compress
@itemx --uncompress
@itemx -Z
-@code{tar} will use the @code{compress} program when reading or writing the
-archive. This allows you to directly act on archives while saving
-space. @FIXME-xref{}.
+@command{tar} will use the @command{compress} program when reading or
+writing the archive. This allows you to directly act on archives
+while saving space. @xref{gzip}.
+@opindex confirmation, summary
@item --confirmation
-(See @samp{--interactive}; @FIXME-pxref{}.)
+(See @option{--interactive}.) @xref{interactive}.
+
+@opindex delay-directory-restore, summary
+@item --delay-directory-restore
+Delay setting modification times and permissions of extracted
+directories until the end of extraction. @xref{Directory Modification Times and Permissions}.
+
+@opindex dereference, summary
@item --dereference
@itemx -h
-When creating a @code{tar} archive, @code{tar} will archive the file that a symbolic
-link points to, rather than archiving the symlink. @FIXME-xref{}.
+When creating a @command{tar} archive, @command{tar} will archive the
+file that a symbolic link points to, rather than archiving the
+symlink. @xref{dereference}.
+@opindex directory, summary
@item --directory=@var{dir}
@itemx -C @var{dir}
-When this option is specified, @code{tar} will change its current directory
+When this option is specified, @command{tar} will change its current directory
to @var{dir} before performing any operations. When this option is used
-during archive creation, it is order sensitive. @FIXME-xref{}.
+during archive creation, it is order sensitive. @xref{directory}.
+@opindex exclude, summary
@item --exclude=@var{pattern}
-When performing operations, @code{tar} will skip files that match
-@var{pattern}. @FIXME-xref{}.
+When performing operations, @command{tar} will skip files that match
+@var{pattern}. @xref{exclude}.
+@opindex exclude-from, summary
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Similar to @samp{--exclude}, except @code{tar} will use the list of patterns
-in the file @var{file}. @FIXME-xref{}.
+Similar to @option{--exclude}, except @command{tar} will use the list of
+patterns in the file @var{file}. @xref{exclude}.
+
+@opindex exclude-caches, summary
+@item --exclude-caches
+Automatically excludes all directories
+containing a cache directory tag. @xref{exclude}.
+
+@opindex file, summary
@item --file=@var{archive}
@itemx -f @var{archive}
-@code{tar} will use the file @var{archive} as the @code{tar} archive it
-performs operations on, rather than @code{tar}'s compilation dependent
-default. @FIXME-xref{}.
+@command{tar} will use the file @var{archive} as the @command{tar} archive it
+performs operations on, rather than @command{tar}'s compilation dependent
+default. @xref{file tutorial}.
+@opindex files-from, summary
@item --files-from=@var{file}
@itemx -T @var{file}
-@code{tar} will use the contents of @var{file} as a list of archive members
+@command{tar} will use the contents of @var{file} as a list of archive members
or files to operate on, in addition to those specified on the
-command-line. @FIXME-xref{}.
+command-line. @xref{files}.
+@opindex force-local, summary
@item --force-local
-Forces @code{tar} to interpret the filename given to @samp{--file} as a local
-file, even if it looks like a remote tape drive name. @FIXME-xref{}.
+Forces @command{tar} to interpret the filename given to @option{--file}
+as a local file, even if it looks like a remote tape drive name.
+@xref{local and remote archives}.
+
+@opindex format, summary
+@item --format=@var{format}
+
+Selects output archive format. @var{Format} may be one of the
+following:
+
+@table @samp
+@item v7
+Creates an archive that is compatible with Unix V7 @command{tar}.
+
+@item oldgnu
+Creates an archive that is compatible with GNU @command{tar} version
+1.12 or earlier.
+
+@item gnu
+Creates archive in GNU tar 1.13 format. Basically it is the same as
+@samp{oldgnu} with the only difference in the way it handles long
+numeric fields.
+@item ustar
+Creates a @acronym{POSIX.1-1988} compatible archive.
+
+@item posix
+Creates a @acronym{POSIX.1-2001 archive}.
+
+@end table
+
+@xref{Formats}, for a detailed discussion of these formats.
+
+@opindex group, summary
@item --group=@var{group}
-Files added to the @code{tar} archive will have a group id of @var{group},
+Files added to the @command{tar} archive will have a group id of @var{group},
rather than the group from the source file. @var{group} is first decoded
as a group symbolic name, but if this interpretation fails, it has to be
-a decimal numeric group ID. @FIXME-xref{}.
-
-Also see the comments for the @value{op-owner} option.
+a decimal numeric group ID. @FIXME-xref{}
-@item --gunzip
-
-(See @samp{--gzip}; @FIXME-pxref{}.)
+Also see the comments for the @option{--owner=@var{user}} option.
+@opindex gzip, summary
+@opindex gunzip, summary
+@opindex ungzip, summary
@item --gzip
@itemx --gunzip
@itemx --ungzip
@itemx -z
-This option tells @code{tar} to read or write archives through @code{gzip},
-allowing @code{tar} to directly operate on several kinds of compressed
-archives transparently. @FIXME-xref{}.
+This option tells @command{tar} to read or write archives through
+@command{gzip}, allowing @command{tar} to directly operate on several
+kinds of compressed archives transparently. @xref{gzip}.
+@opindex help, summary
@item --help
-@code{tar} will print out a short message summarizing the operations and
-options to @code{tar} and exit. @FIXME-xref{}.
+@command{tar} will print out a short message summarizing the operations and
+options to @command{tar} and exit. @xref{help}.
-@item --ignore-failed-read
+@opindex ignore-case, summary
+@item --ignore-case
+Ignore case when excluding files. @xref{controlling pattern-matching
+with exclude}.
-Instructs @code{tar} to exit successfully if it encounters an
-unreadable file. @xref{Reading}.
+@opindex ignore-command-error, summary
+@item --ignore-command-error
+Ignore exit codes of subprocesses. @xref{Writing to an External Program}.
-@item --ignore-umask
-@FIXME{does this exist?}
+@opindex ignore-failed-read, summary
+@item --ignore-failed-read
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+Do not exit unsuccessfully merely because an unreadable file was encountered.
+@xref{Reading}.
+@opindex ignore-zeros, summary
@item --ignore-zeros
@itemx -i
-With this option, @code{tar} will ignore zeroed blocks in the archive, which
-normally signals EOF. @xref{Reading}.
+With this option, @command{tar} will ignore zeroed blocks in the
+archive, which normally signals EOF. @xref{Reading}.
+@opindex incremental, summary
@item --incremental
@itemx -G
-Used to inform @code{tar} that it is working with an old GNU-format
-incremental backup archive. It is intended primarily for backwards
-compatibility only. @FIXME-xref{}.
+Used to inform @command{tar} that it is working with an old
+@acronym{GNU}-format incremental backup archive. It is intended
+primarily for backwards compatibility only. @FIXME{incremental and
+listed-incremental}.
+
+@opindex index-file, summary
+@item --index-file=@var{file}
+Send verbose output to @var{file} instead of to standard output.
+
+@opindex info-script, summary
+@opindex new-volume-script, summary
@item --info-script=@var{script-file}
@itemx --new-volume-script=@var{script-file}
@itemx -F @var{script-file}
-When @code{tar} is performing multi-tape backups, @var{script-file} is run
-at the end of each tape. @FIXME-xref{}.
+When @command{tar} is performing multi-tape backups, @var{script-file} is run
+at the end of each tape. If @var{script-file} exits with nonzero status,
+@command{tar} fails immediately. @xref{info-script}, for a detailed
+discussion of @var{script-file}.
+@opindex interactive, summary
@item --interactive
@itemx --confirmation
@itemx -w
-Specifies that @code{tar} should ask the user for confirmation before
+Specifies that @command{tar} should ask the user for confirmation before
performing potentially destructive options, such as overwriting files.
-@FIXME-xref{}.
+@xref{interactive}.
+
+@opindex keep-newer-files, summary
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive copies
+when extracting files from an archive.
+
+@opindex keep-old-files, summary
@item --keep-old-files
@itemx -k
-When extracting files from an archive, @code{tar} will not overwrite existing
-files if this option is present. @xref{Writing}.
+Do not overwrite existing files when extracting files from an archive.
+@xref{Keep Old Files}.
+@opindex label, summary
@item --label=@var{name}
@itemx -V @var{name}
-When creating an archive, instructs @code{tar} to write @var{name} as a name
-record in the archive. When extracting or listing archives, @code{tar} will
-only operate on archives that have a label matching the pattern
-specified in @var{name}. @FIXME-xref{}.
+When creating an archive, instructs @command{tar} to write @var{name}
+as a name record in the archive. When extracting or listing archives,
+@command{tar} will only operate on archives that have a label matching
+the pattern specified in @var{name}. @xref{Tape Files}.
+@opindex listed-incremental, summary
@item --listed-incremental=@var{snapshot-file}
@itemx -g @var{snapshot-file}
-During a @samp{--create} operation, specifies that the archive that
-@code{tar} creates is a new GNU-format incremental backup, using
-@var{snapshot-file} to determine which files to backup.
-With other operations, informs @code{tar} that the archive is in incremental
-format. @FIXME-xref{}.
+During a @option{--create} operation, specifies that the archive that
+@command{tar} creates is a new @acronym{GNU}-format incremental
+backup, using @var{snapshot-file} to determine which files to backup.
+With other operations, informs @command{tar} that the archive is in
+incremental format. @FIXME{incremental and listed-incremental}.
+@opindex mode, summary
@item --mode=@var{permissions}
-When adding files to an archive, @code{tar} will use @var{permissions}
-for the archive members, rather than the permissions from the files.
-The program @code{chmod} and this @code{tar} option share the same syntax
-for what @var{permissions} might be. @xref{File permissions, Permissions,
-File permissions, filetutils, GNU file utilities}. This reference also
-has useful information for those not being overly familiar with the Unix
+When adding files to an archive, @command{tar} will use
+@var{permissions} for the archive members, rather than the permissions
+from the files. The program @command{chmod} and this @command{tar}
+option share the same syntax for what @var{permissions} might be.
+@xref{File permissions, Permissions, File permissions, fileutils,
+@acronym{GNU} file utilities}. This reference also has useful
+information for those not being overly familiar with the Unix
permission system.
Of course, @var{permissions} might be plainly specified as an octal number.
permissions for everybody, while retaining executable bits on directories
or on any other file already marked as executable.
+@opindex multi-volume, summary
@item --multi-volume
@itemx -M
-Informs @code{tar} that it should create or otherwise operate on a
-multi-volume @code{tar} archive. @FIXME-xref{}.
+Informs @command{tar} that it should create or otherwise operate on a
+multi-volume @command{tar} archive. @xref{Using Multiple Tapes}.
+@opindex new-volume-script, summary
@item --new-volume-script
(see --info-script)
+@opindex seek, summary
+@item --seek
+@itemx -n
+
+Assume that the archive media supports seeks to arbitrary
+locations. Usually @command{tar} determines automatically whether
+the archive can be seeked or not. This option is intended for use
+in cases when such recognition fails.
+
+@opindex newer, summary
@item --newer=@var{date}
@itemx --after-date=@var{date}
@itemx -N
-When creating an archive, @code{tar} will only add files that have changed
-since @var{date}. @FIXME-xref{}.
+When creating an archive, @command{tar} will only add files that have changed
+since @var{date}. If @var{date} begins with @samp{/} or @samp{.}, it
+is taken to be the name of a file whose data modification time specifies
+the date. @xref{after}.
-@item --newer-mtime
+@opindex newer-mtime, summary
+@item --newer-mtime=@var{date}
-In conjunction with @samp{--newer}, @code{tar} will only add files whose
-contents have changed (as opposed to just @samp{--newer}, which will
+Like @option{--newer}, but add only files whose
+contents have changed (as opposed to just @option{--newer}, which will
also back up files for which any status information has changed).
+@opindex no-anchored, summary
+@item --no-anchored
+An exclude pattern can match any subsequence of the name's components.
+@xref{controlling pattern-matching with exclude}.
+
+@opindex no-delay-directory-restore, summary
+@item --no-delay-directory-restore
+
+Setting modification times and permissions of extracted
+directories when all files from this directory has been
+extracted. This is the default. @xref{Directory Modification Times and Permissions}.
+
+@opindex no-ignore-case, summary
+@item --no-ignore-case
+Use case-sensitive matching when excluding files.
+@xref{controlling pattern-matching with exclude}.
+
+@opindex no-ignore-command-error, summary
+@item --no-ignore-command-error
+Print warnings about subprocesses terminated with a non-zero exit
+code. @xref{Writing to an External Program}.
+
+@opindex no-quote-chars, summary
+@item --no-quote-chars=@var{string}
+Do not quote characters from @var{string}, even if the selected
+quoting style implies they should be quoted (@FIXME-pxref{Quoting Styles}).
+
+@opindex no-recursion, summary
@item --no-recursion
-With this option, @code{tar} will not recurse into directories unless a
-directory is explicitly named as an argument to @code{tar}. @FIXME-xref{}.
+With this option, @command{tar} will not recurse into directories.
+@xref{recurse}.
+
+@opindex no-same-owner, summary
+@item --no-same-owner
+@itemx -o
+
+When extracting an archive, do not attempt to preserve the owner
+specified in the @command{tar} archive. This the default behavior
+for ordinary users.
+
+@opindex no-same-permissions, summary
+@item --no-same-permissions
+
+When extracting an archive, subtract the user's umask from files from
+the permissions specified in the archive. This is the default behavior
+for ordinary users.
+
+@opindex no-wildcards, summary
+@item --no-wildcards
+Do not use wildcards when excluding files.
+@xref{controlling pattern-matching with exclude}.
+@opindex no-wildcards-match-slash, summary
+@item --no-wildcards-match-slash
+Wildcards do not match @samp{/} when excluding files.
+@xref{controlling pattern-matching with exclude}.
+
+@opindex null, summary
@item --null
-When @code{tar} is using the @samp{--files-from} option, this option
-instructs @code{tar} to expect filenames terminated with @kbd{NUL}, so
-@code{tar} can correctly work with file names that contain newlines.
-@FIXME-xref{}.
+When @command{tar} is using the @option{--files-from} option, this option
+instructs @command{tar} to expect filenames terminated with @option{NUL}, so
+@command{tar} can correctly work with file names that contain newlines.
+@xref{nul}.
+@opindex numeric-owner, summary
@item --numeric-owner
-This option will notify @code{tar} that it should use numeric user and group
-IDs when creating a @code{tar} file, rather than names. @FIXME-xref{}.
+This option will notify @command{tar} that it should use numeric user
+and group IDs when creating a @command{tar} file, rather than names.
+@xref{Attributes}.
-@item --old-archive
+@item -o
+When extracting files, this option is a synonym for
+@option{--no-same-owner}, i.e. it prevents @command{tar} from
+restoring ownership of files being extracted.
+
+When creating an archive, @option{-o} is a synonym for
+@option{--old-archive}. This behavior is for compatibility
+with previous versions of @GNUTAR{}, and will be
+removed in the future releases.
+
+@xref{Changes}, for more information.
+
+@opindex occurrence, summary
+@item --occurrence[=@var{number}]
+
+This option can be used in conjunction with one of the subcommands
+@option{--delete}, @option{--diff}, @option{--extract} or
+@option{--list} when a list of files is given either on the command
+line or via @option{-T} option.
+
+This option instructs @command{tar} to process only the @var{number}th
+occurrence of each named file. @var{Number} defaults to 1, so
+
+@smallexample
+tar -x -f archive.tar --occurrence filename
+@end smallexample
+
+@noindent
+will extract the first occurrence of @file{filename} from @file{archive.tar}
+and will terminate without scanning to the end of the archive.
-(See @samp{--portability}; @FIXME-pxref{}.)
+@opindex old-archive, summary
+@item --old-archive
+Synonym for @option{--format=v7}.
+@opindex one-file-system, summary
@item --one-file-system
@itemx -l
-
-Used when creating an archive. Prevents @code{tar} from recursing into
+Used when creating an archive. Prevents @command{tar} from recursing into
directories that are on different file systems from the current
-directory. @FIXME-xref{}.
+directory.
+
+Earlier versions of @GNUTAR{} understood @option{-l} as a
+synonym for @option{--one-file-system}. Although such usage is still
+allowed in the present version, it is @emph{strongly discouraged}.
+The future versions of @GNUTAR{} will use @option{-l} as
+a synonym for @option{--check-links}.
+
+@xref{Changes}, for more information.
+
+@opindex overwrite, summary
+@item --overwrite
+
+Overwrite existing files and directory metadata when extracting files
+from an archive. @xref{Overwrite Old Files}.
+
+@opindex overwrite-dir, summary
+@item --overwrite-dir
+Overwrite the metadata of existing directories when extracting files
+from an archive. @xref{Overwrite Old Files}.
+
+@opindex owner, summary
@item --owner=@var{user}
-Specifies that @code{tar} should use @var{user} as the owner of members
+Specifies that @command{tar} should use @var{user} as the owner of members
when creating archives, instead of the user associated with the source
file. @var{user} is first decoded as a user symbolic name, but if
this interpretation fails, it has to be a decimal numeric user ID.
-@FIXME-xref{}.
+@FIXME-xref{}
There is no value indicating a missing number, and @samp{0} usually means
@code{root}. Some people like to force @samp{0} as the value to offer in
their distributions for the owner of files, because the @code{root} user is
anonymous anyway, so that might as well be the owner of anonymous archives.
-@item --portability
-@itemx --old-archive
-@itemx -o
+This option does not affect extraction from archives.
+
+@opindex quote-chars, summary
+@item --quote-chars=@var{string}
+Always quote characters from @var{string}, even if the selected
+quoting style would not quote them (@FIXME-pxref{Quoting Styles}).
+
+@opindex quoting-style, summary
+@item --quoting-style=@var{style}
+Set quoting style to use when printing member and file names
+(@FIXME-pxref{Quoting Styles}). Valid @var{style} values are:
+@code{literal}, @code{shell}, @code{shell-always}, @code{c},
+@code{escape}, @code{locale}, and @code{clocale}. Default quoting
+style is @code{escape}, unless overridden while configuring the
+package.
+
+@opindex pax-option, summary
+@item --pax-option=@var{keyword-list}
+@FIXME{Such a detailed description does not belong there, move it elsewhere.}
+This option is meaningful only with @acronym{POSIX.1-2001} archives
+(@pxref{posix}). It modifies the way @command{tar} handles the
+extended header keywords. @var{Keyword-list} is a comma-separated
+list of keyword options, each keyword option taking one of
+the following forms:
-Tells @code{tar} to create an archive that is compatible with Unix V7
-@code{tar}. @FIXME-xref{}.
+@table @asis
+@item delete=@var{pattern}
+When used with one of archive-creation commands,
+this option instructs @command{tar} to omit from extended header records
+that it produces any keywords matching the string @var{pattern}.
-@item --posix
+When used in extract or list mode, this option instructs tar
+to ignore any keywords matching the given @var{pattern} in the extended
+header records. In both cases, matching is performed using the pattern
+matching notation described in @acronym{POSIX 1003.2}, 3.13
+(See @cite{glob(7)}). For example:
-Instructs @code{tar} to create a POSIX compliant @code{tar} archive. @FIXME-xref{}.
+@smallexample
+--pax-option delete=security.*
+@end smallexample
+would suppress security-related information.
+
+@item exthdr.name=@var{string}
+
+This keyword allows user control over the name that is written into the
+ustar header blocks for the extended headers. The name is obtained
+from @var{string} after substituting the following meta-characters:
+
+@multitable @columnfractions .30 .70
+@headitem Meta-character @tab Replaced By
+@item %d @tab The directory name of the file, equivalent to the
+result of the @command{dirname} utility on the translated pathname.
+@item %f @tab The filename of the file, equivalent to the result
+of the @command{basename} utility on the translated pathname.
+@item %p @tab The process ID of the @command{tar} process.
+@item %% @tab A @samp{%} character.
+@end multitable
+
+Any other @samp{%} characters in @var{string} produce undefined
+results.
+
+If no option @samp{exthdr.name=string} is specified, @command{tar}
+will use the following default value:
+
+@smallexample
+%d/PaxHeaders.%p/%f
+@end smallexample
+
+@item globexthdr.name=@var{string}
+This keyword allows user control over the name that is written into
+the ustar header blocks for global extended header records. The name
+shall will be obtained from the contents of @var{string}, after the
+following character substitutions have been made:
+
+@multitable @columnfractions .30 .70
+@headitem Meta-character @tab Replaced By
+@item %n @tab An integer that represents the
+sequence number of the global extended header record in the archive,
+starting at 1.
+@item %p @tab The process ID of the @command{tar} process.
+@item %% @tab A @samp{%} character.
+@end multitable
+
+Any other @samp{%} characters in string produce undefined results.
+
+If no option @samp{globexthdr.name=string} is specified, @command{tar}
+will use the following default value:
+
+@smallexample
+$TMPDIR/GlobalHead.%p.%n
+@end smallexample
+
+@noindent
+where @samp{$TMPDIR} represents the value of the @var{TMPDIR}
+environment variable. If @var{TMPDIR} is not set, @command{tar}
+uses @samp{/tmp}.
+
+@item @var{keyword}=@var{value}
+When used with one of archive-creation commands, these keyword/value pairs
+will be included at the beginning of the archive in a global extended
+header record. When used with one of archive-reading commands,
+@command{tar} will behave as if it has encountered these keyword/value
+pairs at the beginning of the archive in a global extended header
+record.
+
+@item @var{keyword}:=@var{value}
+When used with one of archive-creation commands, these keyword/value pairs
+will be included as records at the beginning of an extended header for
+each file. This is effectively equivalent to @var{keyword}=@var{value}
+form except that it creates no global extended header records.
+
+When used with one of archive-reading commands, @command{tar} will
+behave as if these keyword/value pairs were included as records at the
+end of each extended header; thus, they will override any global or
+file-specific extended header record keywords of the same names.
+For example, in the command:
+
+@smallexample
+tar --format=posix --create \
+ --file archive --pax-option gname:=user .
+@end smallexample
+
+the group name will be forced to a new value for all files
+stored in the archive.
+@end table
+
+@opindex portability, summary
+@item --portability
+@itemx --old-archive
+Synonym for @option{--format=v7}.
+
+@opindex posix, summary
+@item --posix
+Same as @option{--format=posix}.
+
+@opindex preserve, summary
@item --preserve
-Synonymous with specifying both @samp{--preserve-permissions} and
-@samp{--same-order}. @FIXME-xref{}.
+Synonymous with specifying both @option{--preserve-permissions} and
+@option{--same-order}. @xref{Setting Access Permissions}.
+@opindex preserve-order, summary
@item --preserve-order
-(See @samp{--same-order}; @pxref{Reading}.)
+(See @option{--same-order}; @pxref{Reading}.)
+@opindex preserve-permissions, summary
+@opindex same-permissions, summary
@item --preserve-permissions
@itemx --same-permissions
@itemx -p
-When @code{tar} is extracting an archive, it normally subtracts the users'
-umask from the permissions specified in the archive and uses that
-number as the permissions to create the destination file. Specifying
-this option instructs @code{tar} that it should use the permissions directly
-from the archive. @xref{Writing}.
+When @command{tar} is extracting an archive, it normally subtracts the
+users' umask from the permissions specified in the archive and uses
+that number as the permissions to create the destination file.
+Specifying this option instructs @command{tar} that it should use the
+permissions directly from the archive. @xref{Setting Access Permissions}.
+@opindex read-full-records, summary
@item --read-full-records
@itemx -B
-Specifies that @code{tar} should reblock its input, for reading from pipes on
-systems with buggy implementations. @xref{Reading}.
+Specifies that @command{tar} should reblock its input, for reading
+from pipes on systems with buggy implementations. @xref{Reading}.
+@opindex record-size, summary
@item --record-size=@var{size}
-Instructs @code{tar} to use @var{size} bytes per record when accessing the
-archive. @FIXME-xref{}.
+Instructs @command{tar} to use @var{size} bytes per record when accessing the
+archive. @xref{Blocking Factor}.
+
+@opindex recursion, summary
+@item --recursion
+With this option, @command{tar} recurses into directories.
+@xref{recurse}.
+
+@opindex recursive-unlink, summary
@item --recursive-unlink
-Similar to the @samp{--unlink-first} option, removing existing
+Remove existing
directory hierarchies before extracting directories of the same name
-from the archive. @xref{Writing}.
+from the archive. @xref{Recursive Unlink}.
+@opindex remove-files, summary
@item --remove-files
-Directs @code{tar} to remove the source file from the file system after
-appending it to an archive. @FIXME-xref{}.
+Directs @command{tar} to remove the source file from the file system after
+appending it to an archive. @xref{remove files}.
+
+@opindex restrict, summary
+@item --restrict
+
+Disable use of some potentially harmful @command{tar} options.
+Currently this option disables shell invocaton from multi-volume menu
+(@pxref{Using Multiple Tapes}).
+
+@opindex rmt-command, summary
+@item --rmt-command=@var{cmd}
+Notifies @command{tar} that it should use @var{cmd} instead of
+the default @file{/usr/libexec/rmt} (@pxref{Remote Tape Server}).
+
+@opindex rsh-command, summary
@item --rsh-command=@var{cmd}
-Notifies @code{tar} that is should use @var{cmd} to communicate with remote
-devices. @FIXME-xref{}.
+Notifies @command{tar} that is should use @var{cmd} to communicate with remote
+devices. @xref{Device}.
+@opindex same-order, summary
@item --same-order
@itemx --preserve-order
@itemx -s
-This option is an optimization for @code{tar} when running on machines with
-small amounts of memory. It informs @code{tar} that the list of file
+This option is an optimization for @command{tar} when running on machines with
+small amounts of memory. It informs @command{tar} that the list of file
arguments has already been sorted to match the order of files in the
archive. @xref{Reading}.
+@opindex same-owner, summary
@item --same-owner
-When extracting an archive, @code{tar} will attempt to preserve the owner
-specified in the @code{tar} archive with this option present. @FIXME-xref{}.
+When extracting an archive, @command{tar} will attempt to preserve the owner
+specified in the @command{tar} archive with this option present.
+This is the default behavior for the superuser; this option has an
+effect only for ordinary users. @xref{Attributes}.
+@opindex same-permissions, summary
@item --same-permissions
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+(See @option{--preserve-permissions}; @pxref{Setting Access Permissions}.)
+
+@opindex show-defaults, summary
+@item --show-defaults
+
+Displays the default options used by @command{tar} and exits
+successfully. This option is intended for use in shell scripts.
+Here is an example of what you can see using this option:
+
+@smallexample
+$ tar --show-defaults
+--format=gnu -f- -b20 --quoting-style=escape \
+--rmt-command=/usr/libexec/rmt --rsh-command=/usr/bin/rsh
+@end smallexample
+@opindex show-omitted-dirs, summary
@item --show-omitted-dirs
-Instructs @code{tar} to mention directories its skipping over when operating
-on a @code{tar} archive. @FIXME-xref{}.
+Instructs @command{tar} to mention directories its skipping over when
+operating on a @command{tar} archive. @xref{show-omitted-dirs}.
+
+@opindex show-stored-names, summary
+@item --show-stored-names
+
+This option has effect only when used in conjunction with one of
+archive creation operations. It instructs tar to list the member names
+stored in the archive, as opposed to the actual file
+names. @xref{listing member and file names}.
+@opindex sparse, summary
@item --sparse
@itemx -S
-Invokes a GNU extension when adding files to an archive that handles
-sparse files efficiently. @FIXME-xref{}.
+Invokes a @acronym{GNU} extension when adding files to an archive that handles
+sparse files efficiently. @xref{sparse}.
+@opindex starting-file, summary
@item --starting-file=@var{name}
@itemx -K @var{name}
-This option affects extraction only; @code{tar} will skip extracting
+This option affects extraction only; @command{tar} will skip extracting
files in the archive until it finds one that matches @var{name}.
@xref{Scarce}.
+@opindex strip-components, summary
+@item --strip-components=@var{number}
+Strip given @var{number} of leading components from file names before
+extraction.@footnote{This option was called @option{--strip-path} in
+version 1.14.} For example, if archive @file{archive.tar} contained
+@file{/some/file/name}, then running
+
+@smallexample
+tar --extract --file archive.tar --strip-components=2
+@end smallexample
+
+@noindent
+would extracted this file to file @file{name}.
+
+@opindex suffix, summary
@item --suffix=@var{suffix}
-Alters the suffix @code{tar} uses when backing up files from the default
-@samp{~}. @FIXME-xref{}.
+Alters the suffix @command{tar} uses when backing up files from the default
+@samp{~}. @xref{backup}.
+@opindex tape-length, summary
@item --tape-length=@var{num}
@itemx -L @var{num}
-Specifies the length of tapes that @code{tar} is writing as being
-@w{@var{num} x 1024} bytes long. @FIXME-xref{}.
+Specifies the length of tapes that @command{tar} is writing as being
+@w{@var{num} x 1024} bytes long. @xref{Using Multiple Tapes}.
+
+@opindex test-label, summary
+@item --test-label
+
+Reads the volume label. If an argument is specified, test whether it
+matches the volume label. @xref{--test-label option}.
+@opindex to-command, summary
+@item --to-command=@var{command}
+
+During extraction @command{tar} will pipe extracted files to the
+standard input of @var{command}. @xref{Writing to an External Program}.
+
+@opindex to-stdout, summary
@item --to-stdout
@itemx -O
-During extraction, @code{tar} will extract files to stdout rather than to the
-file system. @xref{Writing}.
+During extraction, @command{tar} will extract files to stdout rather
+than to the file system. @xref{Writing to Standard Output}.
+@opindex totals, summary
@item --totals
Displays the total number of bytes written after creating an archive.
-@FIXME-xref{}.
+@xref{verbose}.
+@opindex touch, summary
@item --touch
@itemx -m
-Sets the modification time of extracted files to the extraction time,
-rather than the modification time stored in the archive.
-@xref{Writing}.
+Sets the data modification time of extracted files to the extraction time,
+rather than the data modification time stored in the archive.
+@xref{Data Modification Times}.
+@opindex uncompress, summary
@item --uncompress
-(See @samp{--compress}; @FIXME-pxref{}.)
+(See @option{--compress}. @pxref{gzip})
+@opindex ungzip, summary
@item --ungzip
-(See @samp{--gzip}; @FIXME-pxref{}.)
+(See @option{--gzip}. @pxref{gzip})
+@opindex unlink-first, summary
@item --unlink-first
@itemx -U
-Directs @code{tar} to remove the corresponding file from the file system
-before extracting it from the archive. @xref{Writing}.
+Directs @command{tar} to remove the corresponding file from the file
+system before extracting it from the archive. @xref{Unlink First}.
+@opindex use-compress-program, summary
@item --use-compress-program=@var{prog}
-Instructs @code{tar} to access the archive through @var{prog}, which is
-presumed to be a compression program of some sort. @FIXME-xref{}.
+Instructs @command{tar} to access the archive through @var{prog}, which is
+presumed to be a compression program of some sort. @xref{gzip}.
+
+@opindex utc, summary
+@item --utc
+
+Display file modification dates in @acronym{UTC}. This option implies
+@option{--verbose}.
+@opindex verbose, summary
@item --verbose
@itemx -v
-Specifies that @code{tar} should be more verbose about the operations its
+Specifies that @command{tar} should be more verbose about the operations its
performing. This option can be specified multiple times for some
-operations to increase the amount of information displayed. @FIXME-xref{}.
+operations to increase the amount of information displayed.
+@xref{verbose}.
+@opindex verify, summary
@item --verify
@itemx -W
Verifies that the archive was correctly written when creating an
-archive. @FIXME-xref{}.
+archive. @xref{verify}.
+@opindex version, summary
@item --version
-@code{tar} will print an informational message about what version it is and a
-copyright message, some credits, and then exit. @FIXME-xref{}.
+Print information about the program's name, version, origin and legal
+status, all on standard output, and then exit successfully.
+@xref{help}.
+@opindex volno-file, summary
@item --volno-file=@var{file}
-Used in conjunction with @samp{--multi-volume}. @code{tar} will keep track
+Used in conjunction with @option{--multi-volume}. @command{tar} will keep track
of which volume of a multi-volume archive its working in @var{file}.
-@FIXME-xref{}.
+@xref{volno-file}.
+
+@opindex wildcards, summary
+@item --wildcards
+Use wildcards when excluding files.
+@xref{controlling pattern-matching with exclude}.
+
+@opindex wildcards-match-slash, summary
+@item --wildcards-match-slash
+Wildcards match @samp{/} when excluding files.
+@xref{controlling pattern-matching with exclude}.
@end table
-@node Short Option Summary, , Option Summary, All Options
+@node Short Option Summary
@subsection Short Options Cross Reference
Here is an alphabetized list of all of the short option forms, matching
them with the equivalent long option.
-@table @kbd
+@table @option
@item -A
-@samp{--concatenate}
+@option{--concatenate}
@item -B
-@samp{--read-full-records}
+@option{--read-full-records}
@item -C
-@samp{--directory}
+@option{--directory}
@item -F
-@samp{--info-script}
+@option{--info-script}
@item -G
-@samp{--incremental}
+@option{--incremental}
@item -K
-@samp{--starting-file}
+@option{--starting-file}
@item -L
-@samp{--tape-length}
+@option{--tape-length}
@item -M
-@samp{--multi-volume}
+@option{--multi-volume}
@item -N
-@samp{--newer}
+@option{--newer}
@item -O
-@samp{--to-stdout}
+@option{--to-stdout}
@item -P
-@samp{--absolute-names}
+@option{--absolute-names}
@item -R
-@samp{--block-number}
+@option{--block-number}
@item -S
-@samp{--sparse}
+@option{--sparse}
@item -T
-@samp{--files-from}
+@option{--files-from}
@item -U
-@samp{--unlink-first}
+@option{--unlink-first}
@item -V
-@samp{--label}
+@option{--label}
@item -W
-@samp{--verify}
+@option{--verify}
@item -X
-@samp{--exclude-from}
+@option{--exclude-from}
@item -Z
-@samp{--compress}
+@option{--compress}
@item -b
-@samp{--blocking-factor}
+@option{--blocking-factor}
@item -c
-@samp{--create}
+@option{--create}
@item -d
-@samp{--compare}
+@option{--compare}
@item -f
-@samp{--file}
+@option{--file}
@item -g
-@samp{--listed-incremental}
+@option{--listed-incremental}
@item -h
-@samp{--dereference}
+@option{--dereference}
@item -i
-@samp{--ignore-zeros}
+@option{--ignore-zeros}
+
+@item -j
+
+@option{--bzip2}
@item -k
-@samp{--keep-old-files}
+@option{--keep-old-files}
@item -l
-@samp{--one-file-system}
+@option{--one-file-system}. Use of this short option is deprecated. It
+is retained for compatibility with the earlier versions of GNU
+@command{tar}, and will be changed in future releases.
+
+@xref{Changes}, for more information.
@item -m
-@samp{--touch}
+@option{--touch}
@item -o
-@samp{--portability}
+When creating --- @option{--no-same-owner}, when extracting ---
+@option{--portability}.
+
+The later usage is deprecated. It is retained for compatibility with
+the earlier versions of @GNUTAR{}. In the future releases
+@option{-o} will be equivalent to @option{--no-same-owner} only.
@item -p
-@samp{--preserve-permissions}
+@option{--preserve-permissions}
@item -r
-@samp{--append}
+@option{--append}
@item -s
-@samp{--same-order}
+@option{--same-order}
@item -t
-@samp{--list}
+@option{--list}
@item -u
-@samp{--update}
+@option{--update}
@item -v
-@samp{--verbose}
+@option{--verbose}
@item -w
-@samp{--interactive}
+@option{--interactive}
@item -x
-@samp{--extract}
-
-@item -y
-
-@samp{--bzip2}
+@option{--extract}
@item -z
-@samp{--gzip}
+@option{--gzip}
@end table
-@node help, verbose, All Options, tar invocation
-@section GNU @code{tar} documentation
+@node help
+@section @GNUTAR{} documentation
+
+@cindex Getting program version number
+@opindex version
+@cindex Version of the @command{tar} program
+Being careful, the first thing is really checking that you are using
+@GNUTAR{}, indeed. The @option{--version} option
+causes @command{tar} to print information about its name, version,
+origin and legal status, all on standard output, and then exit
+successfully. For example, @w{@samp{tar --version}} might print:
-Being careful, the first thing is really checking that you are using GNU
-@code{tar}, indeed. The @value{op-version} option will generate a message
-giving confirmation that you are using GNU @code{tar}, with the precise
-version of GNU @code{tar} you are using. @code{tar} identifies itself
-and prints the version number to the standard output, then immediately
-exits successfully, without doing anything else, ignoring all other
-options. For example, @w{@samp{tar --version}} might return:
+@smallexample
+tar (GNU tar) 1.15.2
+Copyright (C) 2006 Free Software Foundation, Inc.
+This is free software. You may redistribute copies of it under the terms of
+the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
+There is NO WARRANTY, to the extent permitted by law.
-@example
-tar (GNU tar) @value{VERSION}
-@end example
+Written by John Gilmore and Jay Fenlason.
+@end smallexample
@noindent
The first occurrence of @samp{tar} in the result above is the program
-name in the package (for example, @code{rmt} is another program), while
-the second occurrence of @samp{tar} is the name of the package itself,
-containing possibly many programs. The package is currently named
-@samp{tar}, after the name of the main program it contains@footnote{There
-are plans to merge the @code{cpio} and @code{tar} packages into a single one
-which would be called @code{paxutils}. So, who knows if, one of this days,
-the @value{op-version} would not yield @w{@samp{tar (GNU paxutils) 3.2}}}.
-
+name in the package (for example, @command{rmt} is another program),
+while the second occurrence of @samp{tar} is the name of the package
+itself, containing possibly many programs. The package is currently
+named @samp{tar}, after the name of the main program it
+contains@footnote{There are plans to merge the @command{cpio} and
+@command{tar} packages into a single one which would be called
+@code{paxutils}. So, who knows if, one of this days, the
+@option{--version} would not output @w{@samp{tar (@acronym{GNU}
+paxutils) 3.2}}}.
+
+@cindex Obtaining help
+@cindex Listing all @command{tar} options
+@opindex help, introduction
Another thing you might want to do is checking the spelling or meaning
-of some particular @code{tar} option, without resorting to this manual,
-for once you have carefully read it. GNU @code{tar} has a short help
-feature, triggerable through the @value{op-help} option. By using this
-option, @code{tar} will print a usage message listing all available
-options on standard output, then exit successfully, without doing
-anything else and ignoring all other options. Even if this is only a
-brief summary, it may be several screens long. So, if you are not
-using some kind of scrollable window, you might prefer to use something
-like:
+of some particular @command{tar} option, without resorting to this
+manual, for once you have carefully read it. @GNUTAR{}
+has a short help feature, triggerable through the
+@option{--help} option. By using this option, @command{tar} will
+print a usage message listing all available options on standard
+output, then exit successfully, without doing anything else and
+ignoring all other options. Even if this is only a brief summary, it
+may be several screens long. So, if you are not using some kind of
+scrollable window, you might prefer to use something like:
-@example
+@smallexample
$ @kbd{tar --help | less}
-@end example
+@end smallexample
@noindent
-presuming, here, that you like using @code{less} for a pager. Other
-popular pagers are @code{more} and @code{pg}. If you know about some
+presuming, here, that you like using @command{less} for a pager. Other
+popular pagers are @command{more} and @command{pg}. If you know about some
@var{keyword} which interests you and do not want to read all the
-@value{op-help} output, another common idiom is doing:
+@option{--help} output, another common idiom is doing:
-@example
+@smallexample
tar --help | grep @var{keyword}
-@end example
+@end smallexample
@noindent
-for getting only the pertinent lines.
-
-The perceptive reader would have noticed some contradiction in the
-previous paragraphs. It is written that both @value{op-version} and
-@value{op-help} print something, and have all other options ignored. In
-fact, they cannot ignore each other, and one of them has to win. We do
-not specify which is stronger, here; experiment if you really wonder!
-
-The short help output is quite succint, and you might have to get back
-to the full documentation for precise points. If you are reading this
-paragraph, you already have the @code{tar} manual in some form. This
-manual is available in printed form, as a kind of small book. It may
-printed out of the GNU @code{tar} distribution, provided you have @TeX{}
-already installed somewhere, and a laser printer around. Just configure
-the distribution, execute the command @w{@samp{make dvi}}, then print
-@file{doc/tar.dvi} the usual way (contact your local guru to know how).
-If GNU @code{tar} has been conveniently installed at your place, this
+for getting only the pertinent lines. Notice, however, that some
+@command{tar} options have long description lines and the above
+command will list only the first of them.
+
+The exact look of the option summary displayed by @kbd{tar --help} is
+configurable. @xref{Configuring Help Summary}, for a detailed description.
+
+@opindex usage
+If you only wish to check the spelling of an option, running @kbd{tar
+--usage} may be a better choice. This will display a terse list of
+@command{tar} option without accompanying explanations.
+
+The short help output is quite succinct, and you might have to get
+back to the full documentation for precise points. If you are reading
+this paragraph, you already have the @command{tar} manual in some
+form. This manual is available in a variety of forms from
+@url{http://www.gnu.org/software/tar/manual}. It may printed out of the @GNUTAR{}
+distribution, provided you have @TeX{} already installed somewhere,
+and a laser printer around. Just configure the distribution, execute
+the command @w{@samp{make dvi}}, then print @file{doc/tar.dvi} the
+usual way (contact your local guru to know how). If @GNUTAR{}
+has been conveniently installed at your place, this
manual is also available in interactive, hypertextual form as an Info
file. Just call @w{@samp{info tar}} or, if you do not have the
-@code{info} program handy, use the Info reader provided within GNU
-Emacs, calling @samp{tar} from the main Info menu.
-
-There is currently no @code{man} page for GNU @code{tar}. If you observe
-such a @code{man} page on the system you are running, either it does not
-long to GNU @code{tar}, or it has not been produced by GNU. Currently,
-GNU @code{tar} documentation is provided in Texinfo format only, if we
-except, of course, the short result of @kbd{tar --help}.
-
-@node verbose, interactive, help, tar invocation
-@section Checking @code{tar} progress
-
-@cindex Progress information
-@cindex Status information
-@cindex Information on progress and status of operations
-@cindex Verbose operation
-@cindex Block number where error occured
-@cindex Error message, block number of
-@cindex Version of the @code{tar} program
+@command{info} program handy, use the Info reader provided within
+@acronym{GNU} Emacs, calling @samp{tar} from the main Info menu.
+
+There is currently no @code{man} page for @GNUTAR{}.
+If you observe such a @code{man} page on the system you are running,
+either it does not belong to @GNUTAR{}, or it has not
+been produced by @acronym{GNU}. Some package maintainers convert
+@kbd{tar --help} output to a man page, using @command{help2man}. In
+any case, please bear in mind that the authoritative source of
+information about @GNUTAR{} is this Texinfo documentation.
+
+@node defaults
+@section Obtaining @GNUTAR{} default values
+
+@opindex show-defaults
+@GNUTAR{} has some predefined defaults that are used when you do not
+explicitely specify another values. To obtain a list of such
+defaults, use @option{--show-defaults} option. This will output the
+values in the form of @command{tar} command line options:
-@cindex Getting more information during the operation
-@cindex Information during operation
-@cindex Feedback from @code{tar}
+@smallexample
+@group
+@kbd{tar --show-defaults}
+--format=gnu -f- -b20 --rmt-command=/etc/rmt --rsh-command=/usr/bin/rsh
+@end group
+@end smallexample
-Typically, @code{tar} performs most operations without reporting any
-information to the user except error messages. When using @code{tar}
+@noindent
+The above output shows that this version of @GNUTAR{} defaults to
+using @samp{gnu} archive format (@pxref{Formats}), it uses standard
+output as the archive, if no @option{--file} option has been given
+(@pxref{file tutorial}), the default blocking factor is 20
+(@pxref{Blocking Factor}). It also shows the default locations where
+@command{tar} will look for @command{rmt} and @command{rsh} binaries.
+
+@node verbose
+@section Checking @command{tar} progress
+
+Typically, @command{tar} performs most operations without reporting any
+information to the user except error messages. When using @command{tar}
with many options, particularly ones with complicated or
difficult-to-predict behavior, it is possible to make serious mistakes.
-@code{tar} provides several options that make observing @code{tar}
-easier. These options cause @code{tar} to print information as it
+@command{tar} provides several options that make observing @command{tar}
+easier. These options cause @command{tar} to print information as it
progresses in its job, and you might want to use them just for being
more careful about what is going on, or merely for entertaining
yourself. If you have encountered a problem when operating on an
message in order to solve the problem. The following options can be
helpful diagnostic tools.
-Normally, the @value{op-list} command to list an archive prints just
-the file names (one per line) and the other commands are silent.
-When used with most operations, the @value{op-verbose} option causes
-@code{tar} to print the name of each file or archive member as it
-is processed. This and the other options which make @code{tar} print
-status information can be useful in monitoring @code{tar}.
-
-With @value{op-create} or @value{op-extract}, @value{op-verbose} used once
-just prints the names of the files or members as they are processed.
-Using it twice causes @code{tar} to print a longer listing (reminiscent
-of @samp{ls -l}) for each member. Since @value{op-list} already prints
-the names of the members, @value{op-verbose} used once with @value{op-list}
-causes @code{tar} to print an @samp{ls -l} type listing of the files
-in the archive. The following examples both extract members with
-long list output:
-
-@example
+@cindex Verbose operation
+@opindex verbose
+Normally, the @option{--list} (@option{-t}) command to list an archive
+prints just the file names (one per line) and the other commands are
+silent. When used with most operations, the @option{--verbose}
+(@option{-v}) option causes @command{tar} to print the name of each
+file or archive member as it is processed. This and the other options
+which make @command{tar} print status information can be useful in
+monitoring @command{tar}.
+
+With @option{--create} or @option{--extract}, @option{--verbose} used
+once just prints the names of the files or members as they are processed.
+Using it twice causes @command{tar} to print a longer listing
+(reminiscent of @samp{ls -l}) for each member. Since @option{--list}
+already prints the names of the members, @option{--verbose} used once
+with @option{--list} causes @command{tar} to print an @samp{ls -l}
+type listing of the files in the archive. The following examples both
+extract members with long list output:
+
+@smallexample
$ @kbd{tar --extract --file=archive.tar --verbose --verbose}
-$ @kbd{tar xvv archive.tar}
-@end example
+$ @kbd{tar xvvf archive.tar}
+@end smallexample
Verbose output appears on the standard output except when an archive is
being written to the standard output, as with @samp{tar --create
--file=- --verbose} (@samp{tar cfv -}, or even @samp{tar cv}---if the
installer let standard output be the default archive). In that case
-@code{tar} writes verbose output to the standard error stream.
+@command{tar} writes verbose output to the standard error stream.
+
+If @option{--index-file=@var{file}} is specified, @command{tar} sends
+verbose output to @var{file} rather than to standard output or standard
+error.
-The @value{op-totals} option---which is only meaningful when used with
-@value{op-create}---causes @code{tar} to print the total
+@cindex Obtaining total status information
+@opindex totals
+The @option{--totals} option---which is only meaningful when used with
+@option{--create} (@option{-c})---causes @command{tar} to print the total
amount written to the archive, after it has been fully created.
-The @value{op-checkpoint} option prints an occasional message
-as @code{tar} reads or writes the archive. In fact, it print
-directory names while reading the archive. It is designed for
+@cindex Progress information
+@opindex checkpoint
+The @option{--checkpoint} option prints an occasional message
+as @command{tar} reads or writes the archive. In fact, it prints
+a message each 10 records read or written. It is designed for
those who don't need the more detailed (and voluminous) output of
-@value{op-block-number}, but do want visual confirmation that @code{tar}
+@option{--block-number} (@option{-R}), but do want visual confirmation that @command{tar}
is actually making forward progress.
@FIXME{There is some confusion here. It seems that -R once wrote a
message at @samp{every} record read or written.}
-The @value{op-show-omitted-dirs} option, when reading an archive---with
-@value{op-list} or @value{op-extract}, for example---causes a message
+@opindex show-omitted-dirs
+@anchor{show-omitted-dirs}
+The @option{--show-omitted-dirs} option, when reading an archive---with
+@option{--list} or @option{--extract}, for example---causes a message
to be printed for each directory in the archive which is skipped.
This happens regardless of the reason for skipping: the directory might
not have been named on the command line (implicitly or explicitly),
-it might be excluded by the use of the @value{op-exclude} option, or
+it might be excluded by the use of the @option{--exclude=@var{pattern}} option, or
some other reason.
-If @value{op-block-number} is used, @code{tar} prints, along with every
-message it would normally produce, the block number within the archive
-where the message was triggered. Also, supplementary messages are
-triggered when reading blocks full of NULs, or when hitting end of file on
-the archive. As of now, if the archive if properly terminated with a NUL
-block, the reading of the file may stop before end of file is met, so the
-position of end of file will not usually show when @value{op-block-number}
-is used. Note that GNU @code{tar} drains the archive before exiting when
-reading the archive from a pipe.
+@opindex block-number
+@cindex Block number where error occurred
+@anchor{block-number}
+If @option{--block-number} (@option{-R}) is used, @command{tar} prints, along with
+every message it would normally produce, the block number within the
+archive where the message was triggered. Also, supplementary messages
+are triggered when reading blocks full of NULs, or when hitting end of
+file on the archive. As of now, if the archive if properly terminated
+with a NUL block, the reading of the file may stop before end of file
+is met, so the position of end of file will not usually show when
+@option{--block-number} (@option{-R}) is used. Note that @GNUTAR{}
+drains the archive before exiting when reading the
+archive from a pipe.
+@cindex Error message, block number of
This option is especially useful when reading damaged archives, since
it helps pinpoint the damaged sections. It can also be used with
-@value{op-list} when listing a file-system backup tape, allowing you to
+@option{--list} (@option{-t}) when listing a file-system backup tape, allowing you to
choose among several backup tapes when retrieving a file later, in
favor of the tape where the file appears earliest (closest to the
-front of the tape). @FIXME-xref{when the node name is set and the
-backup section written}.
+front of the tape). @xref{backup}.
-@node interactive, , verbose, tar invocation
+@node interactive
@section Asking for Confirmation During Operations
@cindex Interactive operation
-Typically, @code{tar} carries out a command without stopping for
+Typically, @command{tar} carries out a command without stopping for
further instructions. In some situations however, you may want to
exclude some files and archive members from the operation (for instance
if disk or storage space is tight). You can do this by excluding
certain files automatically (@pxref{Choosing}), or by performing
-an operation interactively, using the @value{op-interactive} option.
-@code{tar} also accepts @samp{--confirmation} for this option.
+an operation interactively, using the @option{--interactive} (@option{-w}) option.
+@command{tar} also accepts @option{--confirmation} for this option.
-When the @value{op-interactive} option is specified, before
-reading, writing, or deleting files, @code{tar} first prints a message
+@opindex interactive
+When the @option{--interactive} (@option{-w}) option is specified, before
+reading, writing, or deleting files, @command{tar} first prints a message
for each such file, telling what operation it intends to take, then asks
for confirmation on the terminal. The actions which require
confirmation include adding a file to the archive, extracting a file
from the archive, deleting a file from the archive, and deleting a file
from disk. To confirm the action, you must type a line of input
beginning with @samp{y}. If your input line begins with anything other
-than @samp{y}, @code{tar} skips that file.
+than @samp{y}, @command{tar} skips that file.
-If @code{tar} is reading the archive from the standard input,
-@code{tar} opens the file @file{/dev/tty} to support the interactive
+If @command{tar} is reading the archive from the standard input,
+@command{tar} opens the file @file{/dev/tty} to support the interactive
communications.
Verbose output is normally sent to standard output, separate from
read from that named pipe. This has the advantage of letting standard
output free to receive verbose output, all separate from errors.
-@node operations, Backups, tar invocation, Top
-@chapter GNU @code{tar} Operations
+@node operations
+@chapter @GNUTAR{} Operations
@menu
* Basic tar::
* Advanced tar::
+* create options::
* extract options::
* backup::
* Applications::
* looking ahead::
@end menu
-@node Basic tar, Advanced tar, operations, operations
-@section Basic GNU @code{tar} Operations
+@node Basic tar
+@section Basic @GNUTAR{} Operations
-The basic @code{tar} operations, @value{op-create}, @value{op-list} and
-@value{op-extract}, are currently presented and described in the tutorial
+The basic @command{tar} operations, @option{--create} (@option{-c}),
+@option{--list} (@option{-t}) and @option{--extract} (@option{--get},
+@option{-x}), are currently presented and described in the tutorial
chapter of this manual. This section provides some complementary notes
for these operations.
-@table @asis
-@item @value{op-create}
+@table @option
+@opindex create, complementary notes
+@item --create
+@itemx -c
Creating an empty archive would have some kind of elegance. One can
-initialize an empty archive and later use @value{op-append} for adding
-all members. Some applications would not welcome making an exception
-in the way of adding the first archive member. On the other hand,
-many people reported that it is dangerously too easy for @code{tar}
-to destroy a magnetic tape with an empty archive@footnote{This is well
-described in @cite{Unix-haters Handbook}, by Simson Garfinkel, Daniel
-Weise & Steven Strassmann, IDG Books, ISBN 1-56884-203-1.}. The two most
-common errors are:
+initialize an empty archive and later use @option{--append}
+(@option{-r}) for adding all members. Some applications would not
+welcome making an exception in the way of adding the first archive
+member. On the other hand, many people reported that it is
+dangerously too easy for @command{tar} to destroy a magnetic tape with
+an empty archive@footnote{This is well described in @cite{Unix-haters
+Handbook}, by Simson Garfinkel, Daniel Weise & Steven Strassmann, IDG
+Books, ISBN 1-56884-203-1.}. The two most common errors are:
@enumerate
@item
Mistakingly using @code{create} instead of @code{extract}, when the
intent was to extract the full contents of an archive. This error
-is likely: keys @kbd{c} and @kbd{x} are right next ot each other on
+is likely: keys @kbd{c} and @kbd{x} are right next to each other on
the QWERTY keyboard. Instead of being unpacked, the archive then
gets wholly destroyed. When users speak about @dfn{exploding} an
archive, they usually mean something else :-).
@end enumerate
So, recognizing the likelihood and the catastrophical nature of these
-errors, GNU @code{tar} now takes some distance from elegance, and
-cowardly refuses to create an archive when @value{op-create} option is
-given, there are no arguments besides options, and @value{op-files-from}
-option is @emph{not} used. To get around the cautiousness of GNU
-@code{tar} and nevertheless create an archive with nothing in it,
-one may still use, as the value for the @value{op-files-from} option,
-a file with no names in it, as shown in the following commands:
-
-@example
+errors, @GNUTAR{} now takes some distance from elegance, and
+cowardly refuses to create an archive when @option{--create} option is
+given, there are no arguments besides options, and
+@option{--files-from} (@option{-T}) option is @emph{not} used. To get
+around the cautiousness of @GNUTAR{} and nevertheless create an
+archive with nothing in it, one may still use, as the value for the
+@option{--files-from} option, a file with no names in it, as shown in
+the following commands:
+
+@smallexample
@kbd{tar --create --file=empty-archive.tar --files-from=/dev/null}
@kbd{tar cfT empty-archive.tar /dev/null}
-@end example
+@end smallexample
-@item @value{op-extract}
+@opindex extract, complementary notes
+@item --extract
+@itemx --get
+@itemx -x
-A socket is stored, within a GNU @code{tar} archive, as a pipe.
+A socket is stored, within a @GNUTAR{} archive, as a pipe.
-@item @value{op-list}
+@item @option{--list} (@option{-t})
-GNU @code{tar} now shows dates as @samp{1996-11-09}, while it used to
-show them as @samp{Nov 11 1996}. (One can revert to the old behavior by
-defining @code{USE_OLD_CTIME} in @file{src/list.c} before reinstalling.)
-But preferrably, people you should get used to ISO 8601 dates. Local
-American dates should be made available again with full date localisation
-support, once ready. In the meantime, programs not being localisable
-for dates should prefer international dates, that's really the way to go.
+@GNUTAR{} now shows dates as @samp{1996-08-30},
+while it used to show them as @samp{Aug 30 1996}. Preferably,
+people should get used to ISO 8601 dates. Local American dates should
+be made available again with full date localization support, once
+ready. In the meantime, programs not being localizable for dates
+should prefer international dates, that's really the way to go.
Look up @url{http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html} if you
are curious, it contains a detailed explanation of the ISO 8601 standard.
@end table
-@node Advanced tar, extract options, Basic tar, operations
-@section Advanced GNU @code{tar} Operations
+@node Advanced tar
+@section Advanced @GNUTAR{} Operations
-Now that you have learned the basics of using GNU @code{tar}, you may
-want to learn about further ways in which @code{tar} can help you.
+Now that you have learned the basics of using @GNUTAR{}, you may want
+to learn about further ways in which @command{tar} can help you.
This chapter presents five, more advanced operations which you probably
won't use on a daily basis, but which serve more specialized functions.
We also explain the different styles of options and why you might want
-to use one or another, or a combination of them in your @code{tar}
+to use one or another, or a combination of them in your @command{tar}
commands. Additionally, this chapter includes options which allow you to
-define the output from @code{tar} more carefully, and provide help and
+define the output from @command{tar} more carefully, and provide help and
error correction in special circumstances.
@FIXME{check this after the chapter is actually revised to make sure
@menu
* Operations::
-* current state::
* append::
* update::
* concatenate::
* compare::
@end menu
-@node Operations, current state, Advanced tar, Advanced tar
-@subsection The Five Advanced @code{tar} Operations
+@node Operations
+@subsection The Five Advanced @command{tar} Operations
@UNREVISED
In the last chapter, you learned about the first three operations to
-@code{tar}. This chapter presents the remaining five operations to
-@code{tar}: @samp{--append}, @samp{--update}, @samp{--concatenate},
-@samp{--delete}, and @samp{--compare}.
+@command{tar}. This chapter presents the remaining five operations to
+@command{tar}: @option{--append}, @option{--update}, @option{--concatenate},
+@option{--delete}, and @option{--compare}.
You are not likely to use these operations as frequently as those
covered in the last chapter; however, since they perform specialized
The five operations that we will cover in this chapter are:
-@table @kbd
+@table @option
@item --append
@itemx -r
Add new entries to an archive that already exists.
Compare archive members to their counterparts in the file system.
@end table
-@node current state, append, Operations, Advanced tar
-@ifinfo
-@subsection The Current State of the Practice Files
-@end ifinfo
-
-Currently, the listing of the directory using @code{ls} is as follows:
-
-@example
-
-@end example
-
-@noindent
-The archive file @samp{collection.tar} looks like this:
-
-@example
-$ @kbd{tar -tvf collection.tar}
-
-@end example
-
-@noindent
-The archive file @samp{music.tar} looks like this:
-
-@example
-$ @kbd{tar -tvf music.tar}
-
-@end example
-
-@FIXME{need to fill in the above!!!}
-
-@node append, update, current state, Advanced tar
-@subsection How to Add Files to Existing Archives: @code{--append}
+@node append
+@subsection How to Add Files to Existing Archives: @option{--append}
@UNREVISED
+@opindex append
If you want to add files to an existing archive, you don't need to
-create a new archive; you can use @value{op-append}. The archive must
-already exist in order to use @samp{--append}. (A related operation
-is the @samp{--update} operation; you can use this to add newer
-versions of archive members to an existing archive. To learn how to
-do this with @samp{--update}, @pxref{update}.)
-
-@FIXME{Explain in second paragraph whether you can get to the previous
-version -- explain whole situation somewhat more clearly.}
+create a new archive; you can use @option{--append} (@option{-r}).
+The archive must already exist in order to use @option{--append}. (A
+related operation is the @option{--update} operation; you can use this
+to add newer versions of archive members to an existing archive. To learn how to
+do this with @option{--update}, @pxref{update}.)
-If you use @value{op-append} to add a file that has the same name as an
+If you use @option{--append} to add a file that has the same name as an
archive member to an archive containing that archive member, then the
old member is not deleted. What does happen, however, is somewhat
-complex. @code{tar} @emph{allows} you to have infinite numbers of files
+complex. @command{tar} @emph{allows} you to have infinite number of files
with the same name. Some operations treat these same-named members no
differently than any other set of archive members: for example, if you
-view an archive with @value{op-list}, you will see all of those members
-listed, with their modification times, owners, etc.
+view an archive with @option{--list} (@option{-t}), you will see all
+of those members listed, with their data modification times, owners, etc.
Other operations don't deal with these members as perfectly as you might
-prefer; if you were to use @value{op-extract} to extract the archive,
+prefer; if you were to use @option{--extract} to extract the archive,
only the most recently added copy of a member with the same name as four
other members would end up in the working directory. This is because
-@samp{--extract} extracts an archive in the order the members appeared
+@option{--extract} extracts an archive in the order the members appeared
in the archive; the most recently archived members will be extracted
-last. Additionally, an extracted member will @emph{overwrite} a file of
-the same name which existed in the directory already, and @code{tar}
-will not prompt you about this. Thus, only the most recently archived
-member will end up being extracted, as it will overwrite the one
+last. Additionally, an extracted member will @emph{replace} a file of
+the same name which existed in the directory already, and @command{tar}
+will not prompt you about this@footnote{Unless you give it
+@option{--keep-old-files} option, or the disk copy is newer than the
+the one in the archive and you invoke @command{tar} with
+@option{--keep-newer-files} option}. Thus, only the most recently archived
+member will end up being extracted, as it will replace the one
extracted before it, and so on.
+There exists a special option that allows you to get around this
+behavior and extract (or list) only a particular copy of the file.
+This is @option{--occurrence} option. If you run @command{tar} with
+this option, it will extract only the first copy of the file. You
+may also give this option an argument specifying the number of
+copy to be extracted. Thus, for example if the archive
+@file{archive.tar} contained three copies of file @file{myfile}, then
+the command
+
+@smallexample
+tar --extract --file archive.tar --occurrence=2 myfile
+@end smallexample
+
+@noindent
+would extract only the second copy. @xref{Option
+Summary,---occurrence}, for the description of @option{--occurrence}
+option.
+
@FIXME{ hag -- you might want to incorporate some of the above into the
-MMwtSN node; not sure. i didn't know how to make it simpler...}
+MMwtSN node; not sure. i didn't know how to make it simpler...
-There are a few ways to get around this. @FIXME-xref{Multiple Members
-with the Same Name}.
+There are a few ways to get around this. (maybe xref Multiple Members
+with the Same Name.}
@cindex Members, replacing with other members
@cindex Replacing members with other members
-If you want to replace an archive member, use @value{op-delete} to
+If you want to replace an archive member, use @option{--delete} to
delete the member you want to remove from the archive, , and then use
-@samp{--append} to add the member you want to be in the archive. Note
+@option{--append} to add the member you want to be in the archive. Note
that you can not change the order of the archive; the most recently
-added member will still appear last. In this sense, you cannot truely
+added member will still appear last. In this sense, you cannot truly
``replace'' one member with another. (Replacing one member with another
will not work on certain types of media, such as tapes; see @ref{delete}
and @ref{Media}, for more information.)
* multiple::
@end menu
-@node appending files, multiple, append, append
+@node appending files
@subsubsection Appending Files to an Archive
@UNREVISED
@cindex Adding files to an Archive
@cindex Archives, Appending files to
The simplest way to add a file to an already existing archive is the
-@value{op-append} operation, which writes specified files into the
+@option{--append} (@option{-r}) operation, which writes specified files into the
archive whether or not they are already among the archived files.
-When you use @samp{--append}, you @emph{must} specify file name
+When you use @option{--append}, you @emph{must} specify file name
arguments, as there is no default. If you specify a file that already
exists in the archive, another copy of the file will be added to the
end of the archive. As with other operations, the member names of the
newly added files will be exactly the same as their names given on the
-command line. The @value{op-verbose} option will print out the names
-of the files as they are written into the archive.
+command line. The @option{--verbose} (@option{-v}) option will print
+out the names of the files as they are written into the archive.
-@samp{--append} cannot be performed on some tape drives, unfortunately,
+@option{--append} cannot be performed on some tape drives, unfortunately,
due to deficiencies in the formats those tape drives use. The archive
-must be a valid @code{tar} archive, or else the results of using this
+must be a valid @command{tar} archive, or else the results of using this
operation will be unpredictable. @xref{Media}.
-To demonstrate using @samp{--append} to add a file to an archive,
+To demonstrate using @option{--append} to add a file to an archive,
create a file called @file{rock} in the @file{practice} directory.
Make sure you are in the @file{practice} directory. Then, run the
-following @code{tar} command to add @file{rock} to
+following @command{tar} command to add @file{rock} to
@file{collection.tar}:
-@example
+@smallexample
$ @kbd{tar --append --file=collection.tar rock}
-@end example
+@end smallexample
@noindent
-If you now use the @value{op-list} operation, you will see that
+If you now use the @option{--list} (@option{-t}) operation, you will see that
@file{rock} has been added to the archive:
-@example
+@smallexample
$ @kbd{tar --list --file=collection.tar}
--rw-rw-rw- me user 28 1996-10-18 16:31 jazz
--rw-rw-rw- me user 21 1996-09-23 16:44 blues
--rw-rw-rw- me user 20 1996-09-23 16:44 folk
--rw-rw-rw- me user 20 1996-09-23 16:44 rock
-@end example
+-rw-r--r-- me user 28 1996-10-18 16:31 jazz
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+-rw-r--r-- me user 20 1996-09-23 16:44 folk
+-rw-r--r-- me user 20 1996-09-23 16:44 rock
+@end smallexample
@FIXME{in theory, dan will (soon) try to turn this node into what it's
title claims it will become...}
-@node multiple, , appending files, append
+@node multiple
@subsubsection Multiple Files with the Same Name
-You can use @value{op-append} to add copies of files which have been
+You can use @option{--append} (@option{-r}) to add copies of files which have been
updated since the archive was created. (However, we do not recommend
-doing this since there is another @code{tar} option called
-@samp{--update}; @pxref{update} for more information. We describe this
-use of @samp{--append} here for the sake of completeness.) @FIXME{is
+doing this since there is another @command{tar} option called
+@option{--update}; @pxref{update} for more information. We describe this
+use of @option{--append} here for the sake of completeness.) @FIXME{is
this really a good idea, to give this whole description for something
which i believe is basically a Stupid way of doing something? certain
aspects of it show ways in which tar is more broken than i'd personally
like to admit to, specifically the last sentence. On the other hand, i
-don't think it's a good idea to be saying that re explicitly don't
+don't think it's a good idea to be saying that we explicitly don't
recommend using something, but i can't see any better way to deal with
-the situation.} When you extract the archive, the older version will be
+the situation.}When you extract the archive, the older version will be
effectively lost. This works because files are extracted from an
archive in the order in which they were archived. Thus, when the
-archive is extracted, a file archived later in time will overwrite a
+archive is extracted, a file archived later in time will replace a
file of the same name which was archived earlier, even though the older
version of the file will remain in the archive unless you delete all
versions of the file.
@file{blues} is in the archive @file{collection.tar}. If you change the
file and append the new version of the file to the archive, there will
be two copies in the archive. When you extract the archive, the older
-version of the file will be extracted first, and then overwritten by the
+version of the file will be extracted first, and then replaced by the
newer version when it is extracted.
You can append the new, changed copy of the file @file{blues} to the
archive in this way:
-@example
+@smallexample
$ @kbd{tar --append --verbose --file=collection.tar blues}
blues
-@end example
+@end smallexample
@noindent
-Because you specified the @samp{--verbose} option, @code{tar} has
+Because you specified the @option{--verbose} option, @command{tar} has
printed the name of the file being appended as it was acted on. Now
list the contents of the archive:
-@example
+@smallexample
$ @kbd{tar --list --verbose --file=collection.tar}
--rw-rw-rw- me user 28 1996-10-18 16:31 jazz
--rw-rw-rw- me user 21 1996-09-23 16:44 blues
--rw-rw-rw- me user 20 1996-09-23 16:44 folk
--rw-rw-rw- me user 20 1996-09-23 16:44 rock
--rw-rw-rw- me user 58 1996-10-24 18:30 blues
-@end example
+-rw-r--r-- me user 28 1996-10-18 16:31 jazz
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+-rw-r--r-- me user 20 1996-09-23 16:44 folk
+-rw-r--r-- me user 20 1996-09-23 16:44 rock
+-rw-r--r-- me user 58 1996-10-24 18:30 blues
+@end smallexample
@noindent
The newest version of @file{blues} is now at the end of the archive
(note the different creation dates and file sizes). If you extract
the archive, the older version of the file @file{blues} will be
-overwritten by the newer version. You can confirm this by extracting
-the archive and running @samp{ls} on the directory. @xref{Writing},
-for more information. (@emph{Please note:} This is the case unless
-you employ the @value{op-backup} option; @FIXME-ref{Multiple Members
-with the Same Name}.)
+replaced by the newer version. You can confirm this by extracting
+the archive and running @samp{ls} on the directory.
+
+If you wish to extract the first occurrence of the file @file{blues}
+from the archive, use @option{--occurrence} option, as shown in
+the following example:
+
+@smallexample
+$ @kbd{tar --extract -vv --occurrence --file=collection.tar blues}
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+@end smallexample
-@node update, concatenate, append, Advanced tar
+@xref{Writing}, for more information on @option{--extract} and
+@xref{Option Summary, --occurrence}, for the description of
+@option{--occurrence} option.
+
+@node update
@subsection Updating an Archive
@UNREVISED
@cindex Updating an archive
-In the previous section, you learned how to use @value{op-append} to add
-a file to an existing archive. A related operation is
-@value{op-update}. The @samp{--update} operation updates a @code{tar}
-archive by comparing the date of the specified archive members against
-the date of the file with the same name. If the file has been modified
-more recently than the archive member, then the newer version of the
-file is added to the archive (as with @value{op-append}).
-
-Unfortunately, you cannot use @samp{--update} with magnetic tape drives.
+@opindex update
+In the previous section, you learned how to use @option{--append} to
+add a file to an existing archive. A related operation is
+@option{--update} (@option{-u}). The @option{--update} operation
+updates a @command{tar} archive by comparing the date of the specified
+archive members against the date of the file with the same name. If
+the file has been modified more recently than the archive member, then
+the newer version of the file is added to the archive (as with
+@option{--append}).
+
+Unfortunately, you cannot use @option{--update} with magnetic tape drives.
The operation will fail.
@FIXME{other examples of media on which --update will fail? need to ask
charles and/or mib/thomas/dave shevett..}
-Both @samp{--update} and @samp{--append} work by adding to the end
+Both @option{--update} and @option{--append} work by adding to the end
of the archive. When you extract a file from the archive, only the
version stored last will wind up in the file system, unless you use
-the @value{op-backup} option (@FIXME-ref{Multiple Members with the
-Same Name}).
+the @option{--backup} option. @FIXME-ref{Multiple Members with the
+Same Name}
@menu
* how to update::
@end menu
-@node how to update, , update, update
-@subsubsection How to Update an Archive Using @code{--update}
+@node how to update
+@subsubsection How to Update an Archive Using @option{--update}
-You must use file name arguments with the @value{op-update} operation.
-If you don't specify any files, @code{tar} won't act on any files and
+You must use file name arguments with the @option{--update} (@option{-u}) operation.
+If you don't specify any files, @command{tar} won't act on any files and
won't tell you that it didn't do anything (which may end up confusing
you).
@FIXME{note: the above parenthetical added because in fact, this
behavior just confused the author. :-) }
-To see the @samp{--update} option at work, create a new file,
+To see the @option{--update} option at work, create a new file,
@file{classical}, in your practice directory, and some extra text to the
-file @file{blues}, using any text editor. Then invoke @code{tar} with
-the @samp{update} operation and the @value{op-verbose} option specified,
+file @file{blues}, using any text editor. Then invoke @command{tar} with
+the @samp{update} operation and the @option{--verbose} (@option{-v}) option specified,
using the names of all the files in the practice directory as file name
arguments:
-@example
+@smallexample
$ @kbd{tar --update -v -f collection.tar blues folk rock classical}
blues
classical
$
-@end example
+@end smallexample
@noindent
-Because we have specified verbose mode, @code{tar} prints out the names
+Because we have specified verbose mode, @command{tar} prints out the names
of the files it is working on, which in this case are the names of the
files that needed to be updated. If you run @samp{tar --list} and look
at the archive, you will see @file{blues} and @file{classical} at its
the one at the end will be newer and larger, since you added text before
updating it.
-(The reason @code{tar} does not overwrite the older file when updating
+(The reason @command{tar} does not overwrite the older file when updating
it is because writing to the middle of a section of tape is a difficult
process. Tapes are not designed to go backward. @xref{Media}, for more
information about tapes.
-@value{op-update} is not suitable for performing backups for two
-reasons: it does not change directory content entries, and it lengthens
-the archive every time it is used. The GNU @code{tar} options intended
-specifically for backups are more efficient. If you need to run
-backups, please consult @ref{Backups}.
+@option{--update} (@option{-u}) is not suitable for performing backups for two
+reasons: it does not change directory content entries, and it
+lengthens the archive every time it is used. The @GNUTAR{}
+options intended specifically for backups are more
+efficient. If you need to run backups, please consult @ref{Backups}.
-@node concatenate, delete, update, Advanced tar
-@subsection Combining Archives with @code{--concatenate}
+@node concatenate
+@subsection Combining Archives with @option{--concatenate}
@cindex Adding archives to an archive
@cindex Concatenating Archives
+@opindex concatenate
+@opindex catenate
+@c @cindex @option{-A} described
Sometimes it may be convenient to add a second archive onto the end of
an archive rather than adding individual files to the archive. To add
one or more archives to the end of another archive, you should use the
-@value{op-concatenate} operation.
-
-To use @samp{--concatenate}, name the archives to be concatenated on the
-command line. (Nothing happens if you don't list any.) The members,
-and their member names, will be copied verbatim from those archives. If
-this causes multiple members to have the same name, it does not delete
-any members; all the members with the same name coexist. For
-information on how this affects reading the archive, @FIXME-ref{Multiple
-Members with the Same Name}.
-
-To demonstrate how @samp{--concatenate} works, create two small archives
+@option{--concatenate} (@option{--catenate}, @option{-A}) operation.
+
+To use @option{--concatenate}, give the first archive with
+@option{--file} option and name the rest of archives to be
+concatenated on the command line. The members, and their member
+names, will be copied verbatim from those archives to the first one.
+@FIXME-ref{This can cause multiple members to have the same name, for
+information on how this affects reading the archive, Multiple
+Members with the Same Name.}
+The new, concatenated archive will be called by the same name as the
+one given with the @option{--file} option. As usual, if you omit
+@option{--file}, @command{tar} will use the value of the environment
+variable @env{TAPE}, or, if this has not been set, the default archive name.
+
+@FIXME{There is no way to specify a new name...}
+
+To demonstrate how @option{--concatenate} works, create two small archives
called @file{bluesrock.tar} and @file{folkjazz.tar}, using the relevant
files from @file{practice}:
-@example
+@smallexample
$ @kbd{tar -cvf bluesrock.tar blues rock}
blues
classical
$ @kbd{tar -cvf folkjazz.tar folk jazz}
folk
jazz
-@end example
+@end smallexample
@noindent
If you like, You can run @samp{tar --list} to make sure the archives
contain what they are supposed to:
-@example
+@smallexample
$ @kbd{tar -tvf bluesrock.tar}
--rw-rw-rw- melissa user 105 1997-01-21 19:42 blues
--rw-rw-rw- melissa user 33 1997-01-20 15:34 rock
+-rw-r--r-- melissa user 105 1997-01-21 19:42 blues
+-rw-r--r-- melissa user 33 1997-01-20 15:34 rock
$ @kbd{tar -tvf folkjazz.tar}
--rw-rw-rw- melissa user 20 1996-09-23 16:44 folk
--rw-rw-rw- melissa user 65 1997-01-30 14:15 jazz
-@end example
+-rw-r--r-- melissa user 20 1996-09-23 16:44 folk
+-rw-r--r-- melissa user 65 1997-01-30 14:15 jazz
+@end smallexample
-We can concatenate these two archives with @code{tar}:
+We can concatenate these two archives with @command{tar}:
-@example
+@smallexample
$ @kbd{cd ..}
$ @kbd{tar --concatenate --file=bluesrock.tar jazzfolk.tar}
-@end example
+@end smallexample
If you now list the contents of the @file{bluesclass.tar}, you will see
that now it also contains the archive members of @file{jazzfolk.tar}:
-@example
+@smallexample
$ @kbd{tar --list --file=bluesrock.tar}
blues
rock
jazz
folk
-@end example
+@end smallexample
-When you use @samp{--concatenate}, the source and target archives must
-already exist and must have been created using compatable format
-parameters (@FIXME-pxref{Matching Format Parameters}). The new,
-concatenated archive will be called by the same name as the first
-archive listed on the command line. @FIXME{is there a way to specify a
-new name?}
+When you use @option{--concatenate}, the source and target archives must
+already exist and must have been created using compatible format
+parameters. Notice, that @command{tar} does not check whether the
+archives it concatenates have compatible formats, it does not
+even check if the files are really tar archives.
-Like @value{op-append}, this operation cannot be performed on some
+Like @option{--append} (@option{-r}), this operation cannot be performed on some
tape drives, due to deficiencies in the formats those tape drives use.
-@cindex @code{concatenate} vs @code{cat}
-@cindex @code{cat} vs @code{concatenate}
-It may seem more intuitive to you to want or try to use @code{cat} to
-concatenate two archives instead of using the @samp{--concatenate}
-operation; after all, @code{cat} is the utility for combining files.
+@cindex @code{concatenate} vs @command{cat}
+@cindex @command{cat} vs @code{concatenate}
+It may seem more intuitive to you to want or try to use @command{cat} to
+concatenate two archives instead of using the @option{--concatenate}
+operation; after all, @command{cat} is the utility for combining files.
-However, @code{tar} archives incorporate an end-of-file marker which
+However, @command{tar} archives incorporate an end-of-file marker which
must be removed if the concatenated archives are to be read properly as
-one archive. @samp{--concatenate} removes the end-of-archive marker
+one archive. @option{--concatenate} removes the end-of-archive marker
from the target archive before each new archive is appended. If you use
-@code{cat} to combine the archives, the result will not be a valid
-@code{tar} format archive. If you need to retrieve files from an
-archive that was added to using the @code{cat} utility, use the
-@value{op-ignore-zeros} option. @xref{Ignore Zeros}, for further
+@command{cat} to combine the archives, the result will not be a valid
+@command{tar} format archive. If you need to retrieve files from an
+archive that was added to using the @command{cat} utility, use the
+@option{--ignore-zeros} (@option{-i}) option. @xref{Ignore Zeros}, for further
information on dealing with archives improperly combined using the
-@code{cat} shell utility.
+@command{cat} shell utility.
-@FIXME{this shouldn't go here. where should it go?} You must specify
-the source archives using @value{op-file} (@value{pxref-file}). If you
-do not specify the target archive, @code{tar} uses the value of the
-environment variable @code{TAPE}, or, if this has not been set, the
-default archive name.
-
-@node delete, compare, concatenate, Advanced tar
-@subsection Removing Archive Members Using @samp{--delete}
+@node delete
+@subsection Removing Archive Members Using @option{--delete}
@UNREVISED
@cindex Deleting files from an archive
@cindex Removing files from an archive
-You can remove members from an archive by using the @value{op-delete}
-option. Specify the name of the archive with @value{op-file} and then
-specify the names of the members to be deleted; if you list no member
-names, nothing will be deleted. The @value{op-verbose} option will
-cause @code{tar} to print the names of the members as they are deleted.
-As with @value{op-extract}, you must give the exact member names when
-using @samp{tar --delete}. @samp{--delete} will remove all versions of
-the named file from the archive. The @samp{--delete} operation can run
-very slowly.
+@opindex delete
+You can remove members from an archive by using the @option{--delete}
+option. Specify the name of the archive with @option{--file}
+(@option{-f}) and then specify the names of the members to be deleted;
+if you list no member names, nothing will be deleted. The
+@option{--verbose} option will cause @command{tar} to print the names
+of the members as they are deleted. As with @option{--extract}, you
+must give the exact member names when using @samp{tar --delete}.
+@option{--delete} will remove all versions of the named file from the
+archive. The @option{--delete} operation can run very slowly.
-Unlike other operations, @samp{--delete} has no short form.
+Unlike other operations, @option{--delete} has no short form.
-@cindex Tapes, using @code{--delete} and
+@cindex Tapes, using @option{--delete} and
@cindex Deleting from tape archives
This operation will rewrite the archive. You can only use
-@samp{--delete} on an archive if the archive device allows you to
+@option{--delete} on an archive if the archive device allows you to
write to any point on the media, such as a disk; because of this, it
does not work on magnetic tapes. Do not try to delete an archive member
from a magnetic tape; the action will not succeed, and you will be
@file{collection.tar} in the @file{practice} directory, make sure you
are in that directory, and then,
-@example
+@smallexample
$ @kbd{tar --list --file=collection.tar}
blues
folk
jazz
rock
$
-@end example
+@end smallexample
@FIXME{I changed the order of these nodes around and haven't had a chance
to fix the above example's results, yet. I have to play with this and
follow it and see what it actually does!}
-The @value{op-delete} option has been reported to work properly when
-@code{tar} acts as a filter from @code{stdin} to @code{stdout}.
+The @option{--delete} option has been reported to work properly when
+@command{tar} acts as a filter from @code{stdin} to @code{stdout}.
-@node compare, , delete, Advanced tar
+@node compare
@subsection Comparing Archive Members with the File System
@cindex Verifying the currency of an archive
@UNREVISED
-The @samp{--compare} (@samp{-d}), or @samp{--diff} operation compares
+@opindex compare
+The @option{--compare} (@option{-d}), or @option{--diff} operation compares
specified archive members against files with the same names, and then
reports differences in file size, mode, owner, modification date and
contents. You should @emph{only} specify archive member names, not file
-names. If you do not name any members, then @code{tar} will compare the
+names. If you do not name any members, then @command{tar} will compare the
entire archive. If a file is represented in the archive but does not
-exist in the file system, @code{tar} reports a difference.
+exist in the file system, @command{tar} reports a difference.
You have to specify the record size of the archive when modifying an
archive with a non-default record size.
-@code{tar} ignores files in the file system that do not have
+@command{tar} ignores files in the file system that do not have
corresponding members in the archive.
The following example compares the archive members @file{rock},
@file{blues} and @file{funk} in the archive @file{bluesrock.tar} with
files of the same name in the file system. (Note that there is no file,
-@file{funk}; @code{tar} will report an error message.)
+@file{funk}; @command{tar} will report an error message.)
-@example
+@smallexample
$ @kbd{tar --compare --file=bluesrock.tar rock blues funk}
rock
blues
tar: funk not found in archive
-@end example
+@end smallexample
-@noindent
-@FIXME{what does this actually depend on? i'm making a guess,
-here.}Depending on the system where you are running @code{tar} and the
-version you are running, @code{tar} may have a different error message,
-such as:
+The spirit behind the @option{--compare} (@option{--diff}, @option{-d}) option is to check whether the
+archive represents the current state of files on disk, more than validating
+the integrity of the archive media. For this later goal, @xref{verify}.
-@example
-funk: does not exist
-@end example
+@node create options
+@section Options Used by @option{--create}
-@FIXME-xref{somewhere, for more information about format parameters.
-Melissa says: such as "format variations"? But why? Clearly I don't
-get it yet; I'll deal when I get to that section.}
+@opindex create, additional options
+The previous chapter described the basics of how to use
+@option{--create} (@option{-c}) to create an archive from a set of files.
+@xref{create}. This section described advanced options to be used with
+@option{--create}.
-The spirit behind the @value{op-compare} option is to check whether the
-archive represents the current state of files on disk, more than validating
-the integrity of the archive media. For this later goal, @xref{verify}.
+@menu
+* Ignore Failed Read::
+@end menu
+
+@node Ignore Failed Read
+@subsection Ignore Fail Read
+
+@table @option
+@item --ignore-failed-read
+Do not exit with nonzero on unreadable files or directories.
+@end table
-@node extract options, backup, Advanced tar, operations
-@section Options Used by @code{--extract}
+@node extract options
+@section Options Used by @option{--extract}
@UNREVISED
@FIXME{i need to get dan to go over these options with me and see if
there's a better way of organizing them.}
-The previous chapter showed how to use @value{op-extract} to extract
-an archive into the filesystem. Various options cause @code{tar} to
+@opindex extract, additional options
+The previous chapter showed how to use @option{--extract} to extract
+an archive into the file system. Various options cause @command{tar} to
extract more information than just file contents, such as the owner,
the permissions, the modification date, and so forth. This section
-presents options to be used with @samp{--extract} when certain special
+presents options to be used with @option{--extract} when certain special
considerations arise. You may review the information presented in
@ref{extract} for more basic information about the
-@samp{--extract} operation.
+@option{--extract} operation.
@menu
* Reading:: Options to Help Read Archives
-* Writing:: Changing How @code{tar} Writes Files
+* Writing:: Changing How @command{tar} Writes Files
* Scarce:: Coping with Scarce Resources
@end menu
-@node Reading, Writing, extract options, extract options
+@node Reading
@subsection Options to Help Read Archives
@cindex Options when reading archives
-@cindex Reading incomplete records
-@cindex Records, incomplete
-@cindex End-of-archive entries, ignoring
-@cindex Ignoring end-of-archive entries
-@cindex Large lists of file names on small machines
-@cindex Small memory
-@cindex Running out of space
@UNREVISED
-Normally, @code{tar} will request data in full record increments from
+@cindex Reading incomplete records
+@cindex Records, incomplete
+@opindex read-full-records
+Normally, @command{tar} will request data in full record increments from
an archive storage device. If the device cannot return a full record,
-@code{tar} will report an error. However, some devices do not always
+@command{tar} will report an error. However, some devices do not always
return full records, or do not require the last record of an archive to
be padded out to the next record boundary. To keep reading until you
obtain a full record, or to accept an incomplete record if it contains
-an end-of-archive marker, specify the @value{op-read-full-records} option
-in conjunction with the @value{op-extract} or @value{op-list} operations.
-@value{xref-read-full-records}.
+an end-of-archive marker, specify the @option{--read-full-records} (@option{-B}) option
+in conjunction with the @option{--extract} or @option{--list} operations.
+@xref{Blocking}.
-The @value{op-read-full-records} option is turned on by default when
-@code{tar} reads an archive from standard input, or from a remote
+The @option{--read-full-records} (@option{-B}) option is turned on by default when
+@command{tar} reads an archive from standard input, or from a remote
machine. This is because on BSD Unix systems, attempting to read a
pipe returns however much happens to be in the pipe, even if it is
-less than was requested. If this option were not enabled, @code{tar}
+less than was requested. If this option were not enabled, @command{tar}
would fail as soon as it read an incomplete record from the pipe.
If you're not sure of the blocking factor of an archive, you can
-read the archive by specifying @value{op-read-full-records} and
-@value{op-blocking-factor}, using a blocking factor larger than what the
-archive uses. This lets you avoid having to determine the blocking factor
-of an archive. @value{xref-blocking-factor}.
+read the archive by specifying @option{--read-full-records} (@option{-B}) and
+@option{--blocking-factor=@var{512-size}} (@option{-b
+@var{512-size}}), using a blocking factor larger than what the archive
+uses. This lets you avoid having to determine the blocking factor
+of an archive. @xref{Blocking Factor}.
@menu
* read full records::
* Ignore Zeros::
-* Ignore Failed Read::
@end menu
-@node read full records, Ignore Zeros, Reading, Reading
+@node read full records
@unnumberedsubsubsec Reading Full Records
@FIXME{need sentence or so of intro here}
-@table @kbd
+@table @option
+@opindex read-full-records
@item --read-full-records
@item -B
-Use in conjunction with @value{op-extract} to read an archive which
-contains incomplete records, or one which has a blocking factor less
-than the one specified.
+Use in conjunction with @option{--extract} (@option{--get},
+@option{-x}) to read an archive which contains incomplete records, or
+one which has a blocking factor less than the one specified.
@end table
-@node Ignore Zeros, Ignore Failed Read, read full records, Reading
+@node Ignore Zeros
@unnumberedsubsubsec Ignoring Blocks of Zeros
-Normally, @code{tar} stops reading when it encounters a block of zeros
+@cindex End-of-archive blocks, ignoring
+@cindex Ignoring end-of-archive blocks
+@opindex ignore-zeros
+Normally, @command{tar} stops reading when it encounters a block of zeros
between file entries (which usually indicates the end of the archive).
-@value{op-ignore-zeros} allows @code{tar} to completely read an archive
-which contains a block of zeros before the end (i.e.@: a damaged
-archive, or one which was created by @code{cat}-ing several archives
-together).
-
-The @value{op-ignore-zeros} option is turned off by default because many
-versions of @code{tar} write garbage after the end-of-archive entry,
-since that part of the media is never supposed to be read. GNU
-@code{tar} does not write after the end of an archive, but seeks to
-maintain compatablity among archiving utilities.
-
-@table @kbd
+@option{--ignore-zeros} (@option{-i}) allows @command{tar} to
+completely read an archive which contains a block of zeros before the
+end (i.e., a damaged archive, or one that was created by concatenating
+several archives together).
+
+The @option{--ignore-zeros} (@option{-i}) option is turned off by default because many
+versions of @command{tar} write garbage after the end-of-archive entry,
+since that part of the media is never supposed to be read. @GNUTAR{}
+does not write after the end of an archive, but seeks to
+maintain compatiblity among archiving utilities.
+
+@table @option
@item --ignore-zeros
@itemx -i
-To ignore blocks of zeros (ie.@: end-of-archive entries) which may be
+To ignore blocks of zeros (i.e., end-of-archive entries) which may be
encountered while reading an archive. Use in conjunction with
-@value{op-extract} or @value{op-list}.
-@end table
-
-@node Ignore Failed Read, , Ignore Zeros, Reading
-@unnumberedsubsubsec Ignore Fail Read
-
-@FIXME{Is this in the right place? It doesn't exist anywhere else in
-the book (except the appendix), and has no further explanation. For that
-matter, what does it mean?!}
-
-@table @kbd
-@item --ignore-failed-read
-Do not exit with nonzero on unreadable files or directories.
+@option{--extract} or @option{--list}.
@end table
-@node Writing, Scarce, Reading, extract options
-@subsection Changing How @code{tar} Writes Files
-@cindex Overwriting old files, prevention
-@cindex Protecting old files
-@cindex Modification times of extracted files
-@cindex Permissions of extracted files
-@cindex Modes of extracted files
-@cindex Writing extracted files to standard output
-@cindex Standard output, writing extracted files to
+@node Writing
+@subsection Changing How @command{tar} Writes Files
@UNREVISED
-@FIXME{need to mention the brand new option, --backup}
+@FIXME{Introductory paragraph}
@menu
-* Prevention Overwriting::
+* Dealing with Old Files::
+* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
+* Directory Modification Times and Permissions::
* Writing to Standard Output::
+* Writing to an External Program::
* remove files::
@end menu
-@node Prevention Overwriting, Keep Old Files, Writing, Writing
-@unnumberedsubsubsec Options to Prevent Overwriting Files
+@node Dealing with Old Files
+@unnumberedsubsubsec Options Controlling the Overwriting of Existing Files
-Normally, @code{tar} writes extracted files into the file system without
+@opindex overwrite-dir, introduced
+When extracting files, if @command{tar} discovers that the extracted
+file already exists, it normally replaces the file by removing it before
+extracting it, to prevent confusion in the presence of hard or symbolic
+links. (If the existing file is a symbolic link, it is removed, not
+followed.) However, if a directory cannot be removed because it is
+nonempty, @command{tar} normally overwrites its metadata (ownership,
+permission, etc.). The @option{--overwrite-dir} option enables this
+default behavior. To be more cautious and preserve the metadata of
+such a directory, use the @option{--no-overwrite-dir} option.
+
+@cindex Overwriting old files, prevention
+@opindex keep-old-files, introduced
+To be even more cautious and prevent existing files from being replaced, use
+the @option{--keep-old-files} (@option{-k}) option. It causes @command{tar} to refuse
+to replace or update a file that already exists, i.e., a file with the
+same name as an archive member prevents extraction of that archive
+member. Instead, it reports an error.
+
+@opindex overwrite, introduced
+To be more aggressive about altering existing files, use the
+@option{--overwrite} option. It causes @command{tar} to overwrite
+existing files and to follow existing symbolic links when extracting.
+
+@cindex Protecting old files
+Some people argue that @GNUTAR{} should not hesitate
+to overwrite files with other files when extracting. When extracting
+a @command{tar} archive, they expect to see a faithful copy of the
+state of the file system when the archive was created. It is debatable
+that this would always be a proper behavior. For example, suppose one
+has an archive in which @file{usr/local} is a link to
+@file{usr/local2}. Since then, maybe the site removed the link and
+renamed the whole hierarchy from @file{/usr/local2} to
+@file{/usr/local}. Such things happen all the time. I guess it would
+not be welcome at all that @GNUTAR{} removes the
+whole hierarchy just to make room for the link to be reinstated
+(unless it @emph{also} simultaneously restores the full
+@file{/usr/local2}, of course!) @GNUTAR{} is indeed
+able to remove a whole hierarchy to reestablish a symbolic link, for
+example, but @emph{only if} @option{--recursive-unlink} is specified
+to allow this behavior. In any case, single files are silently
+removed.
+
+@opindex unlink-first, introduced
+Finally, the @option{--unlink-first} (@option{-U}) option can improve performance in
+some cases by causing @command{tar} to remove files unconditionally
+before extracting them.
+
+@node Overwrite Old Files
+@unnumberedsubsubsec Overwrite Old Files
+
+@table @option
+@opindex overwrite
+@item --overwrite
+Overwrite existing files and directory metadata when extracting files
+from an archive.
+
+This causes @command{tar} to write extracted files into the file system without
regard to the files already on the system; i.e., files with the same
names as archive members are overwritten when the archive is extracted.
+It also causes @command{tar} to extract the ownership, permissions,
+and time stamps onto any preexisting files or directories.
If the name of a corresponding file name is a symbolic link, the file
pointed to by the symbolic link will be overwritten instead of the
symbolic link itself (if this is possible). Moreover, special devices,
empty directories and even symbolic links are automatically removed if
-they are found to be on the way of the proper extraction.
-
-To prevent @code{tar} from extracting an archive member from an archive
-if doing so will overwrite a file in the file system, use
-@value{op-keep-old-files} in conjunction with @samp{--extract}. When
-this option is specified, @code{tar} will report an error stating the
-name of the files in conflict instead of overwriting the file with the
-corresponding extracted archive member.
-
-@FIXME{these two P's have problems. i don't understand what they're
-trying to talk about well enough to fix them; i may have just made them
-worse (in particular the first of the two). waiting to talk with hag.}
-
-The @value{op-unlink-first} option removes existing files, symbolic links,
-empty directories, devices, etc., @emph{prior} to extracting over them.
-In particular, using this option will prevent replacing an already existing
-symbolic link by the name of an extracted file, since the link itself
-is removed prior to the extraction, rather than the file it points to.
-On some systems, the backing store for the executable @emph{is} the
-original program text. You could use the @value{op-unlink-first} option
-to prevent segmentation violations or other woes when extracting arbitrary
-executables over currently running copies. Note that if something goes
-wrong with the extraction and you @emph{did} use this option, you might
-end up with no file at all. Without this option, if something goes wrong
-with the extraction, the existing file is not overwritten and preserved.
-
-@FIXME{huh?} If you specify the @value{op-recursive-unlink} option,
-@code{tar} removes @emph{anything} that keeps you from extracting a file
-as far as current permissions will allow it. This could include removal
-of the contents of a full directory hierarchy. For example, someone
-using this feature may be very surprised at the results when extracting
-a directory entry from the archive. This option can be dangerous; be
-very aware of what you are doing if you choose to use it.
-
-@menu
-* Keep Old Files::
-* Unlink First::
-* Recursive Unlink::
-@end menu
+they are in the way of extraction.
+
+Be careful when using the @option{--overwrite} option, particularly when
+combined with the @option{--absolute-names} (@option{-P}) option, as this combination
+can change the contents, ownership or permissions of any file on your
+system. Also, many systems do not take kindly to overwriting files that
+are currently being executed.
+
+@opindex overwrite-dir
+@item --overwrite-dir
+Overwrite the metadata of directories when extracting files from an
+archive, but remove other files before extracting.
+@end table
-@node Keep Old Files, Unlink First, Prevention Overwriting, Writing
+@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
-@table @kbd
+@table @option
+@opindex keep-old-files
@item --keep-old-files
@itemx -k
-Do not overwrite existing files from archive. The
-@value{op-keep-old-files} option prevents @code{tar} from over-writing
-existing files with files with the same name from the archive.
-The @value{op-keep-old-files} option is meaningless with @value{op-list}.
-Prevents @code{tar} from overwriting files in the file system during
-extraction.
+Do not replace existing files from archive. The
+@option{--keep-old-files} (@option{-k}) option prevents @command{tar}
+from replacing existing files with files with the same name from the
+archive. The @option{--keep-old-files} option is meaningless with
+@option{--list} (@option{-t}). Prevents @command{tar} from replacing
+files in the file system during extraction.
+@end table
+
+@node Keep Newer Files
+@unnumberedsubsubsec Keep Newer Files
+
+@table @option
+@opindex keep-newer-files
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive
+copies. This option is meaningless with @option{--list} (@option{-t}).
@end table
-@node Unlink First, Recursive Unlink, Keep Old Files, Writing
+@node Unlink First
@unnumberedsubsubsec Unlink First
-@table @kbd
+@table @option
+@opindex unlink-first
@item --unlink-first
@itemx -U
-Try removing files before extracting over them, instead of trying to
-overwrite them.
+Remove files before extracting over them.
+This can make @command{tar} run a bit faster if you know in advance
+that the extracted files all need to be removed. Normally this option
+slows @command{tar} down slightly, so it is disabled by default.
@end table
-@node Recursive Unlink, Modification Times, Unlink First, Writing
+@node Recursive Unlink
@unnumberedsubsubsec Recursive Unlink
-@table @kbd
+@table @option
+@opindex recursive-unlink
@item --recursive-unlink
When this option is specified, try removing files and directory hierarchies
before extracting over them. @emph{This is a dangerous option!}
@end table
-Some people argue that GNU @code{tar} should not hesitate to overwrite
-files with other files when extracting. When extracting a @code{tar}
-archive, they expect to see a faithful copy of the state of the filesystem
-when the archive was created. It is debatable that this would always
-be a proper behaviour. For example, suppose one has an archive in
-which @file{usr/local} is a link to @file{usr/local2}. Since then,
-maybe the site removed the link and renamed the whole hierarchy from
-@file{/usr/local2} to @file{/usr/local}. Such things happen all the time.
-I guess it would not be welcome at all that GNU @code{tar} removes the
-whole hierarchy just to make room for the link to be reinstated (unless it
-@emph{also} simultaneously restores the full @file{/usr/local2}, of course!
-GNU @code{tar} is indeed able to remove a whole hierarchy to reestablish a
-symbolic link, for example, but @emph{only if} @value{op-recursive-unlink}
-is specified to allow this behaviour. In any case, single files are
-silently removed.
-
-@node Modification Times, Setting Access Permissions, Recursive Unlink, Writing
-@unnumberedsubsubsec Setting Modification Times
-
-Normally, @code{tar} sets the modification times of extracted files to
-the modification times recorded for the files in the archive, but
+If you specify the @option{--recursive-unlink} option,
+@command{tar} removes @emph{anything} that keeps you from extracting a file
+as far as current permissions will allow it. This could include removal
+of the contents of a full directory hierarchy.
+
+@node Data Modification Times
+@unnumberedsubsubsec Setting Data Modification Times
+
+@cindex Data modification times of extracted files
+@cindex Modification times of extracted files
+Normally, @command{tar} sets the data modification times of extracted
+files to the corresponding times recorded for the files in the archive, but
limits the permissions of extracted files by the current @code{umask}
setting.
-To set the modification times of extracted files to the time when
-the files were extracted, use the @value{op-touch} option in
-conjunction with @value{op-extract}.
+To set the data modification times of extracted files to the time when
+the files were extracted, use the @option{--touch} (@option{-m}) option in
+conjunction with @option{--extract} (@option{--get}, @option{-x}).
-@table @kbd
+@table @option
+@opindex touch
@item --touch
@itemx -m
-Sets the modification time of extracted archive members to the time
+Sets the data modification time of extracted archive members to the time
they were extracted, not the time recorded for them in the archive.
-Use in conjunction with @value{op-extract}.
+Use in conjunction with @option{--extract} (@option{--get}, @option{-x}).
@end table
-@node Setting Access Permissions, Writing to Standard Output, Modification Times, Writing
+@node Setting Access Permissions
@unnumberedsubsubsec Setting Access Permissions
+@cindex Permissions of extracted files
+@cindex Modes of extracted files
To set the modes (access permissions) of extracted files to those
-recorded for those files in the archive, use @samp{--same-persmissions}
-in conjunction with the @value{op-extract} operation. @FIXME{Should be
-aliased to ignore-umask.}
+recorded for those files in the archive, use @option{--same-permissions}
+in conjunction with the @option{--extract} (@option{--get},
+@option{-x}) operation. @FIXME{Should be aliased to ignore-umask.}
-@table @kbd
+@table @option
+@opindex preserve-permission
+@opindex same-permission
@item --preserve-permission
@itemx --same-permission
-@itemx --ignore-umask
+@c @itemx --ignore-umask
@itemx -p
Set modes of extracted archive members to those recorded in the
archive, instead of current umask settings. Use in conjunction with
-@value{op-extract}.
+@option{--extract} (@option{--get}, @option{-x}).
@end table
-@FIXME{Following paragraph needs to be rewritten: why doesnt' this cat
-files together, why is this useful. is it really useful with
-more than one file?}
+@node Directory Modification Times and Permissions
+@unnumberedsubsubsec Directory Modification Times and Permissions
+
+After sucessfully extracting a file member, @GNUTAR{} normally
+restores its permissions and modification times, as described in the
+previous sections. This cannot be done for directories, because
+after extracting a directory @command{tar} will almost certainly
+extract files into that directory and this will cause the directory
+modification time to be updated. Moreover, restoring that directory
+permissions may not permit file creation within it. Thus, restoring
+directory permissions and modification times must be delayed at least
+until all files have been extracted into that directory. @GNUTAR{}
+restores directories using the following approach.
+
+The extracted directories are created with the mode specified in the
+archive, as modified by the umask of the user, which gives sufficient
+permissions to allow file creation. The meta-information about the
+directory is recorded in the temporary list of directories. When
+preparing to extract next archive member, @GNUTAR{} checks if the
+directory prefix of this file contains the remembered directory. If
+it does not, the program assumes that all files have been extracted
+into that directory, restores its modification time and permissions
+and removes its entry from the internal list. This approach allows
+to correctly restore directory meta-information in the majority of
+cases, while keeping memory requirements sufficiently small. It is
+based on the fact, that most @command{tar} archives use the predefined
+order of members: first the directory, then all the files and
+subdirectories in that directory.
+
+However, this is not always true. The most important exception are
+incremental archives (@pxref{Incremental Dumps}). The member order in
+an incremental archive is reversed: first all directory members are
+stored, followed by other (non-directory) members. So, when extracting
+from incremental archives, @GNUTAR{} alters the above procedure. It
+remebers all restored directories, and restores their meta-data
+only after the entire archive has been processed. Notice, that you do
+not need to specity any special options for that, as @GNUTAR{}
+automatically detects archives in incremental format.
+
+There may be cases, when such processing is required for normal archives
+too. Consider the following example:
+
+@smallexample
+@group
+$ @kbd{tar --no-recursion -cvf archive \
+ foo foo/file1 bar bar/file foo/file2}
+foo/
+foo/file1
+bar/
+bar/file
+foo/file2
+@end group
+@end smallexample
+
+During the normal operation, after encountering @file{bar}
+@GNUTAR{} will assume that all files from the directory @file{foo}
+were already extracted and will therefore restore its timestamp and
+permission bits. However, after extracting @file{foo/file2} the
+directory timestamp will be offset again.
+
+To correctly restore directory meta-information in such cases, use
+@option{delay-directory-restore} command line option:
+
+@table @option
+@opindex delay-directory-restore
+@item --delay-directory-restore
+Delays restoring of the modification times and permissions of extracted
+directories until the end of extraction. This way, correct
+meta-information is restored even if the archive has unusual member
+ordering.
+
+@opindex no-delay-directory-restore
+@item --no-delay-directory-restore
+Cancel the effect of the previous @option{--delay-directory-restore}.
+Use this option if you have used @option{--delay-directory-restore} in
+@env{TAR_OPTIONS} variable (@pxref{TAR_OPTIONS}) and wish to
+temporarily disable it.
+@end table
-@node Writing to Standard Output, remove files, Setting Access Permissions, Writing
+@node Writing to Standard Output
@unnumberedsubsubsec Writing to Standard Output
+@cindex Writing extracted files to standard output
+@cindex Standard output, writing extracted files to
To write the extracted files to the standard output, instead of
-creating the files on the file system, use @value{op-to-stdout} in
-conjunction with @value{op-extract}. This option is useful if you are
+creating the files on the file system, use @option{--to-stdout} (@option{-O}) in
+conjunction with @option{--extract} (@option{--get}, @option{-x}). This option is useful if you are
extracting files to send them through a pipe, and do not need to
preserve them in the file system. If you extract multiple members,
they appear on standard output concatenated, in the order they are
found in the archive.
-@table @kbd
+@table @option
+@opindex to-stdout
@item --to-stdout
@itemx -O
-Writes files to the standard output. Used in conjunction with
-@value{op-extract}. Extract files to standard output. When this option
-is used, instead of creating the files specified, @code{tar} writes
+Writes files to the standard output. Use only in conjunction with
+@option{--extract} (@option{--get}, @option{-x}). When this option is
+used, instead of creating the files specified, @command{tar} writes
the contents of the files extracted to its standard output. This may
be useful if you are only extracting the files in order to send them
-through a pipe. This option is meaningless with @value{op-list}.
+through a pipe. This option is meaningless with @option{--list}
+(@option{-t}).
+@end table
+
+This can be useful, for example, if you have a tar archive containing
+a big file and don't want to store the file on disk before processing
+it. You can use a command like this:
+
+@smallexample
+tar -xOzf foo.tgz bigfile | process
+@end smallexample
+
+or even like this if you want to process the concatenation of the files:
+
+@smallexample
+tar -xOzf foo.tgz bigfile1 bigfile2 | process
+@end smallexample
+
+Hovewer, @option{--to-command} may be more convenient for use with
+multiple files. See the next section.
+
+@node Writing to an External Program
+@unnumberedsubsubsec Writing to an External Program
+
+You can instruct @command{tar} to send the contents of each extracted
+file to the standard input of an external program:
+
+@table @option
+@opindex to-program
+@item --to-program=@var{command}
+Extract files and pipe their contents to the standard input of
+@var{command}. When this option is used, instead of creating the
+files specified, @command{tar} invokes @var{command} and pipes the
+contents of the files to its standard output. @var{Command} may
+contain command line arguments. The program is executed via
+@code{sh -c}. Notice, that @var{command} is executed once for each regular file
+extracted. Non-regular files (directories, etc.) are ignored when this
+option is used.
@end table
-@FIXME{Why would you want to do such a thing, how are files separated on
-the standard output? is this useful with more that one file? Are
-pipes the real reason?}
+The command can obtain the information about the file it processes
+from the following environment variables:
+
+@table @var
+@vrindex TAR_FILETYPE, to-command environment
+@item TAR_FILETYPE
+Type of the file. It is a single letter with the following meaning:
+
+@multitable @columnfractions 0.10 0.90
+@item f @tab Regular file
+@item d @tab Directory
+@item l @tab Symbolic link
+@item h @tab Hard link
+@item b @tab Block device
+@item c @tab Character device
+@end multitable
+
+Currently only regular files are supported.
+
+@vrindex TAR_MODE, to-command environment
+@item TAR_MODE
+File mode, an octal number.
+
+@vrindex TAR_FILENAME, to-command environment
+@item TAR_FILENAME
+The name of the file.
+
+@vrindex TAR_REALNAME, to-command environment
+@item TAR_REALNAME
+Name of the file as stored in the archive.
+
+@vrindex TAR_UNAME, to-command environment
+@item TAR_UNAME
+Name of the file owner.
+
+@vrindex TAR_GNAME, to-command environment
+@item TAR_GNAME
+Name of the file owner group.
+
+@vrindex TAR_ATIME, to-command environment
+@item TAR_ATIME
+Time of last access. It is a decimal number, representing seconds
+since the epoch. If the archive provides times with nanosecond
+precision, the nanoseconds are appended to the timestamp after a
+decimal point.
+
+@vrindex TAR_MTIME, to-command environment
+@item TAR_MTIME
+Time of last modification.
+
+@vrindex TAR_CTIME, to-command environment
+@item TAR_CTIME
+Time of last status change.
+
+@vrindex TAR_SIZE, to-command environment
+@item TAR_SIZE
+Size of the file.
+
+@vrindex TAR_UID, to-command environment
+@item TAR_UID
+UID of the file owner.
+
+@vrindex TAR_GID, to-command environment
+@item TAR_GID
+GID of the file owner.
+@end table
+
+In addition to these variables, @env{TAR_VERSION} contains the
+@GNUTAR{} version number.
+
+If @var{command} exits with a non-0 status, @command{tar} will print
+an error message similar to the following:
+
+@smallexample
+tar: 2345: Child returned status 1
+@end smallexample
+
+Here, @samp{2345} is the PID of the finished process.
+
+If this behavior is not wanted, use @option{--ignore-command-error}:
-@node remove files, , Writing to Standard Output, Writing
+@table @option
+@opindex ignore-command-error
+@item --ignore-command-error
+Ignore exit codes of subprocesses. Notice that if the program
+exits on signal or otherwise terminates abnormally, the error message
+will be printed even if this option is used.
+
+@opindex no-ignore-command-error
+@item --no-ignore-command-error
+Cancel the effect of any previous @option{--ignore-command-error}
+option. This option is useful if you have set
+@option{--ignore-command-error} in @env{TAR_OPTIONS}
+(@pxref{TAR_OPTIONS}) and wish to temporarily cancel it.
+@end table
+
+@node remove files
@unnumberedsubsubsec Removing Files
@FIXME{the various macros in the front of the manual think that this
option goes in this section. i have no idea; i only know it's nowhere
else in the book...}
-@table @kbd
+@table @option
+@opindex remove-files
@item --remove-files
Remove files after adding them to the archive.
@end table
-@node Scarce, , Writing, extract options
+@node Scarce
@subsection Coping with Scarce Resources
-@cindex Middle of the archive, starting in the
-@cindex Running out of space during extraction
-@cindex Disk space, running out of
-@cindex Space on the disk, recovering from lack of
@UNREVISED
+@cindex Small memory
+@cindex Running out of space
+
@menu
* Starting File::
* Same Order::
@end menu
-@node Starting File, Same Order, Scarce, Scarce
+@node Starting File
@unnumberedsubsubsec Starting File
-@table @kbd
+@table @option
+@opindex starting-file
@item --starting-file=@var{name}
@itemx -K @var{name}
Starts an operation in the middle of an archive. Use in conjunction
-with @value{op-extract} or @value{op-list}.
+with @option{--extract} (@option{--get}, @option{-x}) or @option{--list} (@option{-t}).
@end table
+@cindex Middle of the archive, starting in the
If a previous attempt to extract files failed due to lack of disk
-space, you can use @value{op-starting-file} to start extracting only
-after member @var{name} of the archive. This assumes, of course, that
-there is now free space, or that you are now extracting into a
-different file system. (You could also choose to suspend @code{tar},
-remove unnecessary files from the file system, and then restart the
-same @code{tar} operation. In this case, @value{op-starting-file} is
-not necessary. @value{xref-incremental}, @value{xref-interactive},
-and @value{ref-exclude}.)
-
-@node Same Order, , Starting File, Scarce
+space, you can use @option{--starting-file=@var{name}} (@option{-K
+@var{name}}) to start extracting only after member @var{name} of the
+archive. This assumes, of course, that there is now free space, or
+that you are now extracting into a different file system. (You could
+also choose to suspend @command{tar}, remove unnecessary files from
+the file system, and then restart the same @command{tar} operation.
+In this case, @option{--starting-file} is not necessary.
+@xref{Incremental Dumps}, @xref{interactive}, and @ref{exclude}.)
+
+@node Same Order
@unnumberedsubsubsec Same Order
-@table @kbd
+@table @option
+@cindex Large lists of file names on small machines
+@opindex same-order
+@opindex preserve-order
@item --same-order
@itemx --preserve-order
@itemx -s
To process large lists of file names on machines with small amounts of
-memory. Use in conjunction with @value{op-compare},
-@value{op-list}
-or @value{op-extract}.
+memory. Use in conjunction with @option{--compare} (@option{--diff},
+@option{-d}), @option{--list} (@option{-t}) or @option{--extract}
+(@option{--get}, @option{-x}).
@end table
-@FIXME{we don't need/want --preserve to exist any more (from melissa:
-ie, don't want that *version* of the option to exist, or don't want
-the option to exist in either version?}
-
-@FIXME{i think this explanation is lacking.}
-
-The @value{op-same-order} option tells @code{tar} that the list of file
+The @option{--same-order} (@option{--preserve-order}, @option{-s}) option tells @command{tar} that the list of file
names to be listed or extracted is sorted in the same order as the
files in the archive. This allows a large list of names to be used,
even on a small machine that would not otherwise be able to hold all
This option is probably never needed on modern computer systems.
-@node backup, Applications, extract options, operations
+@node backup
@section Backup options
@cindex backup options
-GNU @code{tar} offers options for making backups of files before writing
-new versions. These options control the details of these backups.
-They may apply to the archive itself before it is created or rewritten,
-as well as individual extracted members. Other GNU programs (@code{cp},
-@code{install}, @code{ln}, and @code{mv}, for example) offer similar
-options.
+@GNUTAR{} offers options for making backups of files
+before writing new versions. These options control the details of
+these backups. They may apply to the archive itself before it is
+created or rewritten, as well as individual extracted members. Other
+@acronym{GNU} programs (@command{cp}, @command{install}, @command{ln},
+and @command{mv}, for example) offer similar options.
Backup options may prove unexpectedly useful when extracting archives
containing many members having identical name, or when extracting archives
file are kept.
@table @samp
-
-@item --backup
-@opindex --backup
-@cindex backups, making
-Make backups of files that are about to be overwritten or removed.
+@item --backup[=@var{method}]
+@opindex backup
+@vindex VERSION_CONTROL
+@cindex backups
+Back up files that are about to be overwritten or removed.
Without this option, the original versions are destroyed.
-@item --suffix=@var{suffix}
-@opindex --suffix
-@cindex backup suffix
-@vindex SIMPLE_BACKUP_SUFFIX
-Append @var{suffix} to each backup file made with @samp{-b}. If this
-option is not specified, the value of the @code{SIMPLE_BACKUP_SUFFIX}
-environment variable is used. And if @code{SIMPLE_BACKUP_SUFFIX} is not
-set, the default is @samp{~}, just as in Emacs.
-
-@item --version-control=@var{method}
-@opindex --version-control
-@vindex VERSION_CONTROL
-@cindex backup files, type made
-Use @var{method} to determine the type of backups made with @value{op-backup}.
-If this option is not specified, the value of the @code{VERSION_CONTROL}
-environment variable is used. And if @code{VERSION_CONTROL} is not set,
-the default backup type is @samp{existing}.
+Use @var{method} to determine the type of backups made.
+If @var{method} is not specified, use the value of the @env{VERSION_CONTROL}
+environment variable. And if @env{VERSION_CONTROL} is not set,
+use the @samp{existing} method.
@vindex version-control @r{Emacs variable}
This option corresponds to the Emacs variable @samp{version-control};
-the same values for @var{method} are accepted as in Emacs. This options
-also more descriptive name. The valid @var{method}s (unique
-abbreviations are accepted):
+the same values for @var{method} are accepted as in Emacs. This option
+also allows more descriptive names. The valid @var{method}s are:
@table @samp
@item t
@itemx numbered
-@opindex numbered @r{backup method}
+@cindex numbered @r{backup method}
Always make numbered backups.
@item nil
@itemx existing
-@opindex existing @r{backup method}
+@cindex existing @r{backup method}
Make numbered backups of files that already have them, simple backups
of the others.
@item never
@itemx simple
-@opindex simple @r{backup method}
+@cindex simple @r{backup method}
Always make simple backups.
@end table
+@item --suffix=@var{suffix}
+@opindex suffix
+@cindex backup suffix
+@vindex SIMPLE_BACKUP_SUFFIX
+Append @var{suffix} to each backup file made with @option{--backup}. If this
+option is not specified, the value of the @env{SIMPLE_BACKUP_SUFFIX}
+environment variable is used. And if @env{SIMPLE_BACKUP_SUFFIX} is not
+set, the default is @samp{~}, just as in Emacs.
+
@end table
-Some people express the desire to @emph{always} use the @var{op-backup}
+Some people express the desire to @emph{always} use the @option{--backup}
option, by defining some kind of alias or script. This is not as easy
-as one may thing, due to the fact old style options should appear first
-and consume arguments a bit inpredictably for an alias or script. But,
+as one may think, due to the fact that old style options should appear first
+and consume arguments a bit unpredictably for an alias or script. But,
if you are ready to give up using old style options, you may resort to
using something like (a Bourne shell function here):
-@example
+@smallexample
tar () @{ /usr/local/bin/tar --backup $*; @}
-@end example
+@end smallexample
-@node Applications, looking ahead, backup, operations
-@section Notable @code{tar} Usages
+@node Applications
+@section Notable @command{tar} Usages
@UNREVISED
@FIXME{Using Unix file linking capability to recreate directory
structures---linking files into one subdirectory and then
-@code{tar}ring that directory.}
+@command{tar}ring that directory.}
@FIXME{Nice hairy example using absolute-names, newer, etc.}
computer system, transfer the archive to another system, and extract
the contents there. The basic transfer medium might be magnetic tape,
Internet FTP, or even electronic mail (though you must encode the
-archive with @code{uuencode} in order to transport it properly by
+archive with @command{uuencode} in order to transport it properly by
mail). Both machines do not have to use the same operating system, as
-long as they both support the @code{tar} program.
+long as they both support the @command{tar} program.
For example, here is how you might copy a directory's contents from
one disk to another, while preserving the dates, modes, owners and
medium is a @dfn{pipe}, which is one a Unix redirection mechanism:
@smallexample
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
@end smallexample
@noindent
The command also works using short option forms:
-@FIXME{The following using standard input/output correct??}
@smallexample
-$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
+$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
@end smallexample
@noindent
-This is one of the easiest methods to transfer a @code{tar} archive.
+This is one of the easiest methods to transfer a @command{tar} archive.
-@node looking ahead, , Applications, operations
+@node looking ahead
@section Looking Ahead: The Rest of this Manual
You have now seen how to use all eight of the operations available to
-@code{tar}, and a number of the possible options. The next chapter
+@command{tar}, and a number of the possible options. The next chapter
explains how to choose and change file and archive names, how to use
files to store names of other files which you can then call as
-arguments to @code{tar} (this can help you save time if you expect to
-archive the same list of files a number of times), and how to
+arguments to @command{tar} (this can help you save time if you expect to
+archive the same list of files a number of times), and so forth.
@FIXME{in case it's not obvious, i'm making this up in some sense
-based on my imited memory of what the next chapter *really* does. i
+based on my limited memory of what the next chapter *really* does. i
just wanted to flesh out this final section a little bit so i'd
-remember to sitck it in here. :-)}
+remember to stick it in here. :-)}
If there are too many files to conveniently list on the command line,
-you can list the names in a file, and @code{tar} will read that file.
-@value{xref-files-from}.
+you can list the names in a file, and @command{tar} will read that file.
+@xref{files}.
-There are various ways of causing @code{tar} to skip over some files,
+There are various ways of causing @command{tar} to skip over some files,
and not archive them. @xref{Choosing}.
-@node Backups, Choosing, operations, Top
+@node Backups
@chapter Performing Backups and Restoring Files
@UNREVISED
-GNU @code{tar} is distributed along with the scripts which the Free
-Software Foundation uses for performing backups. There is no corresponding
-scripts available yet for doing restoration of files. Even if there is
-a good chance those scripts may be satisfying to you, they are not the
-only scripts or methods available for doing backups and restore. You may
-well create your own, or use more sophisticated packages dedicated to
-that purpose.
+@GNUTAR{} is distributed along with the scripts
+which the Free Software Foundation uses for performing backups. There
+is no corresponding scripts available yet for doing restoration of
+files. Even if there is a good chance those scripts may be satisfying
+to you, they are not the only scripts or methods available for doing
+backups and restore. You may well create your own, or use more
+sophisticated packages dedicated to that purpose.
Some users are enthusiastic about @code{Amanda} (The Advanced Maryland
Automatic Network Disk Archiver), a backup system developed by James
da Silva @file{jds@@cs.umd.edu} and available on many Unix systems.
This is free software, and it is available at these places:
-@example
+@smallexample
http://www.cs.umd.edu/projects/amanda/amanda.html
ftp://ftp.cs.umd.edu/pub/amanda
-@end example
+@end smallexample
-@ifclear PUBLISH
+@FIXME{
Here is a possible plan for a future documentation about the backuping
-scripts which are provided within the GNU @code{tar} distribution.
+scripts which are provided within the @GNUTAR{}
+distribution.
-@example
-.* dumps
-. + what are dumps
-
-. + different levels of dumps
-. - full dump = dump everything
-. - level 1, level 2 dumps etc, -
- A level n dump dumps everything changed since the last level
- n-1 dump (?)
-
-. + how to use scripts for dumps (ie, the concept)
-. - scripts to run after editing backup specs (details)
-
-. + Backup Specs, what is it.
-. - how to customize
-. - actual text of script [/sp/dump/backup-specs]
-
-. + Problems
-. - rsh doesn't work
-. - rtape isn't installed
-. - (others?)
-
-. + the --incremental option of tar
-
-. + tapes
-. - write protection
-. - types of media
-. : different sizes and types, useful for different things
-. - files and tape marks
+@itemize @bullet
+@item dumps
+ @itemize @minus
+ @item what are dumps
+ @item different levels of dumps
+ @itemize +
+ @item full dump = dump everything
+ @item level 1, level 2 dumps etc
+ A level @var{n} dump dumps everything changed since the last level
+ @var{n}-1 dump (?)
+ @end itemize
+ @item how to use scripts for dumps (ie, the concept)
+ @itemize +
+ @item scripts to run after editing backup specs (details)
+ @end itemize
+ @item Backup Specs, what is it.
+ @itemize +
+ @item how to customize
+ @item actual text of script [/sp/dump/backup-specs]
+ @end itemize
+ @item Problems
+ @itemize +
+ @item rsh doesn't work
+ @item rtape isn't installed
+ @item (others?)
+ @end itemize
+ @item the @option{--incremental} option of tar
+ @item tapes
+ @itemize +
+ @item write protection
+ @item types of media, different sizes and types, useful for different things
+ @item files and tape marks
one tape mark between files, two at end.
-. - positioning the tape
+ @item positioning the tape
MT writes two at end of write,
- backspaces over one when writing again.
-@end example
-
-@end ifclear
+ backspaces over one when writing again.
+ @end itemize
+ @end itemize
+@end itemize
+}
-This chapter documents both the provided FSF scripts and @code{tar}
+This chapter documents both the provided shell scripts and @command{tar}
options which are more specific to usage as a backup tool.
To @dfn{back up} a file system means to create archives that contain
all the files in that file system. Those archives can then be used to
restore any or all of those files (for instance if a disk crashes or a
-file is accidently deleted). File system @dfn{backups} are also
+file is accidentally deleted). File system @dfn{backups} are also
called @dfn{dumps}.
@menu
-* Full Dumps:: Using @code{tar} to Perform Full Dumps
-* Inc Dumps:: Using @code{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Full Dumps:: Using @command{tar} to Perform Full Dumps
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
* Scripted Restoration:: Using the Restore Script
@end menu
-@node Full Dumps, Inc Dumps, Backups, Backups
-@section Using @code{tar} to Perform Full Dumps
+@node Full Dumps
+@section Using @command{tar} to Perform Full Dumps
@UNREVISED
@cindex full dumps
@cindex corrupted archives
Full dumps should only be made when no other people or programs
-are modifying files in the filesystem. If files are modified while
-@code{tar} is making the backup, they may not be stored properly in
+are modifying files in the file system. If files are modified while
+@command{tar} is making the backup, they may not be stored properly in
the archive, in which case you won't be able to restore them if you
have to. (Files not being modified are written with no trouble, and do
not corrupt the entire archive.)
-You will want to use the @value{op-label} option to give the archive a
+You will want to use the @option{--label=@var{archive-label}}
+(@option{-V @var{archive-label}}) option to give the archive a
volume label, so you can tell what this archive is even if the label
falls off the tape, or anything like that.
-Unless the filesystem you are dumping is guaranteed to fit on
-one volume, you will need to use the @value{op-multi-volume} option.
+Unless the file system you are dumping is guaranteed to fit on
+one volume, you will need to use the @option{--multi-volume} (@option{-M}) option.
Make sure you have enough tapes on hand to complete the backup.
-If you want to dump each filesystem separately you will need to use
-the @value{op-one-file-system} option to prevent @code{tar} from crossing
-filesystem boundaries when storing (sub)directories.
-
-The @value{op-incremental} option is not needed, since this is a complete
-copy of everything in the filesystem, and a full restore from this
-backup would only be done onto a completely empty disk.
-
-Unless you are in a hurry, and trust the @code{tar} program (and your
-tapes), it is a good idea to use the @value{op-verify} option, to make
-sure your files really made it onto the dump properly. This will
-also detect cases where the file was modified while (or just after)
-it was being archived. Not all media (notably cartridge tapes) are
-capable of being verified, unfortunately.
-
-@value{op-listed-incremental} take a file name argument always. If the
-file doesn't exist, run a level zero dump, creating the file. If the
-file exists, uses that file to see what has changed.
-
-@value{op-incremental} @FIXME{look it up}
-
-@value{op-incremental} handle old GNU-format incremental backup.
-
-This option should only be used when creating an incremental backup of
-a filesystem. When the @value{op-incremental} option is used, @code{tar}
-writes, at the beginning of the archive, an entry for each of the
-directories that will be operated on. The entry for a directory
-includes a list of all the files in the directory at the time the
-dump was done, and a flag for each file indicating whether the file
-is going to be put in the archive. This information is used when
-doing a complete incremental restore.
-
-Note that this option causes @code{tar} to create a non-standard
-archive that may not be readable by non-GNU versions of the @code{tar}
-program.
-
-The @value{op-incremental} option means the archive is an incremental
-backup. Its meaning depends on the command that it modifies.
-
-If the @value{op-incremental} option is used with @value{op-list}, @code{tar}
-will list, for each directory in the archive, the list of files in
-that directory at the time the archive was created. This information
-is put out in a format that is not easy for humans to read, but which
-is unambiguous for a program: each file name is preceded by either a
-@samp{Y} if the file is present in the archive, an @samp{N} if the
-file is not included in the archive, or a @samp{D} if the file is
-a directory (and is included in the archive). Each file name is
-terminated by a null character. The last file is followed by an
-additional null and a newline to indicate the end of the data.
-
-If the @value{op-incremental} option is used with @value{op-extract}, then
-when the entry for a directory is found, all files that currently
-exist in that directory but are not listed in the archive @emph{are
-deleted from the directory}.
-
-This behavior is convenient when you are restoring a damaged file
-system from a succession of incremental backups: it restores the
-entire state of the file system to that which obtained when the backup
-was made. If you don't use @value{op-incremental}, the file system will
-probably fill up with files that shouldn't exist any more.
-
-@value{op-listed-incremental} handle new GNU-format incremental backup.
-This option handles new GNU-format incremental backup. It has much the
-same effect as @value{op-incremental}, but also the time when the dump
-is done and the list of directories dumped is written to the given
-@var{file}. When restoring, only files newer than the saved time are
-restored, and the direcotyr list is used to speed up operations.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @code{tar} to
-use the file @var{file}, which contains information about the state
-of the filesystem at the time of the last backup, to decide which
-files to include in the archive being created. That file will then
-be updated by @code{tar}. If the file @var{file} does not exist when
-this option is specified, @code{tar} will create it, and include all
-appropriate files in the archive.
-
-The file, which is archive independent, contains the date it was last
-modified and a list of devices, inode numbers and directory names.
-@code{tar} will archive files with newer mod dates or inode change
-times, and directories with an unchanged inode number and device but
-a changed directory name. The file is updated after the files to
-be archived are determined, but before the new archive is actually
-created.
-
-GNU @code{tar} actually writes the file twice: once before the data
-and written, and once after.
-
-@node Inc Dumps, incremental and listed-incremental, Full Dumps, Backups
-@section Using @code{tar} to Perform Incremental Dumps
-@UNREVISED
+If you want to dump each file system separately you will need to use
+the @option{--one-file-system} (@option{-l}) option to prevent
+@command{tar} from crossing file system boundaries when storing
+(sub)directories.
+
+The @option{--incremental} (@option{-G}) (@pxref{Incremental Dumps})
+option is not needed, since this is a complete copy of everything in
+the file system, and a full restore from this backup would only be
+done onto a completely
+empty disk.
+
+Unless you are in a hurry, and trust the @command{tar} program (and your
+tapes), it is a good idea to use the @option{--verify} (@option{-W})
+option, to make sure your files really made it onto the dump properly.
+This will also detect cases where the file was modified while (or just
+after) it was being archived. Not all media (notably cartridge tapes)
+are capable of being verified, unfortunately.
+
+@node Incremental Dumps
+@section Using @command{tar} to Perform Incremental Dumps
+
+@dfn{Incremental backup} is a special form of @GNUTAR{} archive that
+stores additional metadata so that exact state of the file system
+can be restored when extracting the archive.
+
+@GNUTAR{} currently offers two options for handling incremental
+backups: @option{--listed-incremental=@var{snapshot-file}} (@option{-g
+@var{snapshot-file}}) and @option{--incremental} (@option{-G}).
+
+@opindex listed-incremental
+The option @option{--listed-incremental} instructs tar to operate on
+an incremental archive with additional metadata stored in a standalone
+file, called a @dfn{snapshot file}. The purpose of this file is to help
+determine which files have been changed, added or deleted since the
+last backup, so that the next incremental backup will contain only
+modified files. The name of the snapshot file is given as an argument
+to the option:
+
+@table @option
+@item --listed-incremental=@var{file}
+@itemx -g @var{file}
+ Handle incremental backups with snapshot data in @var{file}.
+@end table
-@cindex incremental dumps
-@cindex dumps, incremental
+To create an incremental backup, you would use
+@option{--listed-incremental} together with @option{--create}
+(@pxref{create}). For example:
-Performing incremental dumps is similar to performing full dumps,
-although a few more options will usually be needed.
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.1.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+@end smallexample
-You will need to use the @samp{-N @var{date}} option to tell @code{tar}
-to only store files that have been modified since @var{date}.
-@var{date} should be the date and time of the last full/incremental
-dump.
+This will create in @file{archive.1.tar} an incremental backup of
+the @file{/usr} file system, storing additional metadata in the file
+@file{/var/log/usr.snar}. If this file does not exist, it will be
+created. The created archive will then be a @dfn{level 0 backup};
+please see the next section for more on backup levels.
-A standard scheme is to do a @emph{monthly} (full) dump once a month,
-a @emph{weekly} dump once a week of everything since the last monthly
-and a @emph{daily} every day of everything since the last (weekly or
-monthly) dump.
-
-Here is a copy of the script used to dump the filesystems of the
-machines here at the Free Software Foundation. This script is run via
-@code{cron} late at night when people are least likely to be using the
-machines. This script dumps several filesystems from several machines
-at once (via NFS). The operator is responsible for ensuring that all
-the machines will be up at the time the dump happens. If a machine is
-not running, its files will not be dumped, and the next day's
-incremental dump will @emph{not} store files that would have gone onto
-that dump.
-
-@example
-#!/bin/csh
-# Dump thingie
-set now = `date`
-set then = `cat date.nfs.dump`
-/u/hack/bin/tar -c -G -v\
- -f /dev/rtu20\
- -b 126\
- -N "$then"\
- -V "Dump from $then to $now"\
- /alpha-bits/gp\
- /gnu/hack\
- /hobbes/u\
- /spiff/u\
- /sugar-bombs/u
-echo $now > date.nfs.dump
-mt -f /dev/rtu20 rew
-@end example
-
-Output from this script is stored in a file, for the operator to
-read later.
-
-This script uses the file @file{date.nfs.dump} to store the date/time
-of the last dump.
-
-Since this is a streaming tape drive, no attempt to verify the archive
-is done. This is also why the high blocking factor (126) is used.
-The tape drive must also be rewound by the @code{mt} command after
-the dump is made.
-
-@node incremental and listed-incremental, Backup Levels, Inc Dumps, Backups
-@section The Incremental Options
-@UNREVISED
+Otherwise, if the file @file{/var/log/usr.snar} exists, it
+determines which files are modified. In this case only these files will be
+stored in the archive. Suppose, for example, that after running the
+above command, you delete file @file{/usr/doc/old} and create
+directory @file{/usr/local/db} with the following contents:
+
+@smallexample
+$ @kbd{ls /usr/local/db}
+/usr/local/db/data
+/usr/local/db/index
+@end smallexample
-@value{op-incremental} is used in conjunction with @value{op-create},
-@value{op-extract} or @value{op-list} when backing up and restoring file
-systems. An archive cannot be extracted or listed with the
-@value{op-incremental} option specified unless it was created with the
-option specified. This option should only be used by a script, not by
-the user, and is usually disregarded in favor of
-@value{op-listed-incremental}, which is described below.
-
-@value{op-incremental} in conjunction with @value{op-create} causes
-@code{tar} to write, at the beginning of the archive, an entry for
-each of the directories that will be archived. The entry for a
-directory includes a list of all the files in the directory at the
-time the archive was created and a flag for each file indicating
-whether or not the file is going to be put in the archive.
-
-Note that this option causes @code{tar} to create a non-standard
-archive that may not be readable by non-GNU versions of the @code{tar}
-program.
-
-@value{op-incremental} in conjunction with @value{op-extract} causes
-@code{tar} to read the lists of directory contents previously stored
-in the archive, @emph{delete} files in the file system that did not
-exist in their directories when the archive was created, and then
-extract the files in the archive.
-
-This behavior is convenient when restoring a damaged file system from
-a succession of incremental backups: it restores the entire state of
-the file system to that which obtained when the backup was made. If
-@value{op-incremental} isn't specified, the file system will probably
-fill up with files that shouldn't exist any more.
-
-@value{op-incremental} in conjunction with @value{op-list}, causes
-@code{tar} to print, for each directory in the archive, the list of
-files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is followed
-by an additional null and a newline to indicate the end of the data.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @code{tar}
-to use the file @var{snapshot-file}, which contains information about
-the state of the file system at the time of the last backup, to decide
-which files to include in the archive being created. That file will
-then be updated by @code{tar}. If the file @var{file} does not exist
-when this option is specified, @code{tar} will create it, and include
-all appropriate files in the archive.
-
-The file @var{file}, which is archive independent, contains the date
-it was last modified and a list of devices, inode numbers and
-directory names. @code{tar} will archive files with newer mod dates
-or inode change times, and directories with an unchanged inode number
-and device but a changed directory name. The file is updated after
-the files to be archived are determined, but before the new archive is
-actually created.
-
-Despite it should be obvious that a device has a non-volatile value, NFS
-devices have non-dependable values when an automounter gets in the picture.
-This led to a great deal of spurious redumping in incremental dumps,
-so it is somewhat useless to compare two NFS devices numbers over time.
-So @code{tar} now considers all NFS devices as being equal when it comes
-to comparing directories; this is fairly gross, but there does not seem
+Some time later you create another incremental backup. You will
+then see:
+
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+tar: usr/local/db: Directory is new
+usr/local/db/
+usr/local/db/data
+usr/local/db/index
+@end smallexample
+
+@noindent
+The created archive @file{archive.2.tar} will contain only these
+three members. This archive is called a @dfn{level 1 backup}. Notice
+that @file{/var/log/usr.snar} will be updated with the new data, so if
+you plan to create more @samp{level 1} backups, it is necessary to
+create a working copy of the snapshot file before running
+@command{tar}. The above example will then be modified as follows:
+
+@smallexample
+$ @kbd{cp /var/log/usr.snar /var/log/usr.snar-1}
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar-1 \
+ /usr}
+@end smallexample
+
+Incremental dumps depend crucially on time stamps, so the results are
+unreliable if you modify a file's time stamps during dumping (e.g.,
+with the @option{--atime-preserve=replace} option), or if you set the clock
+backwards.
+
+Metadata stored in snapshot files include device numbers, which,
+obviously is supposed to be a non-volatile value. However, it turns
+out that NFS devices have undependable values when an automounter
+gets in the picture. This can lead to a great deal of spurious
+redumping in incremental dumps, so it is somewhat useless to compare
+two NFS devices numbers over time. The solution implemented currently
+is to considers all NFS devices as being equal when it comes to
+comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
-@FIXME{this section needs to be written}
+Note that incremental archives use @command{tar} extensions and may
+not be readable by non-@acronym{GNU} versions of the @command{tar} program.
+
+@opindex listed-incremental, using with @option{--extract}
+@opindex extract, using with @option{--listed-incremental}
+To extract from the incremental dumps, use
+@option{--listed-incremental} together with @option{--extract}
+option (@pxref{extracting files}). In this case, @command{tar} does
+not need to access snapshot file, since all the data necessary for
+extraction are stored in the archive itself. So, when extracting, you
+can give whatever argument to @option{--listed-incremental}, the usual
+practice is to use @option{--listed-incremental=/dev/null}.
+Alternatively, you can use @option{--incremental}, which needs no
+arguments. In general, @option{--incremental} (@option{-G}) can be
+used as a shortcut for @option{--listed-incremental} when listing or
+extracting incremental backups (for more information, regarding this
+option, @pxref{incremental-op}).
+
+When extracting from the incremental backup @GNUTAR{} attempts to
+restore the exact state the file system had when the archive was
+created. In particular, it will @emph{delete} those files in the file
+system that did not exist in their directories when the archive was
+created. If you have created several levels of incremental files,
+then in order to restore the exact contents the file system had when
+the last level was created, you will need to restore from all backups
+in turn. Continuing our example, to restore the state of @file{/usr}
+file system, one would do@footnote{Notice, that since both archives
+were created withouth @option{-P} option (@pxref{absolute}), these
+commands should be run from the root file system.}:
+
+@smallexample
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.1.tar}
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.2.tar}
+@end smallexample
+
+To list the contents of an incremental archive, use @option{--list}
+(@pxref{list}), as usual. To obtain more information about the
+archive, use @option{--listed-incremental} or @option{--incremental}
+combined with two @option{--verbose} options@footnote{Two
+@option{--verbose} options were selected to avoid breaking usual
+verbose listing output (@option{--list --verbose}) when using in
+scripts.
+
+@opindex incremental, using with @option{--list}
+@opindex listed-incremental, using with @option{--list}
+@opindex list, using with @option{--incremental}
+@opindex list, using with @option{--listed-incremental}
+Versions of @GNUTAR{} up to 1.15.1 used to dump verbatim binary
+contents of the DUMPDIR header (with terminating nulls) when
+@option{--incremental} or @option{--listed-incremental} option was
+given, no matter what the verbosity level. This behavior, and,
+especially, the binary output it produced were considered incovenient
+and were changed in version 1.16}:
+
+@smallexample
+@kbd{tar --list --incremental --verbose --verbose archive.tar}
+@end smallexample
+
+This command will print, for each directory in the archive, the list
+of files in that directory at the time the archive was created. This
+information is put out in a format which is both human-readable and
+unambiguous for a program: each file name is printed as
+
+@smallexample
+@var{x} @var{file}
+@end smallexample
-@node Backup Levels, Backup Parameters, incremental and listed-incremental, Backups
+@noindent
+where @var{x} is a letter describing the status of the file: @samp{Y}
+if the file is present in the archive, @samp{N} if the file is not
+included in the archive, or a @samp{D} if the file is a directory (and
+is included in the archive).@FIXME-xref{dumpdir format}. Each such
+line is terminated by a newline character. The last line is followed
+by an additional newline to indicate the end of the data.
+
+@anchor{incremental-op}The option @option{--incremental} (@option{-G})
+gives the same behavior as @option{--listed-incremental} when used
+with @option{--list} and @option{--extract} options. When used with
+@option{--create} option, it creates an incremental archive without
+creating snapshot file. Thus, it is impossible to create several
+levels of incremental backups with @option{--incremental} option.
+
+@node Backup Levels
@section Levels of Backups
-@UNREVISED
An archive containing all the files in the file system is called a
@dfn{full backup} or @dfn{full dump}. You could insure your data by
are daily re-archived.
It is more efficient to do a full dump only occasionally. To back up
-files between full dumps, you can a incremental dump. A @dfn{level
+files between full dumps, you can use @dfn{incremental dumps}. A @dfn{level
one} dump archives all the files that have changed since the last full
dump.
files changed or created since the last daily backup. (Doing dumps
more than once a day is usually not worth the trouble).
-GNU @code{tar} comes with scripts you can use to do full and level-one
-dumps. Using scripts (shell programs) to perform backups and
-restoration is a convenient and reliable alternative to typing out
-file name lists and @code{tar} commands by hand.
+@GNUTAR{} comes with scripts you can use to do full
+and level-one (actually, even level-two and so on) dumps. Using
+scripts (shell programs) to perform backups and restoration is a
+convenient and reliable alternative to typing out file name lists
+and @command{tar} commands by hand.
Before you use these scripts, you need to edit the file
@file{backup-specs}, which specifies parameters used by the backup
-scripts and by the restore script. @FIXME{There is no such restore
-script!}. @FIXME-xref{Script Syntax}. Once the backup parameters
-are set, you can perform backups or restoration by running the
-appropriate script.
-
-The name of the restore script is @code{restore}. @FIXME{There is
-no such restore script!}. The names of the level one and full backup
-scripts are, respectively, @code{level-1} and @code{level-0}.
-The @code{level-0} script also exists under the name @code{weekly}, and
-the @code{level-1} under the name @code{daily}---these additional names
-can be changed according to your backup schedule. @FIXME-xref{Scripted
-Restoration}, for more information on running the restoration script.
-@FIXME-xref{Scripted Backups}, for more information on running the
-backup scripts.
-
-@emph{Please Note:} The backup scripts and the restoration scripts are
+scripts and by the restore script. This file is usually located
+in @file{/etc/backup} directory. @xref{Backup Parameters}, for its
+detailed description. Once the backup parameters are set, you can
+perform backups or restoration by running the appropriate script.
+
+The name of the backup script is @code{backup}. The name of the
+restore script is @code{restore}. The following sections describe
+their use in detail.
+
+@emph{Please Note:} The backup and restoration scripts are
designed to be used together. While it is possible to restore files by
hand from an archive which was created using a backup script, and to create
an archive by hand which could then be extracted using the restore script,
-it is easier to use the scripts. @FIXME{There is no such restore script!}.
-@value{xref-incremental}, and @value{xref-listed-incremental},
-before making such an attempt.
-
-@FIXME{shorten node names}
+it is easier to use the scripts. @xref{Incremental Dumps}, before
+making such an attempt.
-@node Backup Parameters, Scripted Backups, Backup Levels, Backups
+@node Backup Parameters
@section Setting Parameters for Backups and Restoration
-@UNREVISED
The file @file{backup-specs} specifies backup parameters for the
-backup and restoration scripts provided with @code{tar}. You must
+backup and restoration scripts provided with @command{tar}. You must
edit @file{backup-specs} to fit your system configuration and schedule
before using these scripts.
-@FIXME{This about backup scripts needs to be written: BS is a shell
-script .... thus ... @file{backup-specs} is in shell script syntax.}
+Syntactically, @file{backup-specs} is a shell script, containing
+mainly variable assignments. However, any valid shell construct
+is allowed in this file. Particularly, you may wish to define
+functions within that script (e.g., see @code{RESTORE_BEGIN} below).
+For more information about shell script syntax, please refer to
+@url{http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#ta
+g_02, the definition of the Shell Command Language}. See also
+@ref{Top,,Bash Features,bashref,Bash Reference Manual}.
-@FIXME-xref{Script Syntax}, for an explanation of this syntax.
+The shell variables controlling behavior of @code{backup} and
+@code{restore} are described in the following subsections.
-@FIXME{Whats a parameter .... looked at by the backup scripts
-... which will be expecting to find ... now syntax ... value is linked
-to lame ... @file{backup-specs} specifies the following parameters:}
+@menu
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
+* backup-specs example:: An Example Text of @file{Backup-specs}
+@end menu
-@table @samp
-@item ADMINISTRATOR
-The user name of the backup administrator.
+@node General-Purpose Variables
+@subsection General-Purpose Variables
-@item BACKUP_HOUR
+@defvr {Backup variable} ADMINISTRATOR
+The user name of the backup administrator. @code{Backup} scripts
+sends a backup report to this address.
+@end defvr
+
+@defvr {Backup variable} BACKUP_HOUR
The hour at which the backups are done. This can be a number from 0
-to 23, or the string @samp{now}.
+to 23, or the time specification in form @var{hours}:@var{minutes},
+or the string @samp{now}.
+
+This variable is used by @code{backup}. Its value may be overridden
+using @option{--time} option (@pxref{Scripted Backups}).
+@end defvr
+
+@defvr {Backup variable} TAPE_FILE
-@item TAPE_FILE
-The device @code{tar} writes the archive to. This device should be
-attached to the host on which the dump scripts are run.
+The device @command{tar} writes the archive to. If @var{TAPE_FILE}
+is a remote archive (@pxref{remote-dev}), backup script will suppose
+that your @command{mt} is able to access remote devices. If @var{RSH}
+(@pxref{RSH}) is set, @option{--rsh-command} option will be added to
+invocations of @command{mt}.
+@end defvr
-@FIXME{examples for all ...}
+@defvr {Backup variable} BLOCKING
-@item TAPE_STATUS
-The command to use to obtain the status of the archive device,
-including error count. On some tape drives there may not be such a
-command; in that case, simply use `TAPE_STATUS=false'.
+The blocking factor @command{tar} will use when writing the dump archive.
+@xref{Blocking Factor}.
+@end defvr
-@item BLOCKING
-The blocking factor @code{tar} will use when writing the dump archive.
-@value{xref-blocking-factor}.
+@defvr {Backup variable} BACKUP_DIRS
-@item BACKUP_DIRS
-A list of file systems to be dumped. You can include any directory
-name in the list---subdirectories on that file system will be
+A list of file systems to be dumped (for @code{backup}), or restored
+(for @code{restore}). You can include any directory
+name in the list --- subdirectories on that file system will be
included, regardless of how they may look to other networked machines.
Subdirectories on other file systems will be ignored.
-The host name specifies which host to run @code{tar} on, and should
+The host name specifies which host to run @command{tar} on, and should
normally be the host that actually contains the file system. However,
-the host machine must have GNU @code{tar} installed, and must be able
-to access the directory containing the backup scripts and their
-support files using the same file name that is used on the machine
-where the scripts are run (ie. what @code{pwd} will print when in that
-directory on that machine). If the host that contains the file system
-does not have this capability, you can specify another host as long as
-it can access the file system through NFS.
+the host machine must have @GNUTAR{} installed, and
+must be able to access the directory containing the backup scripts and
+their support files using the same file name that is used on the
+machine where the scripts are run (ie. what @command{pwd} will print
+when in that directory on that machine). If the host that contains
+the file system does not have this capability, you can specify another
+host as long as it can access the file system through NFS.
+
+If the list of file systems is very long you may wish to put it
+in a separate file. This file is usually named
+@file{/etc/backup/dirs}, but this name may be overridden in
+@file{backup-specs} using @code{DIRLIST} variable.
+@end defvr
+
+@defvr {Backup variable} DIRLIST
+
+A path to the file containing the list of the file systems to backup
+or restore. By default it is @file{/etc/backup/dirs}.
+@end defvr
+
+@defvr {Backup variable} BACKUP_FILES
+
+A list of individual files to be dumped (for @code{backup}), or restored
+(for @code{restore}). These should be accessible from the machine on
+which the backup script is run.
+
+If the list of file systems is very long you may wish to store it
+in a separate file. This file is usually named
+@file{/etc/backup/files}, but this name may be overridden in
+@file{backup-specs} using @code{FILELIST} variable.
+@end defvr
-@item BACKUP_FILES
-A list of individual files to be dumped. These should be accessible
-from the machine on which the backup script is run.
+@defvr {Backup variable} FILELIST
-@FIXME{Same file name, be specific. Through NFS ...}
+A path to the file containing the list of the individual files to backup
+or restore. By default it is @file{/etc/backup/files}.
+@end defvr
+@defvr {Backup variable} MT
+
+Full file name of @command{mt} binary.
+@end defvr
+
+@defvr {Backup variable} RSH
+@anchor{RSH}
+Full file name of @command{rsh} binary or its equivalent. You may wish to
+set it to @code{ssh}, to improve security. In this case you will have
+to use public key authentication.
+@end defvr
+
+@defvr {Backup variable} RSH_COMMAND
+
+Full file name of @command{rsh} binary on remote mashines. This will
+be passed via @option{--rsh-command} option to the remote invocation
+of @GNUTAR{}.
+@end defvr
+
+@defvr {Backup variable} VOLNO_FILE
+
+Name of temporary file to hold volume numbers. This needs to be accessible
+by all the machines which have file systems to be dumped.
+@end defvr
+
+@defvr {Backup variable} XLIST
+
+Name of @dfn{exclude file list}. An @dfn{exclude file list} is a file
+located on the remote machine and containing the list of files to
+be excluded from the backup. Exclude file lists are searched in
+/etc/tar-backup directory. A common use for exclude file lists
+is to exclude files containing security-sensitive information
+(e.g., @file{/etc/shadow} from backups).
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} SLEEP_TIME
+
+Time to sleep between dumps of any two successive file systems
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} DUMP_REMIND_SCRIPT
+
+Script to be run when it's time to insert a new tape in for the next
+volume. Administrators may want to tailor this script for their site.
+If this variable isn't set, @GNUTAR{} will display its built-in prompt
+@FIXME-xref{describe it somewhere!}, and will expect confirmation from
+the console.
+@end defvr
+
+@defvr {Backup variable} SLEEP_MESSAGE
+
+Message to display on the terminal while waiting for dump time. Usually
+this will just be some literal text.
+@end defvr
+
+@defvr {Backup variable} TAR
+
+Full file name of the @GNUTAR{} executable. If this is not set, backup
+scripts will search @command{tar} in the current shell path.
+@end defvr
+
+@node Magnetic Tape Control
+@subsection Magnetic Tape Control
+
+Backup scripts access tape device using special @dfn{hook functions}.
+These functions take a single argument -- the name of the tape
+device. Their names are kept in the following variables:
+
+@defvr {Backup variable} MT_BEGIN
+The name of @dfn{begin} function. This function is called before
+accessing the drive. By default it retensions the tape:
+
+@smallexample
+MT_BEGIN=mt_begin
+
+mt_begin() @{
+ mt -f "$1" retension
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_REWIND
+The name of @dfn{rewind} function. The default definition is as
+follows:
+
+@smallexample
+MT_REWIND=mt_rewind
+
+mt_rewind() @{
+ mt -f "$1" rewind
+@}
+@end smallexample
+
+@end defvr
+
+@defvr {Backup variable} MT_OFFLINE
+The name of the function switching the tape off line. By default
+it is defined as follows:
+
+@smallexample
+MT_OFFLINE=mt_offline
+
+mt_offline() @{
+ mt -f "$1" offl
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_STATUS
+The name of the function used to obtain the status of the archive device,
+including error count. Default definition:
+
+@smallexample
+MT_STATUS=mt_status
+
+mt_status() @{
+ mt -f "$1" status
+@}
+@end smallexample
+@end defvr
+
+@node User Hooks
+@subsection User Hooks
+
+@dfn{User hooks} are shell functions executed before and after
+each @command{tar} invocation. Thus, there are @dfn{backup
+hooks}, which are executed before and after dumping each file
+system, and @dfn{restore hooks}, executed before and
+after restoring a file system. Each user hook is a shell function
+taking four arguments:
+
+@deffn {User Hook Function} hook @var{level} @var{host} @var{fs} @var{fsname}
+Its arguments are:
+
+@table @var
+@item level
+Current backup or restore level.
+
+@item host
+Name or IP address of the host machine being dumped or restored.
+
+@item fs
+Full path name to the file system being dumped or restored.
+
+@item fsname
+File system name with directory separators replaced with colons. This
+is useful, e.g., for creating unique files.
@end table
+@end deffn
-@menu
-* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-@end menu
+Following variables keep the names of user hook functions
+
+@defvr {Backup variable} DUMP_BEGIN
+Dump begin function. It is executed before dumping the file system.
+@end defvr
+
+@defvr {Backup variable} DUMP_END
+Executed after dumping the file system.
+@end defvr
+
+@defvr {Backup variable} RESTORE_BEGIN
+Executed before restoring the file system.
+@end defvr
-@node backup-specs example, Script Syntax, Backup Parameters, Backup Parameters
+@defvr {Backup variable} RESTORE_END
+Executed after restoring the file system.
+@end defvr
+
+@node backup-specs example
@subsection An Example Text of @file{Backup-specs}
-@UNREVISED
-The following is the text of @file{backup-specs} as it appears at FSF:
+The following is an example of @file{backup-specs}:
-@example
+@smallexample
# site-specific parameters for file system backup.
ADMINISTRATOR=friedman
BACKUP_HOUR=1
TAPE_FILE=/dev/nrsmt0
-TAPE_STATUS="mts -t $TAPE_FILE"
+
+# Use @code{ssh} instead of the less secure @code{rsh}
+RSH=/usr/bin/ssh
+RSH_COMMAND=/usr/bin/ssh
+
+# Override MT_STATUS function:
+my_status() @{
+ mts -t $TAPE_FILE
+@}
+MT_STATUS=my_status
+
+# Disable MT_OFFLINE function
+MT_OFFLINE=:
+
BLOCKING=124
BACKUP_DIRS="
- albert:/fs/fsf
- apple-gunkies:/gd
- albert:/fs/gd2
- albert:/fs/gp
- geech:/usr/jla
- churchy:/usr/roland
- albert:/
- albert:/usr
- apple-gunkies:/
- apple-gunkies:/usr
- gnu:/hack
- gnu:/u
- apple-gunkies:/com/mailer/gnu
- apple-gunkies:/com/archive/gnu"
+ albert:/fs/fsf
+ apple-gunkies:/gd
+ albert:/fs/gd2
+ albert:/fs/gp
+ geech:/usr/jla
+ churchy:/usr/roland
+ albert:/
+ albert:/usr
+ apple-gunkies:/
+ apple-gunkies:/usr
+ gnu:/hack
+ gnu:/u
+ apple-gunkies:/com/mailer/gnu
+ apple-gunkies:/com/archive/gnu"
BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
-@end example
+@end smallexample
-@node Script Syntax, , backup-specs example, Backup Parameters
-@subsection Syntax for @file{Backup-specs}
-@UNREVISED
+@node Scripted Backups
+@section Using the Backup Scripts
-@file{backup-specs} is in shell script syntax. The following
-conventions should be considered when editing the script:
-@FIXME{"conventions?"}
+The syntax for running a backup script is:
-A quoted string is considered to be contiguous, even if it is on more
-than one line. Therefore, you cannot include commented-out lines
-within a multi-line quoted string. BACKUP_FILES and BACKUP_DIRS are
-the two most likely parameters to be multi-line.
+@smallexample
+backup --level=@var{level} --time=@var{time}
+@end smallexample
-A quoted string typically cannot contain wildcards. In
-@file{backup-specs}, however, the parameters BACKUP_DIRS and
-BACKUP_FILES can contain wildcards.
+The @option{level} option requests the dump level. Thus, to produce
+a full dump, specify @code{--level=0} (this is the default, so
+@option{--level} may be omitted if its value is @code{0}).
+@footnote{For backward compatibility, the @code{backup} will also
+try to deduce the requested dump level from the name of the
+script itself. If the name consists of a string @samp{level-}
+followed by a single decimal digit, that digit is taken as
+the dump level number. Thus, you may create a link from @code{backup}
+to @code{level-1} and then run @code{level-1} whenever you need to
+create a level one dump.}
-@node Scripted Backups, Scripted Restoration, Backup Parameters, Backups
-@section Using the Backup Scripts
-@UNREVISED
+The @option{--time} option determines when should the backup be
+run. @var{Time} may take three forms:
-The syntax for running a backup script is:
+@table @asis
+@item @var{hh}:@var{mm}
+
+The dump must be run at @var{hh} hours @var{mm} minutes.
-@example
-@file{script-name} [@var{time-to-be-run}]
-@end example
+@item @var{hh}
-where @var{time-to-be-run} can be a specific system time, or can be
-@kbd{now}. If you do not specify a time, the script runs at the time
-specified in @file{backup-specs} (@FIXME-pxref{Script Syntax}).
+The dump must be run at @var{hh} hours
+
+@item now
+
+The dump must be run immediately.
+@end table
You should start a script with a tape or disk mounted. Once you
start a script, it prompts you for new tapes or disks as it
needs them. Media volumes don't have to correspond to archive
-files---a multi-volume archive can be started in the middle of a
+files --- a multi-volume archive can be started in the middle of a
tape that already contains the end of another multi-volume archive.
The @code{restore} script prompts for media by its archive volume,
so to avoid an error message you should keep track of which tape
-(or disk) contains which volume of the archive. @FIXME{There is
-no such restore script!}. @FIXME-xref{Scripted Restoration}.
-@FIXME{Have file names changed?}
+(or disk) contains which volume of the archive (@pxref{Scripted
+Restoration}).
The backup scripts write two files on the file system. The first is a
record file in @file{/etc/tar-backup/}, which is used by the scripts
to store and retrieve information about which files were dumped. This
file is not meant to be read by humans, and should not be deleted by
-them. @FIXME-xref{incremental and listed-incremental}, for a more
-detailed explanation of this file.
+them. @xref{Snapshot Files}, for a more detailed explanation of this
+file.
The second file is a log file containing the names of the file systems
and files dumped, what time the backup was made, and any error
messages that were generated, as well as how much space was left in
the media volume after the last volume of the archive was written.
You should check this log file after every backup. The file name is
-@file{log-@var{mmm-ddd-yyyy}-level-1} or
-@file{log-@var{mmm-ddd-yyyy}-full}.
+@file{log-@var{mm-dd-yyyy}-level-@var{n}}, where @var{mm-dd-yyyy}
+represents current date, and @var{n} represents current dump level number.
The script also prints the name of each system being dumped to the
standard output.
-@node Scripted Restoration, , Scripted Backups, Backups
-@section Using the Restore Script
-@UNREVISED
+Following is the full list of options accepted by @code{backup}
+script:
+
+@table @option
+@item -l @var{level}
+@itemx --level=@var{level}
+Do backup level @var{level} (default 0).
-@ifset PUBLISH
+@item -f
+@itemx --force
+Force backup even if today's log file already exists.
-The @code{tar} distribution does not provide restoring scripts.
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
-@end ifset
+@item -t @var{start-time}
+@itemx --time=@var{start-time}
+Wait till @var{time}, then do backup.
-@ifclear PUBLISH
+@item -h
+@itemx --help
+Display short help message and exit.
-@quotation
-@strong{Warning:} The GNU @code{tar} distribution does @emph{not}
-provide any such @code{restore} script yet. This section is only
-listed here for documentation maintenance purposes. In any case,
-all contents is subject to change as things develop.
-@end quotation
+@item -V
+@itemx --version
+Display information about the program's name, version, origin and legal
+status, all on standard output, and then exit successfully.
+@end table
-@FIXME{A section on non-scripted restore may be a good idea.}
+
+@node Scripted Restoration
+@section Using the Restore Script
To restore files that were archived using a scripted backup, use the
-@code{restore} script. The syntax for the script is:
+@code{restore} script. Its usage is quite straightforward. In the
+simplest form, invoke @code{restore --all}, it will
+then restore all the file systems and files specified in
+@file{backup-specs} (@pxref{General-Purpose Variables,BACKUP_DIRS}).
+
+You may select the file systems (and/or files) to restore by
+giving @code{restore} list of @dfn{patterns} in its command
+line. For example, running
+
+@smallexample
+restore 'albert:*'
+@end smallexample
+
+@noindent
+will restore all file systems on the machine @samp{albert}. A more
+complicated example:
+
+@smallexample
+restore 'albert:*' '*:/var'
+@end smallexample
+
+@noindent
+This command will restore all file systems on the machine @samp{albert}
+as well as @file{/var} file system on all machines.
-where ***** are the file systems to restore from, and
-***** is a regular expression which specifies which files to
-restore. If you specify --all, the script restores all the files
-in the file system.
+By default @code{restore} will start restoring files from the lowest
+available dump level (usually zero) and will continue through
+all available dump levels. There may be situations where such a
+thorough restore is not necessary. For example, you may wish to
+restore only files from the recent level one backup. To do so,
+use @option{--level} option, as shown in the example below:
+
+@smallexample
+restore --level=1
+@end smallexample
+
+The full list of options accepted by @code{restore} follows:
+
+@table @option
+@item -a
+@itemx --all
+Restore all file systems and files specified in @file{backup-specs}
+
+@item -l @var{level}
+@itemx --level=@var{level}
+Start restoring from the given backup level, instead of the default 0.
+
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
+
+@item -h
+@itemx --help
+Display short help message and exit.
+
+@item -V
+@itemx --version
+Display information about the program's name, version, origin and legal
+status, all on standard output, and then exit successfully.
+@end table
You should start the restore script with the media containing the
first volume of the archive mounted. The script will prompt for other
volumes as they are needed. If the archive is on tape, you don't need
to rewind the tape to to its beginning---if the tape head is
positioned past the beginning of the archive, the script will rewind
-the tape as needed. @FIXME-xref{Media}, for a discussion of tape
-positioning.
-
-If you specify @samp{--all} as the @var{files} argument, the
-@code{restore} script extracts all the files in the archived file
-system into the active file system.
+the tape as needed. @FIXME-xref{Media, for a discussion of tape
+positioning.}
@quotation
@strong{Warning:} The script will delete files from the active file
system if they were not in the file system when the archive was made.
@end quotation
-@value{xref-incremental}, and @value{ref-listed-incremental},
-for an explanation of how the script makes that determination.
+@xref{Incremental Dumps}, for an explanation of how the script makes
+that determination.
-@FIXME{this may be an option, not a given}
-
-@end ifclear
-
-@node Choosing, Date input formats, Backups, Top
-@chapter Choosing Files and Names for @code{tar}
+@node Choosing
+@chapter Choosing Files and Names for @command{tar}
@UNREVISED
@FIXME{Melissa (still) Doesn't Really Like This ``Intro'' Paragraph!!!}
-Certain options to @code{tar} enable you to specify a name for your
+Certain options to @command{tar} enable you to specify a name for your
archive. Other options let you decide which files to include or exclude
from the archive, based on when or whether files were modified, whether
the file names do or don't match specified patterns, or whether files
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
@end menu
-@node file, Selecting Archive Members, Choosing, Choosing
+@node file
@section Choosing and Naming Archive Files
-@cindex Naming an archive
-@cindex Archive Name
-@cindex Directing output
-@cindex Choosing an archive file
-@cindex Where is the archive?
@UNREVISED
@FIXME{should the title of this section actually be, "naming an
archive"?}
-By default, @code{tar} uses an archive file name that was compiled when
+@cindex Naming an archive
+@cindex Archive Name
+@cindex Choosing an archive file
+@cindex Where is the archive?
+By default, @command{tar} uses an archive file name that was compiled when
it was built on the system; usually this name refers to some physical
-tape drive on the machine. However, the person who installed @code{tar}
+tape drive on the machine. However, the person who installed @command{tar}
on the system may not set the default to a meaningful value as far as
most users are concerned. As a result, you will usually want to tell
-@code{tar} where to find (or create) the archive. The @value{op-file}
+@command{tar} where to find (or create) the archive. The @option{--file=@var{archive-name}} (@option{-f @var{archive-name}})
option allows you to either specify or name a file to use as the archive
instead of the default archive file location.
-@table @kbd
+@table @option
+@opindex file, short description
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Name the archive to create or operate on. Use in conjunction with
any operation.
@end table
-For example, in this @code{tar} command,
+For example, in this @command{tar} command,
-@example
+@smallexample
$ @kbd{tar -cvf collection.tar blues folk jazz}
-@end example
+@end smallexample
@noindent
@file{collection.tar} is the name of the archive. It must directly
-follow the @samp{-f} option, since whatever directly follows @samp{-f}
+follow the @option{-f} option, since whatever directly follows @option{-f}
@emph{will} end up naming the archive. If you neglect to specify an
archive name, you may end up overwriting a file in the working directory
-with the archive you create since @code{tar} will use this file's name
+with the archive you create since @command{tar} will use this file's name
for the archive name.
An archive can be saved as a file in the file system, sent through a
@cindex Writing new archives
@cindex Archive creation
-If you do not name the archive, @code{tar} uses the value of the
-environment variable @code{TAPE} as the file name for the archive. If
-that is not available, @code{tar} uses a default, compiled-in archive
-name, usually that for tape unit zero (ie. @file{/dev/tu00}).
-@code{tar} always needs an archive name.
+If you do not name the archive, @command{tar} uses the value of the
+environment variable @env{TAPE} as the file name for the archive. If
+that is not available, @command{tar} uses a default, compiled-in archive
+name, usually that for tape unit zero (ie. @file{/dev/tu00}).
+@command{tar} always needs an archive name.
-If you use @file{-} as an @var{archive-name}, @code{tar} reads the
+If you use @file{-} as an @var{archive-name}, @command{tar} reads the
archive from standard input (when listing or extracting files), or
writes it to standard output (when creating an archive). If you use
@file{-} as an @var{archive-name} when modifying an archive,
-@code{tar} reads the original archive from its standard input and
+@command{tar} reads the original archive from its standard input and
writes the entire new archive to its standard output.
@FIXME{might want a different example here; this is already used in
"notable tar usages".}
-@example
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
-@end example
+@smallexample
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+@end smallexample
@FIXME{help!}
@cindex Standard input and output
@cindex tar to standard input and output
+@anchor{remote-dev}
To specify an archive file on a device attached to a remote machine,
use the following:
-@example
+@smallexample
@kbd{--file=@var{hostname}:/@var{dev}/@var{file name}}
-@end example
+@end smallexample
@noindent
-@code{tar} will complete the remote connection, if possible, and
+@command{tar} will complete the remote connection, if possible, and
prompt you for a username and password. If you use
-@samp{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @code{tar}
+@option{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @command{tar}
will complete the remote connection, if possible, using your username
as the username on the remote machine.
+@cindex Local and remote archives
+@anchor{local and remote archives}
If the archive file name includes a colon (@samp{:}), then it is assumed
to be a file on another machine. If the archive file is
@samp{@var{user}@@@var{host}:@var{file}}, then @var{file} is used on the
-host @var{host}. The remote host is accessed using the @code{rsh}
+host @var{host}. The remote host is accessed using the @command{rsh}
program, with a username of @var{user}. If the username is omitted
(along with the @samp{@@} sign), then your user name will be used.
-(This is the normal @code{rsh} behavior.) It is necessary for the
-remote machine, in addition to permitting your @code{rsh} access, to
-have the @file{/usr/ucb/rmt} program installed. If you need to use a
-file whose name includes a colon, then the remote tape drive behavior
-can be inhibited by using the @value{op-force-local} option.
+(This is the normal @command{rsh} behavior.) It is necessary for the
+remote machine, in addition to permitting your @command{rsh} access, to
+have the @file{rmt} program installed (This command is included in
+the @GNUTAR{} distribution and by default is installed under
+@file{@var{prefix}/libexec/rmt}, were @var{prefix} means your
+installation prefix). If you need to use a file whose name includes a
+colon, then the remote tape drive behavior
+can be inhibited by using the @option{--force-local} option.
@FIXME{i know we went over this yesterday, but bob (and now i do again,
too) thinks it's out of the middle of nowhere. it doesn't seem to tie
here?>>. bob also comments that if Amanda isn't free software, we
shouldn't mention it..}
-When the archive is being created to @file{/dev/null}, GNU @code{tar}
-tries to minimize input and output operations. The Amanda backup
-system, when used with GNU @code{tar}, has an initial sizing pass which
-uses this feature.
+When the archive is being created to @file{/dev/null}, @GNUTAR{}
+tries to minimize input and output operations. The
+Amanda backup system, when used with @GNUTAR{}, has
+an initial sizing pass which uses this feature.
-@node Selecting Archive Members, files, file, Choosing
+@node Selecting Archive Members
@section Selecting Archive Members
@cindex Specifying files to act on
@cindex Specifying archive members
@dfn{File Name arguments} specify which files in the file system
-@code{tar} operates on, when creating or adding to an archive, or which
-archive members @code{tar} operates on, when reading or deleting from
+@command{tar} operates on, when creating or adding to an archive, or which
+archive members @command{tar} operates on, when reading or deleting from
an archive. @xref{Operations}.
To specify file names, you can include them as the last arguments on
@kbd{tar} @var{operation} [@var{option1} @var{option2} @dots{}] [@var{file name-1} @var{file name-2} @dots{}]
@end smallexample
+If a file name begins with dash (@samp{-}), preceede it with
+@option{--add-file} option to preventit from being treated as an
+option.
+
If you specify a directory name as a file name argument, all the files
-in that directory are operated on by @code{tar}.
+in that directory are operated on by @command{tar}.
-If you do not specify files when @code{tar} is invoked with
-@value{op-create}, @code{tar} operates on all the non-directory files in
-the working directory. If you specify either @value{op-list} or
-@value{op-extract}, @code{tar} operates on all the archive members in the
+If you do not specify files when @command{tar} is invoked with
+@option{--create} (@option{-c}), @command{tar} operates on all the non-directory files in
+the working directory. If you specify either @option{--list} (@option{-t}) or
+@option{--extract} (@option{--get}, @option{-x}), @command{tar} operates on all the archive members in the
archive. If you specify any operation other than one of these three,
-@code{tar} does nothing.
+@command{tar} does nothing.
-By default, @code{tar} takes file names from the command line. However,
+By default, @command{tar} takes file names from the command line. However,
there are other ways to specify file or member names, or to modify the
-manner in which @code{tar} selects the files or members upon which to
-operate; @FIXME{add xref here}. In general, these methods work both for
+manner in which @command{tar} selects the files or members upon which to
+operate. @FIXME{add xref here}In general, these methods work both for
specifying the names of files and archive members.
-@node files, exclude, Selecting Archive Members, Choosing
+@node files
@section Reading Names from a File
-@UNREVISED
@cindex Reading file names from a file
@cindex Lists of file names
@cindex File Name arguments, alternatives
Instead of giving the names of files or archive members on the command
line, you can put the names into a file, and then use the
-@value{op-files-from} option to @code{tar}. Give the name of the file
+@option{--files-from=@var{file-of-names}} (@option{-T @var{file-of-names}}) option to @command{tar}. Give the name of the file
which contains the list of files to include as the argument to
-@samp{--files-from}. In the list, the file names should be separated by
+@option{--files-from}. In the list, the file names should be separated by
newlines. You will frequently use this option when you have generated
-the list of files to archive with the @code{find} utility.
+the list of files to archive with the @command{find} utility.
-@table @kbd
+@table @option
+@opindex files-from
@item --files-from=@var{file name}
@itemx -T @var{file name}
Get names to extract or create from file @var{file name}.
@end table
-If you give a single dash as a file name for @samp{--files-from}, (i.e.,
-you specify either @samp{--files-from=-} or @samp{-T -}), then the file
+If you give a single dash as a file name for @option{--files-from}, (i.e.,
+you specify either @code{--files-from=-} or @code{-T -}), then the file
names are read from standard input.
-Unless you are running @code{tar} with @samp{--create}, you can not use
-both @samp{--files-from=-} and @samp{--file=-} (@samp{-f -}) in the same
+Unless you are running @command{tar} with @option{--create}, you can not use
+both @code{--files-from=-} and @code{--file=-} (@code{-f -}) in the same
command.
+Any number of @option{-T} options can be given in the command line.
+
@FIXME{add bob's example, from his message on 2-10-97}
-The following example shows how to use @code{find} to generate a list of
+The following example shows how to use @command{find} to generate a list of
files smaller than 400K in length and put that list into a file
-called @file{small-files}. You can then use the @samp{-T} option to
-@code{tar} to specify the files from that file, @file{small-files}, to
-create the archive @file{little.tgz}. (The @samp{-z} option to
-@code{tar} compresses the archive with @code{gzip}; @pxref{gzip} for
+called @file{small-files}. You can then use the @option{-T} option to
+@command{tar} to specify the files from that file, @file{small-files}, to
+create the archive @file{little.tgz}. (The @option{-z} option to
+@command{tar} compresses the archive with @command{gzip}; @pxref{gzip} for
more information.)
-@example
-$ @kbd{find . -size -400 -print > small-files}
+@smallexample
+$ @kbd{find . -size -400 -print > small-files}
$ @kbd{tar -c -v -z -T small-files -f little.tgz}
-@end example
+@end smallexample
+
+@noindent
+In the file list given by @option{-T} option, any file name beginning
+with @samp{-} character is considered a @command{tar} option and is
+processed accordingly.@footnote{Versions of @GNUTAR{} up to 1.15.1
+recognized only @option{-C} option in file lists, and only if the
+option and its argument occupied two consecutive lines.} For example,
+the common use of this feature is to change to another directory by
+specifying @option{-C} option:
+
+@smallexample
+@group
+$ @kbd{cat list}
+-C/etc
+passwd
+hosts
+-C/lib
+libc.a
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end group
+@end smallexample
+
+@noindent
+In this example, @command{tar} will first switch to @file{/etc}
+directory and add files @file{passwd} and @file{hosts} to the
+archive. Then it will change to @file{/lib} directory and will archive
+the file @file{libc.a}. Thus, the resulting archive @file{foo.tar} will
+contain:
+
+@smallexample
+@group
+$ @kbd{tar tf foo.tar}
+passwd
+hosts
+libc.a
+@end group
+@end smallexample
+
+@noindent
+@opindex directory, using in @option{--files-from} argument
+Notice that the option parsing algorithm used with @option{-T} is
+stricter than the one used by shell. Namely, when specifying option
+arguments, you should observe the following rules:
+
+@itemize @bullet
+@item
+When using short (single-letter) option form, its argument must
+immediately follow the option letter, without any intervening
+whitespace. For example: @code{-Cdir}.
+
+@item
+When using long option form, the option argument must be separated
+from the option by a single equal sign. No whitespace is allowed on
+any side of the equal sign. For example: @code{--directory=dir}.
+
+@item
+For both short and long option forms, the option argument can be given
+on the next line after the option name, e.g.:
+
+@smallexample
+@group
+--directory
+dir
+@end group
+@end smallexample
@noindent
-@FIXME{say more here to conclude the example/section?}
+and
+
+@smallexample
+@group
+-C
+dir
+@end group
+@end smallexample
+@end itemize
+
+@opindex add-file
+If you happen to have a file whose name starts with @samp{-},
+precede it with @option{--add-file} option to prevent it from
+being recognized as an option. For example: @code{--add-file --my-file}.
@menu
* nul::
@end menu
-@node nul, , files, files
-@ifinfo
-@unnumberedsubsec @kbd{NUL} Terminated File Names
-@end ifinfo
+@node nul
+@subsection @code{NUL} Terminated File Names
-@cindex File names, terminated by @kbd{NUL}
-@cindex @kbd{NUL} terminated file names
-The @value{op-null} option causes @value{op-files-from} to read file
+@cindex File names, terminated by @code{NUL}
+@cindex @code{NUL} terminated file names
+The @option{--null} option causes @option{--files-from=@var{file-of-names}} (@option{-T @var{file-of-names}}) to read file
names terminated by a @code{NUL} instead of a newline, so files whose
-names contain newlines can be archived using @samp{--files-from}.
+names contain newlines can be archived using @option{--files-from}.
-@table @kbd
+@table @option
+@opindex null
@item --null
-Only consider @kbd{NUL} terminated file names, instead of files that
+Only consider @code{NUL} terminated file names, instead of files that
terminate in a newline.
@end table
-The @samp{--null} option is just like the one in GNU @code{xargs} and
-@code{cpio}, and is useful with the @samp{-print0} predicate of GNU
-@code{find}. In @code{tar}, @samp{--null} also causes
-@value{op-directory} options to be treated as file names to archive, in
-case there are any files out there called @file{-C}.
+The @option{--null} option is just like the one in @acronym{GNU}
+@command{xargs} and @command{cpio}, and is useful with the
+@option{-print0} predicate of @acronym{GNU} @command{find}. In
+@command{tar}, @option{--null} also disables special handling for
+file names that begin with dash.
-This example shows how to use @code{find} to generate a list of files
+This example shows how to use @command{find} to generate a list of files
larger than 800K in length and put that list into a file called
-@file{long-files}. The @samp{-print0} option to @code{find} just just
-like @samp{-print}, except that it separates files with a @kbd{NUL}
-rather than with a newline. You can then run @code{tar} with both the
-@samp{--null} and @samp{-T} options to specify that @code{tar} get the
+@file{long-files}. The @option{-print0} option to @command{find} is just
+like @option{-print}, except that it separates files with a @code{NUL}
+rather than with a newline. You can then run @command{tar} with both the
+@option{--null} and @option{-T} options to specify that @command{tar} get the
files from that file, @file{long-files}, to create the archive
-@file{big.tgz}. The @samp{--null} option to @code{tar} will cause
-@code{tar} to recognize the @kbd{NUL} separator between files.
+@file{big.tgz}. The @option{--null} option to @command{tar} will cause
+@command{tar} to recognize the @code{NUL} separator between files.
-@example
-$ @kbd{find . -size +800 -print0 > long-files}
+@smallexample
+$ @kbd{find . -size +800 -print0 > long-files}
$ @kbd{tar -c -v --null --files-from=long-files --file=big.tar}
-@end example
+@end smallexample
@FIXME{say anything else here to conclude the section?}
-@node exclude, Wildcards, files, Choosing
+@node exclude
@section Excluding Some Files
+@UNREVISED
+
@cindex File names, excluding files by
@cindex Excluding files by name and pattern
@cindex Excluding files by file system
-@UNREVISED
-
To avoid operating on files whose names match a particular pattern,
-use the @value{op-exclude} or @value{op-exclude-from} options.
+use the @option{--exclude} or @option{--exclude-from} options.
-@table @kbd
+@table @option
+@opindex exclude
@item --exclude=@var{pattern}
-Causes @code{tar} to ignore files that match the @var{pattern}.
+Causes @command{tar} to ignore files that match the @var{pattern}.
@end table
@findex exclude
-The @value{op-exclude} option will prevent any file or member which
-matches the shell wildcards (@var{pattern}) from being operated on
-(@var{pattern} can be a single file name or a more complex expression).
-For example, if you want to create an archive with all the contents of
-the working directory except for files whose names end in @file{.o}, you
-can use the command @samp{tar -cf arch.tar --exclude='*.o' .}.
-
-A @var{pattern} containing @samp{/} excludes a file if an initial prefix
-of the file name matches @var{pattern}; a @var{pattern} without @samp{/}
-excludes a file if it matches any of its file name components. For
-example, the pattern @samp{b*/RCS} excludes @file{blob/RCS} and
-@file{blob/RCS/f} but not @file{a/blob/RCS} or @file{blob/sub/RCS},
-whereas the pattern @samp{RCS} excludes all these file names.
-
-You may give multiple @samp{--exclude} options.
+The @option{--exclude=@var{pattern}} option prevents any file or member whose name
+matches the shell wildcard (@var{pattern}) from being operated on.
+For example, to create an archive with all the contents of the directory
+@file{src} except for files whose names end in @file{.o}, use the
+command @samp{tar -cf src.tar --exclude='*.o' src}.
-@table @kbd
+You may give multiple @option{--exclude} options.
+
+@table @option
+@opindex exclude-from
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Causes @code{tar} to ignore files that match the patterns listed in
+Causes @command{tar} to ignore files that match the patterns listed in
@var{file}.
@end table
@findex exclude-from
-Use the @samp{--exclude-from=@var{file-of-patterns}} option to read a
-list of shell wildcards, one per line, from @var{file}; @code{tar} will
-ignore files matching those regular expressions. Thus if @code{tar} is
+Use the @option{--exclude-from} option to read a
+list of patterns, one per line, from @var{file}; @command{tar} will
+ignore files matching those patterns. Thus if @command{tar} is
called as @w{@samp{tar -c -X foo .}} and the file @file{foo} contains a
single line @file{*.o}, no files whose names end in @file{.o} will be
added to the archive.
@FIXME{do the exclude options files need to have stuff separated by
newlines the same as the files-from option does?}
+@table @option
+@opindex exclude-caches
+@item --exclude-caches
+Causes @command{tar} to ignore directories containing a cache directory tag.
+@end table
+
+@findex exclude-caches
+When creating an archive, the @option{--exclude-caches} option causes
+@command{tar} to exclude all directories that contain a @dfn{cache
+directory tag}. A cache directory tag is a short file with the
+well-known name @file{CACHEDIR.TAG} and having a standard header
+specified in @url{http://www.brynosaurus.com/cachedir/spec.html}.
+Various applications write cache directory tags into directories they
+use to hold regenerable, non-precious data, so that such data can be
+more easily excluded from backups.
+
@menu
+* controlling pattern-matching with exclude::
* problems with exclude::
@end menu
-@node problems with exclude, , exclude, exclude
-@unnumberedsubsec Problems with Using the @code{exclude} Options
+@node controlling pattern-matching with exclude
+@unnumberedsubsec Controlling Pattern-Matching with the @code{exclude} Options
+
+Normally, a pattern matches a name if an initial subsequence of the
+name's components matches the pattern, where @samp{*}, @samp{?}, and
+@samp{[...]} are the usual shell wildcards, @samp{\} escapes wildcards,
+and wildcards can match @samp{/}.
+
+Other than optionally stripping leading @samp{/} from names
+(@pxref{absolute}), patterns and names are used as-is. For
+example, trailing @samp{/} is not trimmed from a user-specified name
+before deciding whether to exclude it.
+
+However, this matching procedure can be altered by the options listed
+below. These options accumulate. For example:
-@FIXME{put in for the editor's/editors' amusement, but should be taken
-out in the final draft, just in case! : }
+@smallexample
+--ignore-case --exclude='makefile' --no-ignore-case ---exclude='readme'
+@end smallexample
+
+ignores case when excluding @samp{makefile}, but not when excluding
+@samp{readme}.
+
+@table @option
+@opindex anchored
+@opindex no-anchored
+@item --anchored
+@itemx --no-anchored
+If anchored, a pattern must match an initial subsequence
+of the name's components. Otherwise, the pattern can match any
+subsequence. Default is @option{--no-anchored}.
+
+@opindex ignore-case
+@opindex no-ignore-case
+@item --ignore-case
+@itemx --no-ignore-case
+When ignoring case, upper-case patterns match lower-case names and vice versa.
+When not ignoring case (the default), matching is case-sensitive.
+
+@opindex wildcards
+@opindex no-wildcards
+@item --wildcards
+@itemx --no-wildcards
+When using wildcards (the default), @samp{*}, @samp{?}, and @samp{[...]}
+are the usual shell wildcards, and @samp{\} escapes wildcards.
+Otherwise, none of these characters are special, and patterns must match
+names literally.
+
+@opindex wildcards-match-slash
+@opindex no-wildcards-match-slash
+@item --wildcards-match-slash
+@itemx --no-wildcards-match-slash
+When wildcards match slash (the default), a wildcard like @samp{*} in
+the pattern can match a @samp{/} in the name. Otherwise, @samp{/} is
+matched only by @samp{/}.
+
+@end table
-@ignore
-subtitled: getting screwed using exclewed
-@end ignore
+The @option{--recursion} and @option{--no-recursion} options
+(@pxref{recurse}) also affect how exclude patterns are interpreted. If
+recursion is in effect, a pattern excludes a name if it matches any of
+the name's parent directories.
+@node problems with exclude
+@unnumberedsubsec Problems with Using the @code{exclude} Options
+
+@opindex exclude, potential problems with
Some users find @samp{exclude} options confusing. Here are some common
pitfalls:
@itemize @bullet
@item
-The main operating mode of @code{tar} does not act on a path name
+The main operating mode of @command{tar} does not act on a path name
explicitly listed on the command line if one of its file name
components is excluded. In the example above, if
you create an archive and exclude files that end with @samp{*.o}, but
listed, @samp{dir.o/foo} will be excluded from the archive.
@item
-You can sometimes confuse the meanings of @value{op-exclude} and
-@value{op-exclude-from}. Be careful: use @value{op-exclude} when files
+You can sometimes confuse the meanings of @option{--exclude} and
+@option{--exclude-from}. Be careful: use @option{--exclude} when files
to be excluded are given as a pattern on the command line. Use
-@samp{--exclude-from=@var{file-of-patterns}} to introduce the name of a
-file which contains a list of patterns, one per line; each of these
-patterns can exclude zero, one, or many files.
+@option{--exclude-from} to introduce the name of a file which contains
+a list of patterns, one per line; each of these patterns can exclude
+zero, one, or many files.
@item
-When you use @value{op-exclude}, be sure to quote the @var{pattern}
-parameter, so GNU @code{tar} sees wildcard characters like @samp{*}.
-If you do not do this, the shell might expand the @samp{*} itself
-using files at hand, so @code{tar} might receive a list of files
-instead of one pattern, or none at all, making the command somewhat
-illegal. This might not correspond to what you want.
+When you use @option{--exclude=@var{pattern}}, be sure to quote the @var{pattern}
+parameter, so @GNUTAR{} sees wildcard characters
+like @samp{*}. If you do not do this, the shell might expand the
+@samp{*} itself using files at hand, so @command{tar} might receive a
+list of files instead of one pattern, or none at all, making the
+command somewhat illegal. This might not correspond to what you want.
For example, write:
-@example
+@smallexample
$ @kbd{tar -c -f @var{archive.tar} --exclude '*.o' @var{directory}}
-@end example
+@end smallexample
@noindent
rather than:
-@example
+@smallexample
$ @kbd{tar -c -f @var{archive.tar} --exclude *.o @var{directory}}
-@end example
+@end smallexample
@item
You must use use shell syntax, or globbing, rather than @code{regexp}
-syntax, when using exclude options in @code{tar}. If you try to use
+syntax, when using exclude options in @command{tar}. If you try to use
@code{regexp} syntax to describe files to be excluded, your command
might fail.
@item
-In earlier versions of @code{tar}, what is now the
-@samp{--exclude-from=@var{file-of-patterns}} option was called
-@samp{--exclude-@var{pattern}} instead. Now,
-@samp{--exclude=@var{pattern}} applies to patterns listed on the command
-line and @samp{--exclude-from=@var{file-of-patterns}} applies to
-patterns listed in a file.
+In earlier versions of @command{tar}, what is now the
+@option{--exclude-from} option was called @option{--exclude} instead.
+Now, @option{--exclude} applies to patterns listed on the command
+line and @option{--exclude-from} applies to patterns listed in a
+file.
@end itemize
-@node Wildcards, after, exclude, Choosing
+@node Wildcards
@section Wildcards Patterns and Matching
@dfn{Globbing} is the operation by which @dfn{wildcard} characters,
@samp{*} or @samp{?} for example, are replaced and expanded into all
-existing files matching the given pattern. However, @code{tar} often
+existing files matching the given pattern. However, @command{tar} often
uses wildcard patterns for matching (or globbing) archive members instead
-of actual files in the filesystem. Wildcard patterns are also used for
-verifying volume labels of @code{tar} archives. This section has the
-purpose of explaining wildcard syntax for @code{tar}.
+of actual files in the file system. Wildcard patterns are also used for
+verifying volume labels of @command{tar} archives. This section has the
+purpose of explaining wildcard syntax for @command{tar}.
@FIXME{the next few paragraphs need work.}
a directory prefix of a matched string, then it matches the full matched
string: excluding a directory also excludes all the files beneath it.
-There are some discussions floating in the air and asking for modifications
-in the way GNU @code{tar} accomplishes wildcard matches. We perceive
-any change of semantics in this area as a delicate thing to impose on
-GNU @code{tar} users. On the other hand, the GNU project should be
-progressive enough to correct any ill design: compatibility at all price
-is not always a good attitude. In conclusion, it is @emph{possible}
-that slight amendments be later brought to the previous description.
-Your opinions on the matter are welcome.
-
-@node after, recurse, Wildcards, Choosing
+@node after
@section Operating Only on New Files
+@UNREVISED
+
@cindex Excluding file by age
+@cindex Data Modification time, excluding files by
@cindex Modification time, excluding files by
@cindex Age, excluding files by
-@UNREVISED
-
-The @value{op-after-date} option causes @code{tar} to only work on files
-whose modification or inode-changed times are newer than the @var{date}
-given. If you use this option when creating or appending to an archive,
-the archive will only include new files. If you use @samp{--after-date}
-when extracting an archive, @code{tar} will only extract files newer
-than the @var{date} you specify.
-
-If you only want @code{tar} to make the date comparison based on
-modification of the actual contents of the file (rather than inode
-changes), then use the @value{op-newer-mtime} option.
+The @option{--after-date=@var{date}} (@option{--newer=@var{date}},
+@option{-N @var{date}}) option causes @command{tar} to only work on
+files whose data modification or status change times are newer than
+the @var{date} given. If @var{date} starts with @samp{/} or @samp{.},
+it is taken to be a file name; the data modification time of that file
+is used as the date. If you use this option when creating or appending
+to an archive, the archive will only include new files. If you use
+@option{--after-date} when extracting an archive, @command{tar} will
+only extract files newer than the @var{date} you specify.
+
+If you only want @command{tar} to make the date comparison based on
+modification of the file's data (rather than status
+changes), then use the @option{--newer-mtime=@var{date}} option.
You may use these options with any operation. Note that these options
-differ from the @value{op-update} operation in that they allow you to
-specify a particular date against which @code{tar} can compare when
-deciding whether or not to archive the files.
+differ from the @option{--update} (@option{-u}) operation in that they
+allow you to specify a particular date against which @command{tar} can
+compare when deciding whether or not to archive the files.
-@table @kbd
+@table @option
+@opindex after-date
+@opindex newer
@item --after-date=@var{date}
@itemx --newer=@var{date}
@itemx -N @var{date}
Only store files newer than @var{date}.
-Acts on files only if their modification or inode-changed times are
+Acts on files only if their data modification or status change times are
later than @var{date}. Use in conjunction with any operation.
+If @var{date} starts with @samp{/} or @samp{.}, it is taken to be a file
+name; the data modification time of that file is used as the date.
+
+@opindex newer-mtime
@item --newer-mtime=@var{date}
-Acts like @value{op-after-date}, but only looks at modification times.
+Acts like @option{--after-date}, but only looks at data modification times.
@end table
-These options limit @code{tar} to only operating on files which have
-been modified after the date specified. A file is considered to have
-changed if the contents have been modified, or if the owner,
+These options limit @command{tar} to operate only on files which have
+been modified after the date specified. A file's status is considered to have
+changed if its contents have been modified, or if its owner,
permissions, and so forth, have been changed. (For more information on
how to specify a date, see @ref{Date input formats}; remember that the
entire date argument must be quoted if it contains any spaces.)
-Gurus would say that @value{op-after-date} tests both the @code{mtime}
-(time the contents of the file were last modified) and @code{ctime}
-(time the file's status was last changed: owner, permissions, etc)
-fields, while @value{op-newer-mtime} tests only @code{mtime} field.
+Gurus would say that @option{--after-date} tests both the data
+modification time (@code{mtime}, the time the contents of the file
+were last modified) and the status change time (@code{ctime}, the time
+the file's status was last changed: owner, permissions, etc.@:)
+fields, while @option{--newer-mtime} tests only the @code{mtime}
+field.
-To be precise, @value{op-after-date} checks @emph{both} @code{mtime} and
+To be precise, @option{--after-date} checks @emph{both} @code{mtime} and
@code{ctime} and processes the file if either one is more recent than
-@var{date}, while @value{op-newer-mtime} only checks @code{mtime} and
-disregards @code{ctime}. Neither uses @code{atime} (the last time the
+@var{date}, while @option{--newer-mtime} only checks @code{mtime} and
+disregards @code{ctime}. Neither does it use @code{atime} (the last time the
contents of the file were looked at).
Date specifiers can have embedded spaces. Because of this, you may need
@FIXME{Need example of --newer-mtime with quoted argument.}
@quotation
-@strong{Please Note:} @value{op-after-date} and @value{op-newer-mtime}
+@strong{Please Note:} @option{--after-date} and @option{--newer-mtime}
should not be used for incremental backups. Some files (such as those
in renamed directories) are not selected properly by these options.
-@xref{incremental and listed-incremental}.
+@xref{Incremental Dumps}.
@end quotation
-To select files newer than the modification time of a file that already
-exists, you can use the @samp{--reference} (@samp{-r}) option of GNU
-@code{date}, available in GNU shell utilities 1.13 or later. It returns
-the timestamp of that already existing file; this timestamp expands to
-become the referent date which @samp{--newer} uses to determine which
-files to archive. For example, you could say,
-
-@example
-$ @kbd{tar -cf @var{archive.tar} --newer="`date -r @var{file}`" /home}
-@end example
-
@noindent
-which tells @FIXME{need to fill this in!}.
+@FIXME{which tells -- need to fill this in!}
-@node recurse, one, after, Choosing
+@node recurse
@section Descending into Directories
+@UNREVISED
@cindex Avoiding recursion in directories
@cindex Descending directories, avoiding
@cindex Directories, avoiding recursion
@cindex Recursion in directories, avoiding
-@UNREVISED
@FIXME{arrggh! this is still somewhat confusing to me. :-< }
@FIXME{show dan bob's comments, from 2-10-97}
-Usually, @code{tar} will recursively explore all directories (either
-those given on the command line or through the @value{op-files-from}
+Usually, @command{tar} will recursively explore all directories (either
+those given on the command line or through the @option{--files-from}
option) for the various files they contain. However, you may not always
-want @code{tar} to act this way.
-
-The @value{op-no-recursion} option inhibits @code{tar}'s recursive descent
-into specified directories. If you specify @samp{--no-recursion}, you can
-use the @code{find} utility for hunting through levels of directories to
-construct a list of file names which you could then pass to @code{tar}.
-@code{find} allows you to be more selective when choosing which files to
-archive; see @ref{files} for more information on using @code{find} with
-@code{tar}, or look.
-
-@table @kbd
+want @command{tar} to act this way.
+
+@opindex no-recursion
+The @option{--no-recursion} option inhibits @command{tar}'s recursive descent
+into specified directories. If you specify @option{--no-recursion}, you can
+use the @command{find} utility for hunting through levels of directories to
+construct a list of file names which you could then pass to @command{tar}.
+@command{find} allows you to be more selective when choosing which files to
+archive; see @ref{files} for more information on using @command{find} with
+@command{tar}, or look.
+
+@table @option
@item --no-recursion
-Prevents @code{tar} from recursively descending directories.
+Prevents @command{tar} from recursively descending directories.
+
+@opindex recursion
+@item --recursion
+Requires @command{tar} to recursively descend directories.
+This is the default.
@end table
-When you use @samp{--no-recursion}, GNU @code{tar} grabs directory entries
-themselves, but does not descend on them recursively. Many people use
-@code{find} for locating files they want to back up, and since
-@code{tar} @emph{usually} recursively descends on directories, they have
-to use the @samp{@w{! -d}} option to @code{find} @FIXME{needs more
-explanation or a cite to another info file} as they usually do not want
-all the files in a directory. They then use the @value{op-file-from}
-option to archive the files located via @code{find}.
+When you use @option{--no-recursion}, @GNUTAR{} grabs
+directory entries themselves, but does not descend on them
+recursively. Many people use @command{find} for locating files they
+want to back up, and since @command{tar} @emph{usually} recursively
+descends on directories, they have to use the @samp{@w{! -d}} option
+to @command{find} @FIXME{needs more explanation or a cite to another
+info file}as they usually do not want all the files in a directory.
+They then use the @option{--files-from} option to archive the files
+located via @command{find}.
The problem when restoring files archived in this manner is that the
directories themselves are not in the archive; so the
-@value{op-same-permissions} option does not affect them---while users
-might really like it to. Specifying @value{op-no-recursion} is a way to
-tell @code{tar} to grab only the directory entries given to it, adding
+@option{--same-permissions} (@option{--preserve-permissions},
+@option{-p}) option does not affect them---while users might really
+like it to. Specifying @option{--no-recursion} is a way to tell
+@command{tar} to grab only the directory entries given to it, adding
no new files on its own.
-@FIXME{example here}
+The @option{--no-recursion} option also applies when extracting: it
+causes @command{tar} to extract only the matched directory entries, not
+the files under those directories.
+
+The @option{--no-recursion} option also affects how exclude patterns
+are interpreted (@pxref{controlling pattern-matching with exclude}).
+
+The @option{--no-recursion} and @option{--recursion} options apply to
+later options and operands, and can be overridden by later occurrences
+of @option{--no-recursion} and @option{--recursion}. For example:
+
+@smallexample
+$ @kbd{tar -cf jams.tar --no-recursion grape --recursion grape/concord}
+@end smallexample
+
+@noindent
+creates an archive with one entry for @file{grape}, and the recursive
+contents of @file{grape/concord}, but no entries under @file{grape}
+other than @file{grape/concord}.
-@node one, , recurse, Choosing
-@section Crossing Filesystem Boundaries
+@node one
+@section Crossing File System Boundaries
@cindex File system boundaries, not crossing
@UNREVISED
-@code{tar} will normally automatically cross file system boundaries in
+@command{tar} will normally automatically cross file system boundaries in
order to archive files which are part of a directory tree. You can
-change this behavior by running @code{tar} and specifying
-@value{op-one-file-system}. This option only affects files that are
+change this behavior by running @command{tar} and specifying
+@option{--one-file-system} (@option{-l}). This option only affects files that are
archived because they are in a directory that is being archived;
-@code{tar} will still archive files explicitly named on the command line
-or through @value{op-files-from}, regardless of where they reside.
+@command{tar} will still archive files explicitly named on the command line
+or through @option{--files-from}, regardless of where they reside.
-@table @kbd
+@table @option
+@opindex one-file-system
@item --one-file-system
@itemx -l
-Prevents @code{tar} from crossing file system boundaries when
+Prevents @command{tar} from crossing file system boundaries when
archiving. Use in conjunction with any write operation.
@end table
-The @samp{--one-file-system} option causes @code{tar} to modify its
+The @option{--one-file-system} option causes @command{tar} to modify its
normal behavior in archiving the contents of directories. If a file in
-a directory is not on the same filesystem as the directory itself, then
-@code{tar} will not archive that file. If the file is a directory
-itself, @code{tar} will not archive anything beneath it; in other words,
-@code{tar} will not cross mount points.
+a directory is not on the same file system as the directory itself, then
+@command{tar} will not archive that file. If the file is a directory
+itself, @command{tar} will not archive anything beneath it; in other words,
+@command{tar} will not cross mount points.
It is reported that using this option, the mount point is is archived,
but nothing under it.
This option is useful for making full or incremental archival backups of
a file system. If this option is used in conjunction with
-@value{op-verbose}, files that are excluded are mentioned by name on the
+@option{--verbose} (@option{-v}), files that are excluded are mentioned by name on the
standard error.
@menu
* absolute:: Absolute File Names
@end menu
-@node directory, absolute, one, one
+@node directory
@subsection Changing the Working Directory
+@UNREVISED
@FIXME{need to read over this node now for continuity; i've switched
things around some.}
@cindex Changing directory mid-stream
@cindex Directory, changing mid-stream
@cindex Working directory, specifying
-@UNREVISED
-
To change the working directory in the middle of a list of file names,
either on the command line or in a file specified using
-@value{op-files-from}, use @value{op-directory}. This will change the
-working directory to the directory @var{directory} after that point in
-the list.
+@option{--files-from} (@option{-T}), use @option{--directory} (@option{-C}).
+This will change the working directory to the specified directory
+after that point in the list.
-@table @kbd
+@table @option
+@opindex directory
@item --directory=@var{directory}
@itemx -C @var{directory}
Changes the working directory in the middle of a command line.
For example,
-@example
+@smallexample
$ @kbd{tar -c -f jams.tar grape prune -C food cherry}
-@end example
+@end smallexample
@noindent
will place the files @file{grape} and @file{prune} from the current
Contrast this with the command,
-@example
+@smallexample
$ @kbd{tar -c -f jams.tar grape prune -C food red/cherry}
-@end example
+@end smallexample
@noindent
which records the third file in the archive under the name
@samp{tar --extract}, the third file will be written in a subdirectory
named @file{orange-colored}.
-You can use the @samp{--directory} option to make the archive
+You can use the @option{--directory} option to make the archive
independent of the original name of the directory holding the files.
The following command places the files @file{/etc/passwd},
@file{/etc/hosts}, and @file{/lib/libc.a} into the archive
@file{foo.tar}:
-@example
+@smallexample
$ @kbd{tar -c -f foo.tar -C /etc passwd hosts -C /lib libc.a}
-@end example
+@end smallexample
@noindent
However, the names of the archive members will be exactly what they were
They will not appear to be related by file name to the original
directories where those files were located.
-Note that @samp{--directory} options are interpreted consecutively. If
-@samp{--directory} specifies a relative file name, it is interpreted
+Note that @option{--directory} options are interpreted consecutively. If
+@option{--directory} specifies a relative file name, it is interpreted
relative to the then current directory, which might not be the same as
-the original current working directory of @code{tar}, due to a previous
-@samp{--directory} option.
+the original current working directory of @command{tar}, due to a previous
+@option{--directory} option.
+
+When using @option{--files-from} (@pxref{files}), you can put various
+@command{tar} options (including @option{-C}) in the file list. Notice,
+however, that in this case the option and its argument may not be
+separated by whitespace. If you use short option, its argument must
+either follow the option letter immediately, without any intervening
+whitespace, or occupy the next line. Otherwise, if you use long
+option, separate its argument by an equal sign.
+
+For instance, the file list for the above example will be:
+
+@smallexample
+@group
+-C
+/etc
+passwd
+hosts
+-C
+/lib
+libc.a
+@end group
+@end smallexample
+
+@noindent
+To use it, you would invoke @command{tar} as follows:
+
+@smallexample
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end smallexample
-@FIXME{dan: does this mean that you *can* use the short option form, but
-you can *not* use the long option form with --files-from? or is this
-totally screwed?}
+Notice also that you can only use the short option variant in the file
+list, i.e., always use @option{-C}, not @option{--directory}.
-When using @samp{--files-from} (@pxref{files}), you can put @samp{-C}
-options in the file list. Unfortunately, you cannot put
-@samp{--directory} options in the file list. (This interpretation can
-be disabled by using the @value{op-null} option.)
+The interpretation of @option{--directory} is disabled by
+@option{--null} option.
-@node absolute, , directory, one
+@node absolute
@subsection Absolute File Names
@UNREVISED
-@table @kbd
-@item -P
-@itemx --absolute-names
-Do not strip leading slashes from file names.
+@table @option
+@opindex absolute-names
+@item --absolute-names
+@itemx -P
+Do not strip leading slashes from file names, and permit file names
+containing a @file{..} file name component.
@end table
-By default, GNU @code{tar} drops a leading @samp{/} on input or output.
-This option turns off this behavior; it is equivalent to changing to the
-root directory before running @code{tar} (except it also turns off the
-usual warning message).
+By default, @GNUTAR{} drops a leading @samp{/} on
+input or output, and complains about file names containing a @file{..}
+component. This option turns off this behavior.
-When @code{tar} extracts archive members from an archive, it strips any
+When @command{tar} extracts archive members from an archive, it strips any
leading slashes (@samp{/}) from the member name. This causes absolute
member names in the archive to be treated as relative file names. This
allows you to have such members extracted wherever you want, instead of
being restricted to extracting the member in the exact directory named
in the archive. For example, if the archive member has the name
-@file{/etc/passwd}, @code{tar} will extract it as if the name were
+@file{/etc/passwd}, @command{tar} will extract it as if the name were
really @file{etc/passwd}.
-Other @code{tar} programs do not do this. As a result, if you create an
-archive whose member names start with a slash, they will be difficult
-for other people with a non-GNU @code{tar} program to use. Therefore,
-GNU @code{tar} also strips leading slashes from member names when
-putting members into the archive. For example, if you ask @code{tar} to
-add the file @file{/bin/ls} to an archive, it will do so, but the member
-name will be @file{bin/ls}.
-
-If you use the @value{op-absolute-names} option, @code{tar} will do
-neither of these transformations.
+File names containing @file{..} can cause problems when extracting, so
+@command{tar} normally warns you about such files when creating an
+archive, and rejects attempts to extracts such files.
+
+Other @command{tar} programs do not do this. As a result, if you
+create an archive whose member names start with a slash, they will be
+difficult for other people with a non-@GNUTAR{}
+program to use. Therefore, @GNUTAR{} also strips
+leading slashes from member names when putting members into the
+archive. For example, if you ask @command{tar} to add the file
+@file{/bin/ls} to an archive, it will do so, but the member name will
+be @file{bin/ls}.@footnote{A side effect of this is that when
+@option{--create} is used with @option{--verbose} the resulting output
+is not, generally speaking, the same as the one you'd get running
+@kbd{tar --list} command. This may be important if you use some
+scripts for comparing both outputs. @xref{listing member and file names},
+for the information on how to handle this case.}
+
+If you use the @option{--absolute-names} (@option{-P}) option,
+@command{tar} will do none of these transformations.
To archive or extract files relative to the root directory, specify
-the @value{op-absolute-names} option.
+the @option{--absolute-names} (@option{-P}) option.
-Normally, @code{tar} acts on files relative to the working
+Normally, @command{tar} acts on files relative to the working
directory---ignoring superior directory names when archiving, and
ignoring leading slashes when extracting.
-When you specify @value{op-absolute-names}, @code{tar} stores file names
-including all superior directory names, and preserves leading slashes.
-If you only invoked @code{tar} from the root directory you would never
-need the @value{op-absolute-names} option, but using this option may be
-more convenient than switching to root.
+When you specify @option{--absolute-names} (@option{-P}),
+@command{tar} stores file names including all superior directory
+names, and preserves leading slashes. If you only invoked
+@command{tar} from the root directory you would never need the
+@option{--absolute-names} option, but using this option
+may be more convenient than switching to root.
@FIXME{Should be an example in the tutorial/wizardry section using this
to transfer files between systems.}
@FIXME{Is write access an issue?}
-@table @kbd
+@table @option
@item --absolute-names
-Preserves full file names (inclusing superior dirctory names) when
+Preserves full file names (including superior directory names) when
archiving files. Preserves leading slash when extracting files.
@end table
@FIXME{this is still horrible; need to talk with dan on monday.}
-@code{tar} prints out a message about removing the @samp{/} from file
-names. This message appears once per GNU @code{tar} invocation. It
-represents something which ought to be told; ignoring what it means can
-cause very serious surprises, later.
+@command{tar} prints out a message about removing the @samp{/} from
+file names. This message appears once per @GNUTAR{}
+invocation. It represents something which ought to be told; ignoring
+what it means can cause very serious surprises, later.
Some people, nevertheless, do not want to see this message. Wanting to
-play really dangerously, one may of course redirect @code{tar} standard
-error to the sink. For example, under @code{sh}:
+play really dangerously, one may of course redirect @command{tar} standard
+error to the sink. For example, under @command{sh}:
-@example
+@smallexample
$ @kbd{tar -c -f archive.tar /home 2> /dev/null}
-@end example
+@end smallexample
@noindent
Another solution, both nicer and simpler, would be to change to
the @file{/} directory first, and then avoid absolute notation.
For example:
-@example
+@smallexample
$ @kbd{(cd / && tar -c -f archive.tar home)}
$ @kbd{tar -c -f archive.tar -C / home}
-@end example
-
-@node Date input formats, Formats, Choosing, Top
-@chapter Date input formats
-
-@cindex date input formats
-@findex getdate
+@end smallexample
-@quotation
-Our units of temporal measurement, from seconds on up to months, are so
-complicated, asymmetrical and disjunctive so as to make coherent mental
-reckoning in time all but impossible. Indeed, had some tyrannical god
-contrived to enslave our minds to time, to make it all but impossible
-for us to escape subjection to sodden routines and unpleasant surprises,
-he could hardly have done better than handing down our present system.
-It is like a set of trapezoidal building blocks, with no vertical or
-horizontal surfaces, like a language in which the simplest thought
-demands ornate constructions, useless particles and lengthy
-circumlocutions. Unlike the more successful patterns of language and
-science, which enable us to face experience boldly or at least
-level-headedly, our system of temporal calculation silently and
-persistently encourages our terror of time.
-
-@dots{} It is as though architects had to measure length in feet, width
-in meters and height in ells; as though basic instruction manuals
-demanded a knowledge of five different languages. It is no wonder then
-that we often look into our own immediate past or future, last Tuesday
-or a week from Sunday, with feelings of helpless confusion. @dots{}
-
---- Robert Grudin, @cite{Time and the Art of Living}.
-@end quotation
+@include getdate.texi
-This section describes the textual date representations that GNU
-programs accept. These are the strings you, as a user, can supply as
-arguments to the various programs. The C interface (via the
-@code{getdate} function) is not described here.
+@node Formats
+@chapter Controlling the Archive Format
-@cindex beginning of time, for Unix
-@cindex epoch, for Unix
-Although the date syntax here can represent any possible time since zero
-A.D., computer integers are not big enough for such a (comparatively)
-long time. The earliest date semantically allowed on Unix systems is
-midnight, 1 January 1970 UCT.
+@cindex Tar archive formats
+Due to historical reasons, there are several formats of tar archives.
+All of them are based on the same principles, but have some subtle
+differences that often make them incompatible with each other.
-@menu
-* General date syntax:: Common rules.
-* Calendar date item:: 19 Dec 1994.
-* Time of day item:: 9:20pm.
-* Timezone item:: EST, DST, BST, UCT, AHST, ...
-* Day of week item:: Monday and others.
-* Relative item in date strings:: next tuesday, 2 years ago.
-* Pure numbers in date strings:: 19931219, 1440.
-* Authors of getdate:: Bellovin, Salz, Berets, et al.
-@end menu
+GNU tar is able to create and handle archives in a variety of formats.
+The most frequently used formats are (in alphabetical order):
+@table @asis
+@item gnu
+Format used by @GNUTAR{} versions up to 1.13.25. This format derived
+from an early @acronym{POSIX} standard, adding some improvements such as
+sparse file handling and incremental archives. Unfortunately these
+features were implemented in a way incompatible with other archive
+formats.
-@node General date syntax, Calendar date item, Date input formats, Date input formats
-@section General date syntax
+Archives in @samp{gnu} format are able to hold pathnames of unlimited
+length.
-@cindex general date syntax
+@item oldgnu
+Format used by @GNUTAR{} of versions prior to 1.12.
-@cindex items in date strings
-A @dfn{date} is a string, possibly empty, containing many items
-separated by whitespace. The whitespace may be omitted when no
-ambiguity arises. The empty string means the beginning of today (i.e.,
-midnight). Order of the items is immaterial. A date string may contain
-many flavors of items:
+@item v7
+Archive format, compatible with the V7 implementation of tar. This
+format imposes a number of limitations. The most important of them
+are:
-@itemize @bullet
-@item calendar date items
-@item time of the day items
-@item time zone items
-@item day of the week items
-@item relative items
-@item pure numbers.
-@end itemize
+@enumerate
+@item The maximum length of a file name is limited to 99 characters.
+@item The maximum length of a symbolic link is limited to 99 characters.
+@item It is impossible to store special files (block and character
+devices, fifos etc.)
+@item Maximum value of user or group ID is limited to 2097151 (7777777
+octal)
+@item V7 archives do not contain symbolic ownership information (user
+and group name of the file owner).
+@end enumerate
-@noindent We describe each of these item types in turn, below.
-
-@cindex numbers, written-out
-@cindex ordinal numbers
-@findex first @r{in date strings}
-@findex next @r{in date strings}
-@findex last @r{in date strings}
-A few numbers may be written out in words in most contexts. This is
-most useful for specifying day of the week items or relative items (see
-below). Here is the list: @samp{first} for 1, @samp{next} for 2,
-@samp{third} for 3, @samp{fourth} for 4, @samp{fifth} for 5,
-@samp{sixth} for 6, @samp{seventh} for 7, @samp{eighth} for 8,
-@samp{ninth} for 9, @samp{tenth} for 10, @samp{eleventh} for 11 and
-@samp{twelfth} for 12. Also, @samp{last} means exactly @math{-1}.
-
-@cindex months, written-out
-When a month is written this way, it is still considered to be written
-numerically, instead of being ``spelled in full''; this changes the
-allowed strings.
-
-@cindex case, ignored in dates
-@cindex comments, in dates
-Alphabetic case is completely ignored in dates. Comments may be introduced
-between round parentheses, as long as included parentheses are properly
-nested. Hyphens not followed by a digit are currently ignored. Leading
-zeros on numbers are ignored.
-
-
-@node Calendar date item, Time of day item, General date syntax, Date input formats
-@section Calendar date item
-
-@cindex calendar date item
-
-A @dfn{calendar date item} specifies a day of the year. It is
-specified differently, depending on whether the month is specified
-numerically or literally. All these strings specify the same calendar date:
-
-@example
-1970-09-17 # ISO 8601.
-70-9-17 # This century assumed by default.
-70-09-17 # Leading zeros are ignored.
-9/17/72 # Common U.S. writing.
-24 September 1972
-24 Sept 72 # September has a special abbreviation.
-24 Sep 72 # Three-letter abbreviations always allowed.
-Sep 24, 1972
-24-sep-72
-24sep72
-@end example
-
-The year can also be omitted. In this case, the last specified year is
-used, or the current year if none. For example:
-
-@example
-9/17
-sep 17
-@end example
-
-Here are the rules.
-
-@cindex ISO 8601 date format
-@cindex date format, ISO 8601
-For numeric months, the ISO 8601 format
-@samp{@var{year}-@var{month}-@var{day}} is allowed, where @var{year} is
-any positive number, @var{month} is a number between 01 and 12, and
-@var{day} is a number between 01 and 31. A leading zero must be present
-if a number is less than ten. If @var{year} is less than 100, then 1900
-is added to it to force a date in this century. The construct
-@samp{@var{month}/@var{day}/@var{year}}, popular in the United States,
-is accepted. Also @samp{@var{month}/@var{day}}, omitting the year.
-
-@cindex month names in date strings
-@cindex abbreviations for months
-Literal months may be spelled out in full: @samp{January},
-@samp{February}, @samp{March}, @samp{April}, @samp{May}, @samp{June},
-@samp{July}, @samp{August}, @samp{September}, @samp{October},
-@samp{November} or @samp{December}. Literal months may be abbreviated
-to their first three letters, possibly followed by an abbreviating dot.
-It is also permitted to write @samp{Sept} instead of @samp{September}.
-
-When months are written literally, the calendar date may be given as any
-of the following:
+This format has traditionally been used by Automake when producing
+Makefiles. This practice will change in the future, in the meantime,
+however this means that projects containing filenames more than 99
+characters long will not be able to use @GNUTAR{} @value{VERSION} and
+Automake prior to 1.9.
-@example
-@var{day} @var{month} @var{year}
-@var{day} @var{month}
-@var{month} @var{day} @var{year}
-@var{day}-@var{month}-@var{year}
-@end example
-
-Or, omitting the year:
-
-@example
-@var{month} @var{day}
-@end example
-
-
-@node Time of day item, Timezone item, Calendar date item, Date input formats
-@section Time of day item
-
-@cindex time of day item
-
-A @dfn{time of day item} in date strings specifies the time on a given
-day. Here are some examples, all of which represent the same time:
-
-@example
-20:02:0
-20:02
-8:02pm
-20:02-0500 # In EST (Eastern U.S. Standard Time).
-@end example
-
-More generally, the time of the day may be given as
-@samp{@var{hour}:@var{minute}:@var{second}}, where @var{hour} is
-a number between 0 and 23, @var{minute} is a number between 0 and
-59, and @var{second} is a number between 0 and 59. Alternatively,
-@samp{:@var{second}} can be omitted, in which case it is taken to
-be zero.
-
-@findex am @r{in date strings}
-@findex pm @r{in date strings}
-@findex midnight @r{in date strings}
-@findex noon @r{in date strings}
-If the time is followed by @samp{am} or @samp{pm} (or @samp{a.m.}
-or @samp{p.m.}), @var{hour} is restricted to run from 1 to 12, and
-@samp{:@var{minute}} may be omitted (taken to be zero). @samp{am}
-indicates the first half of the day, @samp{pm} indicates the second
-half of the day. In this notation, 12 is the predecessor of 1:
-midnight is @samp{12am} while noon is @samp{12pm}.
-(This is the zero-oriented interpretation of @samp{12am} and @samp{12pm},
-as opposed to the old tradition derived from Latin
-which uses @samp{12m} for noon and @samp{12pm} for midnight.)
-
-@cindex timezone correction
-@cindex minutes, timezone correction by
-The time may alternatively be followed by a timezone correction,
-expressed as @samp{@var{s}@var{hh}@var{mm}}, where @var{s} is @samp{+}
-or @samp{-}, @var{hh} is a number of zone hours and @var{mm} is a number
-of zone minutes. When a timezone correction is given this way, it
-forces interpretation of the time in UTC, overriding any previous
-specification for the timezone or the local timezone. The @var{minute}
-part of the time of the day may not be elided when a timezone correction
-is used. This is the only way to specify a timezone correction by
-fractional parts of an hour.
-
-Either @samp{am}/@samp{pm} or a timezone correction may be specified,
-but not both.
-
-
-@node Timezone item, Day of week item, Time of day item, Date input formats
-@section Timezone item
-
-@cindex timezone item
-
-A @dfn{timezone item} specifies an international timezone, indicated by
-a small set of letters. Any included period is ignored. Military
-timezone designations use a single letter. Currently, only integral
-zone hours may be represented in a timezone item. See the previous
-section for a finer control over the timezone correction.
-
-Here are many non-daylight-savings-time timezones, indexed by the zone
-hour value.
+@item ustar
+Archive format defined by @acronym{POSIX.1-1988} specification. It stores
+symbolic ownership information. It is also able to store
+special files. However, it imposes several restrictions as well:
-@table @asis
-@item +000
-@cindex Greenwich Mean Time
-@cindex Universal Coordinated Time
-@cindex Western European Time
-@samp{GMT} for Greenwich Mean, @samp{UT} or @samp{UTC} for Universal
-(Coordinated), @samp{WET} for Western European and @samp{Z} for
-militaries.
-@item +100
-@cindex West African Time
-@samp{WAT} for West Africa and
-@samp{A} for militaries.
-@item +200
-@cindex Azores Time
-@samp{AT} for Azores and @samp{B} for militaries.
-@item +300
-@samp{C} for militaries.
-@item +400
-@cindex Atlantic Standard Time
-@samp{AST} for Atlantic Standard and @samp{D} for militaries.
-@item +500
-@cindex Eastern Standard Time
-@samp{E} for militaries and @samp{EST} for Eastern Standard.
-@item +600
-@cindex Central Standard Time
-@samp{CST} for Central Standard and @samp{F} for militaries.
-@item +700
-@cindex Mountain Standard Time
-@samp{G} for militaries and @samp{MST} for Mountain Standard.
-@item +800
-@cindex Pacific Standard Time
-@samp{H} for militaries and @samp{PST} for Pacific Standard.
-@item +900
-@cindex Yukon Standard Time
-@samp{I} for militaries and @samp{YST} for Yukon Standard.
-@item +1000
-@cindex Alaska-Hawaii Time
-@cindex Central Alaska Time
-@cindex Hawaii Standard Time
-@samp{AHST} for Alaska-Hawaii Standard, @samp{CAT} for Central Alaska,
-@samp{HST} for Hawaii Standard and @samp{K} for militaries.
-@item +1100
-@cindex Nome Standard Time
-@samp{L} for militaries and @samp{NT} for Nome.
-@item +1200
-@cindex International Date Line West
-@samp{IDLW} for International Date Line West and @samp{M} for
-militaries.
-@item -100
-@cindex Central European Time
-@cindex Middle European Time
-@cindex Middle European Winter Time
-@cindex French Winter Time
-@cindex Swedish Winter Time
-@samp{CET} for Central European, @samp{FWT} for French Winter,
-@samp{MET} for Middle European, @samp{MEWT} for Middle European
-Winter, @samp{N} for militaries and @samp{SWT} for Swedish Winter.
-@item -200
-@cindex Eastern European Time
-@cindex USSR Zone
-@samp{EET} for Eastern European, USSR Zone 1 and @samp{O} for militaries.
-@item -300
-@cindex Baghdad Time
-@samp{BT} for Baghdad, USSR Zone 2 and @samp{P} for militaries.
-@item -400
-@samp{Q} for militaries and @samp{ZP4} for USSR Zone 3.
-@item -500
-@samp{R} for militaries and @samp{ZP5} for USSR Zone 4.
-@item -600
-@samp{S} for militaries and @samp{ZP6} for USSR Zone 5.
-@item -700
-@cindex West Australian Standard Time
-@samp{T} for militaries and @samp{WAST} for West Australian Standard.
-@item -800
-@cindex China Coast Time
-@samp{CCT} for China Coast, USSR Zone 7 and @samp{U} for militaries.
-@item -900
-@cindex Japan Standard Time
-@samp{JST} for Japan Standard, USSR Zone 8 and @samp{V} for militaries.
-@item -1000
-@cindex East Australian Standard Time
-@cindex Guam Standard Time
-@samp{EAST} for East Australian Standard, @samp{GST} for Guam
-Standard, USSR Zone 9 and @samp{W} for militaries.
-@item -1100
-@samp{X} for militaries.
-@item -1200
-@cindex International Date Line East
-@cindex New Zealand Standard Time
-@samp{IDLE} for International Date Line East, @samp{NZST} for
-New Zealand Standard, @samp{NZT} for New Zealand and @samp{Y} for
-militaries.
-@end table
+@enumerate
+@item The maximum length of a file name is limited to 256 characters,
+provided that the filename can be split at directory separator in
+two parts, first of them being at most 155 bytes long. So, in most
+cases the maximum file name length will be shorter than 256
+characters.
+@item The maximum length of a symbolic link name is limited to
+100 characters.
+@item Maximum size of a file the archive is able to accomodate
+is 8GB
+@item Maximum value of UID/GID is 2097151.
+@item Maximum number of bits in device major and minor numbers is 21.
+@end enumerate
-@cindex daylight savings time
-Here are many DST timezones, indexed by the zone hour value. Also, by
-following a non-DST timezone by the string @samp{DST} in a separate word
-(that is, separated by some whitespace), the corresponding DST timezone
-may be specified.
+@item star
+Format used by J@"org Schilling @command{star}
+implementation. @GNUTAR{} is able to read @samp{star} archives but
+currently does not produce them.
+
+@item posix
+Archive format defined by @acronym{POSIX.1-2001} specification. This is the
+most flexible and feature-rich format. It does not impose any
+restrictions on file sizes or filename lengths. This format is quite
+recent, so not all tar implementations are able to handle it properly.
+However, this format is designed in such a way that any tar
+implementation able to read @samp{ustar} archives will be able to read
+most @samp{posix} archives as well, with the only exception that any
+additional information (such as long file names etc.) will in such
+case be extracted as plain text files along with the files it refers to.
+
+This archive format will be the default format for future versions
+of @GNUTAR{}.
-@table @asis
-@item 0
-@samp{BST} for British Summer.
-@item +400
-@samp{ADT} for Atlantic Daylight.
-@item +500
-@samp{EDT} for Eastern Daylight.
-@item +600
-@samp{CDT} for Central Daylight.
-@item +700
-@samp{MDT} for Mountain Daylight.
-@item +800
-@samp{PDT} for Pacific Daylight.
-@item +900
-@samp{YDT} for Yukon Daylight.
-@item +1000
-@samp{HDT} for Hawaii Daylight.
-@item -100
-@samp{MEST} for Middle European Summer, @samp{MESZ} for Middle European
-Summer, @samp{SST} for Swedish Summer and @samp{FST} for French Summer.
-@item -700
-@samp{WADT} for West Australian Daylight.
-@item -1000
-@samp{EADT} for Eastern Australian Daylight.
-@item -1200
-@samp{NZDT} for New Zealand Daylight.
@end table
+The following table summarizes the limitations of each of these
+formats:
-@node Day of week item, Relative item in date strings, Timezone item, Date input formats
-@section Day of week item
-
-@cindex day of week item
-
-The explicit mention of a day of the week will forward the date
-(only if necessary) to reach that day of the week in the future.
-
-Days of the week may be spelled out in full: @samp{Sunday},
-@samp{Monday}, @samp{Tuesday}, @samp{Wednesday}, @samp{Thursday},
-@samp{Friday} or @samp{Saturday}. Days may be abbreviated to their
-first three letters, optionally followed by a period. The special
-abbreviations @samp{Tues} for @samp{Tuesday}, @samp{Wednes} for
-@samp{Wednesday} and @samp{Thur} or @samp{Thurs} for @samp{Thursday} are
-also allowed.
-
-@findex next @var{day}
-@findex last @var{day}
-A number may precede a day of the week item to move forward
-supplementary weeks. It is best used in expression like @samp{third
-monday}. In this context, @samp{last @var{day}} or @samp{next
-@var{day}} is also acceptable; they move one week before or after
-the day that @var{day} by itself would represent.
-
-A comma following a day of the week item is ignored.
-
-
-@node Relative item in date strings, Pure numbers in date strings, Day of week item, Date input formats
-@section Relative item in date strings
-
-@cindex relative items in date strings
-@cindex displacement of dates
-
-@dfn{Relative items} adjust a date (or the current date if none) forward
-or backward. The effects of relative items accumulate. Here are some
-examples:
-
-@example
-1 year
-1 year ago
-3 years
-2 days
-@end example
-
-@findex year @r{in date strings}
-@findex month @r{in date strings}
-@findex fortnight @r{in date strings}
-@findex week @r{in date strings}
-@findex day @r{in date strings}
-@findex hour @r{in date strings}
-@findex minute @r{in date strings}
-The unit of time displacement may be selected by the string @samp{year}
-or @samp{month} for moving by whole years or months. These are fuzzy
-units, as years and months are not all of equal duration. More precise
-units are @samp{fortnight} which is worth 14 days, @samp{week} worth 7
-days, @samp{day} worth 24 hours, @samp{hour} worth 60 minutes,
-@samp{minute} or @samp{min} worth 60 seconds, and @samp{second} or
-@samp{sec} worth one second. An @samp{s} suffix on these units is
-accepted and ignored.
-
-@findex ago @r{in date strings}
-The unit of time may be preceded by a multiplier, given as an optionally
-signed number. Unsigned numbers are taken as positively signed. No
-number at all implies 1 for a multiplier. Following a relative item by
-the string @samp{ago} is equivalent to preceding the unit by a
-multiplicator with value @math{-1}.
-
-@findex day @r{in date strings}
-@findex tomorrow @r{in date strings}
-@findex yesterday @r{in date strings}
-The string @samp{tomorrow} is worth one day in the future (equivalent
-to @samp{day}), the string @samp{yesterday} is worth
-one day in the past (equivalent to @samp{day ago}).
-
-@findex now @r{in date strings}
-@findex today @r{in date strings}
-@findex this @r{in date strings}
-The strings @samp{now} or @samp{today} are relative items corresponding
-to zero-valued time displacement, these strings come from the fact
-a zero-valued time displacement represents the current time when not
-otherwise change by previous items. They may be used to stress other
-items, like in @samp{12:00 today}. The string @samp{this} also has
-the meaning of a zero-valued time displacement, but is preferred in
-date strings like @samp{this thursday}.
-
-When a relative item makes the resulting date to cross the boundary
-between DST and non-DST (or vice-versa), the hour is adjusted according
-to the local time.
-
-
-@node Pure numbers in date strings, Authors of getdate, Relative item in date strings, Date input formats
-@section Pure numbers in date strings
-
-@cindex pure numbers in date strings
-
-The precise intepretation of a pure decimal number is dependent of
-the context in the date string.
-
-If the decimal number is of the form @var{yyyy}@var{mm}@var{dd} and no
-other calendar date item (@pxref{Calendar date item}) appears before it
-in the date string, then @var{yyyy} is read as the year, @var{mm} as the
-month number and @var{dd} as the day of the month, for the specified
-calendar date.
-
-If the decimal number is of the form @var{hh}@var{mm} and no other time
-of day item appears before it in the date string, then @var{hh} is read
-as the hour of the day and @var{mm} as the minute of the hour, for the
-specified time of the day. @var{mm} can also be omitted.
-
-If both a calendar date and a time of day appear to the left of a number
-in the date string, but no relative item, then the number overrides the
-year.
-
-
-@node Authors of getdate, , Pure numbers in date strings, Date input formats
-@section Authors of @code{getdate}
-
-@cindex authors of @code{getdate}
-
-@cindex Bellovin, Steven M.
-@cindex Salz, Rich
-@cindex Berets, Jim
-@cindex MacKenzie, David
-@cindex Meyering, Jim
-@code{getdate} was originally implemented by Steven M. Bellovin
-(@samp{smb@@research.att.com}) while at the University of North Carolina
-at Chapel Hill. The code was later tweaked by a couple of people on
-Usenet, then completely overhauled by Rich $alz (@samp{rsalz@@bbn.com})
-and Jim Berets (@samp{jberets@@bbn.com}) in August, 1990. Various
-revisions for the GNU system were made by David MacKenzie, Jim Meyering,
-and others.
-
-@cindex Pinard, F.
-@cindex Berry, K.
-This chapter was originally produced by Fran@,{c}ois Pinard
-(@samp{pinard@@iro.umontreal.ca}) from the @file{getdate.y} source code,
-and then edited by K.@: Berry (@samp{kb@@cs.umb.edu}).
-
-@node Formats, Media, Date input formats, Top
-@chapter Controlling the Archive Format
+@multitable @columnfractions .10 .20 .20 .20 .20
+@headitem Format @tab UID @tab File Size @tab Path Name @tab Devn
+@item gnu @tab 1.8e19 @tab Unlimited @tab Unlimited @tab 63
+@item oldgnu @tab 1.8e19 @tab Unlimited @tab Unlimited @tab 63
+@item v7 @tab 2097151 @tab 8GB @tab 99 @tab n/a
+@item ustar @tab 2097151 @tab 8GB @tab 256 @tab 21
+@item posix @tab Unlimited @tab Unlimited @tab Unlimited @tab Unlimited
+@end multitable
-@FIXME{need an intro here}
+The default format for @GNUTAR{} is defined at compilation
+time. You may check it by running @command{tar --help}, and examining
+the last lines of its output. Usually, @GNUTAR{} is configured
+to create archives in @samp{gnu} format, however, future version will
+switch to @samp{posix}.
@menu
-* Portability:: Making @code{tar} Archives More Portable
+* Portability:: Making @command{tar} Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
-* Extensions:: GNU Extensions to the Archive Format
-* cpio:: Comparison of @code{tar} and @code{cpio}
+* Extensions:: @acronym{GNU} Extensions to the Archive Format
+* cpio:: Comparison of @command{tar} and @command{cpio}
@end menu
-@node Portability, Compression, Formats, Formats
-@section Making @code{tar} Archives More Portable
+@node Portability
+@section Making @command{tar} Archives More Portable
-Creating a @code{tar} archive on a particular system that is meant to be
-useful later on many other machines and with other versions of @code{tar}
-is more challenging than you might think. @code{tar} archive formats
+Creating a @command{tar} archive on a particular system that is meant to be
+useful later on many other machines and with other versions of @command{tar}
+is more challenging than you might think. @command{tar} archive formats
have been evolving since the first versions of Unix. Many such formats
-are around, and are not always comptible with each other. This section
-discusses a few problems, and gives some advice about making @code{tar}
+are around, and are not always compatible with each other. This section
+discusses a few problems, and gives some advice about making @command{tar}
archives more portable.
-One golden rule is simplicity. For example, limit your @code{tar}
+One golden rule is simplicity. For example, limit your @command{tar}
archives to contain only regular files and directories, avoiding
other kind of special files. Do not attempt to save sparse files or
contiguous files as such. Let's discuss a few more problems, in turn.
+@FIXME{Discuss GNU extensions (incremental backups, multi-volume
+archives and archive labels) in GNU and PAX formats.}
+
@menu
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: POSIX archives
+* ustar:: Ustar Archives
+* gnu:: GNU and old GNU format archives.
+* posix:: @acronym{POSIX} archives
* Checksumming:: Checksumming Problems
+* Large or Negative Values:: Large files, negative time stamps, etc.
@end menu
-@node Portable Names, dereference, Portability, Portability
+@node Portable Names
@subsection Portable Names
-Use @emph{straight} file and directory names, made up of printable
-ASCII characters, avoiding colons, slashes, backslashes, spaces, and
-other @emph{dangerous} characters. Avoid deep directory nesting.
-Accounting for oldish System V machines, limit your file and directory
-names to 14 characters or less.
+Use portable file and member names. A name is portable if it contains
+only ASCII letters and digits, @samp{/}, @samp{.}, @samp{_}, and
+@samp{-}; it cannot be empty, start with @samp{-} or @samp{//}, or
+contain @samp{/-}. Avoid deep directory nesting. For portability to
+old Unix hosts, limit your file name components to 14 characters or
+less.
-If you intend to have your @code{tar} archives to be read under MSDOS,
-you should not rely on case distinction for file names, and you might
-use the GNU @code{doschk} program for helping you further diagnosing
-illegal MSDOS names, which are even more limited than System V's.
+If you intend to have your @command{tar} archives to be read under
+MSDOS, you should not rely on case distinction for file names, and you
+might use the @acronym{GNU} @command{doschk} program for helping you
+further diagnosing illegal MSDOS names, which are even more limited
+than System V's.
-@node dereference, old, Portable Names, Portability
+@node dereference
@subsection Symbolic Links
@cindex File names, using symbolic links
@cindex Symbolic link as file name
-Normally, when @code{tar} archives a symbolic link, it writes a
+@opindex dereference
+Normally, when @command{tar} archives a symbolic link, it writes a
block to the archive naming the target of the link. In that way, the
-@code{tar} archive is a faithful record of the filesystem contents.
-@value{op-dereference} is used with @value{op-create}, and causes @code{tar}
-to archive the files symbolic links point to, instead of the links
-themselves. When this option is used, when @code{tar} encounters a
-symbolic link, it will archive the linked-to file, instead of simply
-recording the presence of a symbolic link.
+@command{tar} archive is a faithful record of the file system contents.
+@option{--dereference} (@option{-h}) is used with @option{--create} (@option{-c}), and causes
+@command{tar} to archive the files symbolic links point to, instead of
+the links themselves. When this option is used, when @command{tar}
+encounters a symbolic link, it will archive the linked-to file,
+instead of simply recording the presence of a symbolic link.
The name under which the file is stored in the file system is not
recorded in the archive. To record both the symbolic link name and
the file name in the system, archive the file under both names. If
-all links were recorded automatically by @code{tar}, an extracted file
+all links were recorded automatically by @command{tar}, an extracted file
might be linked to a file name that no longer exists in the file
system.
-If a linked-to file is encountered again by @code{tar} while creating
+If a linked-to file is encountered again by @command{tar} while creating
the same archive, an entire second copy of it will be stored. (This
@emph{might} be considered a bug.)
So, for portable archives, do not archive symbolic links as such,
-and use @value{op-dereference}: many systems do not support
+and use @option{--dereference} (@option{-h}): many systems do not support
symbolic links, and moreover, your distribution might be unusable if
it contains unresolved symbolic links.
-@node old, posix, dereference, Portability
+@node old
@subsection Old V7 Archives
@cindex Format, old style
@cindex Old style format
@cindex Old style archives
+@cindex v7 archive format
-Certain old versions of @code{tar} cannot handle additional
-information recorded by newer @code{tar} programs. To create an
+Certain old versions of @command{tar} cannot handle additional
+information recorded by newer @command{tar} programs. To create an
archive in V7 format (not ANSI), which can be read by these old
-versions, specify the @value{op-old-archive} option in
-conjunction with the @value{op-create}. @code{tar} also
-accepts @samp{--portability} for this option. When you specify it,
-@code{tar} leaves out information about directories, pipes, fifos,
+versions, specify the @option{--format=v7} option in
+conjunction with the @option{--create} (@option{-c}) (@command{tar} also
+accepts @option{--portability} or @samp{op-old-archive} for this
+option). When you specify it,
+@command{tar} leaves out information about directories, pipes, fifos,
contiguous files, and device files, and specifies file ownership by
group and user IDs instead of group and user names.
-When updating an archive, do not use @value{op-old-archive}
-unless the archive was created with using this option.
+When updating an archive, do not use @option{--format=v7}
+unless the archive was created using this option.
In most cases, a @emph{new} format archive can be read by an @emph{old}
-@code{tar} program without serious trouble, so this option should
-seldom be needed. On the other hand, most modern @code{tar}s are
+@command{tar} program without serious trouble, so this option should
+seldom be needed. On the other hand, most modern @command{tar}s are
able to read old format archives, so it might be safer for you to
-always use @value{op-old-archive} for your distributions.
-
-@node posix, Checksumming, old, Portability
-@subsection GNU @code{tar} and POSIX @code{tar}
-
-GNU @code{tar} was based on an early draft of the POSIX 1003.1
-@code{ustar} standard. GNU extensions to @code{tar}, such as the
-support for file names longer than 100 characters, use portions of the
-@code{tar} header record which were specified in that POSIX draft as
-unused. Subsequent changes in POSIX have allocated the same parts of
-the header record for other purposes. As a result, GNU @code{tar} is
-incompatible with the current POSIX spec, and with @code{tar} programs
-that follow it.
-
-We plan to reimplement these GNU extensions in a new way which is
-upward compatible with the latest POSIX @code{tar} format, but we
-don't know when this will be done.
-
-In the mean time, there is simply no telling what might happen if you
-read a GNU @code{tar} archive, which uses the GNU extensions, using
-some other @code{tar} program. So if you want to read the archive
-with another @code{tar} program, be sure to write it using the
-@samp{--old-archive} option (@samp{-o}).
-
-@FIXME{is there a way to tell which flavor of tar was used to write a
-particular archive before you try to read it?}
-
-Traditionally, old @code{tar}s have a limit of 100 characters. GNU
-@code{tar} attempted two different approaches to overcome this limit,
-using and extending a format specified by a draft of some P1003.1.
-The first way was not that successful, and involved @file{@@MaNgLeD@@}
-file names, or such; while a second approach used @file{././@@LongLink}
-and other tricks, yielding better success. In theory, GNU @code{tar}
-should be able to handle file names of practically unlimited length.
-So, if GNU @code{tar} fails to dump and retrieve files having more
-than 100 characters, then there is a bug in GNU @code{tar}, indeed.
-
-But, being strictly POSIX, the limit was still 100 characters.
-For various other purposes, GNU @code{tar} used areas left unassigned
-in the POSIX draft. POSIX later revised P1003.1 @code{ustar} format by
-assigning previously unused header fields, in such a way that the upper
-limit for file name length was raised to 256 characters. However, the
-actual POSIX limit oscillates between 100 and 256, depending on the
-precise location of slashes in full file name (this is rather ugly).
-Since GNU @code{tar} use the same fields for quite other purposes,
-it became incompatible with the latest POSIX standards.
-
-For longer or non-fitting file names, we plan to use yet another set
-of GNU extensions, but this time, complying with the provisions POSIX
-offers for extending the format, rather than conflicting with it.
-Whenever an archive uses old GNU @code{tar} extension format or POSIX
-extensions, would it be for very long file names or other specialities,
-this archive becomes non-portable to other @code{tar} implementations.
-In fact, anything can happen. The most forgiving @code{tar}s will
-merely unpack the file using a wrong name, and maybe create another
-file named something like @file{@@LongName}, with the true file name
-in it. @code{tar}s not protecting themselves may segment violate!
-
-Compatibility concerns make all this thing more difficult, as we
-will have to support @emph{all} these things together, for a while.
-GNU @code{tar} should be able to produce and read true POSIX format
-files, while being able to detect old GNU @code{tar} formats, besides
-old V7 format, and process them conveniently. It would take years
-before this whole area stabilizes@dots{}
-
-There are plans to raise this 100 limit to 256, and yet produce POSIX
-conformant archives. Past 256, I do not know yet if GNU @code{tar}
-will go non-POSIX again, or merely refuse to archive the file.
-
-There are plans so GNU @code{tar} support more fully the latest POSIX
-format, while being able to read old V7 format, GNU (semi-POSIX plus
-extension), as well as full POSIX. One may ask if there is part of
-the POSIX format that we still cannot support. This simple question
-has a complex answer. Maybe that, on intimate look, some strong
-limitations will pop up, but until now, nothing sounds too difficult
-(but see below). I only have these few pages of POSIX telling about
-`Extended tar Format' (P1003.1-1990 -- section 10.1.1), and there are
-references to other parts of the standard I do not have, which should
-normally enforce limitations on stored file names (I suspect things
-like fixing what @kbd{/} and @kbd{@key{NUL}} means). There are also
-some points which the standard does not make clear, Existing practice
-will then drive what I should do.
-
-POSIX mandates that, when a file name cannot fit within 100 to
-256 characters (the variance comes from the fact a @kbd{/} is
-ideally needed as the 156'th character), or a link name cannot
-fit within 100 characters, a warning should be issued and the file
-@emph{not} be stored. Unless some @value{op-posix} option is given
-(or @code{POSIXLY_CORRECT} is set), I suspect that GNU @code{tar}
-should disobey this specification, and automatically switch to using
-GNU extensions to overcome file name or link name length limitations.
-
-There is a problem, however, which I did not intimately studied yet.
-Given a truly POSIX archive with names having more than 100 characters,
-I guess that GNU @code{tar} up to 1.11.8 will process it as if it were an
-old V7 archive, and be fooled by some fields which are coded differently.
-So, the question is to decide if the next generation of GNU @code{tar}
-should produce POSIX format by default, whenever possible, producing
-archives older versions of GNU @code{tar} might not be able to read
-correctly. I fear that we will have to suffer such a choice one of these
-days, if we want GNU @code{tar} to go closer to POSIX. We can rush it.
-Another possibility is to produce the current GNU @code{tar} format
-by default for a few years, but have GNU @code{tar} versions from some
-1.@var{POSIX} and up able to recognize all three formats, and let older
-GNU @code{tar} fade out slowly. Then, we could switch to producing POSIX
-format by default, with not much harm to those still having (very old at
-that time) GNU @code{tar} versions prior to 1.@var{POSIX}.
-
-POSIX format cannot represent very long names, volume headers,
-splitting of files in multi-volumes, sparse files, and incremental
-dumps; these would be all disallowed if @value{op-posix} or
-@code{POSIXLY_CORRECT}. Otherwise, if @code{tar} is given long
-names, or @samp{-[VMSgG]}, then it should automatically go non-POSIX.
-I think this is easily granted without much discussion.
-
-Another point is that only @code{mtime} is stored in POSIX
-archives, while GNU @code{tar} currently also store @code{atime}
-and @code{ctime}. If we want GNU @code{tar} to go closer to POSIX,
-my choice would be to drop @code{atime} and @code{ctime} support on
-average. On the other hand, I perceive that full dumps or incremental
-dumps need @code{atime} and @code{ctime} support, so for those special
-applications, POSIX has to be avoided altogether.
-
-A few users requested that @value{op-sparse} be always active by
-default, I think that before replying to them, we have to decide
-if we want GNU @code{tar} to go closer to POSIX on average, while
-producing files. My choice would be to go closer to POSIX in the
-long run. Besides possible double reading, I do not see any point
-of not trying to save files as sparse when creating archives which
-are neither POSIX nor old-V7, so the actual @value{op-sparse} would
-become selected by default when producing such archives, whatever
-the reason is. So, @value{op-sparse} alone might be redefined to force
-GNU-format archives, and recover its previous meaning from this fact.
-
-GNU-format as it exists now can easily fool other POSIX @code{tar},
-as it uses fields which POSIX considers to be part of the file name
-prefix. I wonder if it would not be a good idea, in the long run,
-to try changing GNU-format so any added field (like @code{ctime},
-@code{atime}, file offset in subsequent volumes, or sparse file
-descriptions) be wholly and always pushed into an extension block,
-instead of using space in the POSIX header block. I could manage
-to do that portably between future GNU @code{tar}s. So other POSIX
-@code{tar}s might be at least able to provide kind of correct listings
-for the archives produced by GNU @code{tar}, if not able to process
-them otherwise.
-
-Using these projected extensions might induce older @code{tar}s to fail.
-We would use the same approach as for POSIX. I'll put out a @code{tar}
-capable of reading POSIXier, yet extended archives, but will not produce
-this format by default, in GNU mode. In a few years, when newer GNU
-@code{tar}s will have flooded out @code{tar} 1.11.X and previous, we
-could switch to producing POSIXier extended archives, with no real harm
-to users, as almost all existing GNU @code{tar}s will be ready to read
-POSIXier format. In fact, I'll do both changes at the same time, in a
-few years, and just prepare @code{tar} for both changes, without effecting
-them, from 1.@var{POSIX}. (Both changes: 1---using POSIX convention for
-getting over 100 characters; 2---avoiding mangling POSIX headers for GNU
-extensions, using only POSIX mandated extension techniques).
-
-So, a future @code{tar} will have a @value{op-posix}
-flag forcing the usage of truly POSIX headers, and so, producing
-archives previous GNU @code{tar} will not be able to read.
-So, @emph{once} pretest will announce that feature, it would be
-particularly useful that users test how exchangeable will be archives
-between GNU @code{tar} with @value{op-posix} and other POSIX @code{tar}.
-
-In a few years, when GNU @code{tar} will produce POSIX headers by
-default, @value{op-posix} will have a strong meaning and will disallow
-GNU extensions. But in the meantime, for a long while, @value{op-posix}
-in GNU tar will not disallow GNU extensions like @value{op-label},
-@value{op-multi-volume}, @value{op-sparse}, or very long file or link names.
-However, @value{op-posix} with GNU extensions will use POSIX
-headers with reserved-for-users extensions to headers, and I will be
-curious to know how well or bad POSIX @code{tar}s will react to these.
-
-GNU @code{tar} prior to 1.@var{POSIX}, and after 1.@var{POSIX} without
-@value{op-posix}, generates and checks @samp{ustar@w{ }@w{ }}, with two
-suffixed spaces. This is sufficient for older GNU @code{tar} not to
-recognize POSIX archives, and consequently, wrongly decide those archives
-are in old V7 format. It is a useful bug for me, because GNU @code{tar}
-has other POSIX incompatibilities, and I need to segregate GNU @code{tar}
-semi-POSIX archives from truly POSIX archives, for GNU @code{tar} should
-be somewhat compatible with itself, while migrating closer to latest
-POSIX standards. So, I'll be very careful about how and when I will do
-the correction.
-
-@node Checksumming, , posix, Portability
+always use @option{--format=v7} for your distributions.
+
+@node ustar
+@subsection Ustar Archive Format
+
+@cindex ustar archive format
+Archive format defined by @acronym{POSIX}.1-1988 specification is called
+@code{ustar}. Although it is more flexible than the V7 format, it
+still has many restrictions (@xref{Formats,ustar}, for the detailed
+description of @code{ustar} format). Along with V7 format,
+@code{ustar} format is a good choice for archives intended to be read
+with other implementations of @command{tar}.
+
+To create archive in @code{ustar} format, use @option{--format=ustar}
+option in conjunction with the @option{--create} (@option{-c}).
+
+@node gnu
+@subsection @acronym{GNU} and old @GNUTAR{} format
+
+@cindex GNU archive format
+@cindex Old GNU archive format
+@GNUTAR{} was based on an early draft of the
+@acronym{POSIX} 1003.1 @code{ustar} standard. @acronym{GNU} extensions to
+@command{tar}, such as the support for file names longer than 100
+characters, use portions of the @command{tar} header record which were
+specified in that @acronym{POSIX} draft as unused. Subsequent changes in
+@acronym{POSIX} have allocated the same parts of the header record for
+other purposes. As a result, @GNUTAR{} format is
+incompatible with the current @acronym{POSIX} specification, and with
+@command{tar} programs that follow it.
+
+In the majority of cases, @command{tar} will be configured to create
+this format by default. This will change in the future releases, since
+we plan to make @samp{posix} format the default.
+
+To force creation a @GNUTAR{} archive, use option
+@option{--format=gnu}.
+
+@node posix
+@subsection @GNUTAR{} and @acronym{POSIX} @command{tar}
+
+@cindex POSIX archive format
+@cindex PAX archive format
+The version @value{VERSION} of @GNUTAR{} is able
+to read and create archives conforming to @acronym{POSIX.1-2001} standard.
+
+A @acronym{POSIX} conformant archive will be created if @command{tar}
+was given @option{--format=posix} option.
+
+@node Checksumming
@subsection Checksumming Problems
-SunOS and HP-UX @code{tar} fail to accept archives created using GNU
-@code{tar} and containing non-ASCII file names, that is, file names
-having characters with the eight bit set, because they use signed
-checksums, while GNU @code{tar} uses unsigned checksums while creating
-archives, as per POSIX standards. On reading, GNU @code{tar} computes
-both checksums and accept any. It is somewhat worrying that a lot of
-people may go around doing backup of their files using faulty (or at
-least non-standard) software, not learning about it until it's time
-to restore their missing files with an incompatible file extractor,
-or vice versa.
-
-GNU @code{tar} compute checksums both ways, and accept any on read,
-so GNU tar can read Sun tapes even with their wrong checksums.
-GNU @code{tar} produces the standard checksum, however, raising
-incompatibilities with Sun. That is to say, GNU @code{tar} has not
-been modified to @emph{produce} incorrect archives to be read by buggy
-@code{tar}'s. I've been told that more recent Sun @code{tar} now
-read standard archives, so maybe Sun did a similar patch, after all?
-
-The story seems to be that when Sun first imported @code{tar}
+SunOS and HP-UX @command{tar} fail to accept archives created using
+@GNUTAR{} and containing non-ASCII file names, that
+is, file names having characters with the eight bit set, because they
+use signed checksums, while @GNUTAR{} uses unsigned
+checksums while creating archives, as per @acronym{POSIX} standards. On
+reading, @GNUTAR{} computes both checksums and
+accept any. It is somewhat worrying that a lot of people may go
+around doing backup of their files using faulty (or at least
+non-standard) software, not learning about it until it's time to
+restore their missing files with an incompatible file extractor, or
+vice versa.
+
+@GNUTAR{} compute checksums both ways, and accept
+any on read, so @acronym{GNU} tar can read Sun tapes even with their
+wrong checksums. @GNUTAR{} produces the standard
+checksum, however, raising incompatibilities with Sun. That is to
+say, @GNUTAR{} has not been modified to
+@emph{produce} incorrect archives to be read by buggy @command{tar}'s.
+I've been told that more recent Sun @command{tar} now read standard
+archives, so maybe Sun did a similar patch, after all?
+
+The story seems to be that when Sun first imported @command{tar}
sources on their system, they recompiled it without realizing that
the checksums were computed differently, because of a change in
the default signing of @code{char}'s in their compiler. So they
started computing checksums wrongly. When they later realized their
mistake, they merely decided to stay compatible with it, and with
themselves afterwards. Presumably, but I do not really know, HP-UX
-has chosen that their @code{tar} archives to be compatible with Sun's.
-The current standards do not favor Sun @code{tar} format. In any
+has chosen that their @command{tar} archives to be compatible with Sun's.
+The current standards do not favor Sun @command{tar} format. In any
case, it now falls on the shoulders of SunOS and HP-UX users to get
-a @code{tar} able to read the good archives they receive.
-
-@node Compression, Attributes, Portability, Formats
+a @command{tar} able to read the good archives they receive.
+
+@node Large or Negative Values
+@subsection Large or Negative Values
+@cindex large values
+@cindex future time stamps
+@cindex negative time stamps
+@UNREVISED{}
+
+The above sections suggest to use @samp{oldest possible} archive
+format if in doubt. However, sometimes it is not possible. If you
+attempt to archive a file whose metadata cannot be represented using
+required format, @GNUTAR{} will print error message and ignore such a
+file. You will than have to switch to a format that is able to
+handle such values. The format summary table (@pxref{Formats}) will
+help you to do so.
+
+In particular, when trying to archive files larger than 8GB or with
+timestamps not in the range 1970-01-01 00:00:00 through 2242-03-16
+12:56:31 @sc{utc}, you will have to chose between @acronym{GNU} and
+@acronym{POSIX} archive formats. When considering which format to
+choose, bear in mind that the @acronym{GNU} format uses
+two's-complement base-256 notation to store values that do not fit
+into standard @acronym{ustar} range. Such archives can generally be
+read only by a @GNUTAR{} implementation. Moreover, they sometimes
+cannot be correctly restored on another hosts even by @GNUTAR{}. For
+example, using two's complement representation for negative time
+stamps that assumes a signed 32-bit @code{time_t} generates archives
+that are not portable to hosts with differing @code{time_t}
+representations.
+
+On the other hand, @acronym{POSIX} archives, generally speaking, can
+be extracted by any tar implementation that understands older
+@acronym{ustar} format. The only exception are files larger than 8GB.
+
+@FIXME{Describe how @acronym{POSIX} archives are extracted by non
+POSIX-aware tars.}
+
+@node Compression
@section Using Less Space through Compression
@menu
* sparse:: Archiving Sparse Files
@end menu
-@node gzip, sparse, Compression, Compression
+@node gzip
@subsection Creating and Reading Compressed Archives
@cindex Compressed archives
@cindex Storing archives in compressed format
-@UNREVISED
-@table @kbd
+@GNUTAR{} is able to create and read compressed archives. It supports
+@command{gzip} and @command{bzip2} compression programs. For backward
+compatibilty, it also supports @command{compress} command, although
+we strongly recommend against using it, since there is a patent
+covering the algorithm it uses and you could be sued for patent
+infringement merely by running @command{compress}! Besides, it is less
+effective than @command{gzip} and @command{bzip2}.
+
+Creating a compressed archive is simple: you just specify a
+@dfn{compression option} along with the usual archive creation
+commands. The compression option is @option{-z} (@option{--gzip}) to
+create a @command{gzip} compressed archive, @option{-j}
+(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
+@option{-Z} (@option{--compress}) to use @command{compress} program.
+For example:
+
+@smallexample
+$ @kbd{tar cfz archive.tar.gz .}
+@end smallexample
+
+Reading compressed archive is even simpler: you don't need to specify
+any additional options as @GNUTAR{} recognizes its format
+automatically. Thus, the following commands will list and extract the
+archive created in previous example:
+
+@smallexample
+# List the compressed archive
+$ @kbd{tar tf archive.tar.gz}
+# Extract the compressed archive
+$ @kbd{tar xf archive.tar.gz}
+@end smallexample
+
+The only case when you have to specify a decompression option while
+reading the archive is when reading from a pipe or from a tape drive
+that does not support random access. However, in this case @GNUTAR{}
+will indicate which option you should use. For example:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tf -}
+tar: Archive is compressed. Use -z option
+tar: Error is not recoverable: exiting now
+@end smallexample
+
+If you see such diagnostics, just add the suggested option to the
+invocation of @GNUTAR{}:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tfz -}
+@end smallexample
+
+Notice also, that there are several restrictions on operations on
+compressed archives. First of all, compressed archives cannot be
+modified, i.e., you cannot update (@option{--update} (@option{-u})) them or delete
+(@option{--delete}) members from them. Likewise, you cannot append
+another @command{tar} archive to a compressed archive using
+@option{--append} (@option{-r})). Secondly, multi-volume archives cannot be
+compressed.
+
+The following table summarizes compression options used by @GNUTAR{}.
+
+@table @option
+@opindex gzip
+@opindex ungzip
@item -z
@itemx --gzip
@itemx --ungzip
-Filter the archive through @code{gzip}.
-@end table
-
-@FIXME{ach; these two bits orig from "compare" (?). where to put?} Some
-format parameters must be taken into consideration when modifying an
-archive: @FIXME{???}. Compressed archives cannot be modified.
+Filter the archive through @command{gzip}.
-You can use @samp{--gzip} and @samp{--gunzip} on physical devices
+You can use @option{--gzip} and @option{--gunzip} on physical devices
(tape drives, etc.) and remote files as well as on normal files; data
to or from such devices or remote files is reblocked by another copy
-of the @code{tar} program to enforce the specified (or default) record
+of the @command{tar} program to enforce the specified (or default) record
size. The default compression parameters are used; if you need to
-override them, avoid the @value{op-gzip} option and run @code{gzip}
-explicitly. (Or set the @samp{GZIP} environment variable.)
+override them, set @env{GZIP} environment variable, e.g.:
-The @value{op-gzip} option does not work with the @value{op-multi-volume}
-option, or with the @value{op-update}, @value{op-append},
-@value{op-concatenate}, or @value{op-delete} operations.
-
-It is not exact to say that GNU @code{tar} is to work in concert
-with @code{gzip} in a way similar to @code{zip}, say. Surely, it is
-possible that @code{tar} and @code{gzip} be done with a single call,
-like in:
-
-@example
-$ @kbd{tar cfz archive.tar.gz subdir}
-@end example
-
-@noindent
-to save all of @samp{subdir} into a @code{gzip}'ed archive. Later you
-can do:
-
-@example
-$ @kbd{tar xfz archive.tar.gz}
-@end example
+@smallexample
+$ @kbd{GZIP=--best tar cfz archive.tar.gz subdir}
+@end smallexample
@noindent
-to explode and unpack.
-
-The difference is that the whole archive is compressed. With
-@code{zip}, archive members are archived individually. @code{tar}'s
-method yields better compression. On the other hand, one can view the
-contents of a @code{zip} archive without having to decompress it. As
-for the @code{tar} and @code{gzip} tandem, you need to decompress the
-archive to see its contents. However, this may be done without needing
-disk space, by using pipes internally:
+Another way would be to avoid the @option{--gzip} (@option{--gunzip}, @option{--ungzip}, @option{-z}) option and run
+@command{gzip} explicitly:
-@example
-$ @kbd{tar tfz archive.tar.gz}
-@end example
+@smallexample
+$ @kbd{tar cf - subdir | gzip --best -c - > archive.tar.gz}
+@end smallexample
@cindex corrupted archives
-About corrupted compressed archives: @code{gzip}'ed files have no
+About corrupted compressed archives: @command{gzip}'ed files have no
redundancy, for maximum compression. The adaptive nature of the
compression scheme means that the compression tables are implicitly
spread all over the archive. If you lose a few blocks, the dynamic
-construction of the compression tables becomes unsychronized, and there
+construction of the compression tables becomes unsynchronized, and there
is little chance that you could recover later in the archive.
There are pending suggestions for having a per-volume or per-file
-compression in GNU @code{tar}. This would allow for viewing the
+compression in @GNUTAR{}. This would allow for viewing the
contents without decompression, and for resynchronizing decompression at
every volume or file, in case of corrupted archives. Doing so, we might
-loose some compressibility. But this would have make recovering easier.
+lose some compressibility. But this would have make recovering easier.
So, there are pros and cons. We'll see!
-@table @kbd
-@item -y
+@opindex bzip2
+@item -j
@itemx --bzip2
-Filter the archive through @code{bzip2}. Otherwise like @value{op-gzip}.
+Filter the archive through @code{bzip2}. Otherwise like @option{--gzip}.
+@opindex compress
+@opindex uncompress
@item -Z
@itemx --compress
@itemx --uncompress
-Filter the archive through @code{compress}. Otherwise like @value{op-gzip}.
-
-@item --use-compress-program=@var{prog}
-Filter through @var{prog} (must accept @samp{-d}).
-@end table
-
-@value{op-compress} stores an archive in compressed format. This
-option is useful in saving time over networks and space in pipes, and
-when storage space is at a premium. @value{op-compress} causes
-@code{tar} to compress when writing the archive, or to uncompress when
-reading the archive.
-
-To perform compression and uncompression on the archive, @code{tar}
-runs the @code{compress} utility. @code{tar} uses the default
-compression parameters; if you need to override them, avoid the
-@value{op-compress} option and run the @code{compress} utility
-explicitly. It is useful to be able to call the @code{compress}
-utility from within @code{tar} because the @code{compress} utility by
-itself cannot access remote tape drives.
+Filter the archive through @command{compress}. Otherwise like @option{--gzip}.
-The @value{op-compress} option will not work in conjunction with the
-@value{op-multi-volume} option or the @value{op-append}, @value{op-update},
-@value{op-append} and @value{op-delete} operations. @xref{Operations}, for
-more information on these operations.
+The @acronym{GNU} Project recommends you not use
+@command{compress}, because there is a patent covering the algorithm it
+uses. You could be sued for patent infringement merely by running
+@command{compress}.
-If there is no compress utility available, @code{tar} will report an error.
-@strong{Please note} that the @code{compress} program may be covered by
-a patent, and therefore we recommend you stop using it.
+@opindex use-compress-program
+@item --use-compress-program=@var{prog}
+Use external compression program @var{prog}. Use this option if you
+have a compression program that @GNUTAR{} does not support. There
+are two requirements to which @var{prog} should comply:
-@value{op-bzip2} acts like @value{op-compress}, except that it uses
-the @code{bzip2} utility.
+First, when called without options, it should read data from standard
+input, compress it and output it on standard output.
-@table @kbd
-@item --compress
-@itemx --uncompress
-@itemx -z
-@itemx -Z
-When this option is specified, @code{tar} will compress (when writing
-an archive), or uncompress (when reading an archive). Used in
-conjunction with the @value{op-create}, @value{op-extract}, @value{op-list} and
-@value{op-compare} operations.
+Secondly, if called with @option{-d} argument, it should do exactly
+the opposite, i.e., read the compressed data from the standard input
+and produce uncompressed data on the standard output.
@end table
-You can have archives be compressed by using the @value{op-gzip} option.
-This will arrange for @code{tar} to use the @code{gzip} program to be
-used to compress or uncompress the archive wren writing or reading it.
-
-To use the older, obsolete, @code{compress} program, use the
-@value{op-compress} option. The GNU Project recommends you not use
-@code{compress}, because there is a patent covering the algorithm it
-uses. You could be sued for patent infringment merely by running
-@code{compress}.
-
-I have one question, or maybe it's a suggestion if there isn't a way
-to do it now. I would like to use @value{op-gzip}, but I'd also like the
-output to be fed through a program like GNU @code{ecc} (actually, right
-now that's @samp{exactly} what I'd like to use :-)), basically adding
-ECC protection on top of compression. It seems as if this should be
-quite easy to do, but I can't work out exactly how to go about it.
-Of course, I can pipe the standard output of @code{tar} through
-@code{ecc}, but then I lose (though I haven't started using it yet,
-I confess) the ability to have @code{tar} use @code{rmt} for it's I/O
-(I think).
+@FIXME{I have one question, or maybe it's a suggestion if there isn't a way
+to do it now. I would like to use @option{--gzip}, but I'd also like
+the output to be fed through a program like @acronym{GNU}
+@command{ecc} (actually, right now that's @samp{exactly} what I'd like
+to use :-)), basically adding ECC protection on top of compression.
+It seems as if this should be quite easy to do, but I can't work out
+exactly how to go about it. Of course, I can pipe the standard output
+of @command{tar} through @command{ecc}, but then I lose (though I
+haven't started using it yet, I confess) the ability to have
+@command{tar} use @command{rmt} for it's I/O (I think).
I think the most straightforward thing would be to let me specify a
general set of filters outboard of compression (preferably ordered,
with the options they require specifiable), but beggars shouldn't be
choosers and anything you decide on would be fine with me.
-By the way, I like @code{ecc} but if (as the comments say) it can't
+By the way, I like @command{ecc} but if (as the comments say) it can't
deal with loss of block sync, I'm tempted to throw some time at adding
that capability. Supposing I were to actually do such a thing and
-get it (apparantly) working, do you accept contributed changes to
+get it (apparently) working, do you accept contributed changes to
utilities like that? (Leigh Clayton @file{loc@@soliton.com}, May 1995).
-Isn't that exactly the role of the @value{op-use-compress-prog} option?
+Isn't that exactly the role of the @option{--use-compress-prog=@var{program}} option?
I never tried it myself, but I suspect you may want to write a
@var{prog} script or program able to filter stdin to stdout to
-way you want. It should recognize the @samp{-d} option, for when
+way you want. It should recognize the @option{-d} option, for when
extraction is needed rather than creation.
It has been reported that if one writes compressed data (through the
-@value{op-gzip} or @value{op-compress} options) to a DLT and tries to use
+@option{--gzip} or @option{--compress} options) to a DLT and tries to use
the DLT compression mode, the data will actually get bigger and one will
-end up with less space on the tape.
+end up with less space on the tape.}
-@node sparse, , gzip, Compression
+@node sparse
@subsection Archiving Sparse Files
@cindex Sparse Files
@UNREVISED
-@table @kbd
+@table @option
+@opindex sparse
@item -S
@itemx --sparse
Handle sparse files efficiently.
@end table
This option causes all files to be put in the archive to be tested for
-sparseness, and handled specially if they are. The @value{op-sparse}
-option is useful when many @code{dbm} files, for example, are being
+sparseness, and handled specially if they are. The @option{--sparse}
+(@option{-S}) option is useful when many @code{dbm} files, for example, are being
backed up. Using this option dramatically decreases the amount of
space needed to store such a file.
In later versions, this option may be removed, and the testing and
treatment of sparse files may be done automatically with any special
-GNU options. For now, it is an option needing to be specified on
+@acronym{GNU} options. For now, it is an option needing to be specified on
the command line with the creation or updating of an archive.
-Files in the filesystem occasionally have ``holes.'' A hole in a file
+Files in the file system occasionally have ``holes.'' A hole in a file
is a section of the file's contents which was never written. The
contents of a hole read as all zeros. On many operating systems,
actual disk storage is not allocated for holes, but they are counted
-in the length of the file. If you archive such a file, @code{tar}
-could create an archive longer than the original. To have @code{tar}
-attempt to recognize the holes in a file, use @value{op-sparse}. When
-you use the @value{op-sparse} option, then, for any file using less
-disk space than would be expected from its length, @code{tar} searches
-the file for consecutive stretches of zeros. It then records in the
-archive for the file where the consecutive stretches of zeros are, and
-only archives the ``real contents'' of the file. On extraction (using
-@value{op-sparse} is not needed on extraction) any such files have
-hols created wherever the continuous stretches of zeros were found.
-Thus, if you use @value{op-sparse}, @code{tar} archives won't take
-more space than the original.
+in the length of the file. If you archive such a file, @command{tar}
+could create an archive longer than the original. To have @command{tar}
+attempt to recognize the holes in a file, use @option{--sparse} (@option{-S}). When
+you use this option, then, for any file using less disk space than
+would be expected from its length, @command{tar} searches the file for
+consecutive stretches of zeros. It then records in the archive for
+the file where the consecutive stretches of zeros are, and only
+archives the ``real contents'' of the file. On extraction (using
+@option{--sparse} is not needed on extraction) any such
+files have holes created wherever the continuous stretches of zeros
+were found. Thus, if you use @option{--sparse}, @command{tar} archives
+won't take more space than the original.
A file is sparse if it contains blocks of zeros whose existence is
recorded, but that have no space allocated on disk. When you specify
-the @value{op-sparse} option in conjunction with the @value{op-create}
-operation, @code{tar} tests all files for sparseness while archiving.
-If @code{tar} finds a file to be sparse, it uses a sparse representation of
-the file in the archive. @value{xref-create}, for more information
-about creating archives.
+the @option{--sparse} option in conjunction with the @option{--create}
+(@option{-c}) operation, @command{tar} tests all files for sparseness
+while archiving. If @command{tar} finds a file to be sparse, it uses a
+sparse representation of the file in the archive. @xref{create}, for
+more information about creating archives.
-@value{op-sparse} is useful when archiving files, such as dbm files,
+@option{--sparse} is useful when archiving files, such as dbm files,
likely to contain many nulls. This option dramatically
decreases the amount of space needed to store such an archive.
@quotation
-@strong{Please Note:} Always use @value{op-sparse} when performing file
+@strong{Please Note:} Always use @option{--sparse} when performing file
system backups, to avoid archiving the expanded forms of files stored
sparsely in the system.
Even if your system has no sparse files currently, some may be
-created in the future. If you use @value{op-sparse} while making file
+created in the future. If you use @option{--sparse} while making file
system backups as a matter of course, you can be assured the archive
will never take more space on the media than the files take on disk
(otherwise, archiving a disk filled with sparse files might take
hundreds of tapes). @FIXME-xref{incremental when node name is set.}
@end quotation
-@code{tar} ignores the @value{op-sparse} option when reading an archive.
+@command{tar} ignores the @option{--sparse} option when reading an archive.
-@table @kbd
+@table @option
@item --sparse
@itemx -S
Files stored sparsely in the file system are represented sparsely in
the archive. Use in conjunction with write operations.
@end table
-However, users should be well aware that at archive creation time, GNU
-@code{tar} still has to read whole disk file to locate the @dfn{holes}, and
-so, even if sparse files use little space on disk and in the archive, they
-may sometimes require inordinate amount of time for reading and examining
-all-zero blocks of a file. Although it works, it's painfully slow for a
-large (sparse) file, even though the resulting tar archive may be small.
-(One user reports that dumping a @file{core} file of over 400 megabytes,
-but with only about 3 megabytes of actual data, took about 9 minutes on
-a Sun Sparstation ELC, with full CPU utilisation.)
+However, users should be well aware that at archive creation time,
+@GNUTAR{} still has to read whole disk file to
+locate the @dfn{holes}, and so, even if sparse files use little space
+on disk and in the archive, they may sometimes require inordinate
+amount of time for reading and examining all-zero blocks of a file.
+Although it works, it's painfully slow for a large (sparse) file, even
+though the resulting tar archive may be small. (One user reports that
+dumping a @file{core} file of over 400 megabytes, but with only about
+3 megabytes of actual data, took about 9 minutes on a Sun Sparcstation
+ELC, with full CPU utilization.)
This reading is required in all cases and is not related to the fact
-the @value{op-sparse} option is used or not, so by merely @emph{not}
+the @option{--sparse} option is used or not, so by merely @emph{not}
using the option, you are not saving time@footnote{Well! We should say
-the whole truth, here. When @value{op-sparse} is selected while creating
-an archive, the current @code{tar} algorithm requires sparse files to be
+the whole truth, here. When @option{--sparse} is selected while creating
+an archive, the current @command{tar} algorithm requires sparse files to be
read twice, not once. We hope to develop a new archive format for saving
sparse files in which one pass will be sufficient.}.
-Programs like @code{dump} do not have to read the entire file; by examining
-the file system directly, they can determine in advance exactly where the
-holes are and thus avoid reading through them. The only data it need read
-are the actual allocated data blocks. GNU @code{tar} uses a more portable
-and straightforward archiving approach, it would be fairly difficult that
-it does otherwise. Elizabeth Zwicky writes to @file{comp.unix.internals},
-on 1990-12-10:
+Programs like @command{dump} do not have to read the entire file; by
+examining the file system directly, they can determine in advance
+exactly where the holes are and thus avoid reading through them. The
+only data it need read are the actual allocated data blocks.
+@GNUTAR{} uses a more portable and straightforward
+archiving approach, it would be fairly difficult that it does
+otherwise. Elizabeth Zwicky writes to @file{comp.unix.internals}, on
+1990-12-10:
@quotation
What I did say is that you cannot tell the difference between a hole and an
get it right.
@end quotation
-@node Attributes, Standard, Compression, Formats
+@node Attributes
@section Handling File Attributes
@UNREVISED
-When @code{tar} reads files, this causes them to have the access times
-updated. To have @code{tar} attempt to set the access times back to
-what they were before they were read, use the @value{op-atime-preserve}
-option. This doesn't work for files that you don't own, unless
-you're root, and it doesn't interact with incremental dumps nicely
-(@pxref{Backups}), but it is good enough for some purposes.
+When @command{tar} reads files, it updates their access times. To
+avoid this, use the @option{--atime-preserve[=METHOD]} option, which can either
+reset the access time retroactively or avoid changing it in the first
+place.
Handling of file attributes
-@table @kbd
+@table @option
+@opindex atime-preserve
@item --atime-preserve
-Do not change access times on dumped files.
-
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+Preserve the access times of files that are read. This works only for
+files that you own, unless you have superuser privileges.
+
+@option{--atime-preserve=replace} works on most systems, but it also
+restores the data modification time and updates the status change
+time. Hence it doesn't interact with incremental dumps nicely
+(@pxref{Backups}), and it can set access or data modification times
+incorrectly if other programs access the file while @command{tar} is
+running.
+
+@option{--atime-preserve=system} avoids changing the access time in
+the first place, if the operating system supports this.
+Unfortunately, this may or may not work on any given operating system
+or file system. If @command{tar} knows for sure it won't work, it
+complains right away.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@option{--atime-preserve=replace}, but this is intended to change to
+@option{--atime-preserve=system} when the latter is better-supported.
+
+@opindex touch
@item -m
@itemx --touch
-Do not extract file modified time.
+Do not extract data modification time.
-When this option is used, @code{tar} leaves the modification times
-of the files it extracts as the time when the files were extracted,
-instead of setting it to the time recorded in the archive.
+When this option is used, @command{tar} leaves the data modification times
+of the files it extracts as the times when the files were extracted,
+instead of setting it to the times recorded in the archive.
-This option is meaningless with @value{op-list}.
+This option is meaningless with @option{--list} (@option{-t}).
+@opindex same-owner
@item --same-owner
Create extracted files with the same ownership they have in the
archive.
-When using super-user at extraction time, ownership is always restored.
-So, this option is meaningful only for non-root users, when @code{tar}
+This is the default behavior for the superuser,
+so this option is meaningful only for non-root users, when @command{tar}
is executed on those systems able to give files away. This is
considered as a security flaw by many people, at least because it
makes quite difficult to correctly account users for the disk space
they occupy. Also, the @code{suid} or @code{sgid} attributes of
files are easily and silently lost when files are given away.
-When writing an archive, @code{tar} writes the user id and user name
+When writing an archive, @command{tar} writes the user id and user name
separately. If it can't find a user name (because the user id is not
in @file{/etc/passwd}), then it does not write one. When restoring,
-and doing a @code{chmod} like when you use @value{op-same-permissions}
-(@FIXME{same-owner?}), it tries to look the name (if one was written)
+and doing a @code{chmod} like when you use @option{--same-permissions},
+@FIXME{same-owner?}it tries to look the name (if one was written)
up in @file{/etc/passwd}. If it fails, then it uses the user id
stored in the archive instead.
+@opindex no-same-owner
+@item --no-same-owner
+@itemx -o
+Do not attempt to restore ownership when extracting. This is the
+default behavior for ordinary users, so this option has an effect
+only for the superuser.
+
+@opindex numeric-owner
@item --numeric-owner
-The @value{op-numeric-owner} option allows (ANSI) archives to be written
+The @option{--numeric-owner} option allows (ANSI) archives to be written
without user/group name information or such information to be ignored
when extracting. It effectively disables the generation and/or use
of user/group name information. This option forces extraction using
an emergency floppy with different passwd/group files for example.
It is otherwise impossible to extract files with the right ownerships
if the password file in use during the extraction does not match the
-one belonging to the filesystem(s) being extracted. This occurs,
+one belonging to the file system(s) being extracted. This occurs,
for example, if you are restoring your files after a major crash and
had booted from an emergency floppy with no password file or put your
disk into another machine to do the restore.
-The numeric ids are @emph{always} saved into @code{tar} archives.
+The numeric ids are @emph{always} saved into @command{tar} archives.
The identifying names are added at create time when provided by the
-system, unless @value{op-old-archive} is used. Numeric ids could be
+system, unless @option{--old-archive} (@option{-o}) is used. Numeric ids could be
used when moving archives between a collection of machines using
a centralized management for attribution of numeric ids to users
and groups. This is often made through using the NIS capabilities.
-When making a @code{tar} file for distribution to other sites, it
+When making a @command{tar} file for distribution to other sites, it
is sometimes cleaner to use a single owner for all files in the
distribution, and nicer to specify the write permission bits of the
files as stored in the archive independently of their actual value on
to have some Makefile rule creating a directory, copying all needed
files in that directory, then setting ownership and permissions as
wanted (there are a lot of possible schemes), and only then making a
-@code{tar} archive out of this directory, before cleaning everything
-out. Of course, we could add a lot of options to GNU @code{tar} for
-fine tuning permissions and ownership. This is not the good way,
-I think. GNU @code{tar} is already crowded with options and moreover,
-the approach just explained gives you a great deal of control already.
-
+@command{tar} archive out of this directory, before cleaning
+everything out. Of course, we could add a lot of options to
+@GNUTAR{} for fine tuning permissions and ownership.
+This is not the good way, I think. @GNUTAR{} is
+already crowded with options and moreover, the approach just explained
+gives you a great deal of control already.
+
+@opindex same-permissions, short description
+@opindex preserve-permissions, short description
@item -p
@itemx --same-permissions
@itemx --preserve-permissions
Extract all protection information.
-This option causes @code{tar} to set the modes (access permissions) of
+This option causes @command{tar} to set the modes (access permissions) of
extracted files exactly as recorded in the archive. If this option
is not used, the current @code{umask} setting limits the permissions
-on extracted files.
+on extracted files. This option is by default enabled when
+@command{tar} is executed by a superuser.
+
-This option is meaningless with @value{op-list}.
+This option is meaningless with @option{--list} (@option{-t}).
+@opindex preserve
@item --preserve
-Same as both @value{op-same-permissions} and @value{op-same-order}.
+Same as both @option{--same-permissions} and @option{--same-order}.
-The @value{op-preserve} option has no equivalent short option name.
-It is equivalent to @value{op-same-permissions} plus @value{op-same-order}.
+The @option{--preserve} option has no equivalent short option name.
+It is equivalent to @option{--same-permissions} plus @option{--same-order}.
@FIXME{I do not see the purpose of such an option. (Neither I. FP.)}
@end table
-@node Standard, Extensions, Attributes, Formats
-@section The Standard Format
+@node Standard
+@section Basic Tar Format
@UNREVISED
While an archive may contain many files, the archive itself is a
written to a storage device such as a tape or disk, sent through a
pipe or over a network, saved on the active file system, or even
stored in another archive. An archive file is not easy to read or
-manipulate without using the @code{tar} utility or Tar mode in GNU
-Emacs.
+manipulate without using the @command{tar} utility or Tar mode in
+@acronym{GNU} Emacs.
Physically, an archive consists of a series of file entries terminated
-by an end-of-archive entry, which consists of 512 zero bytes. A file
+by an end-of-archive entry, which consists of two 512 blocks of zero
+bytes. A file
entry usually describes one of the files in the archive (an
@dfn{archive member}), and consists of a file header and the contents
of the file. File headers contain file names and statistics, checksum
-information which @code{tar} uses to detect file corruption, and
+information which @command{tar} uses to detect file corruption, and
information about file types.
Archives are permitted to have more than one member with the same
member name. One way this situation can occur is if more than one
version of a file has been stored in the archive. For information
-about adding new versions of a file to an archive, see @ref{update},
-and to learn more about having more than one archive member with the
-same name, see @FIXME-xref{-backup node, when it's written}.
+about adding new versions of a file to an archive, see @ref{update}.
+@FIXME-xref{To learn more about having more than one archive member with the
+same name, see -backup node, when it's written.}
In addition to entries describing archive members, an archive may
-contain entries which @code{tar} itself uses to store information.
-@value{xref-label}, for an example of such an archive entry.
+contain entries which @command{tar} itself uses to store information.
+@xref{label}, for an example of such an archive entry.
-A @code{tar} archive file contains a series of blocks. Each block
+A @command{tar} archive file contains a series of blocks. Each block
contains @code{BLOCKSIZE} bytes. Although this format may be thought
of as being on magnetic tape, other media are often used.
Each file archived is represented by a header block which describes
the file, followed by zero or more blocks which give the contents
-of the file. At the end of the archive file there may be a block
+of the file. At the end of the archive file there are two 512-byte blocks
filled with binary zeros as an end-of-file marker. A reasonable system
-should write a block of zeros at the end, but must not assume that
-such a block exists when reading an archive.
+should write such end-of-file marker at the end of an archive, but
+must not assume that such a block exists when reading an archive. In
+particular @GNUTAR{} always issues a warning if it does not encounter it.
The blocks may be @dfn{blocked} for physical I/O operations.
Each record of @var{n} blocks (where @var{n} is set by the
-@value{op-blocking-factor} option to @code{tar}) is written with a single
+@option{--blocking-factor=@var{512-size}} (@option{-b @var{512-size}}) option to @command{tar}) is written with a single
@w{@samp{write ()}} operation. On magnetic tapes, the result of
such a write is a single record. When writing an archive,
the last record of blocks should be written at the full size, with
whose last record is shorter than the rest, or which contains garbage
records after a zero block.
-The header block is defined in C as follows. In the GNU @code{tar}
+The header block is defined in C as follows. In the @GNUTAR{}
distribution, this is part of file @file{src/tar.h}:
-@example
+@smallexample
@include header.texi
-@end example
+@end smallexample
All characters in header blocks are represented by using 8-bit
characters in the local variant of ASCII. Each field within the
Bytes representing the contents of files (after the header block
of each file) are not translated in any way and are not constrained
-to represent characters in any character set. The @code{tar} format
+to represent characters in any character set. The @command{tar} format
does not distinguish text files from binary files, and no translation
of file contents is performed.
The @code{name}, @code{linkname}, @code{magic}, @code{uname}, and
-@code{gname} are null-terminated character strings. All other fileds
+@code{gname} are null-terminated character strings. All other fields
are zero-filled octal numbers in ASCII. Each numeric field of width
-@var{w} contains @var{w} minus 2 digits, a space, and a null, except
-@code{size}, and @code{mtime}, which do not contain the trailing null.
+@var{w} contains @var{w} minus 1 digits, and a null.
The @code{name} field is the file name of the file, with directory names
(if any) preceding the file name, separated by slashes.
permissions, the mode bit(s) specifying those special permissions
are ignored. Modes which are not supported by the operating system
restoring files from the archive will be ignored. Unsupported modes
-should be faked up when creating or updating an archive; e.g. the
+should be faked up when creating or updating an archive; e.g., the
group permission could be copied from the @emph{other} permission.
The @code{uid} and @code{gid} fields are the numeric user and group
not support numeric user or group IDs, these fields should be ignored.
The @code{size} field is the size of the file in bytes; linked files
-are archived with this field specified as zero. @FIXME-xref{Modifiers}, in
-particular the @value{op-incremental} option.
+are archived with this field specified as zero. @FIXME-xref{Modifiers, in
+particular the @option{--incremental} (@option{-G}) option.}
-The @code{mtime} field is the modification time of the file at the time
-it was archived. It is the ASCII representation of the octal value of
-the last time the file was modified, represented as an integer number of
+The @code{mtime} field is the data modification time of the file at
+the time it was archived. It is the ASCII representation of the octal
+value of the last time the file's contents were modified, represented
+as an integer number of
seconds since January 1, 1970, 00:00 Coordinated Universal Time.
The @code{chksum} field is the ASCII representation of the octal value
The @code{typeflag} field specifies the type of file archived. If a
particular implementation does not recognize or permit the specified
type, the file will be extracted as if it were a regular file. As this
-action occurs, @code{tar} issues a warning to the standard error.
+action occurs, @command{tar} issues a warning to the standard error.
The @code{atime} and @code{ctime} fields are used in making incremental
-backups; they store, respectively, the particular file's access time
-and last inode-change time.
+backups; they store, respectively, the particular file's access and
+status change times.
-The @code{offset} is used by the @value{op-multi-volume} option, when
+The @code{offset} is used by the @option{--multi-volume} (@option{-M}) option, when
making a multi-volume archive. The offset is number of bytes into
the file that we need to restart at to continue the file on the next
tape, i.e., where we store the location that a continued file is
is sparse is to look at the number blocks allocated for it versus the
number of characters in the file; if there are fewer blocks allocated
for the file than would normally be allocated for a file of that
-size, then the file is sparse. This is the method @code{tar} uses to
+size, then the file is sparse. This is the method @command{tar} uses to
detect a sparse file, and once such a file is detected, it is treated
differently from non-sparse files.
the file. Such files can appear to be very large when an @samp{ls
-l} is done on them, when in truth, there may be a very small amount
of important data contained in the file. It is thus undesirable
-to have @code{tar} think that it must back up this entire file, as
+to have @command{tar} think that it must back up this entire file, as
great quantities of room are wasted on empty blocks, which can lead
to running out of room on a tape far earlier than is necessary.
Thus, sparse files are dealt with so that these empty blocks are
is needed to deal with a file. Note that this means that this flag
can only be set when dealing with a sparse file, and it is only set
in the event that the description of the file will not fit in the
-alloted room for sparse structures in the header. In other words,
+allotted room for sparse structures in the header. In other words,
an extended_header is needed.
The @code{extended_header} structure is used for sparse files which
@item @code{REGTYPE}
@itemx @code{AREGTYPE}
These flags represent a regular file. In order to be compatible
-with older versions of @code{tar}, a @code{typeflag} value of
+with older versions of @command{tar}, a @code{typeflag} value of
@code{AREGTYPE} should be silently recognized as a regular file.
New archives should be created using @code{REGTYPE}. Also, for
-backward compatibility, @code{tar} treats a regular file whose name
+backward compatibility, @command{tar} treats a regular file whose name
ends with a slash as a directory.
@item @code{LNKTYPE}
@item @code{A} @dots{} @code{Z}
These are reserved for custom implementations. Some of these are
-used in the GNU modified format, as described below.
+used in the @acronym{GNU} modified format, as described below.
@end table
Other values are reserved for specification in future revisions of
-the P1003 standard, and should not be used by any @code{tar} program.
+the P1003 standard, and should not be used by any @command{tar} program.
The @code{magic} field indicates that this archive was output in
the P1003 archive format. If this field contains @code{TMAGIC},
IEEE Std 1003.2-1992, pages 380-388 (section 4.48) and pages 936-940
(section E.4.48) for @cite{pax - Portable archive interchange}.
-@node Extensions, cpio, Standard, Formats
-@section GNU Extensions to the Archive Format
+@node Extensions
+@section @acronym{GNU} Extensions to the Archive Format
@UNREVISED
-The GNU format uses additional file types to describe new types of
+The @acronym{GNU} format uses additional file types to describe new types of
files in an archive. These are listed below.
@table @code
@item GNUTYPE_DUMPDIR
@itemx 'D'
This represents a directory and a list of files created by the
-@value{op-incremental} option. The @code{size} field gives the total
+@option{--incremental} (@option{-G}) option. The @code{size} field gives the total
size of the associated list of files. Each file name is preceded by
either a @samp{Y} (the file should be in this archive) or an @samp{N}.
(The file is a directory, or is not stored in the archive.) Each file
@item GNUTYPE_MULTIVOL
@itemx 'M'
This represents a file continued from another volume of a multi-volume
-archive created with the @value{op-multi-volume} option. The original
+archive created with the @option{--multi-volume} (@option{-M}) option. The original
type of the file is not given here. The @code{size} field gives the
maximum size of this piece of the file (assuming the volume does
not end before the file is written out). The @code{offset} field
@item GNUTYPE_VOLHDR
@itemx 'V'
This file type is used to mark the volume header that was given with
-the @value{op-label} option when the archive was created. The @code{name}
-field contains the @code{name} given after the @value{op-label} option.
+the @option{--label=@var{archive-label}} (@option{-V @var{archive-label}}) option when the archive was created. The @code{name}
+field contains the @code{name} given after the @option{--label=@var{archive-label}} (@option{-V @var{archive-label}}) option.
The @code{size} field is zero. Only the first file in each volume
of an archive should have this type.
@end table
-You may have trouble reading a GNU format archive on a non-GNU
-system if the options @value{op-incremental}, @value{op-multi-volume},
-@value{op-sparse}, or @value{op-label} were used when writing the archive.
-In general, if @code{tar} does not use the GNU-added fields of the
-header, other versions of @code{tar} should be able to read the
-archive. Otherwise, the @code{tar} program will give an error, the
-most likely one being a checksum error.
-
-@node cpio, , Extensions, Formats
-@section Comparison of @code{tar} and @code{cpio}
+You may have trouble reading a @acronym{GNU} format archive on a
+non-@acronym{GNU} system if the options @option{--incremental} (@option{-G}),
+@option{--multi-volume} (@option{-M}), @option{--sparse} (@option{-S}), or @option{--label=@var{archive-label}} (@option{-V @var{archive-label}}) were
+used when writing the archive. In general, if @command{tar} does not
+use the @acronym{GNU}-added fields of the header, other versions of
+@command{tar} should be able to read the archive. Otherwise, the
+@command{tar} program will give an error, the most likely one being a
+checksum error.
+
+@node cpio
+@section Comparison of @command{tar} and @command{cpio}
@UNREVISED
@FIXME{Reorganize the following material}
-The @code{cpio} archive formats, like @code{tar}, do have maximum
+The @command{cpio} archive formats, like @command{tar}, do have maximum
pathname lengths. The binary and old ASCII formats have a max path
length of 256, and the new ASCII and CRC ASCII formats have a max
-path length of 1024. GNU @code{cpio} can read and write archives
-with arbitrary pathname lengths, but other @code{cpio} implementations
+path length of 1024. @acronym{GNU} @command{cpio} can read and write archives
+with arbitrary pathname lengths, but other @command{cpio} implementations
may crash unexplainedly trying to read them.
-@code{tar} handles symbolic links in the form in which it comes in BSD;
-@code{cpio} doesn't handle symbolic links in the form in which it comes
+@command{tar} handles symbolic links in the form in which it comes in BSD;
+@command{cpio} doesn't handle symbolic links in the form in which it comes
in System V prior to SVR4, and some vendors may have added symlinks
-to their system without enhancing @code{cpio} to know about them.
+to their system without enhancing @command{cpio} to know about them.
Others may have enhanced it in a way other than the way I did it
at Sun, and which was adopted by AT&T (and which is, I think, also
-present in the @code{cpio} that Berkeley picked up from AT&T and put
+present in the @command{cpio} that Berkeley picked up from AT&T and put
into a later BSD release---I think I gave them my changes).
-(SVR4 does some funny stuff with @code{tar}; basically, its @code{cpio}
-can handle @code{tar} format input, and write it on output, and it
+(SVR4 does some funny stuff with @command{tar}; basically, its @command{cpio}
+can handle @command{tar} format input, and write it on output, and it
probably handles symbolic links. They may not have bothered doing
-anything to enhance @code{tar} as a result.)
+anything to enhance @command{tar} as a result.)
-@code{cpio} handles special files; traditional @code{tar} doesn't.
+@command{cpio} handles special files; traditional @command{tar} doesn't.
-@code{tar} comes with V7, System III, System V, and BSD source;
-@code{cpio} comes only with System III, System V, and later BSD
+@command{tar} comes with V7, System III, System V, and BSD source;
+@command{cpio} comes only with System III, System V, and later BSD
(4.3-tahoe and later).
-@code{tar}'s way of handling multiple hard links to a file can handle
+@command{tar}'s way of handling multiple hard links to a file can handle
file systems that support 32-bit inumbers (e.g., the BSD file system);
-@code{cpio}s way requires you to play some games (in its "binary"
+@command{cpio}s way requires you to play some games (in its "binary"
format, i-numbers are only 16 bits, and in its "portable ASCII" format,
they're 18 bits---it would have to play games with the "file system ID"
field of the header to make sure that the file system ID/i-number pairs
of different files were always different), and I don't know which
-@code{cpio}s, if any, play those games. Those that don't might get
+@command{cpio}s, if any, play those games. Those that don't might get
confused and think two files are the same file when they're not, and
make hard links between them.
-@code{tar}s way of handling multiple hard links to a file places only
+@command{tar}s way of handling multiple hard links to a file places only
one copy of the link on the tape, but the name attached to that copy
-is the @emph{only} one you can use to retrieve the file; @code{cpio}s
+is the @emph{only} one you can use to retrieve the file; @command{cpio}s
way puts one copy for every link, but you can retrieve it using any
of the names.
What type of check sum (if any) is used, and how is this calculated.
@end quotation
-See the attached manual pages for @code{tar} and @code{cpio} format.
-@code{tar} uses a checksum which is the sum of all the bytes in the
-@code{tar} header for a file; @code{cpio} uses no checksum.
+See the attached manual pages for @command{tar} and @command{cpio} format.
+@command{tar} uses a checksum which is the sum of all the bytes in the
+@command{tar} header for a file; @command{cpio} uses no checksum.
@quotation
-If anyone knows why @code{cpio} was made when @code{tar} was present
+If anyone knows why @command{cpio} was made when @command{tar} was present
at the unix scene,
@end quotation
-It wasn't. @code{cpio} first showed up in PWB/UNIX 1.0; no
-generally-available version of UNIX had @code{tar} at the time. I don't
+It wasn't. @command{cpio} first showed up in PWB/UNIX 1.0; no
+generally-available version of UNIX had @command{tar} at the time. I don't
know whether any version that was generally available @emph{within AT&T}
-had @code{tar}, or, if so, whether the people within AT&T who did
-@code{cpio} knew about it.
+had @command{tar}, or, if so, whether the people within AT&T who did
+@command{cpio} knew about it.
-On restore, if there is a corruption on a tape @code{tar} will stop at
-that point, while @code{cpio} will skip over it and try to restore the
+On restore, if there is a corruption on a tape @command{tar} will stop at
+that point, while @command{cpio} will skip over it and try to restore the
rest of the files.
The main difference is just in the command syntax and header format.
-@code{tar} is a little more tape-oriented in that everything is blocked
+@command{tar} is a little more tape-oriented in that everything is blocked
to start on a record boundary.
@quotation
Is there any differences between the ability to recover crashed
-archives between the two of them. (Is there any chance of recovering
+archives between the two of them. (Is there any chance of recovering
crashed archives at all.)
@end quotation
-Theoretically it should be easier under @code{tar} since the blocking
+Theoretically it should be easier under @command{tar} since the blocking
lets you find a header with some variation of @samp{dd skip=@var{nn}}.
-However, modern @code{cpio}'s and variations have an option to just
+However, modern @command{cpio}'s and variations have an option to just
search for the next file header after an error with a reasonable chance
-of re-syncing. However, lots of tape driver software won't allow you to
+of resyncing. However, lots of tape driver software won't allow you to
continue past a media error which should be the only reason for getting
out of sync unless a file changed sizes while you were writing the
archive.
@quotation
-If anyone knows why @code{cpio} was made when @code{tar} was present
+If anyone knows why @command{cpio} was made when @command{tar} was present
at the unix scene, please tell me about this too.
@end quotation
Probably because it is more media efficient (by not blocking everything
-and using only the space needed for the headers where @code{tar}
+and using only the space needed for the headers where @command{tar}
always uses 512 bytes per file header) and it knows how to archive
special files.
-You might want to look at the freely available alternatives. The major
-ones are @code{afio}, GNU @code{tar}, and @code{pax}, each of which
-have their own extensions with some backwards compatibility.
+You might want to look at the freely available alternatives. The
+major ones are @command{afio}, @GNUTAR{}, and
+@command{pax}, each of which have their own extensions with some
+backwards compatibility.
-Sparse files were @code{tar}red as sparse files (which you can easily
-test, because the resulting archive gets smaller, and GNU @code{cpio}
-can no longer read it).
+Sparse files were @command{tar}red as sparse files (which you can
+easily test, because the resulting archive gets smaller, and
+@acronym{GNU} @command{cpio} can no longer read it).
-@node Media, Index, Formats, Top
+@node Media
@chapter Tapes and Other Archive Media
@UNREVISED
A few special cases about tape handling warrant more detailed
description. These special cases are discussed below.
-Many complexities surround the use of @code{tar} on tape drives. Since
+Many complexities surround the use of @command{tar} on tape drives. Since
the creation and manipulation of archives located on magnetic tape was
-the original purpose of @code{tar}, it contains many features making
+the original purpose of @command{tar}, it contains many features making
such manipulation easier.
Archives are usually written on dismountable media---tape cartridges,
The amount of data a tape or disk holds depends not only on its size,
but also on how it is formatted. A 2400 foot long reel of mag tape
-holds 40 megabytes of data when formated at 1600 bits per inch. The
+holds 40 megabytes of data when formatted at 1600 bits per inch. The
physically smaller EXABYTE tape cartridge holds 2.3 gigabytes.
Magnetic media are re-usable---once the archive on a tape is no longer
needed, the archive can be erased and the tape or disk used over.
Media quality does deteriorate with use, however. Most tapes or disks
-should be disgarded when they begin to produce data errors. EXABYTE
-tape cartridges should be disgarded when they generate an @dfn{error
+should be discarded when they begin to produce data errors. EXABYTE
+tape cartridges should be discarded when they generate an @dfn{error
count} (number of non-usable bits) of more than 10k.
Magnetic media are written and erased using magnetic fields, and
* Write Protection::
@end menu
-@node Device, Remote Tape Server, Media, Media
+@node Device
@section Device Selection and Switching
@UNREVISED
-@table @kbd
+@table @option
@item -f [@var{hostname}:]@var{file}
@itemx --file=[@var{hostname}:]@var{file}
Use archive file or device @var{file} on @var{hostname}.
@end table
-This option is used to specify the file name of the archive @code{tar}
+This option is used to specify the file name of the archive @command{tar}
works on.
-If the file name is @samp{-}, @code{tar} reads the archive from standard
+If the file name is @samp{-}, @command{tar} reads the archive from standard
input (when listing or extracting), or writes it to standard output
(when creating). If the @samp{-} file name is given when updating an
-archive, @code{tar} will read the original archive from its standard
+archive, @command{tar} will read the original archive from its standard
input, and will write the entire new archive to its standard output.
If the file name contains a @samp{:}, it is interpreted as
@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
-sign (@kbd{@@}), it is treated as @samp{user@@hostname:file name}. In
-either case, @code{tar} will invoke the command @code{rsh} (or
-@code{remsh}) to start up an @file{/etc/rmt} on the remote machine. If
-you give an alternate login name, it will be given to the @code{rsh}.
-Naturally, the remote machine must have an executable @file{/etc/rmt}.
-This program is free software from the University of California, and a
-copy of the source code can be found with the sources for @code{tar};
-it's compiled and installed by default.
-
-If this option is not given, but the environment variable @code{TAPE} is
-set, its value is used; otherwise, old versions of @code{tar} used a default
-archive name (which was picked when @code{tar} was compiled). The
-default is normally set up to be the @dfn{first} tape drive or other
-transportable I/O medium on the system.
-
-Starting with version 1.11.5, GNU @code{tar} uses standard input and
-standard output as the default device, and I will not try anymore
-supporting automatic device detection at installation time. This was
-failing really in too many cases, it was hopeless. This is now
-completely left to the installer to override standard input and standard
-output for default device, if this seems preferrable to him/her.
-Further, I think @emph{most} actual usages of @code{tar} are done with
-pipes or disks, not really tapes, cartridges or diskettes.
+sign (@samp{@@}), it is treated as @samp{user@@hostname:file name}. In
+either case, @command{tar} will invoke the command @command{rsh} (or
+@command{remsh}) to start up an @command{/usr/libexec/rmt} on the remote
+machine. If you give an alternate login name, it will be given to the
+@command{rsh}.
+Naturally, the remote machine must have an executable
+@command{/usr/libexec/rmt}. This program is free software from the
+University of California, and a copy of the source code can be found
+with the sources for @command{tar}; it's compiled and installed by default.
+The exact path to this utility is determined when configuring the package.
+It is @file{@var{prefix}/libexec/rmt}, where @var{prefix} stands for
+your installation prefix. This location may also be overridden at
+runtime by using @option{rmt-command=@var{command}} option (@xref{Option Summary,
+---rmt-command}, for detailed description of this option. @xref{Remote
+Tape Server}, for the description of @command{rmt} command).
+
+If this option is not given, but the environment variable @env{TAPE}
+is set, its value is used; otherwise, old versions of @command{tar}
+used a default archive name (which was picked when @command{tar} was
+compiled). The default is normally set up to be the @dfn{first} tape
+drive or other transportable I/O medium on the system.
+
+Starting with version 1.11.5, @GNUTAR{} uses
+standard input and standard output as the default device, and I will
+not try anymore supporting automatic device detection at installation
+time. This was failing really in too many cases, it was hopeless.
+This is now completely left to the installer to override standard
+input and standard output for default device, if this seems
+preferable. Further, I think @emph{most} actual usages of
+@command{tar} are done with pipes or disks, not really tapes,
+cartridges or diskettes.
Some users think that using standard input and output is running
after trouble. This could lead to a nasty surprise on your screen if
all this mess, using standard input and output as a default really
sounds like the only clean choice left, and a very useful one too.
-GNU @code{tar} reads and writes archive in records, I suspect this is the
-main reason why block devices are preferred over character devices.
-Most probably, block devices are more efficient too. The installer
-could also check for @samp{DEFTAPE} in @file{<sys/mtio.h>}.
+@GNUTAR{} reads and writes archive in records, I
+suspect this is the main reason why block devices are preferred over
+character devices. Most probably, block devices are more efficient
+too. The installer could also check for @samp{DEFTAPE} in
+@file{<sys/mtio.h>}.
-@table @kbd
+@table @option
+@opindex force-local, short description
@item --force-local
Archive file is local even if it contains a colon.
+@opindex rsh-command
@item --rsh-command=@var{command}
-Use remote @var{command} instead of @code{rsh}. This option exists
-so that people who use something other than the standard @code{rsh}
-(e.g., a Kerberized @code{rsh}) can access a remote device.
+Use remote @var{command} instead of @command{rsh}. This option exists
+so that people who use something other than the standard @command{rsh}
+(e.g., a Kerberized @command{rsh}) can access a remote device.
When this command is not used, the shell command found when
-the @code{tar} program was installed is used instead. This is
+the @command{tar} program was installed is used instead. This is
the first found of @file{/usr/ucb/rsh}, @file{/usr/bin/remsh},
@file{/usr/bin/rsh}, @file{/usr/bsd/rsh} or @file{/usr/bin/nsh}.
-The installer may have overriden this by defining the environment
-variable @code{RSH} @emph{at installation time}.
+The installer may have overridden this by defining the environment
+variable @env{RSH} @emph{at installation time}.
@item -[0-7][lmh]
Specify drive and density.
+@opindex multi-volume, short description
@item -M
@itemx --multi-volume
Create/list/extract multi-volume archive.
-This option causes @code{tar} to write a @dfn{multi-volume} archive---one
+This option causes @command{tar} to write a @dfn{multi-volume} archive---one
that may be larger than will fit on the medium used to hold it.
@xref{Multi-Volume Archives}.
+@opindex tape-length, short description
@item -L @var{num}
@itemx --tape-length=@var{num}
Change tape after writing @var{num} x 1024 bytes.
detect end of physical tapes. By being slightly conservative on the
maximum tape length, you might avoid the problem entirely.
+@opindex info-script, short description
+@opindex new-volume-script, short description
@item -F @var{file}
@itemx --info-script=@var{file}
@itemx --new-volume-script=@var{file}
Execute @file{file} at end of each tape. This implies
-@value{op-multi-volume}.
+@option{--multi-volume} (@option{-M}). @xref{info-script}, for a detailed
+description of this option.
@end table
-@node Remote Tape Server, Common Problems and Solutions, Device, Media
+@node Remote Tape Server
@section The Remote Tape Server
@cindex remote tape drive
@pindex rmt
-In order to access the tape drive on a remote machine, @code{tar}
+In order to access the tape drive on a remote machine, @command{tar}
uses the remote tape server written at the University of California at
-Berkeley. The remote tape server must be installed as @file{/etc/rmt}
-on any machine whose tape drive you want to use. @code{tar} calls
-@file{/etc/rmt} by running an @code{rsh} or @code{remsh} to the remote
-machine, optionally using a different login name if one is supplied.
+Berkeley. The remote tape server must be installed as
+@file{@var{prefix}/libexec/rmt} on any machine whose tape drive you
+want to use. @command{tar} calls @command{rmt} by running an
+@command{rsh} or @command{remsh} to the remote machine, optionally
+using a different login name if one is supplied.
A copy of the source for the remote tape server is provided. It is
Copyright @copyright{} 1983 by the Regents of the University of
-California, but can be freely distributed. Instructions for compiling
-and installing it are included in the @file{Makefile}.
+California, but can be freely distributed. It is compiled and
+installed by default.
@cindex absolute file names
-Unless you use the @value{op-absolute-names} option, GNU @code{tar} will
-not allow you to create an archive that contains absolute file names
-(a file name beginning with @samp{/}.) If you try, @code{tar} will
-automatically remove the leading @samp{/} from the file names it
-stores in the archive. It will also type a warning message telling
-you what it is doing.
-
-When reading an archive that was created with a different @code{tar}
-program, GNU @code{tar} automatically extracts entries in the archive
-which have absolute file names as if the file names were not absolute.
-This is an important feature. A visitor here once gave a
-@code{tar} tape to an operator to restore; the operator used Sun @code{tar}
-instead of GNU @code{tar}, and the result was that it replaced large
-portions of our @file{/bin} and friends with versions from the tape;
-needless to say, we were unhappy about having to recover the file system
-from backup tapes.
+Unless you use the @option{--absolute-names} (@option{-P}) option,
+@GNUTAR{} will not allow you to create an archive that contains
+absolute file names (a file name beginning with @samp{/}.) If you try,
+@command{tar} will automatically remove the leading @samp{/} from the
+file names it stores in the archive. It will also type a warning
+message telling you what it is doing.
+
+When reading an archive that was created with a different
+@command{tar} program, @GNUTAR{} automatically
+extracts entries in the archive which have absolute file names as if
+the file names were not absolute. This is an important feature. A
+visitor here once gave a @command{tar} tape to an operator to restore;
+the operator used Sun @command{tar} instead of @GNUTAR{},
+and the result was that it replaced large portions of
+our @file{/bin} and friends with versions from the tape; needless to
+say, we were unhappy about having to recover the file system from
+backup tapes.
For example, if the archive contained a file @file{/usr/bin/computoy},
-GNU @code{tar} would extract the file to @file{usr/bin/computoy},
+@GNUTAR{} would extract the file to @file{usr/bin/computoy},
relative to the current directory. If you want to extract the files in
an archive to the same absolute names that they had when the archive
was created, you should do a @samp{cd /} before extracting the files
-from the archive, or you should either use the @value{op-absolute-names}
+from the archive, or you should either use the @option{--absolute-names}
option, or use the command @samp{tar -C / @dots{}}.
@cindex Ultrix 3.1 and write failure
-Some versions of Unix (Ultrix 3.1 is know to have this problem),
+Some versions of Unix (Ultrix 3.1 is known to have this problem),
can claim that a short write near the end of a tape succeeded,
when it actually failed. This will result in the -M option not
working correctly. The best workaround at the moment is to use a
significantly larger blocking factor than the default 20.
-In order to update an archive, @code{tar} must be able to backspace the
+In order to update an archive, @command{tar} must be able to backspace the
archive in order to reread or rewrite a record that was just read (or
written). This is currently possible only on two kinds of files: normal
disk files (or any other file that can be backspaced with @samp{lseek}),
and industry-standard 9-track magnetic tape (or any other kind of tape
that can be backspaced with the @code{MTIOCTOP} @code{ioctl}.
-This means that the @value{op-append}, @value{op-update},
-@value{op-concatenate}, and @value{op-delete} commands will not work on any
-other kind of file. Some media simply cannot be backspaced, which
-means these commands and options will never be able to work on them.
-These non-backspacing media include pipes and cartridge tape drives.
+This means that the @option{--append}, @option{--concatenate}, and
+@option{--delete} commands will not work on any other kind of file.
+Some media simply cannot be backspaced, which means these commands and
+options will never be able to work on them. These non-backspacing
+media include pipes and cartridge tape drives.
-Some other media can be backspaced, and @code{tar} will work on them
-once @code{tar} is modified to do so.
+Some other media can be backspaced, and @command{tar} will work on them
+once @command{tar} is modified to do so.
-Archives created with the @value{op-multi-volume}, @value{op-label}, and
-@value{op-incremental} options may not be readable by other version
-of @code{tar}. In particular, restoring a file that was split over
-a volume boundary will require some careful work with @code{dd}, if
-it can be done at all. Other versions of @code{tar} may also create
+Archives created with the @option{--multi-volume}, @option{--label}, and
+@option{--incremental} (@option{-G}) options may not be readable by other version
+of @command{tar}. In particular, restoring a file that was split over
+a volume boundary will require some careful work with @command{dd}, if
+it can be done at all. Other versions of @command{tar} may also create
an empty file whose name is that of the volume header. Some versions
-of @code{tar} may create normal files instead of directories archived
-with the @value{op-incremental} option.
+of @command{tar} may create normal files instead of directories archived
+with the @option{--incremental} (@option{-G}) option.
-@node Common Problems and Solutions, Blocking, Remote Tape Server, Media
+@node Common Problems and Solutions
@section Some Common Problems and their Solutions
@ifclear PUBLISH
no such file or directory
not owner
-errors from @code{tar}:
+errors from @command{tar}:
directory checksum error
header format error
@end ifclear
-@node Blocking, Many, Common Problems and Solutions, Media
+@node Blocking
@section Blocking
@UNREVISED
the next two paragraphs, as the remainder of this manual uses those
two terms in a quite consistent way.
-John Gilmore, the writer of the public domain @code{tar} from which
-GNU @code{tar} was originally derived, wrote (June 1995):
+John Gilmore, the writer of the public domain @command{tar} from which
+@GNUTAR{} was originally derived, wrote (June 1995):
@quotation
The nomenclature of tape drives comes from IBM, where I believe
occupy more than one block), etc. The @code{JCL} @samp{DD RECFORM=}
parameter specified this to the operating system.
-The Unix man page on @code{tar} was totally confused about this.
+The Unix man page on @command{tar} was totally confused about this.
When I wrote @code{PD TAR}, I used the historically correct terminology
-(@code{tar} writes data records, which are grouped into blocks).
-It appears that the bogus terminology made it into POSIX (no surprise
+(@command{tar} writes data records, which are grouped into blocks).
+It appears that the bogus terminology made it into @acronym{POSIX} (no surprise
here), and now Fran@,{c}ois has migrated that terminology back
into the source code too.
@end quotation
being lost. In this manual, the term @dfn{block} usually refers to
a disk physical block, @emph{assuming} that each disk block is 512
bytes in length. It is true that some disk devices have different
-physical blocks, but @code{tar} ignore these differences in its own
-format, which is meant to be portable, so a @code{tar} block is always
-512 bytes in length, and @dfn{block} always mean a @code{tar} block.
+physical blocks, but @command{tar} ignore these differences in its own
+format, which is meant to be portable, so a @command{tar} block is always
+512 bytes in length, and @dfn{block} always mean a @command{tar} block.
The term @dfn{logical block} often represents the basic chunk of
allocation of many disk blocks as a single entity, which the operating
system treats somewhat atomically; this concept is only barely used
-in GNU @code{tar}.
+in @GNUTAR{}.
The term @dfn{physical record} is another way to speak of a physical
block, those two terms are somewhat interchangeable. In this manual,
the term @dfn{record} usually refers to a tape physical block,
-@emph{assuming} that the @code{tar} archive is kept on magnetic tape.
+@emph{assuming} that the @command{tar} archive is kept on magnetic tape.
It is true that archives may be put on disk or used with pipes,
-but nevertheless, @code{tar} tries to read and write the archive one
+but nevertheless, @command{tar} tries to read and write the archive one
@dfn{record} at a time, whatever the medium in use. One record is made
up of an integral number of blocks, and this operation of putting many
disk blocks into a single tape block is called @dfn{reblocking}, or
to the application. The term @dfn{unit record} describes a small set
of characters which are transmitted whole to or by the application,
and often refers to a line of text. Those two last terms are unrelated
-to what we call a @dfn{record} in GNU @code{tar}.
+to what we call a @dfn{record} in @GNUTAR{}.
-When writing to tapes, @code{tar} writes the contents of the archive
+When writing to tapes, @command{tar} writes the contents of the archive
in chunks known as @dfn{records}. To change the default blocking
-factor, use the @value{op-blocking-factor} option. Each record will
-then be composed of @var{512-size} blocks. (Each @code{tar} block is
-512 bytes. @xref{Standard}.) Each file written to the archive uses
-at least one full record. As a result, using a larger record size
-can result in more wasted space for small files. On the other hand, a
-larger record size can often be read and written much more efficiently.
+factor, use the @option{--blocking-factor=@var{512-size}} (@option{-b
+@var{512-size}}) option. Each record will then be composed of
+@var{512-size} blocks. (Each @command{tar} block is 512 bytes.
+@xref{Standard}.) Each file written to the archive uses at least one
+full record. As a result, using a larger record size can result in
+more wasted space for small files. On the other hand, a larger record
+size can often be read and written much more efficiently.
Further complicating the problem is that some tape drives ignore the
blocking entirely. For these, a larger record size can still improve
honor the blocking), but not as dramatically as on tape drives that
honor blocking.
-When reading an archive, @code{tar} can usually figure out the record
-size on itself. When this is the case, and a non-standard record size
-was used when the archive was created, @code{tar} will print a message
-about a non-standard blocking factor, and then operate normally. On
-some tape devices, however, @code{tar} cannot figure out the record size
-itself. On most of those, you can specify a blocking factor (with
-@value{op-blocking-factor}) larger than the actual blocking factor, and then use
-the @value{op-read-full-records} option. (If you specify a blocking factor
-with @value{op-blocking-factor} and don't use the @value{op-read-full-records}
-option, then @code{tar} will not attempt to figure out the recording size
-itself.) On some devices, you must always specify the record size
-exactly with @value{op-blocking-factor} when reading, because @code{tar} cannot
-figure it out. In any case, use @value{op-list} before doing any
-extractions to see whether @code{tar} is reading the archive correctly.
-
-@code{tar} blocks are all fixed size (512 bytes), and its scheme for
+When reading an archive, @command{tar} can usually figure out the
+record size on itself. When this is the case, and a non-standard
+record size was used when the archive was created, @command{tar} will
+print a message about a non-standard blocking factor, and then operate
+normally. On some tape devices, however, @command{tar} cannot figure
+out the record size itself. On most of those, you can specify a
+blocking factor (with @option{--blocking-factor}) larger than the
+actual blocking factor, and then use the @option{--read-full-records}
+(@option{-B}) option. (If you specify a blocking factor with
+@option{--blocking-factor} and don't use the
+@option{--read-full-records} option, then @command{tar} will not
+attempt to figure out the recording size itself.) On some devices,
+you must always specify the record size exactly with
+@option{--blocking-factor} when reading, because @command{tar} cannot
+figure it out. In any case, use @option{--list} (@option{-t}) before
+doing any extractions to see whether @command{tar} is reading the archive
+correctly.
+
+@command{tar} blocks are all fixed size (512 bytes), and its scheme for
putting them into records is to put a whole number of them (one or
-more) into each record. @code{tar} records are all the same size;
+more) into each record. @command{tar} records are all the same size;
at the end of the file there's a block containing all zeros, which
is how you tell that the remainder of the last record(s) are garbage.
-In a standard @code{tar} file (no options), the block size is 512
+In a standard @command{tar} file (no options), the block size is 512
and the record size is 10240, for a blocking factor of 20. What the
-@value{op-blocking-factor} option does is sets the blocking factor,
+@option{--blocking-factor} option does is sets the blocking factor,
changing the record size while leaving the block size at 512 bytes.
20 was fine for ancient 800 or 1600 bpi reel-to-reel tape drives;
most tape drives these days prefer much bigger records in order to
to use a factor of the order of 2048, say, giving a record size of
around one megabyte.
-If you use a blocking factor larger than 20, older @code{tar} programs
-might not be able to read the archive, so we recommend this as a limit
-to use in practice. GNU @code{tar}, however, will support arbitrarily
-large record sizes, limited only by the amount of virtual memory or the
-physical characteristics of the tape device.
+If you use a blocking factor larger than 20, older @command{tar}
+programs might not be able to read the archive, so we recommend this
+as a limit to use in practice. @GNUTAR{}, however,
+will support arbitrarily large record sizes, limited only by the
+amount of virtual memory or the physical characteristics of the tape
+device.
@menu
* Format Variations:: Format Variations
* Blocking Factor:: The Blocking Factor of an Archive
@end menu
-@node Format Variations, Blocking Factor, Blocking, Blocking
+@node Format Variations
@subsection Format Variations
@cindex Format Parameters
@cindex Format Options
To specify format parameters when accessing or creating an archive,
you can use the options described in the following sections.
-If you do not specify any format parameters, @code{tar} uses
+If you do not specify any format parameters, @command{tar} uses
default parameters. You cannot modify a compressed archive.
-If you create an archive with the @value{op-blocking-factor} option
-specified (@value{pxref-blocking-factor}), you must specify that
+If you create an archive with the @option{--blocking-factor} option
+specified (@pxref{Blocking Factor}), you must specify that
blocking-factor when operating on the archive. @xref{Formats}, for other
examples of format parameter considerations.
-@node Blocking Factor, , Format Variations, Blocking
+@node Blocking Factor
@subsection The Blocking Factor of an Archive
@cindex Blocking Factor
@cindex Record Size
@cindex Blocks per record
@UNREVISED
+@opindex blocking-factor
The data in an archive is grouped into blocks, which are 512 bytes.
Blocks are read and written in whole number multiples called
-@dfn{records}. The number of blocks in a record (ie. the size of a
+@dfn{records}. The number of blocks in a record (ie. the size of a
record in units of 512 bytes) is called the @dfn{blocking factor}.
-The @value{op-blocking-factor} option specifies the blocking factor of
-an archive. The default blocking factor is typically 20 (ie.@:
-10240 bytes), but can be specified at installation. To find out
-the blocking factor of an existing archive, use @samp{tar --list
---file=@var{archive-name}}. This may not work on some devices.
+The @option{--blocking-factor=@var{512-size}} (@option{-b
+@var{512-size}}) option specifies the blocking factor of an archive.
+The default blocking factor is typically 20 (i.e., 10240 bytes), but
+can be specified at installation. To find out the blocking factor of
+an existing archive, use @samp{tar --list --file=@var{archive-name}}.
+This may not work on some devices.
Records are separated by gaps, which waste space on the archive media.
If you are archiving on magnetic tape, using a larger blocking factor
(and therefore larger records) provides faster throughput and allows you
-to fit more data on a tape (because there are fewer gaps). If you are
+to fit more data on a tape (because there are fewer gaps). If you are
archiving on cartridge, a very large blocking factor (say 126 or more)
-greatly increases performance. A smaller blocking factor, on the other
-hand, may be usefull when archiving small files, to avoid archiving lots
-of nulls as @code{tar} fills out the archive to the end of the record.
+greatly increases performance. A smaller blocking factor, on the other
+hand, may be useful when archiving small files, to avoid archiving lots
+of nulls as @command{tar} fills out the archive to the end of the record.
In general, the ideal record size depends on the size of the
inter-record gaps on the tape you are using, and the average size of the
files you are archiving. @xref{create}, for information on
@FIXME{Need example of using a cartridge with blocking factor=126 or more.}
Archives with blocking factors larger than 20 cannot be read
-by very old versions of @code{tar}, or by some newer versions
-of @code{tar} running on old machines with small address spaces.
-With GNU @code{tar}, the blocking factor of an archive is limited
+by very old versions of @command{tar}, or by some newer versions
+of @command{tar} running on old machines with small address spaces.
+With @GNUTAR{}, the blocking factor of an archive is limited
only by the maximum record size of the device containing the archive,
or by the amount of available virtual memory.
imposed by the device drivers, may yield unexpected diagnostics. For
example, this has been reported:
-@example
+@smallexample
Cannot write to /dev/dlt: Invalid argument
-@end example
+@end smallexample
@noindent
-In such cases, it sometimes happen that the @code{tar} bundled by the
-system is aware of block size idiosyncrasies, while GNU @code{tar} requires
-an explicit specification for the block size, which it cannot guess.
-This yields some people to consider GNU @code{tar} is misbehaving, because
-by comparison, @cite{the bundle @code{tar} works OK}. Adding @w{@kbd{-b
-256}}, for example, might resolve the problem.
+In such cases, it sometimes happen that the @command{tar} bundled by
+the system is aware of block size idiosyncrasies, while @GNUTAR{}
+requires an explicit specification for the block size,
+which it cannot guess. This yields some people to consider
+@GNUTAR{} is misbehaving, because by comparison,
+@cite{the bundle @command{tar} works OK}. Adding @w{@kbd{-b 256}},
+for example, might resolve the problem.
If you use a non-default blocking factor when you create an archive, you
must specify the same blocking factor when you modify that archive. Some
archive devices will also require you to specify the blocking factor when
reading that archive, however this is not typically the case. Usually, you
-can use @value{op-list} without specifying a blocking factor---@code{tar}
+can use @option{--list} (@option{-t}) without specifying a blocking factor---@command{tar}
reports a non-default record size and then lists the archive members as
it would normally. To extract files from an archive with a non-standard
blocking factor (particularly if you're not sure what the blocking factor
-is), you can usually use the @value{op-read-full-records} option while
+is), you can usually use the @option{--read-full-records} (@option{-B}) option while
specifying a blocking factor larger then the blocking factor of the archive
-(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
-@xref{list}, for more information on the @value{op-list}
+(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
+@xref{list}, for more information on the @option{--list} (@option{-t})
operation. @xref{Reading}, for a more detailed explanation of that option.
-@table @kbd
+@table @option
@item --blocking-factor=@var{number}
@itemx -b @var{number}
Specifies the blocking factor of an archive. Can be used with any
-operation, but is usually not necessary with @value{op-list}.
+operation, but is usually not necessary with @option{--list} (@option{-t}).
@end table
Device blocking
-@table @kbd
+@table @option
@item -b @var{blocks}
@itemx --blocking-factor=@var{blocks}
Set record size to @math{@var{blocks} * 512} bytes.
This option is used to specify a @dfn{blocking factor} for the archive.
-When reading or writing the archive, @code{tar}, will do reads and writes
+When reading or writing the archive, @command{tar}, will do reads and writes
of the archive in records of @math{@var{block}*512} bytes. This is true
even when the archive is compressed. Some devices requires that all
-write operations be a multiple of a certain size, and so, @code{tar}
+write operations be a multiple of a certain size, and so, @command{tar}
pads the archive out to the next record boundary.
-The default blocking factor is set when @code{tar} is compiled, and is
+The default blocking factor is set when @command{tar} is compiled, and is
typically 20. Blocking factors larger than 20 cannot be read by very
-old versions of @code{tar}, or by some newer versions of @code{tar}
+old versions of @command{tar}, or by some newer versions of @command{tar}
running on old machines with small address spaces.
With a magnetic tape, larger records give faster throughput and fit
Apparently, Exabyte drives have a physical block size of 8K bytes.
If we choose our blocksize as a multiple of 8k bytes, then the problem
-seems to dissapper. Id est, we are using block size of 112 right
+seems to disappear. Id est, we are using block size of 112 right
now, and we haven't had the problem since we switched@dots{}
-With GNU @code{tar} the blocking factor is limited only by the maximum
-record size of the device containing the archive, or by the amount of
-available virtual memory.
+With @GNUTAR{} the blocking factor is limited only
+by the maximum record size of the device containing the archive, or by
+the amount of available virtual memory.
However, deblocking or reblocking is virtually avoided in a special
case which often occurs in practice, but which requires all the
the archive is directly handled to a local disk, instead of any special
device,
@item
-@value{op-blocking-factor} is not explicitely specified on the @code{tar}
+@option{--blocking-factor} is not explicitly specified on the @command{tar}
invocation.
@end itemize
-In previous versions of GNU @code{tar}, the @samp{--compress-block}
-option (or even older: @samp{--block-compress}) was necessary to
-reblock compressed archives. It is now a dummy option just asking
-not to be used, and otherwise ignored. If the output goes directly
-to a local disk, and not through stdout, then the last write is
-not extended to a full record size. Otherwise, reblocking occurs.
-Here are a few other remarks on this topic:
+If the output goes directly to a local disk, and not through
+stdout, then the last write is not extended to a full record size.
+Otherwise, reblocking occurs. Here are a few other remarks on this
+topic:
@itemize @bullet
@item
-@code{gzip} will complain about trailing garbage if asked to
+@command{gzip} will complain about trailing garbage if asked to
uncompress a compressed archive on tape, there is an option to turn
the message off, but it breaks the regularity of simply having to use
@samp{@var{prog} -d} for decompression. It would be nice if gzip was
Gailly, by sending a copy of this message to him.
@item
-@code{compress} does not show this problem, but as Jean-loup pointed
+@command{compress} does not show this problem, but as Jean-loup pointed
out to Michael, @samp{compress -d} silently adds garbage after
the result of decompression, which tar ignores because it already
recognized its end-of-file indicator. So this bug may be safely
@item
@samp{gzip -d -q} will be silent about the trailing zeros indeed,
but will still return an exit status of 2 which tar reports in turn.
-@code{tar} might ignore the exit status returned, but I hate doing
-that, as it weakens the protection @code{tar} offers users against
-other possible problems at decompression time. If @code{gzip} was
+@command{tar} might ignore the exit status returned, but I hate doing
+that, as it weakens the protection @command{tar} offers users against
+other possible problems at decompression time. If @command{gzip} was
silently skipping trailing zeros @emph{and} also avoiding setting the
exit status in this innocuous case, that would solve this situation.
@item
-@code{tar} should become more solid at not stopping to read a pipe at
+@command{tar} should become more solid at not stopping to read a pipe at
the first null block encountered. This inelegantly breaks the pipe.
-@code{tar} should rather drain the pipe out before exiting itself.
+@command{tar} should rather drain the pipe out before exiting itself.
@end itemize
+@opindex ignore-zeros, short description
@item -i
@itemx --ignore-zeros
Ignore blocks of zeros in archive (means EOF).
-The @value{op-ignore-zeros} option causes @code{tar} to ignore blocks
+The @option{--ignore-zeros} (@option{-i}) option causes @command{tar} to ignore blocks
of zeros in the archive. Normally a block of zeros indicates the
end of the archive, but when reading a damaged archive, or one which
-was created by @code{cat}-ing several archives together, this option
-allows @code{tar} to read the entire archive. This option is not on
-by default because many versions of @code{tar} write garbage after
+was created by concatenating several archives together, this option
+allows @command{tar} to read the entire archive. This option is not on
+by default because many versions of @command{tar} write garbage after
the zeroed blocks.
-Note that this option causes @code{tar} to read to the end of the
+Note that this option causes @command{tar} to read to the end of the
archive file, which may sometimes avoid problems when multiple files
are stored on a single physical tape.
+@opindex read-full-records, short description
@item -B
@itemx --read-full-records
Reblock as we read (for reading 4.2BSD pipes).
-If @value{op-read-full-records} is used, @code{tar} will not panic if an
-attempt to read a record from the archive does not return a full record.
-Instead, @code{tar} will keep reading until it has obtained a full
+If @option{--read-full-records} is used, @command{tar}
+will not panic if an attempt to read a record from the archive does
+not return a full record. Instead, @command{tar} will keep reading
+until it has obtained a full
record.
-This option is turned on by default when @code{tar} is reading
+This option is turned on by default when @command{tar} is reading
an archive from standard input, or from a remote machine. This is
because on BSD Unix systems, a read of a pipe will return however
-much happens to be in the pipe, even if it is less than @code{tar}
-requested. If this option was not used, @code{tar} would fail as
+much happens to be in the pipe, even if it is less than @command{tar}
+requested. If this option was not used, @command{tar} would fail as
soon as it read an incomplete record from the pipe.
This option is also useful with the commands for updating an archive.
required to receive at once the whole record. Further, if there is a
reading error on a huge record, this is less likely that the system will
succeed in recovering the information. So, blocking should not be too
-low, nor it should be too high. @code{tar} uses by default a blocking of
+low, nor it should be too high. @command{tar} uses by default a blocking of
20 for historical reasons, and it does not really matter when reading or
-writing to disk. Current tape technology would easily accomodate higher
+writing to disk. Current tape technology would easily accommodate higher
blockings. Sun recommends a blocking of 126 for Exabytes and 96 for DATs.
We were told that for some DLT drives, the blocking should be a multiple
of 4Kb, preferably 64Kb (@w{@kbd{-b 128}}) or 256 for decent performance.
drive unit that will be used to create the archives) sometimes lowers
the error rates observed at rewriting time.
-I might also use @samp{--number-blocks} instead of
-@samp{--block-number}, so @samp{--block} will then expand to
-@samp{--blocking-factor} unambiguously.
+I might also use @option{--number-blocks} instead of
+@option{--block-number}, so @option{--block} will then expand to
+@option{--blocking-factor} unambiguously.
-@node Many, Using Multiple Tapes, Blocking, Media
+@node Many
@section Many Archives on One Tape
@FIXME{Appropriate options should be moved here from elsewhere.}
device.
A rewinding tape device will bring back the tape to its beginning point
-automatically when this device is opened or closed. Since @code{tar}
+automatically when this device is opened or closed. Since @command{tar}
opens the archive file before using it and closes it afterwards, this
means that a simple:
-@example
+@smallexample
$ @kbd{tar cf /dev/tape @var{directory}}
-@end example
+@end smallexample
@noindent
will reposition the tape to its beginning both prior and after saving
@cindex tape positioning
So, a rewinding device is normally meant to hold one and only one file.
-If you want to put more than one @code{tar} archive on a given tape, you
+If you want to put more than one @command{tar} archive on a given tape, you
will need to avoid using the rewinding version of the tape device. You
will also have to pay special attention to tape positioning. Errors in
-positionning may overwrite the valuable data already on your tape. Many
+positioning may overwrite the valuable data already on your tape. Many
people, burnt by past experiences, will only use rewinding devices and
limit themselves to one file per tape, precisely to avoid the risk of
such errors. Be fully aware that writing at the wrong position on a
To save @var{directory-1} as a first archive at the beginning of a
tape, and leave that tape ready for a second archive, you should use:
-@example
+@smallexample
$ @kbd{mt -f /dev/nrtape rewind}
$ @kbd{tar cf /dev/nrtape @var{directory-1}}
-@end example
+@end smallexample
@cindex tape marks
@dfn{Tape marks} are special magnetic patterns written on the tape
An empty file (that is to say, two tape marks in a row) signal the
logical end of the tape, after which no file exist. Usually,
non-rewinding tape device drivers will react to the close request issued
-by @code{tar} by first writing two tape marks after your archive, and by
+by @command{tar} by first writing two tape marks after your archive, and by
backspacing over one of these. So, if you remove the tape at that time
from the tape drive, it is properly terminated. But if you write
another file at the current position, the second tape mark will be
So, you may now save @var{directory-2} as a second archive after the
first on the same tape by issuing the command:
-@example
+@smallexample
$ @kbd{tar cf /dev/nrtape @var{directory-2}}
-@end example
+@end smallexample
@noindent
and so on for all the archives you want to put on the same tape.
the first 16 tape marks before saving @var{directory-17}, say, by using
these commands:
-@example
+@smallexample
$ @kbd{mt -f /dev/nrtape rewind}
$ @kbd{mt -f /dev/nrtape fsf 16}
$ @kbd{tar cf /dev/nrtape @var{directory-17}}
-@end example
+@end smallexample
In all the previous examples, we put aside blocking considerations, but
you should do the proper things for that as well. @xref{Blocking}.
@menu
* Tape Positioning:: Tape Positions and Tape Marks
-* mt:: The @code{mt} Utility
+* mt:: The @command{mt} Utility
@end menu
-@node Tape Positioning, mt, Many, Many
+@node Tape Positioning
@subsection Tape Positions and Tape Marks
@UNREVISED
If you think of data as a series of records "rrrr"'s, and tape marks as
"*"'s, a tape might look like the following:
-@example
+@smallexample
rrrr*rrrrrr*rrrrr*rr*rrrrr**-------------------------
-@end example
+@end smallexample
Tape devices read and write tapes using a read/write @dfn{tape
head}---a physical part of the device which can only access one
-point on the tape at a time. When you use @code{tar} to read or
+point on the tape at a time. When you use @command{tar} to read or
write archive data from a tape device, the device will begin reading
or writing from wherever on the tape the tape head happens to be,
regardless of which archive or what part of the archive the tape
head is on. Before writing an archive, you should make sure that no
data on the tape will be overwritten (unless it is no longer needed).
Before reading an archive, you should make sure the tape head is at
-the beginning of the archive you want to read. (The @code{restore}
-script will find the archive automatically. @FIXME{There is no such
-restore script!}. @FIXME-xref{Scripted Restoration}). @xref{mt}, for
-an explanation of the tape moving utility.
+the beginning of the archive you want to read. You can do it manually
+via @code{mt} utility (@pxref{mt}). The @code{restore} script does
+that automatically (@pxref{Scripted Restoration}).
If you want to add new archive file entries to a tape, you should
advance the tape to the end of the existing file entries, backspace
to add two archives to the example above, the tape might look like the
following:
-@example
+@smallexample
rrrr*rrrrrr*rrrrr*rr*rrrrr*rrr*rrrr**----------------
-@end example
+@end smallexample
-@node mt, , Tape Positioning, Many
-@subsection The @code{mt} Utility
+@node mt
+@subsection The @command{mt} Utility
@UNREVISED
@FIXME{Is it true that this only works on non-block devices?
should explain the difference, (fixed or variable).}
-@value{xref-blocking-factor}.
+@xref{Blocking Factor}.
-You can use the @code{mt} utility to advance or rewind a tape past a
+You can use the @command{mt} utility to advance or rewind a tape past a
specified number of archive files on the tape. This will allow you
to move to the beginning of an archive before extracting or reading
it, or to the end of all the archives before writing a new one.
@FIXME{Why isn't there an "advance 'til you find two tape marks
together"?}
-The syntax of the @code{mt} command is:
+The syntax of the @command{mt} command is:
-@example
+@smallexample
@kbd{mt [-f @var{tapename}] @var{operation} [@var{number}]}
-@end example
+@end smallexample
where @var{tapename} is the name of the tape device, @var{number} is
the number of times an operation is performed (with a default of one),
@FIXME{is there any use for record operations?}
-@table @kbd
+@table @option
@item eof
@itemx weof
Writes @var{number} tape marks at the current position on the tape.
Moves tape position back @var{number} files.
@item rewind
-Rewinds the tape. (Ignores @var{number}).
+Rewinds the tape. (Ignores @var{number}).
@item offline
@itemx rewoff1
-Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
+Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
@item status
Prints status information about the tape unit.
@FIXME{Is there a better way to frob the spacing on the list?}
-If you don't specify a @var{tapename}, @code{mt} uses the environment
-variable TAPE; if TAPE does not exist, @code{mt} uses the device
+If you don't specify a @var{tapename}, @command{mt} uses the environment
+variable @env{TAPE}; if @env{TAPE} is not set, @command{mt} uses the device
@file{/dev/rmt12}.
-@code{mt} returns a 0 exit status when the operation(s) were
+@command{mt} returns a 0 exit status when the operation(s) were
successful, 1 if the command was unrecognized, and 2 if an operation
failed.
-@FIXME{New node on how to find an archive?}
-
-If you use @value{op-extract} with the @value{op-label} option specified,
-@code{tar} will read an archive label (the tape head has to be positioned
-on it) and print an error if the archive label doesn't match the
-@var{archive-name} specified. @var{archive-name} can be any regular
-expression. If the labels match, @code{tar} extracts the archive.
-@value{xref-label}. @FIXME-xref{Matching Format Parameters}.
-@FIXME{fix cross references} @samp{tar --list --label} will cause
-@code{tar} to print the label.
-
-@FIXME{Program to list all the labels on a tape?}
-
-@node Using Multiple Tapes, label, Many, Media
+@node Using Multiple Tapes
@section Using Multiple Tapes
@UNREVISED
Often you might want to write a large archive, one larger than will fit
on the actual tape you are using. In such a case, you can run multiple
-@code{tar} commands, but this can be inconvenient, particularly if you
-are using options like @value{op-exclude} or dumping entire filesystems.
-Therefore, @code{tar} supports multiple tapes automatically.
-
-Use @value{op-multi-volume} on the command line, and then @code{tar} will,
-when it reaches the end of the tape, prompt for another tape, and
-continue the archive. Each tape will have an independent archive, and
-can be read without needing the other. (As an exception to this, the
-file that @code{tar} was archiving when it ran out of tape will usually
-be split between the two archives; in this case you need to extract from
-the first archive, using @value{op-multi-volume}, and then put in the
-second tape when prompted, so @code{tar} can restore both halves of the
-file.)
-
-GNU @code{tar} multi-volume archives do not use a truly portable format.
-You need GNU @code{tar} at both end to process them properly.
-
-When prompting for a new tape, @code{tar} accepts any of the following
+@command{tar} commands, but this can be inconvenient, particularly if you
+are using options like @option{--exclude=@var{pattern}} or dumping entire file systems.
+Therefore, @command{tar} supports multiple tapes automatically.
+
+Use @option{--multi-volume} (@option{-M}) on the command line, and
+then @command{tar} will, when it reaches the end of the tape, prompt
+for another tape, and continue the archive. Each tape will have an
+independent archive, and can be read without needing the other. (As
+an exception to this, the file that @command{tar} was archiving when
+it ran out of tape will usually be split between the two archives; in
+this case you need to extract from the first archive, using
+@option{--multi-volume}, and then put in the second tape when
+prompted, so @command{tar} can restore both halves of the file.)
+
+@GNUTAR{} multi-volume archives do not use a truly portable format.
+You need @GNUTAR{} at both ends to process them properly.
+
+When prompting for a new tape, @command{tar} accepts any of the following
responses:
@table @kbd
@item ?
-Request @code{tar} to explain possible responses
+Request @command{tar} to explain possible responses
@item q
-Request @code{tar} to exit immediately.
+Request @command{tar} to exit immediately.
@item n @var{file name}
-Request @code{tar} to write the next volume on the file @var{file name}.
+Request @command{tar} to write the next volume on the file @var{file name}.
@item !
-Request @code{tar} to run a subshell.
+Request @command{tar} to run a subshell. This option can be disabled
+by giving @option{--restrict} command line option to @command{tar}.
@item y
-Request @code{tar} to begin writing the next volume.
+Request @command{tar} to begin writing the next volume.
@end table
(You should only type @samp{y} after you have changed the tape;
-otherwise @code{tar} will write over the volume it just finished.)
+otherwise @command{tar} will write over the volume it just finished.)
+
+@cindex End-of-archive info script
+@cindex Info script
+@anchor{info-script}
+@opindex info-script
+@opindex new-volume-script
+If you want more elaborate behavior than this, give @command{tar} the
+@option{--info-script=@var{script-name}}
+(@option{--new-volume-script=@var{script-name}}, @option{-F
+@var{script-name}}) option. The file @var{script-name} is expected to
+be a program (or shell script) to be run instead of the normal
+prompting procedure. It is executed without any command line
+arguments. Additional data is passed to it via the following
+environment variables:
+
+@table @env
+@vrindex TAR_VERSION, info script environment variable
+@item TAR_VERSION
+@GNUTAR{} version number.
+
+@vrindex TAR_ARCHIVE, info script environment variable
+@item TAR_ARCHIVE
+The name of the archive @command{tar} is processing.
+
+@vrindex TAR_VOLUME, info script environment variable
+@item TAR_VOLUME
+Ordinal number of the volume @command{tar} is about to start.
+
+@vrindex TAR_SUBCOMMAND, info script environment variable
+@item TAR_SUBCOMMAND
+Short option describing the operation @command{tar} is executed.
+@xref{Operations}, for a complete list of subcommand options.
+
+@vrindex TAR_FORMAT, info script environment variable
+@item TAR_FORMAT
+Format of the archive being processed. @xref{Formats}, for a complete
+list of archive format names.
+@end table
+
+The info script can instruct @command{tar} to use new archive name,
+by writing in to file descriptor 3 (see below for an
+example).
-If you want more elaborate behavior than this, give @code{tar} the
-@value{op-info-script} option. The file @var{script-name} is expected
-to be a program (or shell script) to be run instead of the normal
-prompting procedure. When the program finishes, @code{tar} will
-immediately begin writing the next volume. The behavior of the
-@samp{n} response to the normal tape-change prompt is not available
-if you use @value{op-info-script}.
+If the info script fails, @command{tar} exits; otherwise, it begins
+writing the next volume.
-The method @code{tar} uses to detect end of tape is not perfect, and
+The method @command{tar} uses to detect end of tape is not perfect, and
fails on some operating systems or on some devices. You can use the
-@value{op-tape-length} option if @code{tar} can't detect the end of the
-tape itself. This option selects @value{op-multi-volume} automatically.
-The @var{size} argument should then be the usable size of the tape.
-But for many devices, and floppy disks in particular, this option is
-never required for real, as far as we know.
-
-The volume number used by @code{tar} in its tape-change prompt
-can be changed; if you give the @value{op-volno-file} option, then
-@var{file-of-number} should be an unexisting file to be created, or else,
-a file already containing a decimal number. That number will be used
-as the volume number of the first volume written. When @code{tar} is
-finished, it will rewrite the file with the now-current volume number.
-(This does not change the volume number written on a tape label, as
-per @value{ref-label}, it @emph{only} affects the number used in
-the prompt.)
-
-If you want @code{tar} to cycle through a series of tape drives, then
-you can use the @samp{n} response to the tape-change prompt. This is
-error prone, however, and doesn't work at all with @value{op-info-script}.
-Therefore, if you give @code{tar} multiple @value{op-file} options, then
-the specified files will be used, in sequence, as the successive volumes
-of the archive. Only when the first one in the sequence needs to be
-used again will @code{tar} prompt for a tape change (or run the info
-script).
-
-Multi-volume archives
-
-With @value{op-multi-volume}, @code{tar} will not abort when it cannot
-read or write any more data. Instead, it will ask you to prepare a new
-volume. If the archive is on a magnetic tape, you should change tapes
-now; if the archive is on a floppy disk, you should change disks, etc.
-
-Each volume of a multi-volume archive is an independent @code{tar}
+@option{--tape-length=@var{size}} (@option{-L @var{size}}) option if
+@command{tar} can't detect the end of the tape itself. This option
+selects @option{--multi-volume} (@option{-M}) automatically. The
+@var{size} argument should then be the usable size of the tape in
+units of 1024 bytes. But for many devices, and floppy disks in
+particular, this option is never required for real, as far as we know.
+
+@cindex Volume number file
+@cindex volno file
+@anchor{volno-file}
+@opindex volno-file
+The volume number used by @command{tar} in its tape-change prompt
+can be changed; if you give the
+@option{--volno-file=@var{file-of-number}} option, then
+@var{file-of-number} should be an unexisting file to be created, or
+else, a file already containing a decimal number. That number will be
+used as the volume number of the first volume written. When
+@command{tar} is finished, it will rewrite the file with the
+now-current volume number. (This does not change the volume number
+written on a tape label, as per @ref{label}, it @emph{only} affects
+the number used in the prompt.)
+
+If you want @command{tar} to cycle through a series of files or tape
+drives, there are three approaches to choose from. First of all, you
+can give @command{tar} multiple @option{--file} options. In this case
+the specified files will be used, in sequence, as the successive
+volumes of the archive. Only when the first one in the sequence needs
+to be used again will @command{tar} prompt for a tape change (or run
+the info script). Secondly, you can use the @samp{n} response to the
+tape-change prompt, and, finally, you can use an info script, that
+writes new archive name to file descriptor. The following example
+illustrates this approach:
+
+@smallexample
+@group
+#! /bin/sh
+echo Preparing volume $TAR_VOLUME of $TAR_ARCHIVE.
+
+name=`expr $TAR_ARCHIVE : '\(.*\)-.*'`
+case $TAR_SUBCOMMAND in
+-c) ;;
+-d|-x|-t) test -r $@{name:-$TAR_ARCHIVE@}-$TAR_VOLUME || exit 1
+ ;;
+*) exit 1
+esac
+
+echo $@{name:-$TAR_ARCHIVE@}-$TAR_VOLUME >&3
+@end group
+@end smallexample
+
+Each volume of a multi-volume archive is an independent @command{tar}
archive, complete in itself. For example, you can list or extract any
-volume alone; just don't specify @value{op-multi-volume}. However, if one
-file in the archive is split across volumes, the only way to extract
-it successfully is with a multi-volume extract command @samp{--extract
---multi-volume} (@samp{-xM}) starting on or before the volume where
-the file begins.
+volume alone; just don't specify @option{--multi-volume}
+(@option{-M}). However, if one file in the archive is split across
+volumes, the only way to extract it successfully is with a
+multi-volume extract command @option{--extract --multi-volume}
+(@option{-xM}) starting on or before the volume where the file begins.
For example, let's presume someone has two tape drives on a system
-named @file{/dev/tape0} and @file{/dev/tape1}. For having GNU
-@code{tar} to switch to the second drive when it needs to write the
+named @file{/dev/tape0} and @file{/dev/tape1}. For having @GNUTAR{}
+to switch to the second drive when it needs to write the
second tape, and then back to the first tape, etc., just do either of:
@smallexample
@menu
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
+
@end menu
-@node Multi-Volume Archives, Tape Files, Using Multiple Tapes, Using Multiple Tapes
+@node Multi-Volume Archives
@subsection Archives Longer than One Tape or Disk
@cindex Multi-volume archives
@UNREVISED
+@opindex multi-volume
To create an archive that is larger than will fit on a single unit of
-the media, use the @value{op-multi-volume} option in conjunction with
-the @value{op-create} option (@pxref{create}). A
-@dfn{multi-volume} archive can be manipulated like any other archive
-(provided the @value{op-multi-volume} option is specified), but is
-stored on more than one tape or disk.
+the media, use the @option{--multi-volume} (@option{-M}) option in conjunction with
+the @option{--create} option (@pxref{create}). A @dfn{multi-volume}
+archive can be manipulated like any other archive (provided the
+@option{--multi-volume} option is specified), but is stored on more
+than one tape or disk.
-When you specify @value{op-multi-volume}, @code{tar} does not report an
+When you specify @option{--multi-volume}, @command{tar} does not report an
error when it comes to the end of an archive volume (when reading), or
the end of the media (when writing). Instead, it prompts you to load
a new storage volume. If the archive is on a magnetic tape, you
You can read each individual volume of a multi-volume archive as if it
were an archive by itself. For example, to list the contents of one
-volume, use @value{op-list}, without @value{op-multi-volume} specified.
+volume, use @option{--list}, without @option{--multi-volume} specified.
To extract an archive member from one volume (assuming it is described
-that volume), use @value{op-extract}, again without
-@value{op-multi-volume}.
+that volume), use @option{--extract}, again without
+@option{--multi-volume}.
-If an archive member is split across volumes (ie. its entry begins on
+If an archive member is split across volumes (ie. its entry begins on
one volume of the media and ends on another), you need to specify
-@value{op-multi-volume} to extract it successfully. In this case, you
+@option{--multi-volume} to extract it successfully. In this case, you
should load the volume where the archive member starts, and use
-@samp{tar --extract --multi-volume}---@code{tar} will prompt for later
+@samp{tar --extract --multi-volume}---@command{tar} will prompt for later
volumes as it needs them. @xref{extracting archives}, for more
information about extracting archives.
-@value{op-info-script} is like @value{op-multi-volume}, except that
-@code{tar} does not prompt you directly to change media volumes when
-a volume is full---instead, @code{tar} runs commands you have stored
-in @var{script-name}. For example, this option can be used to eject
+@option{--info-script=@var{script-name}}
+(@option{--new-volume-script=@var{script-name}}, @option{-F
+@var{script-name}}) (@pxref{info-script}) is like
+@option{--multi-volume} (@option{-M}), except that @command{tar} does
+not prompt you directly to change media volumes when a volume is
+full---instead, @command{tar} runs commands you have stored in
+@var{script-name}. For example, this option can be used to eject
cassettes, or to broadcast messages such as @samp{Someone please come
-change my tape} when performing unattended backups. When @var{script-name}
-is done, @code{tar} will assume that the media has been changed.
+change my tape} when performing unattended backups. When
+@var{script-name} is done, @command{tar} will assume that the media
+has been changed.
Multi-volume archives can be modified like any other archive. To add
files to a multi-volume archive, you need to only mount the last
volume of the archive media (and new volumes, if needed). For all
other operations, you need to use the entire archive.
-If a multi-volume archive was labeled using @value{op-label}
-(@value{pxref-label}) when it was created, @code{tar} will not
-automatically label volumes which are added later. To label subsequent
-volumes, specify @value{op-label} again in conjunction with the
-@value{op-append}, @value{op-update} or @value{op-concatenate} operation.
+If a multi-volume archive was labeled using
+@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
+(@pxref{label}) when it was created, @command{tar} will not
+automatically label volumes which are added later. To label
+subsequent volumes, specify @option{--label=@var{archive-label}} again
+in conjunction with the @option{--append}, @option{--update} or
+@option{--concatenate} operation.
-@cindex Labelling multi-volume archives
+@cindex Labeling multi-volume archives
@FIXME{example}
@FIXME{There should be a sample program here, including an exit
-before end. Is the exit status even checked in tar? :-(}
+before end. Is the exit status even checked in tar? :-(}
-@table @kbd
+@table @option
@item --multi-volume
@itemx -M
Creates a multi-volume archive, when used in conjunction with
-@value{op-create}. To perform any other operation on a multi-volume
-archive, specify @value{op-multi-volume} in conjunction with that
+@option{--create} (@option{-c}). To perform any other operation on a multi-volume
+archive, specify @option{--multi-volume} in conjunction with that
operation.
@item --info-script=@var{program-file}
+@itemx --new-volume-script=@var{program-file}
@itemx -F @var{program-file}
Creates a multi-volume archive via a script. Used in conjunction with
-@value{op-create}.
+@option{--create} (@option{-c}). @xref{info-script}, dor a detailed discussion.
@end table
-Beware that there is @emph{no} real standard about the proper way, for a
-@code{tar} archive, to span volume boundaries. If you have a multi-volume
-created by some vendor's @code{tar}, there is almost no chance you could
-read all the volumes with GNU @code{tar}. The converse is also true:
-you may not expect multi-volume archives created by GNU @code{tar} to
-be fully recovered by vendor's @code{tar}. Since there is little chance
-that, in mixed system configurations, some vendor's @code{tar} will work on
-another vendor's machine, and there is a great chance that GNU @code{tar}
-will work on most of them, your best bet is to install GNU @code{tar}
-on all machines between which you know exchange of files is possible.
-
-@node Tape Files, , Multi-Volume Archives, Using Multiple Tapes
+Beware that there is @emph{no} real standard about the proper way, for
+a @command{tar} archive, to span volume boundaries. If you have a
+multi-volume created by some vendor's @command{tar}, there is almost
+no chance you could read all the volumes with @GNUTAR{}.
+The converse is also true: you may not expect
+multi-volume archives created by @GNUTAR{} to be
+fully recovered by vendor's @command{tar}. Since there is little
+chance that, in mixed system configurations, some vendor's
+@command{tar} will work on another vendor's machine, and there is a
+great chance that @GNUTAR{} will work on most of
+them, your best bet is to install @GNUTAR{} on all
+machines between which you know exchange of files is possible.
+
+@node Tape Files
@subsection Tape Files
@UNREVISED
To give the archive a name which will be recorded in it, use the
-@value{op-label} option. This will write a special block identifying
-@var{volume-label} as the name of the archive to the front of the archive
-which will be displayed when the archive is listed with @value{op-list}.
-If you are creating a multi-volume archive with @value{op-multi-volume}
-(@FIXME-pxref{Using Multiple Tapes}), then the volume label will have
-@samp{Volume @var{nnn}} appended to the name you give, where @var{nnn} is
-the number of the volume of the archive. (If you use the @value{op-label}
-option when reading an archive, it checks to make sure the label on the
-tape matches the one you give. @value{xref-label}.
-
-When @code{tar} writes an archive to tape, it creates a single
+@option{--label=@var{volume-label}} (@option{-V @var{volume-label}})
+option. This will write a special block identifying
+@var{volume-label} as the name of the archive to the front of the
+archive which will be displayed when the archive is listed with
+@option{--list}. If you are creating a multi-volume archive with
+@option{--multi-volume} (@pxref{Using Multiple Tapes}), then the
+volume label will have @samp{Volume @var{nnn}} appended to the name
+you give, where @var{nnn} is the number of the volume of the archive.
+(If you use the @option{--label=@var{volume-label}}) option when
+reading an archive, it checks to make sure the label on the tape
+matches the one you give. @xref{label}.
+
+When @command{tar} writes an archive to tape, it creates a single
tape file. If multiple archives are written to the same tape, one
after the other, they each get written as separate tape files. When
extracting, it is necessary to position the tape at the right place
-before running @code{tar}. To do this, use the @code{mt} command.
-For more information on the @code{mt} command and on the organization
+before running @command{tar}. To do this, use the @command{mt} command.
+For more information on the @command{mt} command and on the organization
of tapes into a sequence of tape files, see @ref{mt}.
People seem to often do:
-@example
+@smallexample
@kbd{--label="@var{some-prefix} `date +@var{some-format}`"}
-@end example
+@end smallexample
or such, for pushing a common date in all volumes or an archive set.
-@node label, verify, Using Multiple Tapes, Media
+@node Tarcat
+@subsection Concatenate Volumes into a Single Archive
+
+@pindex tarcat
+ Sometimes it is necessary to convert existing @GNUTAR{} multi-volume
+archive to a single @command{tar} archive. Simply concatenating all
+volumes into one will not work, since each volume carries an additional
+information at the beginning. @GNUTAR{} is shipped with the shell
+script @command{tarcat} designed for this purpose.
+
+ The script takes a list of files comprising a multi-volume archive
+and creates the resulting archive at the standard output. For example:
+
+@smallexample
+@kbd{tarcat vol.1 vol.2 vol.3 | tar tf -}
+@end smallexample
+
+ The script implements a simple heuristics to determine the format of
+the first volume file and to decide how to process the rest of the
+files. However, it makes no attempt to verify whether the files are
+given in order or even if they are valid @command{tar} archives.
+It uses @command{dd} and does not filter its standard error, so you
+will usually see lots of spurious messages.
+
+@FIXME{The script is not installed. Should we install it?}
+
+@node label
@section Including a Label in the Archive
@cindex Labeling an archive
@cindex Labels on the archive media
@UNREVISED
-@table @kbd
-@item -V @var{name}
-@itemx --label=@var{name}
-Create archive with volume name @var{name}.
-@end table
-
-This option causes @code{tar} to write out a @dfn{volume header} at
-the beginning of the archive. If @value{op-multi-volume} is used, each
-volume of the archive will have a volume header of @samp{@var{name}
-Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
-next, and so on.
-
-@FIXME{Should the arg to --label be a quoted string?? No.}
-
-To avoid problems caused by misplaced paper labels on the archive
+@opindex label
+ To avoid problems caused by misplaced paper labels on the archive
media, you can include a @dfn{label} entry---an archive member which
contains the name of the archive---in the archive itself. Use the
-@value{op-label} option in conjunction with the @value{op-create} operation
-to include a label entry in the archive as it is being created.
-
-If you create an archive using both @value{op-label} and
-@value{op-multi-volume}, each volume of the archive will have an
-archive label of the form @samp{@var{archive-label} Volume @var{n}},
-where @var{n} is 1 for the first volume, 2 for the next, and so on.
-@FIXME-xref{Multi-Volume Archives}, for information on creating multiple
-volume archives.
-
-If you list or extract an archive using @value{op-label}, @code{tar} will
-print an error if the archive label doesn't match the @var{archive-label}
-specified, and will then not list nor extract the archive. In those cases,
-@var{archive-label} argument is interpreted as a globbing-style pattern
-which must match the actual magnetic volume label. @xref{exclude}, for
-a precise description of how match is attempted@footnote{Previous versions
-of @code{tar} used full regular expression matching, or before that, only
-exact string matching, instead of wildcard matchers. We decided for the
-sake of simplicity to use a uniform matching device through @code{tar}.}.
-If the switch @value{op-multi-volume} is being used, the volume label
-matcher will also suffix @var{archive-label} by @w{@samp{ Volume [1-9]*}}
-if the initial match fails, before giving up. Since the volume numbering
-is automatically added in labels at creation time, it sounded logical to
-equally help the user taking care of it when the archive is being read.
-
-The @value{op-label} was once called @samp{--volume}, but is not available
-under that name anymore.
-
-To find out an archive's label entry (or to find out if an archive has
-a label at all), use @samp{tar --list --verbose}. @code{tar} will print the
-label first, and then print archive member information, as in the
-example below:
-
-@example
-$ @kbd{tar --verbose --list --file=iamanarchive}
-V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
--rw-rw-rw- ringo user 40 1990-05-21 13:30 iamafilename
-@end example
+@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
+option in conjunction with the @option{--create} operation to include
+a label entry in the archive as it is being created.
-@table @kbd
+@table @option
@item --label=@var{archive-label}
@itemx -V @var{archive-label}
Includes an @dfn{archive-label} at the beginning of the archive when
the archive is being created, when used in conjunction with the
-@value{op-create} option. Checks to make sure the archive label
-matches the one specified (when used in conjunction with the
-@value{op-extract} option.
+@option{--create} operation. Checks to make sure the archive label
+matches the one specified (when used in conjunction with any other
+operation.
@end table
-To get a common information on all tapes of a series, use the
-@value{op-label} option. For having this information different in each
+ If you create an archive using both
+@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
+and @option{--multi-volume} (@option{-M}), each volume of the archive
+will have an archive label of the form @samp{@var{archive-label}
+Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
+next, and so on. @xref{Using Multiple Tapes}, for information on
+creating multiple volume archives.
+
+@cindex Volume label, listing
+@cindex Listing volume label
+ The volume label will be displayed by @option{--list} along with
+the file contents. If verbose display is requested, it will also be
+explicitely marked as in the example below:
+
+@smallexample
+@group
+$ @kbd{tar --verbose --list --file=iamanarchive}
+V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
+-rw-r--r-- ringo user 40 1990-05-21 13:30 iamafilename
+@end group
+@end smallexample
+
+@opindex test-label
+@anchor{--test-label option}
+ However, @option{--list} option will cause listing entire
+contents of the archive, which may be undesirable (for example, if the
+archive is stored on a tape). You can request checking only the volume
+by specifying @option{--test-label} option. This option reads only the
+first block of an archive, so it can be used with slow storage
+devices. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive}
+iamalabel
+@end group
+@end smallexample
+
+ If @option{--test-label} is used with a single command line
+argument, @command{tar} compares the volume label with the
+argument. It exits with code 0 if the two strings match, and with code
+2 otherwise. In this case no output is displayed. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable'}
+@result{} 0
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable' alabel}
+@result{} 1
+@end group
+@end smallexample
+
+ If you request any operation, other than @option{--create}, along
+with using @option{--label} option, @command{tar} will first check if
+the archive label matches the one specified and will refuse to proceed
+if it does not. Use this as a safety precaution to avoid accidentally
+overwriting existing archives. For example, if you wish to add files
+to @file{archive}, presumably labelled with string @samp{My volume},
+you will get:
+
+@smallexample
+@group
+$ @kbd{tar -rf archive --label 'My volume' .}
+tar: Archive not labeled to match `My volume'
+@end group
+@end smallexample
+
+@noindent
+in case its label does not match. This will work even if
+@file{archive} is not labelled at all.
+
+ Similarly, @command{tar} will refuse to list or extract the
+archive if its label doesn't match the @var{archive-label}
+specified. In those cases, @var{archive-label} argument is interpreted
+as a globbing-style pattern which must match the actual magnetic
+volume label. @xref{exclude}, for a precise description of how match
+is attempted@footnote{Previous versions of @command{tar} used full
+regular expression matching, or before that, only exact string
+matching, instead of wildcard matchers. We decided for the sake of
+simplicity to use a uniform matching device through
+@command{tar}.}. If the switch @option{--multi-volume} (@option{-M}) is being used,
+the volume label matcher will also suffix @var{archive-label} by
+@w{@samp{ Volume [1-9]*}} if the initial match fails, before giving
+up. Since the volume numbering is automatically added in labels at
+creation time, it sounded logical to equally help the user taking care
+of it when the archive is being read.
+
+ The @option{--label} was once called @option{--volume}, but is not
+available under that name anymore.
+
+ You can also use @option{--label} to get a common information on
+all tapes of a series. For having this information different in each
series created through a single script used on a regular basis, just
manage to get some date string as part of the label. For example:
-@example
+@smallexample
+@group
$ @kbd{tar cfMV /dev/tape "Daily backup for `date +%Y-%m-%d`"}
$ @kbd{tar --create --file=/dev/tape --multi-volume \
--volume="Daily backup for `date +%Y-%m-%d`"}
-@end example
-
-Also note that each label has its own date and time, which corresponds
-to when GNU @code{tar} initially attempted to write it, often soon
-after the operator launches @code{tar} or types the carriage return
-telling that the next tape is ready. Comparing date labels does give
-an idea of tape throughput only if the delays for rewinding tapes
-and the operator switching them were negligible, which is ususally
-not the case.
+@end group
+@end smallexample
-@FIXME{was --volume}
+ Also note that each label has its own date and time, which corresponds
+to when @GNUTAR{} initially attempted to write it,
+often soon after the operator launches @command{tar} or types the
+carriage return telling that the next tape is ready. Comparing date
+labels does give an idea of tape throughput only if the delays for
+rewinding tapes and the operator switching them were negligible, which
+is usually not the case.
-@node verify, Write Protection, label, Media
+@node verify
@section Verifying Data as It is Stored
@cindex Verifying a write operation
@cindex Double-checking a write operation
-@table @kbd
+@table @option
@item -W
@itemx --verify
+@opindex verify, short description
Attempt to verify the archive after writing.
@end table
-This option causes @code{tar} to verify the archive after writing it.
+This option causes @command{tar} to verify the archive after writing it.
Each volume is checked after it is written, and any discrepancies
are recorded on the standard error output.
cannot be verified.
You can insure the accuracy of an archive by comparing files in the
-system with archive members. @code{tar} can compare an archive to the
+system with archive members. @command{tar} can compare an archive to the
file system as the archive is being written, to verify a write
operation, or can compare a previously written archive, to insure that
it is up to date.
+@opindex verify, using with @option{--create}
+@opindex create, using with @option{--verify}
To check for discrepancies in an archive immediately after it is
-written, use the @value{op-verify} option in conjunction with
-the @value{op-create} operation. When this option is
-specified, @code{tar} checks archive members against their counterparts
-in the file system, and reports discrepancies on the standard error. In
-multi-volume archives, each volume is verified after it is written,
-before the next volume is written.
+written, use the @option{--verify} (@option{-W}) option in conjunction with
+the @option{--create} operation. When this option is
+specified, @command{tar} checks archive members against their counterparts
+in the file system, and reports discrepancies on the standard error.
To verify an archive, you must be able to read it from before the end
of the last written entry. This option is useful for detecting data
errors on some tapes. Archives written to pipes, some cartridge tape
drives, and some other devices cannot be verified.
-One can explicitely compare an already made archive with the file system
-by using the @value{op-compare} option, instead of using the more automatic
-@value{op-verify} option. @value{xref-compare}.
+One can explicitly compare an already made archive with the file
+system by using the @option{--compare} (@option{--diff}, @option{-d})
+option, instead of using the more automatic @option{--verify} option.
+@xref{compare}.
Note that these two options have a slightly different intent. The
-@value{op-compare} option how identical are the logical contents of some
-archive with what is on your disks, while the @value{op-verify} option is
+@option{--compare} option checks how identical are the logical contents of some
+archive with what is on your disks, while the @option{--verify} option is
really for checking if the physical contents agree and if the recording
-media itself is of dependable quality. So, for the @value{op-verify}
-operation, @code{tar} tries to defeat all in-memory cache pertaining to
+media itself is of dependable quality. So, for the @option{--verify}
+operation, @command{tar} tries to defeat all in-memory cache pertaining to
the archive, while it lets the speed optimization undisturbed for the
-@value{op-compare} option. If you nevertheless use @value{op-compare} for
+@option{--compare} option. If you nevertheless use @option{--compare} for
media verification, you may have to defeat the in-memory cache yourself,
maybe by opening and reclosing the door latch of your recording unit,
forcing some doubt in your operating system about the fact this is really
the same volume as the one just written or read.
-The @value{op-verify} option would not be necessary if drivers were indeed
+The @option{--verify} option would not be necessary if drivers were indeed
able to detect dependably all write failures. This sometimes require many
magnetic heads, some able to read after the writes occurred. One would
not say that drivers unable to detect all cases are necessarily flawed,
as long as programming is concerned.
-@node Write Protection, , verify, Media
+The @option{--verify} (@option{-W}) option will not work in
+conjunction with the @option{--multi-volume} (@option{-M}) option or
+the @option{--append} (@option{-r}), @option{--update} (@option{-u})
+and @option{--delete} operations. @xref{Operations}, for more
+information on these operations.
+
+Also, since @command{tar} normally strips leading @samp{/} from file
+names (@pxref{absolute}), a command like @samp{tar --verify -cf
+/tmp/foo.tar /etc} will work as desired only if the working directory is
+@file{/}, as @command{tar} uses the archive's relative member names
+(e.g., @file{etc/motd}) when verifying the archive.
+
+@node Write Protection
@section Write Protection
Almost all tapes and diskettes, and in a few rare cases, even disks can
be @dfn{write protected}, to protect data on them from being changed.
Once an archive is written, you should write protect the media to prevent
-the archive from being accidently overwritten or deleted. (This will
+the archive from being accidentally overwritten or deleted. (This will
protect the archive from being changed with a tape or floppy drive---it
will not protect it from magnet fields or other physical hazards).
which can be removed from the center of a tape reel, or some other
changeable feature.
-@node Index, , Media, Top
-@unnumbered Index
+@node Changes
+@appendix Changes
+
+This appendix lists some important user-visible changes between
+version @GNUTAR{} @value{VERSION} and previous versions. An up-to-date
+version of this document is available at
+@uref{http://www.gnu.org/@/software/@/tar/manual/changes.html,the
+@GNUTAR{} documentation page}.
+
+@table @asis
+@item Use of short option @option{-o}.
+
+Earlier versions of @GNUTAR{} understood @option{-o} command line
+option as a synonym for @option{--old-archive}.
+
+@GNUTAR{} starting from version 1.13.90 understands this option as
+a synonym for @option{--no-same-owner}. This is compatible with
+UNIX98 @command{tar} implementations.
+
+However, to facilitate transition, @option{-o} option retains its
+old semantics when it is used with one of archive-creation commands.
+Users are encouraged to use @option{--format=oldgnu} instead.
+
+It is especially important, since versions of @acronym{GNU} Automake
+up to and including 1.8.4 invoke tar with this option to produce
+distribution tarballs. @xref{Formats,v7}, for the detailed discussion
+of this issue and its implications.
+
+Future versions of @GNUTAR{} will understand @option{-o} only as a
+synonym for @option{--no-same-owner}.
+
+@item Use of short option @option{-l}
+
+Earlier versions of @GNUTAR{} understood @option{-l} option as a
+synonym for @option{--one-file-system}. Such usage is deprecated.
+For compatibility with other implementations future versions of
+@GNUTAR{} will understand this option as a synonym for
+@option{--check-links}.
+
+@item Use of options @option{--portability} and @option{--old-archive}
+
+These options are deprecated. Please use @option{--format=v7} instead.
+
+@item Use of option @option{--posix}
+
+This option is deprecated. Please use @option{--format=posix} instead.
+@end table
+
+@node Configuring Help Summary
+@appendix Configuring Help Summary
+
+Running @kbd{tar --help} displays the short @command{tar} option
+summary (@pxref{help}). This summary is organised by @dfn{groups} of
+semantically close options. The options within each group are printed
+in the following order: a short option, eventually followed by a list
+of corresponding long option names, followed by a short description of
+the option. For example, here is an excerpt from the actual @kbd{tar
+--help} output:
+
+@verbatim
+ Main operation mode:
+
+ -A, --catenate, --concatenate append tar files to an archive
+ -c, --create create a new archive
+ -d, --diff, --compare find differences between archive and
+ file system
+ --delete delete from the archive
+@end verbatim
+
+@vrindex ARGP_HELP_FMT, environment variable
+The exact visual representation of the help output is configurable via
+@env{ARGP_HELP_FMT} environment variable. The value of this variable
+is a comma-separated list of @dfn{format variable} assignments. There
+are two kinds of format variables. An @dfn{offset variable} keeps the
+offset of some part of help output text from the leftmost column on
+the screen. A @dfn{boolean} variable is a flag that toggles some
+output feature on or off. Depending on the type of the corresponding
+variable, there are two kinds of assignments:
+
+@table @asis
+@item Offset assignment
+
+The assignment to an offset variable has the following syntax:
+
+@smallexample
+@var{variable}=@var{value}
+@end smallexample
+
+@noindent
+where @var{variable} is the variable name, and @var{value} is a
+numeric value to be assigned to the variable.
+
+@item Boolean assignment
+
+To assign @code{true} value to a variable, simply put this variable name. To
+assign @code{false} value, prefix the variable name with @samp{no-}. For
+example:
+
+@smallexample
+@group
+# Assign @code{true} value:
+dup-args
+# Assign @code{false} value:
+no-dup-args
+@end group
+@end smallexample
+@end table
+
+Following variables are declared:
+
+@deftypevr {Help Output} boolean dup-args
+If true, arguments for an option are shown with both short and long
+options, even when a given option has both forms, for example:
+
+@smallexample
+ -f ARCHIVE, --file=ARCHIVE use archive file or device ARCHIVE
+@end smallexample
+
+If false, then if an option has both short and long forms, the
+argument is only shown with the long one, for example:
+
+@smallexample
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+@end smallexample
+
+@noindent
+and a message indicating that the argument is applicable to both
+forms is printed below the options. This message can be disabled
+using @code{dup-args-note} (see below).
+
+The default is false.
+@end deftypevr
+
+@deftypevr {Help Output} boolean dup-args-note
+If this variable is true, which is the default, the following notice
+is displayed at the end of the help output:
+
+@quotation
+Mandatory or optional arguments to long options are also mandatory or
+optional for any corresponding short options.
+@end quotation
+
+Setting @code{no-dup-args-note} inhibits this message. Normally, only one of
+variables @code{dup-args} or @code{dup-args-note} should be set.
+@end deftypevr
+
+@deftypevr {Help Output} offset short-opt-col
+Column in which short options start. Default is 2.
+
+@smallexample
+@group
+$ @kbd{tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=short-opt-col=6 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+@end group
+@end smallexample
+@end deftypevr
+
+@deftypevr {Help Output} offset long-opt-col
+Column in which long options start. Default is 6. For example:
+
+@smallexample
+@group
+$ @kbd{tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=long-opt-col=16 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+@end group
+@end smallexample
+@end deftypevr
+
+@deftypevr {Help Output} offset doc-opt-col
+Column in which @dfn{doc options} start. A doc option isn't actually
+an option, but rather an arbitrary piece of documentation that is
+displayed in much the same manner as the options. For example, in
+the description of @option{--format} option:
+
+@smallexample
+@group
+ -H, --format=FORMAT create archive of the given format.
+
+ FORMAT is one of the following:
+
+ gnu GNU tar 1.13.x format
+ oldgnu GNU format as per tar <= 1.12
+ pax POSIX 1003.1-2001 (pax) format
+ posix same as pax
+ ustar POSIX 1003.1-1988 (ustar) format
+ v7 old V7 tar format
+@end group
+@end smallexample
+
+@noindent
+the format names are doc options. Thus, if you set
+@kbd{ARGP_HELP_FMT=doc-opt-col=6} the above part of the help output
+will look as follows:
+
+@smallexample
+@group
+ -H, --format=FORMAT create archive of the given format.
+
+ FORMAT is one of the following:
+
+ gnu GNU tar 1.13.x format
+ oldgnu GNU format as per tar <= 1.12
+ pax POSIX 1003.1-2001 (pax) format
+ posix same as pax
+ ustar POSIX 1003.1-1988 (ustar) format
+ v7 old V7 tar format
+@end group
+@end smallexample
+@end deftypevr
+
+@deftypevr {Help Output} offset opt-doc-col
+Column in which option description starts. Default is 29.
+
+@smallexample
+@group
+$ @kbd{tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=opt-doc-col=19 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=opt-doc-col=9 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE
+ use archive file or device ARCHIVE
+@end group
+@end smallexample
+
+@noindent
+Notice, that the description starts on a separate line if
+@code{opt-doc-col} value is too small.
+@end deftypevr
+
+@deftypevr {Help Output} offset header-col
+Column in which @dfn{group headers} are printed. A group header is a
+descriptive text preceding an option group. For example, in the
+following text:
+
+@verbatim
+ Main operation mode:
+
+ -A, --catenate, --concatenate append tar files to
+ an archive
+ -c, --create create a new archive
+@end verbatim
+@noindent
+@samp{Main operation mode:} is the group header.
+
+The default value is 1.
+@end deftypevr
+
+@deftypevr {Help Output} offset usage-indent
+Indentation of wrapped usage lines. Affects @option{--usage}
+output. Default is 12.
+@end deftypevr
+
+@deftypevr {Help Output} offset rmargin
+Right margin of the text output. Used for wrapping.
+@end deftypevr
+
+@node Genfile
+@appendix Genfile
+@include genfile.texi
+
+@node Snapshot Files
+@appendix Format of the Incremental Snapshot Files
+@include snapshot.texi
+
+@node Free Software Needs Free Documentation
+@appendix Free Software Needs Free Documentation
+@include freemanuals.texi
+
+@node Copying This Manual
+@appendix Copying This Manual
+
+@menu
+* GNU Free Documentation License:: License for copying this manual
+@end menu
+
+@include fdl.texi
+
+@node Index of Command Line Options
+@appendix Index of Command Line Options
+
+This appendix contains an index of all @GNUTAR{} long command line
+options. The options are listed without the preceeding double-dash.
+
+@FIXME{@itemize
+@item Make sure @emph{all} options are indexed.
+@item Provide an index of short options
+@end itemize}
+
+@printindex op
+
+@node Index
+@appendix Index
@printindex cp
projects / chaz / tar / blobdiff