-\input texinfo
-@c %**start of header
+\input texinfo @c -*-texinfo-*-
+@comment %**start of header
@setfilename tar.info
-@settitle GNU tar
-@finalout
-@smallbook
+@include version.texi
+@settitle GNU tar @value{VERSION}
@setchapternewpage odd
-@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.
+@finalout
-@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{-j})
-@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{create options}
-@set xref-ignore-failed-read @xref{create options}
-@set pxref-ignore-failed-read @pxref{create options}
-
-@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-no-same-owner @kbd{--no-same-owner}
-@set ref-no-same-owner @ref{Attributes}
-@set xref-no-same-owner @xref{Attributes}
-@set pxref-no-same-owner @pxref{Attributes}
-
-@set op-no-same-permissions @kbd{--no-same-permissions}
-@set ref-no-same-permissions @ref{Attributes}
-@set xref-no-same-permissions @xref{Attributes}
-@set pxref-no-same-permissions @pxref{Attributes}
-
-@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-overwrite @kbd{--overwrite}
-@set ref-overwrite @ref{Overwrite Old Files}
-@set xref-overwrite @xref{Overwrite Old Files}
-@set pxref-overwrite @pxref{Overwrite Old Files}
-
-@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-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}
+@smallbook
+@c %**end of header
-@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
@defindex op
@syncodeindex op cp
-@dircategory GNU Packages
+@copying
+
+This manual is for @acronym{GNU} @command{tar} (version
+@value{VERSION}, @value{UPDATED}), which creates and extracts files
+from archives.
+
+Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
+2003, 2004 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.
+* Tar: (tar). Making tape (or disk) archives.
@end direntry
@dircategory Individual utilities
@direntry
-* tar: (tar)tar invocation. Invoking @sc{gnu} @command{tar}
+* tar: (tar)tar invocation. Invoking @GNUTAR{}.
@end direntry
-@ifinfo
-This file documents @sc{gnu} @command{tar}, which creates and extracts
-files from archives.
-
-Copyright 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001 Free Software
-Foundation, Inc.
-
-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 no Invariant Sections, with no
-Front-Cover Texts, and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
-
-@end ifinfo
-
-@shorttitlepage @sc{gnu} @command{tar}
+@shorttitlepage @acronym{GNU} @command{tar}
@titlepage
-@title @sc{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, 2000, 2001
-Free Software Foundation, Inc.
-
-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 no Invariant Sections, with no
-Front-Cover Texts, and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
+@insertcopying
@end titlepage
@ifnottex
@node Top
-@top @sc{gnu} tar: an archiver tool
+@top @acronym{GNU} tar: an archiver tool
+
+@insertcopying
@cindex file archival
@cindex archiving files
-@sc{gnu} @command{tar} creates and extracts files from archives.
-
-This manual documents version @value{VERSION} of @sc{gnu} @command{tar}.
-
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
* Date input formats::
* Formats::
* Media::
+
+Appendices
+
+* Genfile::
+* Snapshot Files::
* Free Software Needs Free Documentation::
* Copying This Manual::
* Index::
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* posix compliance::
-* Authors:: @sc{gnu} @command{tar} Authors
+* Current status:: Current development status of @GNUTAR{}
+* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
Tutorial Introduction to @command{tar}
* extract dir::
* failing commands::
-Invoking @sc{gnu} @command{tar}
+Invoking @GNUTAR{}
* Synopsis::
* using tar options::
* Option Summary::
* Short Option Summary::
-@sc{gnu} @command{tar} Operations
+@GNUTAR{} Operations
* Basic tar::
* Advanced tar::
* Applications::
* looking ahead::
-Advanced @sc{gnu} @command{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{--create}
+Options Used by @option{--create}
* Ignore Failed Read::
-Options Used by @code{--extract}
+Options Used by @option{--extract}
* Reading:: Options to Help Read Archives
* Writing:: Changing How @command{tar} Writes Files
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
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 @command{tar}
* Day of week items:: Monday and others.
* Relative items in date strings:: next tuesday, 2 years ago.
* Pure numbers in date strings:: 19931219, 1440.
-* Authors of getdate:: Bellovin, Eggert, Salz, Berets, et al.
+* Seconds since the Epoch:: @@1078100502.
+* Authors of get_date:: Bellovin, Eggert, Salz, Berets, et al.
Controlling the Archive Format
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
-* Extensions:: @sc{gnu} Extensions to the Archive Format
+* Extensions:: @acronym{GNU} Extensions to the Archive Format
* cpio:: Comparison of @command{tar} and @command{cpio}
Making @command{tar} Archives More Portable
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: @sc{posix} archives
+* posix:: @acronym{POSIX} archives
* Checksumming:: Checksumming Problems
* Large or Negative Values:: Large files, negative time stamps, etc.
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+GNU tar internals and development
+
+* Genfile::
+* Snapshot Files::
+
Copying This Manual
* GNU Free Documentation License:: License for copying this manual
@node Introduction
@chapter Introduction
-Welcome to the @sc{gnu} @command{tar} manual. @sc{gnu} @command{tar} creates
-and manipulates (@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 @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* posix compliance::
-* Authors:: @sc{gnu} @command{tar} Authors
+* Current status:: Current development status of @GNUTAR{}
+* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
@end menu
@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 @sc{gnu}
-@command{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
The third chapter presents the remaining five operations, and
information about using @command{tar} options and option syntax.
-@FIXME{this sounds more like a @sc{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 @sc{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.
+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
@table @asis
@item Storage
Often, @command{tar} archives are used to store related files for
-convenient file transfer over a network. For example, the @sc{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.
+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
all dimensions, even time!)
@item Backup
-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. @sc{gnu} @command{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
+filesystem.
@item Transportation
You can create an archive on one system, transfer it to another system,
this manual, we consistently refer to ``archives'' and ``archive
members'' to make learning to use @command{tar} easier for novice users.
-@node posix compliance
-@section @sc{posix} Compliance
+@node Current status
+@section Current development status of @GNUTAR{}
-@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
-@sc{posix} standards. If you set the shell environment variable
-@env{POSIXLY_CORRECT}, @sc{gnu} @command{tar} will force you to adhere to
-these standards. Therefore, if this variable is set and you violate
-one of the @sc{posix} standards in the way you phrase a command, for
-example, @sc{gnu} @command{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 @sc{posix} standards.
-
-There is a chance in the future that, if you set this environment
-variable, your archives will be forced to comply with @sc{posix} standards,
-also. No @sc{gnu} @command{tar} extensions will be allowed.
+@GNUTAR{} is currently in the process of active development, whose
+primary aims are:
+
+@itemize @bullet
+@item Improve compatibility between @GNUTAR{} and other @command{tar}
+implementations.
+@item Switch to using @acronym{POSIX} archives.
+@item Revise sparse file handling and multiple volume processing.
+@item Merge with the @acronym{GNU} @code{paxutils} project.
+@end itemize
+
+Some of these aims are already attained, while others are still
+being worked upon. From the point of view of an end user, the
+following issues need special mentioning:
+
+@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 @value{op-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 Authors
-@section @sc{gnu} @command{tar} Authors
+@section @GNUTAR{} Authors
-@sc{gnu} @command{tar} was originally written by John Gilmore, and modified by
-many people. The @sc{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.
+@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 @sc{gnu} @command{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 @sc{gnu} @command{tar} 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 @sc{gnu} @command{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}.
+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
If you find problems or have suggestions about this program or manual,
please report them to @file{bug-tar@@gnu.org}.
+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}.
+
@node Tutorial
@chapter Tutorial Introduction to @command{tar}
This chapter guides you through some basic examples of three @command{tar}
-operations: @samp{--create}, @samp{--list}, and @samp{--extract}. If
+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 @command{tar} works.
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
@section Basic @command{tar} Operations and Options
helping you type commands more carefully that they are effectively
``required''. We will discuss them in this chapter.
-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
+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
you used to seeing them. (Note that the ``old style'' option forms
-exist in @sc{gnu} @command{tar} for compatibility with Unix @command{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}. 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}.)
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 @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
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 @command{tar} archive.
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
-@command{tar}: @samp{--file} (which takes an archive file as an argument)
-and @samp{--verbose}. (You are usually not @emph{required} to specify
+@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.)
@end menu
@node file tutorial
-@unnumberedsubsec The @samp{--file} Option
+@unnumberedsubsec The @option{--file} Option
-@table @kbd
+@table @option
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Specify the name of an archive file.
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 specify an archive file
@ref{file}.
@node verbose tutorial
-@unnumberedsubsec The @samp{--verbose} Option
+@unnumberedsubsec The @option{--verbose} Option
-@table @kbd
+@table @option
@item --verbose
@itemx -v
Show the files being worked on as @command{tar} is running.
@value{op-verbose} 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 @samp{--verbose}
+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
+@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 @samp{--verbose} at times to help make something
+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
-@unnumberedsubsec Getting Help: Using the @code{--help} Option
+@unnumberedsubsec Getting Help: Using the @option{--help} Option
-@table @kbd
+@table @option
@item --help
-The @samp{--help} option to @command{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
@command{tar} available on your system.
@end table
One of the basic operations of @command{tar} is @value{op-create}, which
you use to create a @command{tar} archive. We will explain
-@samp{--create} first because, in order to learn about the other
+@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
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
@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
archive file you create.
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).
+(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.
-@FIXME{xref to definitions?}
+(@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, @sc{gnu}
-@command{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
Use @value{op-append} instead. @xref{append}.
@node create verbose
-@subsection Running @samp{--create} with @samp{--verbose}
+@subsection Running @option{--create} with @option{--verbose}
If you include the @value{op-verbose} 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 @command{tar} generated the remaining lines
+@option{--verbose}, except that @command{tar} generated the remaining lines
@iftex
(note the different font styles).
@end iftex
previous example (including the @value{op-verbose} 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, @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
+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, @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 @command{tar} will add this file to the archive.
-Because the @samp{-v} option did not get registered, @command{tar} will not
+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
does what, and therefore where different names have to be placed.
(Placing options in an unusual order can also cause @command{tar} to
report an error if you have set the shell environment variable
-@env{POSIXLY_CORRECT}; @pxref{posix compliance} for more information
-on this.)
+@env{POSIXLY_CORRECT}.)
@node create dir
@subsection Archiving Directories
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
@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
If you give @command{tar} a command such as
-@example
+@smallexample
$ @kbd{tar --create --file=foo.tar .}
-@end example
+@end smallexample
@noindent
-@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.) @sc{gnu} @command{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 @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 @sc{gnu}
-@command{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
+@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
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 @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}
to specify the name of the archive.
-If you use the @value{op-verbose} option with @samp{--list}, then
+If you use the @value{op-verbose} 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
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
+@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
-@cindex File name arguments, using @code{--list} with
-@cindex @code{--list} with file name arguments
+@cindex @option{--show-stored-names} described
+ 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 (not @emph{file}) names when creating the archive.
+@end table
+
+@cindex File name arguments, using @option{--list} with
+@cindex @option{--list} with file name arguments
You can specify one or more individual member names as arguments when
using @samp{list}. In this case, @command{tar} will only list the
names of members you identify. For example, @w{@kbd{tar --list
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
+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.
@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
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
@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
+@end smallexample
When you use a directory name as a file name argument, @command{tar} acts on
all the files (including sub-directories) in that directory.
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
long form of the operation without affecting the performance.
* extracting archives::
* extracting files::
* extract dir::
+* extracting untrusted archives::
* failing commands::
@end menu
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
+@smallexample
-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
+@end smallexample
@node extracting files
@subsection Extracting Specific Files
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?}
+file @file{blues} that you deleted. @FIXME{At the time of this
+writing, atime and ctime are not restored. Since this is a tutorial
+for a beginnig user, it should hardly be mentioned here. Maybe in
+a footnote? --gray}.
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
(@pxref{list}).
You can extract a file to standard output by combining the above options
-with the @option{--to-stdout} option (@pxref{Writing to Standard
+with the @value{op-to-stdout} option (@pxref{Writing to Standard
Output}).
If you give the @value{op-verbose} option, then @value{op-extract} will
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, @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
-@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!).}
+@noindent
+If you were to specify two @value{op-verbose} options, @command{tar}
+would have displayed more detail about the extracted files, as shown
+in the example below:
+
+@smallexample
+$ @kbd{tar -xvvf music.tar practice/folk practice/jazz}
+-rw-rw-rw- me user 28 1996-10-18 16:31 practice/jazz
+-rw-rw-rw- 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 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 @value{op-list} option, possibly combined
+with @value{op-verbose}.
+
@node failing commands
@subsection Commands That Will Fail
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
be in the rest of the manual.}
@node tar invocation
-@chapter Invoking @sc{gnu} @command{tar}
+@chapter Invoking @GNUTAR{}
@UNREVISED
-This chapter is about how one invokes the @sc{gnu} @command{tar} 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.
+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
@node Synopsis
@section General Synopsis of @command{tar}
-The @sc{gnu} @command{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.
@cindex exit status
@cindex return status
-Besides successful exits, @sc{gnu} @command{tar} 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.
-
-@sc{gnu} @command{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.
@node using tar options
@section Using @command{tar} Options
-@sc{gnu} @command{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 @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.
+@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 @value{op-verbose}, which
can be used to specify an option containing whitespace or a backslash.
Note that @command{tar} options are case sensitive. For example, the
-options @samp{-T} and @samp{-t} are different; the first requires an
+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}.
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
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 @emph{may} take an argument (currently, there are
+two such options: @value{op-backup} and @value{op-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
@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, @command{tar} will tell
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 @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 @command{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.
+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{@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
-@sc{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
@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.
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 @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 @command{tar} programs, @sc{gnu} and non-@sc{gnu}, support
-old options. @sc{gnu} @command{tar} 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 @value{op-create} command to create an
-archive.
+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
+@value{op-create} command to create an archive.
@node Mixing
@subsection Mixing Option Styles
-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 @sc{gnu}
-@command{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 @command{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 @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.
+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 @command{tar} archive would be a file named
-@samp{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
+@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
@node Operation Summary
@subsection Operations
-@table @kbd
+@table @option
@item --append
@itemx -r
@item --catenate
@itemx -A
-Same as @samp{--concatenate}. @xref{concatenate}.
+Same as @option{--concatenate}. @xref{concatenate}.
@item --compare
@itemx -d
@item --diff
@itemx -d
-Same @samp{--compare}. @xref{compare}.
+Same @option{--compare}. @xref{compare}.
@item --extract
@itemx -x
@item --get
@itemx -x
-Same as @samp{--extract}. @xref{extract}.
+Same as @option{--extract}. @xref{extract}.
@item --list
@itemx -t
@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 @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.
@xref{update}.
@end table
@node Option Summary
@subsection @command{tar} Options
-@table @kbd
+@table @option
@item --absolute-names
@itemx -P
-Normally when creating an archive, @command{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.
+@FIXME-xref{}
@item --after-date
-(See @samp{--newer}.) @FIXME-pxref{}
+(See @option{--newer}.) @FIXME-pxref{}
@item --anchored
An exclude pattern must match an initial subsequence of the name's components.
@item --backup=@var{backup-type}
-Rather than deleting files from the file system, @command{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}. @FIXME-xref{}
@item --block-number
@itemx -R
@item --bzip2
@itemx -j
-This option tells @command{tar} to read or write archives through @code{bzip2}.
-@FIXME-xref{}
+This option tells @command{tar} to read or write archives through
+@code{bzip2}. @FIXME-xref{}
@item --checkpoint
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 @command{tar} is still running, but don't want to see
-@samp{--verbose} output. @FIXME-xref{}
+@option{--verbose} output. @FIXME-xref{}
+
+@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{Current status}, for more information.
@item --compress
@itemx --uncompress
@itemx -Z
-@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. @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. @FIXME-xref{}
@item --confirmation
-(See @samp{--interactive}.) @FIXME-pxref{}
+(See @option{--interactive}.) @FIXME-pxref{}
@item --dereference
@itemx -h
-When creating a @command{tar} archive, @command{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. @FIXME-xref{}
@item --directory=@var{dir}
@itemx -C @var{dir}
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Similar to @samp{--exclude}, except @command{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}. @FIXME-xref{}
+
+@item --exclude-caches
+
+Automatically excludes all directories
+containing a cache directory tag. @FIXME-xref{}
@item --file=@var{archive}
@itemx -f @var{archive}
@item --force-local
-Forces @command{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.
+@FIXME-xref{}
+
+@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.
@item --group=@var{group}
Also see the comments for the @value{op-owner} option.
-@item --gunzip
-
-(See @samp{--gzip}.) @FIXME-pxref{}
-
@item --gzip
@itemx --gunzip
@itemx --ungzip
@itemx -z
-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. @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. @FIXME-xref{}
@item --help
@item --ignore-zeros
@itemx -i
-With this option, @command{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}.
@item --incremental
@itemx -G
-Used to inform @command{tar} that it is working with an old @sc{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}.
+
+@item --index-file=@var{file}
+
+Send verbose output to @var{file} instead of to standard output.
@item --info-script=@var{script-file}
@itemx --new-volume-script=@var{script-file}
performing potentially destructive options, such as overwriting files.
@FIXME-xref{}
+@item --keep-newer-files
+
+Do not replace existing files that are newer than their archive copies
+when extracting files from an archive.
+
@item --keep-old-files
@itemx -k
@item --label=@var{name}
@itemx -V @var{name}
-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}. @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}. @FIXME-xref{}
@item --listed-incremental=@var{snapshot-file}
@itemx -g @var{snapshot-file}
-During a @samp{--create} operation, specifies that the archive that
-@command{tar} creates is a new @sc{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-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}.
@item --mode=@var{permissions}
-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, @sc{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.
(see --info-script)
+@item -n
+@itemx --seek
+
+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.
+
@item --newer=@var{date}
@itemx --after-date=@var{date}
@itemx -N
@item --newer-mtime=@var{date}
-Like @samp{--newer}, but add only 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).
@item --no-anchored
@FIXME-xref{}
@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; this option has an effect only for the superuser.
+for ordinary users.
@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; this option has an effect only for the superuser.
+for ordinary users.
@item --no-wildcards
Do not use wildcards when excluding files.
@item --null
-When @command{tar} is using the @samp{--files-from} option, this option
-instructs @command{tar} to expect filenames terminated with @kbd{NUL}, so
+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.
@FIXME-xref{}
@item --numeric-owner
-This option will notify @command{tar} that it should use numeric user and group
-IDs when creating a @command{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.
+@FIXME-xref{}
+
+@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.
-@item --old-archive
+@xref{Current status}, for more information.
-(See @samp{--portability}.) @FIXME-pxref{}
+@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.
+
+@item --old-archive
+Synonym for @option{--format=v7}.
@item --one-file-system
@itemx -l
-
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{Current status}, for more information.
@item --overwrite
This option does not affect extraction from archives.
-@item --portability
-@itemx --old-archive
-@itemx -o
+@item --pax-option=@var{keyword-list}
-Tells @command{tar} to create an archive that is compatible with Unix V7
-@command{tar}. @FIXME-xref{}
+This option is meaningful only with @acronym{POSIX.1-2001} archives
+(@FIXME-xref{}). 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:
-@item --posix
+@table @asis
+@item delete=@var{pattern}
+When used with one of archive-creation command (@FIXME-xref{}),
+this option instructs @command{tar} to omit from extended header records
+that it produces any keywords matching the string @var{pattern}.
-Instructs @command{tar} to create a @sc{posix} compliant @command{tar} archive. @FIXME-xref{}
+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 @FIXME-xref{see
+man 7 glob}. For example:
-@item --preserve
+@smallexample
+--pax-option delete=security.*
+@end smallexample
-Synonymous with specifying both @samp{--preserve-permissions} and
-@samp{--same-order}. @FIXME-xref{}
+would suppress security-related information.
-@item --preserve-order
+@item exthdr.name=@var{string}
-(See @samp{--same-order}; @pxref{Reading}.)
+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:
-@item --preserve-permissions
-@itemx --same-permissions
-@itemx -p
+@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
-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{Writing}.
+Any other @samp{%} characters in @var{string} produce undefined
+results.
-@item --read-full-records
-@itemx -B
+If no option @samp{exthdr.name=string} is specified, @command{tar}
+will use the following default value:
-Specifies that @command{tar} should reblock its input, for reading from pipes on
-systems with buggy implementations. @xref{Reading}.
+@smallexample
+%d/PaxHeaders.%p/%f
+@end smallexample
-@item --record-size=@var{size}
+@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:
-Instructs @command{tar} to use @var{size} bytes per record when accessing the
-archive. @FIXME-xref{}
+@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
+
+@item --portability
+@itemx --old-archive
+Synonym for @option{--format=v7}.
+
+@item --posix
+Same as @option{--format=posix}.
+
+@item --preserve
+
+Synonymous with specifying both @option{--preserve-permissions} and
+@option{--same-order}. @FIXME-xref{}
+
+@item --preserve-order
+
+(See @option{--same-order}; @pxref{Reading}.)
+
+@item --preserve-permissions
+@itemx --same-permissions
+@itemx -p
+
+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{Writing}.
+
+@item --read-full-records
+@itemx -B
+
+Specifies that @command{tar} should reblock its input, for reading
+from pipes on systems with buggy implementations. @xref{Reading}.
+
+@item --record-size=@var{size}
+
+Instructs @command{tar} to use @var{size} bytes per record when accessing the
+archive. @FIXME-xref{}
@item --recursion
Directs @command{tar} to remove the source file from the file system after
appending it to an archive. @FIXME-xref{}
+@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}).
+
@item --rsh-command=@var{cmd}
Notifies @command{tar} that is should use @var{cmd} to communicate with remote
@item --same-permissions
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+(See @option{--preserve-permissions}; @pxref{Writing}.)
+
+@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
+@end smallexample
@item --show-omitted-dirs
-Instructs @command{tar} to mention directories its skipping over when operating
-on a @command{tar} archive. @FIXME-xref{}
+Instructs @command{tar} to mention directories its skipping over when
+operating on a @command{tar} archive. @FIXME-xref{}
+
+@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}.
@item --sparse
@itemx -S
-Invokes a @sc{gnu} extension when adding files to an archive that handles
+Invokes a @acronym{GNU} extension when adding files to an archive that handles
sparse files efficiently. @FIXME-xref{}
@item --starting-file=@var{name}
files in the archive until it finds one that matches @var{name}.
@xref{Scarce}.
+@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}.
+
@item --suffix=@var{suffix}
Alters the suffix @command{tar} uses when backing up files from the default
Specifies the length of tapes that @command{tar} is writing as being
@w{@var{num} x 1024} bytes long. @FIXME-xref{}
+@item --test-label
+
+Reads the volume label. If an argument is specified, test whether it
+matches the volume label. @xref{--test-label option}.
+
@item --to-stdout
@itemx -O
-During extraction, @command{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}.
@item --totals
@item --uncompress
-(See @samp{--compress}.) @FIXME-pxref{}
+(See @option{--compress}.) @FIXME-pxref{}
@item --ungzip
-(See @samp{--gzip}.) @FIXME-pxref{}
+(See @option{--gzip}.) @FIXME-pxref{}
@item --unlink-first
@itemx -U
Instructs @command{tar} to access the archive through @var{prog}, which is
presumed to be a compression program of some sort. @FIXME-xref{}
+@item --utc
+
+Display file modification dates in @acronym{UTC}. This option implies
+@option{--verbose}.
+
@item --verbose
@itemx -v
@item --version
-@command{tar} will print an informational message about what version it is and a
-copyright message, some credits, and then exit. @FIXME-xref{}
+@command{tar} will print an informational message about what version
+it is and a copyright message, some credits, and then exit.
+@FIXME-xref{}
@item --volno-file=@var{file}
-Used in conjunction with @samp{--multi-volume}. @command{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{}
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{Current status}, 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}
+@option{--extract}
@item -z
-@samp{--gzip}
+@option{--gzip}
@end table
@node help
-@section @sc{gnu} @command{tar} documentation
-
-Being careful, the first thing is really checking that you are using @sc{gnu}
-@command{tar}, indeed. The @value{op-version} option will generate a message
-giving confirmation that you are using @sc{gnu} @command{tar}, with the precise
-version of @sc{gnu} @command{tar} you are using. @command{tar} identifies itself
-and prints the version number to the standard output, then immediately
+@section @GNUTAR{} documentation
+
+Being careful, the first thing is really checking that you are using
+@GNUTAR{}, indeed. The @value{op-version} option
+will generate a message giving confirmation that you are using
+@GNUTAR{}, with the precise version of @GNUTAR{}
+you are using. @command{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:
-@example
-tar (@sc{gnu} tar) @value{VERSION}
-@end example
+@smallexample
+tar (@acronym{GNU} tar) @value{VERSION}
+@end smallexample
@noindent
The first occurrence of @samp{tar} in the result above is the program
-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 @value{op-version} would not yield @w{@samp{tar (@sc{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
+@value{op-version} would not yield @w{@samp{tar (@acronym{GNU}
+paxutils) 3.2}}}.
Another thing you might want to do is checking the spelling or meaning
-of some particular @command{tar} option, without resorting to this manual,
-for once you have carefully read it. @sc{gnu} @command{tar} has a short help
-feature, triggerable through the @value{op-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:
+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
+@value{op-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 @command{less} for a pager. Other
@var{keyword} which interests you and do not want to read all the
@value{op-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.
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 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 printed form, as a kind of small book. It may
-printed out of the @sc{gnu} @command{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 @sc{gnu} @command{tar} has been conveniently installed at your place, this
+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 printed form, as a kind of small
+book. 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
-@command{info} program handy, use the Info reader provided within @sc{gnu}
-Emacs, calling @samp{tar} from the main Info menu.
-
-There is currently no @code{man} page for @sc{gnu} @command{tar}. If you observe
-such a @code{man} page on the system you are running, either it does not
-long to @sc{gnu} @command{tar}, or it has not been produced by @sc{gnu}. Currently,
-@sc{gnu} @command{tar} documentation is provided in Texinfo format only, if we
+@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 long to @GNUTAR{}, or it has not
+been produced by @acronym{GNU}. Currently, @GNUTAR{}
+documentation is provided in Texinfo format only, if we
except, of course, the short result of @kbd{tar --help}.
@node verbose
in the archive. The following examples both extract members with
long list output:
-@example
+@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
installer let standard output be the default archive). In that case
@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 @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 @command{tar} reads or writes the archive. In fact, it print
-directory names while reading the archive. It is designed for
+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 @command{tar}
is actually making forward progress.
it might be excluded by the use of the @value{op-exclude} option, or
some other reason.
-If @value{op-block-number} 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 @value{op-block-number}
-is used. Note that @sc{gnu} @command{tar} drains the archive before exiting when
-reading the archive from a pipe.
+If @value{op-block-number} 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
+@value{op-block-number} is used. Note that @GNUTAR{}
+drains the archive before exiting when reading the
+archive from a pipe.
This option is especially useful when reading damaged archives, since
it helps pinpoint the damaged sections. It can also be used with
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.
-@command{tar} also accepts @samp{--confirmation} for this option.
+@command{tar} also accepts @option{--confirmation} for this option.
When the @value{op-interactive} option is specified, before
reading, writing, or deleting files, @command{tar} first prints a message
output free to receive verbose output, all separate from errors.
@node operations
-@chapter @sc{gnu} @command{tar} Operations
+@chapter @GNUTAR{} Operations
@menu
* Basic tar::
@end menu
@node Basic tar
-@section Basic @sc{gnu} @command{tar} Operations
+@section Basic @GNUTAR{} Operations
The basic @command{tar} operations, @value{op-create}, @value{op-list} and
@value{op-extract}, are currently presented and described in the tutorial
@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, @sc{gnu} @command{tar} now takes some distance from elegance, and
+errors, @GNUTAR{} 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 @sc{gnu}
-@command{tar} and nevertheless create an archive with nothing in it,
+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 @value{op-files-from} option,
a file with no names in it, as shown in the following commands:
-@example
+@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}
-A socket is stored, within a @sc{gnu} @command{tar} archive, as a pipe.
+A socket is stored, within a @GNUTAR{} archive, as a pipe.
@item @value{op-list}
-@sc{gnu} @command{tar} now shows dates as @samp{1996-08-30}, while it used to
-show them as @samp{Aug 30 1996}. (One can revert to the old behavior by
-defining @code{USE_OLD_CTIME} in @file{src/list.c} before reinstalling.)
-But 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.
+@GNUTAR{} now shows dates as @samp{1996-08-30},
+while it used to show them as @samp{Aug 30 1996}. (One can revert to
+the old behavior by defining @code{USE_OLD_CTIME} in @file{src/list.c}
+before reinstalling.) But 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
-@section Advanced @sc{gnu} @command{tar} Operations
+@section Advanced @GNUTAR{} Operations
-Now that you have learned the basics of using @sc{gnu} @command{tar}, you may
-want to learn about further ways in which @command{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.
@menu
* Operations::
-* current state::
* append::
* update::
* concatenate::
In the last chapter, you learned about the first three operations to
@command{tar}. This chapter presents the remaining five operations to
-@command{tar}: @samp{--append}, @samp{--update}, @samp{--concatenate},
-@samp{--delete}, and @samp{--compare}.
+@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
-@subsection The Current State of the Practice Files
-
-Currently, the listing of the directory using @command{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
-@subsection How to Add Files to Existing Archives: @code{--append}
+@subsection How to Add Files to Existing Archives: @option{--append}
@UNREVISED
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
+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 @samp{--update}, @pxref{update}.)
-
-@FIXME{Explain in second paragraph whether you can get to the previous
-version -- explain whole situation somewhat more clearly.}
+do this with @option{--update}, @pxref{update}.)
If you use @value{op-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. @command{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
prefer; if you were to use @value{op-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{replace} a file of
the same name which existed in the directory already, and @command{tar}
-will not prompt you about this. Thus, only the most recently archived
+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 @value{op-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
+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
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 truly
``replace'' one member with another. (Replacing one member with another
The simplest way to add a file to an already existing archive is the
@value{op-append} 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
command line. The @value{op-verbose} 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 @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 @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
@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
+@end smallexample
@FIXME{in theory, dan will (soon) try to turn this node into what it's
title claims it will become...}
You can use @value{op-append} 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 @command{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
+@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
effectively lost. This works because files are extracted from an
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, @command{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
+@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
replaced 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}.)
+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 @value{op-occurrence} option, as shown in
+the following example:
+
+@smallexample
+$ @kbd{tar --extract -vv --occurrence --file=collection.tar blues}
+-rw-rw-rw- me user 21 1996-09-23 16:44 blues
+@end smallexample
+
+@xref{Writing}, for more information on @value{op-extract} and
+@xref{Option Summary, --occurrence}, for the description of
+@value{op-occurrence} option.
@node update
@subsection 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 @command{tar}
+@value{op-update}. 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 @value{op-append}).
-Unfortunately, you cannot use @samp{--update} with magnetic tape drives.
+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
+the @value{op-backup} option. @FIXME-ref{Multiple Members with the
Same Name}
@menu
@end menu
@node how to update
-@subsubsection How to Update an Archive Using @code{--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, @command{tar} won't act on any files and
@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 @command{tar} with
the @samp{update} operation and the @value{op-verbose} 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, @command{tar} prints out the names
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 @sc{gnu} @command{tar} options intended
-specifically for backups are more efficient. If you need to run
-backups, please consult @ref{Backups}.
+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
-@subsection Combining Archives with @code{--concatenate}
+@subsection Combining Archives with @option{--concatenate}
@cindex Adding archives to an archive
@cindex Concatenating Archives
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
+To use @option{--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
information on how this affects reading the archive, Multiple
Members with the Same Name.}
-To demonstrate how @samp{--concatenate} works, create two small archives
+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
$ @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
+@end smallexample
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
+When you use @option{--concatenate}, the source and target archives must
already exist and must have been created using compatible 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
+archive listed on the command line. @FIXME{is there a way to specify a
new name?}
Like @value{op-append}, this operation cannot be performed on some
@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 @samp{--concatenate}
+concatenate two archives instead of using the @option{--concatenate}
operation; after all, @command{cat} is the utility for combining files.
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
@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
default archive name.
@node delete
-@subsection Removing Archive Members Using @samp{--delete}
+@subsection Removing Archive Members Using @option{--delete}
@UNREVISED
@cindex Deleting files from an archive
@cindex Removing files from an archive
names, nothing will be deleted. The @value{op-verbose} option will
cause @command{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
+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
@cindex Verifying the currency of an archive
@UNREVISED
-The @samp{--compare} (@samp{-d}), or @samp{--diff} operation compares
+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
files of the same name in the file system. (Note that there is no file,
@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,
version you are running, @command{tar} may have a different error message,
such as:
-@example
+@smallexample
funk: does not exist
-@end example
+@end smallexample
@FIXME-xref{somewhere, for more information about format parameters.
Melissa says: such as "format variations"? But why? Clearly I don't
the integrity of the archive media. For this later goal, @xref{verify}.
@node create options
-@section Options Used by @code{--create}
+@section Options Used by @option{--create}
The previous chapter described the basics of how to use
@value{op-create} to create an archive from a set of files.
@xref{create}. This section described advanced options to be used with
-@samp{--create}.
+@option{--create}.
@menu
* Ignore Failed Read::
@node Ignore Failed Read
@subsection Ignore Fail Read
-@table @kbd
+@table @option
@item --ignore-failed-read
Do not exit with nonzero on unreadable files or directories.
@end table
@node extract options
-@section Options Used by @code{--extract}
+@section Options Used by @option{--extract}
@UNREVISED
@FIXME{i need to get dan to go over these options with me and see if
an archive into the filesystem. 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
@FIXME{need sentence or so of intro here}
-@table @kbd
+@table @option
@item --read-full-records
@item -B
Use in conjunction with @value{op-extract} to read an archive which
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 @command{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 concatenating several archives
+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 @value{op-ignore-zeros} 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. @sc{gnu}
-@command{tar} does not write after the end of an archive, but seeks to
+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 @kbd
+@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
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
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} neither removes it nor modifies its ownership,
-permissions, or time stamps.
+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.
-To be more cautious and prevent existing files from being replaced, use
+To be even more cautious and prevent existing files from being replaced, use
the @value{op-keep-old-files} 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
To be more aggressive about altering existing files, use the
@value{op-overwrite} option. It causes @command{tar} to overwrite
existing files and to follow existing symbolic links when extracting.
-The @option{--overwrite-dir} option is somewhat more conservative than
-@value{op-overwrite}: it overwrites metadata (ownership, permission,
-etc.) for directories, but removes other files before extracting them.
-
-Some people argue that @sc{gnu} @command{tar} 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 filesystem
-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 @sc{gnu} @command{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!
-@sc{gnu} @command{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 behavior. In any case, single files are
-silently removed.
+
+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 filesystem 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} @value{op-recursive-unlink} is specified
+to allow this behavior. In any case, single files are silently
+removed.
Finally, the @value{op-unlink-first} option can improve performance in
some cases by causing @command{tar} to remove files unconditionally
@node Overwrite Old Files
@unnumberedsubsubsec Overwrite Old Files
-@table @kbd
+@table @option
@item --overwrite
Overwrite existing files and directory metadata when extracting files
from an archive.
@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
-@table @kbd
+@table @option
@item --keep-old-files
@itemx -k
Do not replace existing files from archive. The
extraction.
@end table
+@node Keep Newer Files
+@unnumberedsubsubsec Keep Newer Files
+
+@table @option
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive
+copies. This option is meaningless with @value{op-list}.
+@end table
+
@node Unlink First
@unnumberedsubsubsec Unlink First
-@table @kbd
+@table @option
@item --unlink-first
@itemx -U
Remove files before extracting over them.
@node Recursive Unlink
@unnumberedsubsubsec Recursive Unlink
-@table @kbd
+@table @option
@item --recursive-unlink
When this option is specified, try removing files and directory hierarchies
before extracting over them. @emph{This is a dangerous option!}
the files were extracted, use the @value{op-touch} option in
conjunction with @value{op-extract}.
-@table @kbd
+@table @option
@item --touch
@itemx -m
Sets the modification time of extracted archive members to the time
@unnumberedsubsubsec Setting Access Permissions
To set the modes (access permissions) of extracted files to those
-recorded for those files in the archive, use @samp{--same-permissions}
+recorded for those files in the archive, use @option{--same-permissions}
in conjunction with the @value{op-extract} operation. @FIXME{Should be
aliased to ignore-umask.}
-@table @kbd
+@table @option
@item --preserve-permission
@itemx --same-permission
@itemx --ignore-umask
they appear on standard output concatenated, in the order they are
found in the archive.
-@table @kbd
+@table @option
@item --to-stdout
@itemx -O
Writes files to the standard output. Used in conjunction with
through a pipe. This option is meaningless with @value{op-list}.
@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?}
+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
@node remove files
@unnumberedsubsubsec Removing Files
option goes in this section. i have no idea; i only know it's nowhere
else in the book...}
-@table @kbd
+@table @option
@item --remove-files
Remove files after adding them to the archive.
@end table
@node Starting File
@unnumberedsubsubsec Starting File
-@table @kbd
+@table @option
@item --starting-file=@var{name}
@itemx -K @var{name}
Starts an operation in the middle of an archive. Use in conjunction
@node Same Order
@unnumberedsubsubsec Same Order
-@table @kbd
+@table @option
@item --same-order
@itemx --preserve-order
@itemx -s
@cindex backup options
-@sc{gnu} @command{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 @sc{gnu} programs (@command{cp},
-@command{install}, @command{ln}, and @command{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
@opindex --suffix
@cindex backup suffix
@vindex SIMPLE_BACKUP_SUFFIX
-Append @var{suffix} to each backup file made with @samp{--backup}. If this
+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.
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 $*; @}
-@end example
+@end smallexample
@node Applications
@section Notable @command{tar} Usages
medium is a @dfn{pipe}, which is one a Unix redirection mechanism:
@smallexample
-$ @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
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 @command{tar} will read that file.
@chapter Performing Backups and Restoring Files
@UNREVISED
-@sc{gnu} @command{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
Here is a possible plan for a future documentation about the backuping
-scripts which are provided within the @sc{gnu} @command{tar} distribution.
+scripts which are provided within the @GNUTAR{}
+distribution.
-@example
+@smallexample
.* dumps
-. + what are dumps
+. + what are dumps
-. + different levels of 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 (?)
+ A level n dump dumps everything changed since the last level
+ n-1 dump (?)
-. + how to use scripts for dumps (ie, the concept)
+. + how to use scripts for dumps (ie, the concept)
. - scripts to run after editing backup specs (details)
-. + Backup Specs, what is it.
+. + Backup Specs, what is it.
. - how to customize
. - actual text of script [/sp/dump/backup-specs]
-. + Problems
+. + Problems
. - rsh doesn't work
. - rtape isn't installed
. - (others?)
-. + the --incremental option of tar
+. + the --incremental option of tar
-. + tapes
+. + tapes
. - write protection
. - types of media
. : different sizes and types, useful for different things
. - positioning the tape
MT writes two at end of write,
backspaces over one when writing again.
-@end example
+@end smallexample
@end ifclear
-This chapter documents both the provided FSF scripts and @command{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
@value{op-incremental} @FIXME{look it up}
-@value{op-incremental} handle old @sc{gnu}-format incremental backup.
+@value{op-incremental} handle old @acronym{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, @command{tar}
doing a complete incremental restore.
Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@sc{gnu} versions of the @command{tar}
-program.
+archive that may not be readable by non-@acronym{GNU} versions of the
+@command{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}, @command{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-list},
+@command{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
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 @sc{gnu}-format incremental backup.
-This option handles new @sc{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
+@value{op-listed-incremental} handle new @acronym{GNU}-format
+incremental backup. This option handles new @acronym{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 directory list is used to speed up operations.
@value{op-listed-incremental} acts like @value{op-incremental}, but when
be archived are determined, but before the new archive is actually
created.
-@sc{gnu} @command{tar} actually writes the file twice: once before the data
-and written, and once after.
-
@node Inc Dumps
@section Using @command{tar} to Perform Incremental Dumps
@UNREVISED
Here is a sample script to dump the directory hierarchies @samp{/usr}
and @samp{/var}.
-@example
-#! /bin/sh
+@smallexample
+#! /bin/sh
tar --create \
--blocking-factor=126 \
--file=/dev/rmt/0 \
--listed-incremental=/var/log/usr-var.snar \
--verbose \
/usr /var
-@end example
+@end smallexample
This script uses the file @file{/var/log/usr-var.snar} as a snapshot to
store information about the previous tar dump.
whether or not the file is going to be put in the archive.
Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@sc{gnu} versions of the @command{tar}
-program.
+archive that may not be readable by non-@acronym{GNU} versions of the
+@command{tar} program.
@value{op-incremental} in conjunction with @value{op-extract} causes
@command{tar} to read the lists of directory contents previously stored
@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
-@command{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-incremental} in conjunction with @value{op-list} and two
+@value{op-verbose} options causes @command{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 newline character.
+The last file is followed by an additional 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 @command{tar}
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.
+actually created.@FIXME-xref{to the description of the file format}.
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 @samp{--atime-preserve} option), or if you set the clock
+unreliable if you modify a file's time stamps during dumping (e.g.,
+with the @option{--atime-preserve} option), or if you set the clock
backwards.
Despite it should be obvious that a device has a non-volatile value, NFS
to comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
+@command{tar} doesn't access @var{snapshot-file} when
+@value{op-extract} or @value{op-list} are specified, but the
+@value{op-listed-incremental} option must still be given. A
+placeholder @var{snapshot-file} can be specified, e.g.,
+@file{/dev/null}.
+
@FIXME{this section needs to be written}
@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).
-@sc{gnu} @command{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 @command{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. @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 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. @value{xref-incremental}, and
+@value{xref-listed-incremental}, before making such an attempt.
@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 @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
+
+@defvr {Backup variable} ADMINISTRATOR
+The user name of the backup administrator. @code{Backup} scripts
+sends a backup report to this address.
+@end defvr
-@item BACKUP_HOUR
+@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
-@item TAPE_FILE
-The device @command{tar} writes the archive to. This device should be
-attached to the host on which the dump scripts are run.
+@defvr {Backup variable} TAPE_FILE
-@FIXME{examples for all ...}
+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
-@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 @samp{TAPE_STATUS=false}.
+@defvr {Backup variable} BLOCKING
-@item BLOCKING
The blocking factor @command{tar} will use when writing the dump archive.
@value{xref-blocking-factor}.
+@end defvr
-@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
+@defvr {Backup variable} BACKUP_DIRS
+
+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 @command{tar} on, and should
normally be the host that actually contains the file system. However,
-the host machine must have @sc{gnu} @command{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 @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.
+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 filesystems 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
+
+@defvr {Backup variable} FILELIST
+
+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 filesystems 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 filesystems
+
+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
-@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.
+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:
-@FIXME{Same file name, be specific. Through NFS ...}
+@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 filesystem being dumped or restored.
+
+@item fsname
+Filesystem 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 filesystem.
+@end defvr
+
+@defvr {Backup variable} DUMP_END
+Executed after dumping the filesystem.
+@end defvr
+
+@defvr {Backup variable} RESTORE_BEGIN
+Executed before restoring the filesystem.
+@end defvr
+
+@defvr {Backup variable} RESTORE_END
+Executed after restoring the filesystem.
+@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"
-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"
-BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
+# Use @code{ssh} instead of the less secure @code{rsh}
+RSH=/usr/bin/ssh
+RSH_COMMAND=/usr/bin/ssh
-@end example
+# Override MT_STATUS function:
+my_status() @{
+ mts -t $TAPE_FILE
+@}
+MT_STATUS=my_status
-@node Script Syntax
-@subsection Syntax for @file{Backup-specs}
-@UNREVISED
+# Disable MT_OFFLINE function
+MT_OFFLINE=:
-@file{backup-specs} is in shell script syntax. The following
-conventions should be considered when editing the script:
-@FIXME{"conventions?"}
+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"
-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.
+BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
-A quoted string typically cannot contain wildcards. In
-@file{backup-specs}, however, the parameters BACKUP_DIRS and
-BACKUP_FILES can contain wildcards.
+@end smallexample
@node Scripted Backups
@section Using the Backup Scripts
-@UNREVISED
The syntax for running a backup script is:
-@example
-@file{script-name} [@var{time-to-be-run}]
-@end example
+@smallexample
+backup --level=@var{level} --time=@var{time}
+@end smallexample
-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 @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.}
+
+The @option{--time} option determines when should the backup be
+run. @var{Time} may take three forms:
+
+@table @asis
+@item @var{hh}:@var{mm}
+
+The dump must be run at @var{hh} hours @var{mm} minutes.
+
+@item @var{hh}
+
+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
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.
+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).
+
+@item -f
+@itemx --force
+Force backup even if today's log file already exists.
+
+@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 -t @var{start-time}
+@itemx --time=@var{start-time}
+Wait till @var{time}, then do backup.
+
+@item -h
+@itemx --help
+Display short help message and exit.
+
+@item -L
+@itemx --license
+Display program license and exit.
+
+@item -V
+@itemx --version
+Display program version and exit.
+@end table
+
+
@node Scripted Restoration
@section Using the Restore Script
-@UNREVISED
-@ifset PUBLISH
+To restore files that were archived using a scripted backup, use the
+@code{restore} script. Its usage is quite straightforward. In the
+simplest form, invoke @code{restore --all}, it will
+then restore all the filesystems and files specified in
+@file{backup-specs} (@pxref{General-Purpose Variables,BACKUP_DIRS}).
-The @command{tar} distribution does not provide restoring scripts.
+You may select the filesystems (and/or files) to restore by
+giving @code{restore} list of @dfn{patterns} in its command
+line. For example, running
-@end ifset
+@smallexample
+restore 'albert:*'
+@end smallexample
-@ifclear PUBLISH
+@noindent
+will restore all filesystems on the machine @samp{albert}. A more
+complicated example:
-@quotation
-@strong{Warning:} The @sc{gnu} @command{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
+@smallexample
+restore 'albert:*' '*:/var'
+@end smallexample
-@FIXME{A section on non-scripted restore may be a good idea.}
+@noindent
+This command will restore all filesystems on the machine @samp{albert}
+as well as @file{/var} filesystem on all machines.
-To restore files that were archived using a scripted backup, use the
-@code{restore} script. The syntax for the script is:
+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 filesystems 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.
-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.
+@item -L
+@itemx --license
+Display program license and exit.
+
+@item -V
+@itemx --version
+Display program version and exit.
+@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
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.
-
@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.
@value{xref-incremental}, and @value{ref-listed-incremental},
for an explanation of how the script makes that determination.
-@FIXME{this may be an option, not a given}
-
-@end ifclear
-
@node Choosing
@chapter Choosing Files and Names for @command{tar}
@UNREVISED
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
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Name the archive to create or operate on. Use in conjunction with
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 @command{tar} will use this file's 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}).
+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}, @command{tar} reads the
@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
@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}}, @command{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.
(along with the @samp{@@} sign), then your user name will be used.
(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{/usr/ucb/rmt} program installed. If you need to use a
-file whose name includes a colon, then the remote tape drive behavior
+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 @value{op-force-local} option.
@FIXME{i know we went over this yesterday, but bob (and now i do again,
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}, @sc{gnu} @command{tar}
-tries to minimize input and output operations. The Amanda backup
-system, when used with @sc{gnu} @command{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
@section Selecting Archive Members
@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 @command{tar}.
@node files
@section Reading Names from a File
-@UNREVISED
@cindex Reading file names from a file
@cindex Lists of file names
line, you can put the names into a file, and then use the
@value{op-files-from} 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 @command{find} utility.
-@table @kbd
+@table @option
@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 @command{tar} with @samp{--create}, you can not use
-both @samp{--files-from=-} and @samp{--file=-} (@samp{-f -}) in the same
-command.
+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 @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 @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.)
+
+@smallexample
+$ @kbd{find . -size -400 -print > small-files}
+$ @kbd{tar -c -v -z -T small-files -f little.tgz}
+@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
+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}.
-@FIXME{add bob's example, from his message on 2-10-97}
+@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}.
-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
-@command{tar} to specify the files from that file, @file{small-files}, to
-create the archive @file{little.tgz}. (The @samp{-z} option to
-@command{tar} compresses the archive with @command{gzip}; @pxref{gzip} for
-more information.)
+@item
+For both short and long option forms, the option argument can be given
+on the next line after the option name, e.g.:
-@example
-$ @kbd{find . -size -400 -print > small-files}
-$ @kbd{tar -c -v -z -T small-files -f little.tgz}
-@end example
+@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
+
+@cindex @option{--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
-@subsection @kbd{NUL} Terminated File Names
+@subsection @code{NUL} Terminated File Names
-@cindex File names, terminated by @kbd{NUL}
-@cindex @kbd{NUL} terminated file names
+@cindex File names, terminated by @code{NUL}
+@cindex @code{NUL} terminated file names
The @value{op-null} option causes @value{op-files-from} 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
@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 @sc{gnu} @command{xargs} and
-@command{cpio}, and is useful with the @samp{-print0} predicate of @sc{gnu}
-@command{find}. In @command{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 @value{op-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}, @value{op-null} also disables special handling for
+file names that begin with dash.
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 @command{find} just just
-like @samp{-print}, except that it separates files with a @kbd{NUL}
+@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
-@samp{--null} and @samp{-T} options to specify that @command{tar} get 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 @command{tar} will cause
-@command{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?}
To avoid operating on files whose names match a particular pattern,
use the @value{op-exclude} or @value{op-exclude-from} options.
-@table @kbd
+@table @option
@item --exclude=@var{pattern}
Causes @command{tar} to ignore files that match the @var{pattern}.
@end table
@file{src} except for files whose names end in @file{.o}, use the
command @samp{tar -cf src.tar --exclude='*.o' src}.
-You may give multiple @samp{--exclude} options.
+You may give multiple @option{--exclude} options.
-@table @kbd
+@table @option
@item --exclude-from=@var{file}
@itemx -X @var{file}
Causes @command{tar} to ignore files that match the patterns listed in
@end table
@findex exclude-from
-Use the @samp{--exclude-from=@var{file-of-patterns}} option to read a
+Use the @option{--exclude-from=@var{file-of-patterns}} 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
@FIXME{do the exclude options files need to have stuff separated by
newlines the same as the files-from option does?}
+@table @option
+@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-patching with exclude::
* problems with exclude::
However, this matching procedure can be altered by the options listed
below. These options accumulate. For example:
-@example
+@smallexample
--ignore-case --exclude='makefile' --no-ignore-case ---exclude='readme'
-@end example
+@end smallexample
ignores case when excluding @samp{makefile}, but not when excluding
@samp{readme}.
@table @option
@item --anchored
@itemx --no-anchored
-If anchored (the default), a pattern must match an initial subsequence
-of the name's components. Otherwise, the pattern can match any subsequence.
+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}.
@item --ignore-case
@itemx --no-ignore-case
You can sometimes confuse the meanings of @value{op-exclude} and
@value{op-exclude-from}. Be careful: use @value{op-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
+@option{--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.
@item
When you use @value{op-exclude}, be sure to quote the @var{pattern}
-parameter, so @sc{gnu} @command{tar} 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.
+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}
@item
In earlier versions of @command{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
+@option{--exclude-from=@var{file-of-patterns}} option was called
+@option{--exclude=@var{pattern}} instead. Now,
+@option{--exclude=@var{pattern}} applies to patterns listed on the command
+line and @option{--exclude-from=@var{file-of-patterns}} applies to
patterns listed in a file.
@end itemize
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 @sc{gnu} @command{tar} accomplishes wildcard matches. We perceive
-any change of semantics in this area as a delicate thing to impose on
-@sc{gnu} @command{tar} users. On the other hand, the @sc{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
@section Operating Only on New Files
@cindex Excluding file by age
given. If @var{date} starts with @samp{/} or @samp{.}, it is taken to
be a file name; the last-modified 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 @samp{--after-date}
+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.
specify a particular date against which @command{tar} can compare when
deciding whether or not to archive the files.
-@table @kbd
+@table @option
@item --after-date=@var{date}
@itemx --newer=@var{date}
@itemx -N @var{date}
want @command{tar} to act this way.
The @value{op-no-recursion} option inhibits @command{tar}'s recursive descent
-into specified directories. If you specify @samp{--no-recursion}, you can
+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 @kbd
+@table @option
@item --no-recursion
Prevents @command{tar} from recursively descending directories.
This is the default.
@end table
-When you use @samp{--no-recursion}, @sc{gnu} @command{tar} 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 @value{op-files-from}
-option to archive the files located via @command{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 @value{op-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
The @value{op-no-recursion} option also affects how exclude patterns
are interpreted (@pxref{controlling pattern-patching with exclude}).
-@FIXME{example here}
+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 --norecursion 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
@section Crossing Filesystem Boundaries
@command{tar} will still archive files explicitly named on the command line
or through @value{op-files-from}, regardless of where they reside.
-@table @kbd
+@table @option
@item --one-file-system
@itemx -l
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 @command{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
@command{tar} will not archive that file. If the file is a directory
working directory to the directory @var{directory} after that point in
the list.
-@table @kbd
+@table @option
@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 @command{tar}, due to a previous
-@samp{--directory} option.
+@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 @value{op-directory} is disabled by
+@value{op-null} option.
@node absolute
@subsection Absolute File Names
@UNREVISED
-@table @kbd
+@table @option
@item -P
@itemx --absolute-names
Do not strip leading slashes from file names, and permit file names
containing a @file{..} file name component.
@end table
-By default, @sc{gnu} @command{tar} drops a leading @samp{/} on input or output,
-and complains about file names containing a @file{..} component.
-This option turns off this behavior.
+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 @command{tar} extracts archive members from an archive, it strips any
leading slashes (@samp{/}) from the member name. This causes absolute
@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-@sc{gnu} @command{tar} program to use. Therefore,
-@sc{gnu} @command{tar} 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}.
+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 @value{op-absolute-names} option, @command{tar} will do
none of these transformations.
@FIXME{Is write access an issue?}
-@table @kbd
+@table @option
@item --absolute-names
Preserves full file names (including superior directory names) when
archiving files. Preserves leading slash when extracting files.
@FIXME{this is still horrible; need to talk with dan on monday.}
-@command{tar} prints out a message about removing the @samp{/} from file
-names. This message appears once per @sc{gnu} @command{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 @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
+@end smallexample
@include getdate.texi
@node Formats
@chapter Controlling the Archive Format
-@FIXME{need an intro here}
+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.
+
+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.
+
+Archives in @samp{gnu} format are able to hold pathnames of unlimited
+length.
+
+@item oldgnu
+Format used by @GNUTAR{} of versions prior to 1.12.
+
+@item v7
+Archive format, compatible with the V7 implementation of tar. This
+format imposes a number of limitations. The most important of them
+are:
+
+@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
+
+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.
+
+@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:
+
+@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
+
+@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{}.
+
+@end table
+
+The following table summarizes the limitations of each of these
+formats:
+
+@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
+
+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 @command{tar} Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
-* Extensions:: @sc{gnu} Extensions to the Archive Format
+* Extensions:: @acronym{GNU} Extensions to the Archive Format
* cpio:: Comparison of @command{tar} and @command{cpio}
@end menu
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: @sc{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
old Unix hosts, limit your file name components to 14 characters or
less.
-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 @sc{gnu} @command{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
@subsection Symbolic Links
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
@command{tar} archive is a faithful record of the filesystem contents.
-@value{op-dereference} is used with @value{op-create}, 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.
+@value{op-dereference} is used with @value{op-create}, 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
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}. @command{tar} also
-accepts @samp{--portability} for this option. When you specify it,
+versions, specify the @value{op-format-v7} option in
+conjunction with the @value{op-create} (@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 @value{op-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}
@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.
+always use @value{op-format-v7} for your distributions.
+
+@node ustar
+@subsection 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 @value{op-format-ustar}
+option in conjunction with the @value{op-create}.
+
+@node gnu
+@subsection @acronym{GNU} and old @GNUTAR{} 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
+@value{op-format-gnu}.
+
+Some @command{tar} options are currently basing on @GNUTAR{}
+format, and can therefore be used only with @samp{gnu}
+or @samp{oldgnu} archive formats. The list of such options follows:
+
+@itemize @bullet
+@item @value{op-label}, when used with @value{op-create}.
+@item @value{op-incremental}
+@item @value{op-multi-volume}
+@end itemize
+
+These options will be re-implemented for the @samp{posix} archive
+format in the future.
@node posix
-@subsection @sc{gnu} @command{tar} and @sc{posix} @command{tar}
-
-@sc{gnu} @command{tar} was based on an early draft of the @sc{posix} 1003.1
-@code{ustar} standard. @sc{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 @sc{posix} draft as
-unused. Subsequent changes in @sc{posix} have allocated the same parts of
-the header record for other purposes. As a result, @sc{gnu} @command{tar} is
-incompatible with the current @sc{posix} spec, and with @command{tar} programs
-that follow it.
-
-We plan to reimplement these @sc{gnu} extensions in a new way which is
-upward compatible with the latest @sc{posix} @command{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 @sc{gnu} @command{tar} archive, which uses the @sc{gnu} extensions, using
-some other @command{tar} program. So if you want to read the archive
-with another @command{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 @command{tar}s have a limit of 100 characters. @sc{gnu}
-@command{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, @sc{gnu} @command{tar}
-should be able to handle file names of practically unlimited length.
-So, if @sc{gnu} @command{tar} fails to dump and retrieve files having more
-than 100 characters, then there is a bug in @sc{gnu} @command{tar}, indeed.
-
-But, being strictly @sc{posix}, the limit was still 100 characters.
-For various other purposes, @sc{gnu} @command{tar} used areas left unassigned
-in the @sc{posix} draft. @sc{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 @sc{posix} limit oscillates between 100 and 256, depending on the
-precise location of slashes in full file name (this is rather ugly).
-Since @sc{gnu} @command{tar} use the same fields for quite other purposes,
-it became incompatible with the latest @sc{posix} standards.
-
-For longer or non-fitting file names, we plan to use yet another set
-of @sc{gnu} extensions, but this time, complying with the provisions @sc{posix}
-offers for extending the format, rather than conflicting with it.
-Whenever an archive uses old @sc{gnu} @command{tar} extension format or @sc{posix}
-extensions, would it be for very long file names or other specialities,
-this archive becomes non-portable to other @command{tar} implementations.
-In fact, anything can happen. The most forgiving @command{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. @command{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.
-@sc{gnu} @command{tar} should be able to produce and read true @sc{posix} format
-files, while being able to detect old @sc{gnu} @command{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 @sc{posix}
-conforming archives. Past 256, I do not know yet if @sc{gnu} @command{tar}
-will go non-@sc{posix} again, or merely refuse to archive the file.
-
-There are plans so @sc{gnu} @command{tar} support more fully the latest @sc{posix}
-format, while being able to read old V7 format, @sc{gnu} (semi-@sc{posix} plus
-extension), as well as full @sc{posix}. One may ask if there is part of
-the @sc{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 @sc{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.
-
-@sc{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 @env{POSIXLY_CORRECT} is set), I suspect that @sc{gnu} @command{tar}
-should disobey this specification, and automatically switch to using
-@sc{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 @sc{posix} archive with names having more than 100 characters,
-I guess that @sc{gnu} @command{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 @sc{gnu} @command{tar}
-should produce @sc{posix} format by default, whenever possible, producing
-archives older versions of @sc{gnu} @command{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 @sc{gnu} @command{tar} to go closer to @sc{posix}. We can rush it.
-Another possibility is to produce the current @sc{gnu} @command{tar} format
-by default for a few years, but have @sc{gnu} @command{tar} versions from some
-1.@var{POSIX} and up able to recognize all three formats, and let older
-@sc{gnu} @command{tar} fade out slowly. Then, we could switch to producing @sc{posix}
-format by default, with not much harm to those still having (very old at
-that time) @sc{gnu} @command{tar} versions prior to 1.@var{POSIX}.
-
-@sc{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
-@env{POSIXLY_CORRECT}. Otherwise, if @command{tar} is given long
-names, or @samp{-[VMSgG]}, then it should automatically go non-@sc{posix}.
-I think this is easily granted without much discussion.
-
-Another point is that only @code{mtime} is stored in @sc{posix}
-archives, while @sc{gnu} @command{tar} currently also store @code{atime}
-and @code{ctime}. If we want @sc{gnu} @command{tar} to go closer to @sc{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, @sc{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 @sc{gnu} @command{tar} to go closer to @sc{posix} on average, while
-producing files. My choice would be to go closer to @sc{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 @sc{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
-@sc{gnu}-format archives, and recover its previous meaning from this fact.
-
-@sc{gnu}-format as it exists now can easily fool other @sc{posix} @command{tar},
-as it uses fields which @sc{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 @sc{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 @sc{posix} header block. I could manage
-to do that portably between future @sc{gnu} @command{tar}s. So other @sc{posix}
-@command{tar}s might be at least able to provide kind of correct listings
-for the archives produced by @sc{gnu} @command{tar}, if not able to process
-them otherwise.
-
-Using these projected extensions might induce older @command{tar}s to fail.
-We would use the same approach as for @sc{posix}. I'll put out a @command{tar}
-capable of reading @sc{posix}ier, yet extended archives, but will not produce
-this format by default, in @sc{gnu} mode. In a few years, when newer @sc{gnu}
-@command{tar}s will have flooded out @command{tar} 1.11.X and previous, we
-could switch to producing @sc{posix}ier extended archives, with no real harm
-to users, as almost all existing @sc{gnu} @command{tar}s will be ready to read
-@sc{posix}ier format. In fact, I'll do both changes at the same time, in a
-few years, and just prepare @command{tar} for both changes, without effecting
-them, from 1.@var{POSIX}. (Both changes: 1---using @sc{posix} convention for
-getting over 100 characters; 2---avoiding mangling @sc{posix} headers for @sc{gnu}
-extensions, using only @sc{posix} mandated extension techniques).
-
-So, a future @command{tar} will have a @value{op-posix}
-flag forcing the usage of truly @sc{posix} headers, and so, producing
-archives previous @sc{gnu} @command{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 @sc{gnu} @command{tar} with @value{op-posix} and other @sc{posix} @command{tar}.
-
-In a few years, when @sc{gnu} @command{tar} will produce @sc{posix} headers by
-default, @value{op-posix} will have a strong meaning and will disallow
-@sc{gnu} extensions. But in the meantime, for a long while, @value{op-posix}
-in @sc{gnu} tar will not disallow @sc{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 @sc{gnu} extensions will use @sc{posix}
-headers with reserved-for-users extensions to headers, and I will be
-curious to know how well or bad @sc{posix} @command{tar}s will react to these.
-
-@sc{gnu} @command{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 @sc{gnu} @command{tar} not to
-recognize @sc{posix} archives, and consequently, wrongly decide those archives
-are in old V7 format. It is a useful bug for me, because @sc{gnu} @command{tar}
-has other @sc{posix} incompatibilities, and I need to segregate @sc{gnu} @command{tar}
-semi-@sc{posix} archives from truly @sc{posix} archives, for @sc{gnu} @command{tar} should
-be somewhat compatible with itself, while migrating closer to latest
-@sc{posix} standards. So, I'll be very careful about how and when I will do
-the correction.
+@subsection @GNUTAR{} and @acronym{POSIX} @command{tar}
+
+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 @value{op-format-posix} option.
+Notice, that currently @acronym{GNU} extensions are not
+allowed with this format. Following is the list of options that
+cannot be used with @value{op-format-posix}:
+
+@itemize @bullet
+@item @value{op-label}, when used with @value{op-create}.
+@item @value{op-incremental}
+@item @value{op-multi-volume}
+@end itemize
+
+This restriction will disappear in the future versions.
@node Checksumming
@subsection Checksumming Problems
-SunOS and HP-UX @command{tar} fail to accept archives created using @sc{gnu}
-@command{tar} and containing non-ASCII file names, that is, file names
-having characters with the eight bit set, because they use signed
-checksums, while @sc{gnu} @command{tar} uses unsigned checksums while creating
-archives, as per @sc{posix} standards. On reading, @sc{gnu} @command{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.
-
-@sc{gnu} @command{tar} compute checksums both ways, and accept any on read,
-so @sc{gnu} tar can read Sun tapes even with their wrong checksums.
-@sc{gnu} @command{tar} produces the standard checksum, however, raising
-incompatibilities with Sun. That is to say, @sc{gnu} @command{tar} 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?
+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
@cindex future time stamps
@cindex negative time stamps
-@sc{posix} @command{tar} format uses fixed-sized unsigned octal strings
+@acronym{POSIX} @command{tar} format uses fixed-sized unsigned octal strings
to represent numeric values. User and group IDs and device major and
minor numbers have unsigned 21-bit representations, and file sizes and
-times have unsigned 33-bit representations. @sc{gnu} @command{tar}
-generates @sc{posix} representations when possible, but for values
-outside the @sc{posix} range it generates two's-complement base-256
+times have unsigned 33-bit representations. @GNUTAR{}
+generates @acronym{POSIX} representations when possible, but for values
+outside the @acronym{POSIX} range it generates two's-complement base-256
strings: uids, gids, and device numbers have signed 57-bit
representations, and file sizes and times have signed 89-bit
-representations. These representations are an extension to @sc{posix}
+representations. These representations are an extension to @acronym{POSIX}
@command{tar} format, so they are not universally portable.
The most common portability problems with out-of-range numeric values
are large files and future or negative time stamps.
-Portable archives should avoid members of 8 GB or larger, as @sc{posix}
+Portable archives should avoid members of 8 GB or larger, as @acronym{POSIX}
@command{tar} format cannot represent them.
-Portable archives should avoid time stamps from the future. @sc{posix}
+Portable archives should avoid time stamps from the future. @acronym{POSIX}
@command{tar} format can represent time stamps in the range 1970-01-01
00:00:00 through 2242-03-16 12:56:31 @sc{utc}. However, many current
hosts use a signed 32-bit @code{time_t}, or internal time stamp format,
portable archives must avoid these time stamps for many years to come.
Portable archives should also avoid time stamps before 1970. These time
-stamps are a common @sc{posix} extension but their @code{time_t}
+stamps are a common @acronym{POSIX} extension but their @code{time_t}
representations are negative. Many traditional @command{tar}
implementations generate a two's complement representation for negative
time stamps that assumes a signed 32-bit @code{time_t}; hence they
generate archives that are not portable to hosts with differing
-@code{time_t} representations. @sc{gnu} @command{tar} recognizes this
+@code{time_t} representations. @GNUTAR{} recognizes this
situation when it is run on host with a signed 32-bit @code{time_t}, but
it issues a warning, as these time stamps are nonstandard and unportable.
@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 (@value{op-update}) them or delete
+(@value{op-delete}) members from them. Likewise, you cannot append
+another @command{tar} archive to a compressed archive using
+@value{op-append}). Secondly, multi-volume archives cannot be
+compressed.
+
+The following table summarizes compression options used by @GNUTAR{}.
+
+@table @option
@item -z
@itemx --gzip
@itemx --ungzip
Filter the archive through @command{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.
-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 @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 @command{gzip}
-explicitly. (Or set the @env{GZIP} environment variable.)
-
-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 @sc{gnu} @command{tar} is to work in concert
-with @command{gzip} in a way similar to @command{zip}, say. Surely, it is
-possible that @command{tar} and @command{gzip} be done with a single call,
-like in:
+override them, set @env{GZIP} environment variable, e.g.:
-@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
-@command{zip}, archive members are archived individually. @command{tar}'s
-method yields better compression. On the other hand, one can view the
-contents of a @command{zip} archive without having to decompress it. As
-for the @command{tar} and @command{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 @value{op-gzip} 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: @command{gzip}'ed files have no
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 @sc{gnu} @command{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
lose some compressibility. But this would have make recovering easier.
So, there are pros and cons. We'll see!
-@table @kbd
@item -j
@itemx --bzip2
Filter the archive through @code{bzip2}. Otherwise like @value{op-gzip}.
@item -Z
@itemx --compress
@itemx --uncompress
-Filter the archive through @command{compress}. Otherwise like @value{op-gzip}.
-
-@item --use-compress-program=@var{prog}
-Filter through @var{prog} (must accept @samp{-d}).
-@end table
+Filter the archive through @command{compress}. Otherwise like
+@value{op-gzip}.
-@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
-@command{tar} to compress when writing the archive, or to uncompress when
-reading the archive.
-
-To perform compression and uncompression on the archive, @command{tar}
-runs the @command{compress} utility. @command{tar} uses the default
-compression parameters; if you need to override them, avoid the
-@value{op-compress} option and run the @command{compress} utility
-explicitly. It is useful to be able to call the @command{compress}
-utility from within @command{tar} because the @command{compress} utility by
-itself cannot access remote tape drives.
-
-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}
-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, @command{tar} will report an error.
-@strong{Please note} that the @command{compress} program may be covered by
-a patent, and therefore we recommend you stop using it.
+@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, @command{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 @command{tar} to use the @command{gzip} program to be
-used to compress or uncompress the archive wren writing or reading it.
-
-To use the older, obsolete, @command{compress} program, use the
-@value{op-compress} option. The @sc{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}.
-
-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 @sc{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).
+@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 @value{op-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,
Isn't that exactly the role of the @value{op-use-compress-prog} 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
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
@subsection Archiving Sparse Files
@cindex Sparse Files
@UNREVISED
-@table @kbd
+@table @option
@item -S
@itemx --sparse
Handle sparse files efficiently.
In later versions, this option may be removed, and the testing and
treatment of sparse files may be done automatically with any special
-@sc{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
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.
+holes created wherever the continuous stretches of zeros were found.
Thus, if you use @value{op-sparse}, @command{tar} archives won't take
more space than the original.
@command{tar} ignores the @value{op-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, @sc{gnu}
-@command{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 Sparcstation ELC, with full CPU utilization.)
+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}
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 @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. @sc{gnu} @command{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
Handling of file attributes
-@table @kbd
+@table @option
@item --atime-preserve
Preserve access times on files that are read.
This doesn't work for files that
stored in the archive instead.
@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.
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
-@command{tar} archive out of this directory, before cleaning everything
-out. Of course, we could add a lot of options to @sc{gnu} @command{tar} for
-fine tuning permissions and ownership. This is not the good way,
-I think. @sc{gnu} @command{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.
@item -p
@itemx --same-permissions
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}.
@end table
@node Standard
-@section The Standard Format
+@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 @command{tar} utility or Tar mode in @sc{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
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
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 @sc{gnu} @command{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
The @code{name}, @code{linkname}, @code{magic}, @code{uname}, and
@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
@item @code{A} @dots{} @code{Z}
These are reserved for custom implementations. Some of these are
-used in the @sc{gnu} modified format, as described below.
+used in the @acronym{GNU} modified format, as described below.
@end table
(section E.4.48) for @cite{pax - Portable archive interchange}.
@node Extensions
-@section @sc{gnu} Extensions to the Archive Format
+@section @acronym{GNU} Extensions to the Archive Format
@UNREVISED
-The @sc{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
@end table
-You may have trouble reading a @sc{gnu} format archive on a non-@sc{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 @command{tar} does not use the @sc{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.
+You may have trouble reading a @acronym{GNU} format archive on a
+non-@acronym{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 @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}
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. @sc{gnu} @command{cpio} can read and write archives
+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.
@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
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 @command{afio}, @sc{gnu} @command{tar}, and @command{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 @command{tar}red as sparse files (which you can easily
-test, because the resulting archive gets smaller, and @sc{gnu} @command{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
@chapter Tapes and Other Archive Media
@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}.
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
+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 @file{/etc/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 @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 @command{tar};
-it's compiled and installed by default.
-
-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, @sc{gnu} @command{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 preferable.
-Further, I think @emph{most} actual usages of @command{tar} are done with
-pipes or disks, not really tapes, cartridges or diskettes.
+@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 @value{op-rmt-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.
-@sc{gnu} @command{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
@item --force-local
Archive file is local even if it contains a colon.
@pindex rmt
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. @command{tar} calls
-@file{/etc/rmt} by running an @command{rsh} or @command{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, @sc{gnu} @command{tar} 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, @sc{gnu} @command{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
-@command{tar} tape to an operator to restore; the operator used Sun @command{tar}
-instead of @sc{gnu} @command{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 @value{op-absolute-names} 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},
-@sc{gnu} @command{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
two terms in a quite consistent way.
John Gilmore, the writer of the public domain @command{tar} from which
-@sc{gnu} @command{tar} was originally derived, wrote (June 1995):
+@GNUTAR{} was originally derived, wrote (June 1995):
@quotation
The nomenclature of tape drives comes from IBM, where I believe
The Unix man page on @command{tar} was totally confused about this.
When I wrote @code{PD TAR}, I used the historically correct terminology
(@command{tar} writes data records, which are grouped into blocks).
-It appears that the bogus terminology made it into @sc{posix} (no surprise
+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
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 @sc{gnu} @command{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,
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 @sc{gnu} @command{tar}.
+to what we call a @dfn{record} in @GNUTAR{}.
When writing to tapes, @command{tar} writes the contents of the archive
in chunks known as @dfn{records}. To change the default blocking
honor the blocking), but not as dramatically as on tape drives that
honor blocking.
-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
-@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 @command{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 @command{tar} cannot
+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 @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 @command{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 @command{tar} cannot
figure it out. In any case, use @value{op-list} before doing any
-extractions to see whether @command{tar} is reading the archive correctly.
+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
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 @command{tar} programs
-might not be able to read the archive, so we recommend this as a limit
-to use in practice. @sc{gnu} @command{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
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.@:
+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
+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
Archives with blocking factors larger than 20 cannot be read
by very old versions of @command{tar}, or by some newer versions
of @command{tar} running on old machines with small address spaces.
-With @sc{gnu} @command{tar}, the blocking factor of an archive is limited
+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 @command{tar} bundled by the
-system is aware of block size idiosyncrasies, while @sc{gnu} @command{tar} requires
-an explicit specification for the block size, which it cannot guess.
-This yields some people to consider @sc{gnu} @command{tar} is misbehaving, because
-by comparison, @cite{the bundle @command{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
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
specifying a blocking factor larger then the blocking factor of the archive
-(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
+(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
@xref{list}, for more information on the @value{op-list}
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
Device blocking
-@table @kbd
+@table @option
@item -b @var{blocks}
@itemx --blocking-factor=@var{blocks}
Set record size to @math{@var{blocks} * 512} bytes.
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 @sc{gnu} @command{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
invocation.
@end itemize
-In previous versions of @sc{gnu} @command{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
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
@section Many Archives on One Tape
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
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
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}.
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
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
+script will find the archive automatically. @FIXME-xref{Scripted Restoration}@xref{mt}, for
an explanation of the tape moving utility.
If you want to add new archive file entries to a tape, you should
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
@subsection The @command{mt} Utility
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.
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,
-@command{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, @command{tar} extracts the archive.
-@value{xref-label}.
-@FIXME-xref{Matching Format Parameters}@FIXME{fix cross
-references}@samp{tar --list --label} will cause @command{tar} to print the
-label.
-
-@FIXME{Program to list all the labels on a tape?}
-
@node Using Multiple Tapes
@section Using Multiple Tapes
@UNREVISED
second tape when prompted, so @command{tar} can restore both halves of the
file.)
-@sc{gnu} @command{tar} multi-volume archives do not use a truly portable format.
-You need @sc{gnu} @command{tar} at both end to process them properly.
+@GNUTAR{} multi-volume archives do not use a truly
+portable format. You need @GNUTAR{} at both end to
+process them properly.
When prompting for a new tape, @command{tar} accepts any of the following
responses:
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
+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 @sc{gnu}
-@command{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
that volume), use @value{op-extract}, again without
@value{op-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
should load the volume where the archive member starts, and use
@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}.
@end table
-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 @sc{gnu} @command{tar}. The converse is also true:
-you may not expect multi-volume archives created by @sc{gnu} @command{tar} 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 @sc{gnu} @command{tar}
-will work on most of them, your best bet is to install @sc{gnu} @command{tar}
-on all machines between which you know exchange of files is possible.
+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
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.
@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 @command{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
+@cindex @option{--label} option introduced
+@cindex @option{-V} option introduced
+ 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
+@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} operation. Checks to make sure the archive label
+matches the one specified (when used in conjunction with any other
+operation.
+@end table
+
+ 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}, @command{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 @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 @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}. @command{tar} will print the
-label first, and then print archive member information, as in the
-example below:
+@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:
-@example
+@smallexample
+@group
$ @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
+@end group
+@end smallexample
-@table @kbd
-@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.
-@end table
+@cindex @option{--test-label} option introduced
+@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 @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 @option{--volume}, but is not available
+under that name anymore.
-To get a common information on all tapes of a series, use the
-@value{op-label} option. For having this information different in each
+ 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 @sc{gnu} @command{tar} 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.
+@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
@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
Attempt to verify the archive after writing.
@appendix Free Software Needs Free Documentation
@include freemanuals.texi
+@node Genfile
+@appendix Genfile
+@include genfile.texi
+
+@node Snapshot Files
+@appendix Format of the Incremental Snapshot Files
+@include snapshot.texi
+
@node Copying This Manual
@appendix Copying This Manual
projects / chaz / tar / blobdiff