@smallbook
@c %**end of header
-@c ======================================================================
-@c This document has three levels of rendition: PUBLISH, DISTRIB or PROOF,
-@c as decided by @set symbols. The PUBLISH rendition does not show
-@c notes or marks asking for revision. Most users will prefer having more
-@c information, even if this information is not fully revised for adequacy,
-@c so DISTRIB is the default for tar distributions. The PROOF rendition
-@c show all marks to the point of ugliness, but is nevertheless useful to
-@c those working on the manual itself.
-@c ======================================================================
-
-@ifclear PUBLISH
-@ifclear DISTRIB
-@ifclear PROOF
-@set DISTRIB
-@end ifclear
-@end ifclear
-@end ifclear
-
-@ifset PUBLISH
-@set RENDITION The book, version
-@end ifset
-
-@ifset DISTRIB
-@set RENDITION FTP release, version
-@end ifset
-
-@ifset PROOF
-@set RENDITION Proof reading version
-@end ifset
-
-@c ---------------------------------------------------------------------
-@c The @FIXME's, @UNREVISED and @c comments are part Fran@,{c}ois's work
-@c plan. These annotations are somewhat precious to him; he asks that I
-@c do not alter them inconsiderately. Much work is needed for GNU tar
-@c internals (the sources, the programs themselves). Revising the
-@c adequacy of the manual while revising the sources, and cleaning them
-@c both at the same time, seems to him like a good way to proceed.
-@c ---------------------------------------------------------------------
-
-@c Output marks for nodes needing revision, but not in PUBLISH rendition.
-
-@macro UNREVISED
-@ifclear PUBLISH
-@quotation
-@emph{(This message will disappear, once this node revised.)}
-@end quotation
-@end ifclear
-@end macro
-
-@c Output various FIXME information only in PROOF rendition.
-
-@macro FIXME{string}
-@allow-recursion
-@quote-arg
-@ifset PROOF
-@strong{<FIXME>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-ref{string}
-@quote-arg
-@ifset PROOF
-@strong{<REF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-pxref{string}
-@quote-arg
-@ifset PROOF
-@strong{<PXREF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-xref{string}
-@quote-arg
-@ifset PROOF
-@strong{<XREF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@c @macro option{entry}
-@c @quote-arg
-@c @opindex{--\entry\}
-@c @value{\entry\}
-@c @end macro
-
-@macro GNUTAR
-@acronym{GNU} @command{tar}
-@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-check-links @kbd{--check-links} (@kbd{-l})
-@set ref-check-links @ref{--check-links}
-@set xref-check-links @xref{--check-links}
-@set pxref-check-links @pxref{--check-links}
-
-@set op-checkpoint @kbd{--checkpoint}
-@set ref-checkpoint @ref{verbose}
-@set xref-checkpoint @xref{verbose}
-@set pxref-checkpoint @pxref{verbose}
-
-@set op-check-links @kbd{--check-links}
-
-@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} (@kbd{-o})
-@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-occurrence @kbd{--occurrence}
-@set ref-occurrence @ref{--occurrence}
-@set xref-occurrence @xref{--occurrence}
-@set pxref-occurrence @pxref{--occurrence}
-
-@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-format @kbd{--format}
-@set ref-format @ref{format}
-@set xref-format @xref{format}
-@set pxref-format @pxref{format}
-
-@set op-format-v7 @kbd{--format=v7}
-@set op-format-gnu @kbd{--format=gnu}
-@set op-format-oldgnu @kbd{--format=oldgnu}
-@set op-format-posix @kbd{--format=posix}
-
-@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-strip-path @kbd{--strip-path}
-@set ref-strip-path @ref{--strip-path}
-@set xref-strip-path @xref{--strip-path}
-@set pxref-strip-path @pxref{--strip-path}
-
-@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}
+@include rendition.texi
+@include value.texi
@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp
@syncodeindex vr cp
@defindex op
-@syncodeindex op cp
@copying
from archives.
Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
-2003 Free Software Foundation, Inc.
+2003, 2004, 2005, 2006 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
@dircategory Individual utilities
@direntry
-* tar: (tar)tar invocation. Invoking @GNUTAR{}
+* tar: (tar)tar invocation. Invoking @GNUTAR{}.
@end direntry
@shorttitlepage @acronym{GNU} @command{tar}
@titlepage
@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
* Date input formats::
* Formats::
* Media::
+
+Appendices
+
+* Changes::
+* Configuring Help Summary::
+* Genfile::
+* Snapshot Files::
* Free Software Needs Free Documentation::
* Copying This Manual::
+* Index of Command Line Options::
* Index::
@detailmenu
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* posix compliance::
-* Current status:: Current development status of @GNUTAR{}
* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
* Styles::
* All Options::
* help::
+* defaults::
* verbose::
* interactive::
* 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::
+* Data Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::
Performing Backups and Restoring Files
* Full Dumps:: Using @command{tar} to Perform Full Dumps
-* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
Setting Parameters for Backups and Restoration
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
Choosing Files and Names for @command{tar}
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
Reading Names from a File
Excluding Some Files
-* controlling pattern-patching with exclude::
+* controlling pattern-matching with exclude::
* problems with exclude::
-Crossing Filesystem Boundaries
+Crossing File System Boundaries
* directory:: Changing Directory
* absolute:: Absolute File Names
* 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
* 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
+* Tarcat:: Concatenate Volumes into a Single Archive
+
+GNU tar internals and development
+
+* Genfile::
+* Snapshot Files::
Copying This Manual
+* Free Software Needs Free Documentation::
* GNU Free Documentation License:: License for copying this manual
@end detailmenu
@chapter Introduction
@GNUTAR{} creates
-and manipulates (@dfn{archives}) which are actually collections of
+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
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* posix compliance::
-* Current status:: Current development status of @GNUTAR{}
* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
@end menu
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
archives. An @dfn{archive} is a single file which contains the contents
of many files, while still identifying the names of the files, their
owner(s), and so forth. (In addition, archives record access
-permissions, user and group, size in bytes, and last modification time.
+permissions, user and group, size in bytes, and data modification time.
Some archives also record the file names in each archived directory, as
well as other file and directory information.) You can use @command{tar}
to @dfn{create} a new archive in a specified directory.
manual, we use the term @dfn{file} to refer only to files accessible in
the normal ways (by @command{ls}, @command{cat}, and so forth), and the term
@dfn{member} to refer only to the members of an archive. Similarly, a
-@dfn{file name} is the name of a file, as it resides in the filesystem,
+@dfn{file name} is the name of a file, as it resides in the file system,
and a @dfn{member name} is the name of an archive member within the
archive.
@cindex extraction
@cindex unpacking
The term @dfn{extraction} refers to the process of copying an archive
-member (or multiple members) into a file in the filesystem. Extracting
+member (or multiple members) into a file in the file system. Extracting
all the members of an archive is often called @dfn{extracting the
archive}. The term @dfn{unpack} can also be used to refer to the
extraction of many or all the members of an archive. Extracting an
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.
+file system.
@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
-
-@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...}
-@FIXME{I did not notice any problems either. Besides, the only piece
-of code that really uses POSIXLY_CORRECT is the one that forces
-creation of POSIX archives. I guess this paragraph should be removed.
-
---gray}
-
-
-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}, @GNUTAR{} 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, @GNUTAR{} 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.
-
-Notice also, that if this environment variable is set, @GNUTAR{}
-will create @acronym{POSIX} archives. Currently this means that
-no @acronym{GNU} extensions will be allowed (@pxref{posix}).
-
-@node Current status
-@section Current development status of @GNUTAR{}
-
-@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.
-@item Revise multiple volume processing.
-@end itemize
-
-The following issues need 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.
-
-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 @samp{--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 @GNUTAR{} Authors
@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, and finally
-Fran@,{c}ois Pinard, with the help of numerous and kind users.
+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
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 @url{savannah.gnu.org}, and
-an active development and maintenance work has started
-again. Currently @GNUTAR{} is being maintained by Paul Eggert, Sergey
+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.
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.
use some basic utilities. For example, you should know how to create,
list, copy, rename, edit, and delete files and directories; how to
change between directories; and how to figure out where you are in the
-filesystem. You should have some basic understanding of directory
+file system. You should have some basic understanding of directory
structure and how files are named according to which directory they are
in. You should understand concepts such as standard output and standard
input, what various definitions of the term ``argument'' mean, and the
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:
+sometimes @samp{like this}.
-@smallexample
-This is an example of a line which would otherwise not fit in this space.
-@end smallexample
-
-@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
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 @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}.)
+@command{tar}. In this book we present a full discussion of this way
+of writing options and operations (@pxref{Old Options}), and we discuss
+the other two styles of writing options (@xref{Mnemonic Options}, and
+@pxref{Short Options}).
In the examples and in the text of this tutorial, we usually use the
long forms of operations and options; but the ``short'' forms produce
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
+@opindex file, tutorial
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Specify the name of an archive file.
@end table
-You can specify an argument for the @value{op-file} option whenever you
+You can specify an argument for the @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option whenever you
use @command{tar}; this option determines the name of the archive file
that @command{tar} will work on.
-If you don't specify this argument, then @command{tar} will use a
-default, usually some physical tape drive attached to your machine.
-If there is no tape drive attached, or the default is not meaningful,
-then @command{tar} will print an error message. The error message might
-look roughly like one of the following:
+@vrindex TAPE
+If you don't specify this argument, then @command{tar} will examine
+the environment variable @env{TAPE}. If it is set, its value will be
+used as the archive name. Otherwise, @command{tar} will use the
+default archive, determined at the compile time. Usually it is
+standard output or some physical tape drive attached to your machine
+(you can verify what the default is by running @kbd{tar
+--show-defaults}, @pxref{defaults}). If there is no tape drive
+attached, or the default is not meaningful, then @command{tar} will
+print an error message. The error message might look roughly like one
+of the following:
@smallexample
tar: can't open /dev/rmt8 : No such device or address
@noindent
To avoid confusion, we recommend that you always specify an archive file
-name by using @value{op-file} when writing your @command{tar} commands.
-For more information on using the @value{op-file} option, see
+name by using @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) when writing your @command{tar} commands.
+For more information on using the @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option, see
@ref{file}.
@node verbose tutorial
-@unnumberedsubsec The @samp{--verbose} Option
+@unnumberedsubsec The @option{--verbose} Option
-@table @kbd
+@table @option
+@opindex verbose, introduced
@item --verbose
@itemx -v
Show the files being worked on as @command{tar} is running.
@end table
-@value{op-verbose} shows details about the results of running
+@option{--verbose} (@option{-v}) shows details about the results of running
@command{tar}. This can be especially useful when the results might not be
obvious. For example, if you want to see the progress of @command{tar} as
-it writes files into the archive, you can use the @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,
-@c FIXME: Describe the exact output format, e.g., how hard links are displayed.
-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
@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
+@opindex help
@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
@section How to Create Archives
@UNREVISED
-One of the basic operations of @command{tar} is @value{op-create}, which
+@cindex Creation of the archive
+@cindex Archive, creation of
+One of the basic operations of @command{tar} is @option{--create} (@option{-c}), which
you use to create a @command{tar} archive. We will explain
-@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
working directory with the archive name you intend to use (in this case,
@samp{collection.tar}), or that you don't care about its contents.
Whenever you use @samp{create}, @command{tar} will erase the current
-contents of the file named by @value{op-file} if it exists. @command{tar}
+contents of the file named by @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) if it exists. @command{tar}
will not tell you if you are about to overwrite an archive unless you
-specify an option which does this. @FIXME{xref to the node for
---backup!}To add files to an existing archive, you need to use a
-different option, such as @value{op-append}; see @ref{append} for
-information on how to do this.
+specify an option which does this (@pxref{backup}, for the
+information on how to do so). To add files to an existing archive,
+you need to use a different option, such as @option{--append} (@option{-r}); see
+@ref{append} for information on how to do this.
@node Creating the archive
@subsection Creating the Archive
+@opindex create, introduced
To place the files @file{blues}, @file{folk}, and @file{jazz} into an
archive named @file{collection.tar}, use the following command:
@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, @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:
@smallexample
will complain. You must have write access to the working directory,
or else you will not be able to create an archive in that directory.
-@emph{Caution}: Do not attempt to use @value{op-create} to add files to
+@emph{Caution}: Do not attempt to use @option{--create} (@option{-c}) to add files to
an existing archive; it will delete the archive and write a new one.
-Use @value{op-append} instead. @xref{append}.
+Use @option{--append} (@option{-r}) instead. @xref{append}.
@node create verbose
-@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,
+@opindex create, using with @option{--verbose}
+@opindex verbose, using with @option{--create}
+If you include the @option{--verbose} (@option{-v}) option on the command line,
@command{tar} will list the files it is acting on as it is working. In
verbose mode, the @code{create} example above would appear as:
@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
@node short create
@subsection Short Forms with @samp{create}
-As we said before, the @value{op-create} operation is one of the most
+As we said before, the @option{--create} (@option{-c}) operation is one of the most
basic uses of @command{tar}, and you will use it countless times.
Eventually, you will probably want to use abbreviated (or ``short'')
forms of options. A full discussion of the three different forms that
options can take appears in @ref{Styles}; for now, here is what the
-previous example (including the @value{op-verbose} option) looks like
+previous example (including the @option{--verbose} (@option{-v}) option) looks like
using short option forms:
@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,
@noindent
It would be very easy to put the wrong string of characters
-immediately following the @samp{-f}, but doing that could sacrifice
+immediately following the @option{-f}, but doing that could sacrifice
valuable data.
For this reason, we recommend that you pay very careful attention to
especially when using short option forms. Not having the option name
written out mnemonically can affect how well you remember which option
does what, and therefore where different names have to be placed.
-(Placing options in an unusual order can also cause @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.)
@node create dir
@subsection Archiving Directories
@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:
write access to the superior directory itself, not only the directory
you are trying archive with @command{tar}. For example, you will probably
not be able to store your home directory in an archive by invoking
-@command{tar} from the root directory; @value{xref-absolute-names}. (Note
+@command{tar} from the root directory; @xref{absolute}. (Note
also that @file{collection.tar}, the original archive file, has itself
been archived. @command{tar} will accept any file as a file to be
archived, regardless of its content. When @file{music.tar} is
@node list
@section How to List Archives
+@opindex list
Frequently, you will find yourself wanting to determine exactly what a
-particular archive contains. You can use the @value{op-list} operation
+particular archive contains. You can use the @option{--list} (@option{-t}) operation
to get the member names as they currently appear in the archive, as well
as various attributes of the files at the time they were archived. For
example, you can examine the archive @file{collection.tar} that you
@end smallexample
@noindent
-Be sure to use a @value{op-file} option just as with @value{op-create}
+Be sure to use a @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option just as with @option{--create} (@option{-c})
to specify the name of the archive.
-If you use the @value{op-verbose} option with @samp{--list}, then
+@opindex list, using with @option{--verbose}
+@opindex verbose, using with @option{--list}
+If you use the @option{--verbose} (@option{-v}) option with @option{--list}, then
@command{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
showing owner, file size, and so forth.
-If you had used @value{op-verbose} mode, the example above would look
+If you had used @option{--verbose} (@option{-v}) mode, the example above would look
like:
@smallexample
$ @kbd{tar --list --verbose --file=collection.tar folk}
--rw-rw-rw- myself user 62 1990-05-23 10:55 folk
+-rw-r--r-- myself user 62 1990-05-23 10:55 folk
+@end smallexample
+
+@cindex listing member and file names
+@anchor{listing member and file names}
+It is important to notice that the output of @kbd{tar --list
+--verbose} does not necessarily match that produced by @kbd{tar
+--create --verbose} while creating the archive. It is because
+@GNUTAR{}, unless told explicitly not to do so, removes some directory
+prefixes from file names before storing them in the archive
+(@xref{absolute}, for more information). In other
+words, in verbose mode @GNUTAR{} shows @dfn{file names} when creating
+an archive and @dfn{member names} when listing it. Consider this
+example:
+
+@smallexample
+@group
+$ @kbd{tar cfv archive /etc/mail}
+tar: Removing leading `/' from member names
+/etc/mail/
+/etc/mail/sendmail.cf
+/etc/mail/aliases
+$ @kbd{tar tf archive}
+etc/mail/
+etc/mail/sendmail.cf
+etc/mail/aliases
+@end group
@end smallexample
-@cindex File name arguments, using @code{--list} with
-@cindex @code{--list} with file name arguments
+@opindex show-stored-names
+ This default behavior can sometimes be inconvenient. You can force
+@GNUTAR{} show member names when creating archive by supplying
+@option{--show-stored-names} option.
+
+@table @option
+@item --show-stored-names
+Print member (as opposed to @emph{file}) names when creating the archive.
+@end table
+
+@cindex File name arguments, using @option{--list} with
+@opindex list, using with file name arguments
You can specify one or more individual member names as arguments when
using @samp{list}. In this case, @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
-@value{op-list}. To find out file attributes, include the
-@value{op-verbose} option.
+@option{--list} (@option{-t}). To find out file attributes, include the
+@option{--verbose} (@option{-v}) option.
For example, to find out about files in the directory @file{practice}, in
the archive file @file{music.tar}, type:
@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
+-rw-r--r-- myself user 42 1990-05-21 13:29 practice/blues
+-rw-r--r-- myself user 62 1990-05-23 10:55 practice/folk
+-rw-r--r-- myself user 40 1990-05-21 13:30 practice/jazz
+-rw-r--r-- myself user 10240 1990-05-31 21:49 practice/collection.tar
@end smallexample
When you use a directory name as a file name argument, @command{tar} acts on
@cindex Retrieving files from an archive
@cindex Resurrecting files from an archive
+@opindex extract
Creating an archive is only half the job---there is no point in storing
files in an archive if you can't retrieve them. The act of retrieving
members from an archive so they can be used and manipulated as
unarchived files again is called @dfn{extraction}. To extract files
-from an archive, use the @value{op-extract} operation. As with
-@value{op-create}, specify the name of the archive with @value{op-file}.
-Extracting an archive does not modify the archive in any way; you can
-extract it multiple times if you want or need to.
+from an archive, use the @option{--extract} (@option{--get} or
+@option{-x}) operation. As with @option{--create}, specify the name
+of the archive with @option{--file} (@option{-f}) option. Extracting
+an archive does not modify the archive in any way; you can extract it
+multiple times if you want or need to.
-Using @samp{--extract}, you can extract an entire archive, or specific
+Using @option{--extract}, you can extract an entire archive, or specific
files. The files can be directories containing other files, or not. As
-with @value{op-create} and @value{op-list}, you may use the short or the
+with @option{--create} (@option{-c}) and @option{--list} (@option{-t}), you may use the short or the
long form of the operation without affecting the performance.
@menu
produces this:
@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
+-rw-r--r-- me user 28 1996-10-18 16:31 jazz
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+-rw-r--r-- me user 20 1996-09-23 16:44 folk
@end smallexample
@node extracting files
@subsection Extracting Specific Files
To extract specific archive members, give their exact member names as
-arguments, as printed by @value{op-list}. If you had mistakenly deleted
+arguments, as printed by @option{--list} (@option{-t}). If you had mistakenly deleted
one of the files you had placed in the archive @file{collection.tar}
earlier (say, @file{blues}), you can extract it from the archive without
-changing the archive's structure. It will be identical to the original
-file @file{blues} that you deleted. @FIXME{check this; will the times,
-permissions, owner, etc be the same, also?}
+changing the archive's structure. Its contents will be identical to the
+original file @file{blues} that you deleted.
First, make sure you are in the @file{practice} directory, and list the
files in the directory. Now, delete the file, @samp{blues}, and list
@noindent
If you list the files in the directory again, you will see that the file
-@file{blues} has been restored, with its original permissions, creation
+@file{blues} has been restored, with its original permissions, data modification
times, and owner.@FIXME{This is only accidentally true, but not in
general. In most cases, one has to be root for restoring the owner, and
use a special option for restoring permissions. Here, it just happens
however, will @emph{not} have been made to the archive member.) The
archive file, @samp{collection.tar}, is the same as it was before you
extracted @samp{blues}. You can confirm this by running @command{tar} with
-@value{op-list}.
+@option{--list} (@option{-t}).
@FIXME{we hope this will change:}Remember that as with other operations,
specifying the exact member name is important. @w{@kbd{tar --extract
--file=bfiles.tar birds}} will fail, because there is no member named
@file{birds}. To extract the member named @file{./birds}, you must
specify @w{@kbd{tar --extract --file=bfiles.tar ./birds}}. To find the
-exact member names of the members of an archive, use @value{op-list}
+exact member names of the members of an archive, use @option{--list} (@option{-t})
(@pxref{list}).
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 @option{--to-stdout} (@option{-O}) option (@pxref{Writing to Standard
Output}).
-If you give the @value{op-verbose} option, then @value{op-extract} will
-print the names of the archive members as it extracts them.
+If you give the @option{--verbose} option, then @option{--extract}
+will print the names of the archive members as it extracts them.
@node extract dir
@subsection Extracting Files that are Directories
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
@smallexample
$ @kbd{tar -xvf music.tar practice/folk practice/jazz}
+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 @option{--verbose} (@option{-v}) 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-r--r-- me user 28 1996-10-18 16:31 practice/jazz
+-rw-r--r-- me user 20 1996-09-23 16:44 practice/folk
+@end smallexample
@noindent
Because you created the directory with @file{practice} as part of the
$ @kbd{tar -xvf ../untrusted.tar}
@end smallexample
+It is also a good practice to examine contents of the archive
+before extracting it, using @option{--list} (@option{-t}) option, possibly combined
+with @option{--verbose} (@option{-v}).
+
@node failing commands
@subsection Commands That Will Fail
Some options are so special they are fully described right in this
chapter. They have the effect of inhibiting the normal operation of
@command{tar} or else, they globally alter the amount of feedback the user
-receives about what is going on. These are the @value{op-help} and
-@value{op-version} (@pxref{help}), @value{op-verbose} (@pxref{verbose})
-and @value{op-interactive} options (@pxref{interactive}).
+receives about what is going on. These are the @option{--help} and
+@option{--version} (@pxref{help}), @option{--verbose} (@pxref{verbose})
+and @option{--interactive} options (@pxref{interactive}).
@menu
* Synopsis::
* Styles::
* All Options::
* help::
+* defaults::
* verbose::
* interactive::
@end menu
(the @command{tar} main command) is usually given first.
Each @var{name} in the synopsis above is interpreted as an archive member
-name when the main command is one of @value{op-compare}, @value{op-delete},
-@value{op-extract}, @value{op-list} or @value{op-update}. When naming
-archive members, you must give the exact name of the member in the
-archive, as it is printed by @value{op-list}. For @value{op-append}
-and @value{op-create}, these @var{name} arguments specify the names
-of either files or directory hierarchies to place in the archive.
+name when the main command is one of @option{--compare}
+(@option{--diff}, @option{-d}), @option{--delete}, @option{--extract}
+(@option{--get}, @option{-x}), @option{--list} (@option{-t}) or
+@option{--update} (@option{-u}). When naming archive members, you
+must give the exact name of the member in the archive, as it is
+printed by @option{--list}. For @option{--append} (@option{-r}) and
+@option{--create} (@option{-c}), these @var{name} arguments specify
+the names of either files or directory hierarchies to place in the archive.
These files or hierarchies should already exist in the file system,
prior to the execution of the @command{tar} command.
@command{tar} interprets relative file names as being relative to the
working directory. @command{tar} will make all file names relative
(by removing leading slashes when archiving or restoring files),
-unless you specify otherwise (using the @value{op-absolute-names}
-option). @value{xref-absolute-names}, for more information about
-@value{op-absolute-names}.
+unless you specify otherwise (using the @option{--absolute-names}
+option). @xref{absolute}, for more information about
+@option{--absolute-names}.
If you give the name of a directory as either a file name or a member
name, then @command{tar} acts recursively on all the files and directories
beneath that directory. For example, the name @file{/} identifies all
-the files in the filesystem to @command{tar}.
+the files in the file system to @command{tar}.
The distinction between file names and archive member names is especially
important when shell globbing is used, and sometimes a source of confusion
Even if @var{name}s are often specified on the command line, they
can also be read from a text file in the file system, using the
-@value{op-files-from} option.
+@option{--files-from=@var{file-of-names}} (@option{-T @var{file-of-names}}) option.
-If you don't use any file name arguments, @value{op-append},
-@value{op-delete} and @value{op-concatenate} will do nothing, while
-@value{op-create} will usually yield a diagnostic and inhibit @command{tar}
-execution. The other operations of @command{tar} (@value{op-list},
-@value{op-extract}, @value{op-compare}, and @value{op-update}) will act
-on the entire contents of the archive.
+If you don't use any file name arguments, @option{--append} (@option{-r}),
+@option{--delete} and @option{--concatenate} (@option{--catenate},
+@option{-A}) will do nothing, while @option{--create} (@option{-c})
+will usually yield a diagnostic and inhibit @command{tar} execution.
+The other operations of @command{tar} (@option{--list},
+@option{--extract}, @option{--compare}, and @option{--update})
+will act on the entire contents of the archive.
@cindex exit status
@cindex return status
@GNUTAR{} returns only a few exit statuses. I'm really
aiming simplicity in that area, for now. If you are not using the
-@value{op-compare} option, zero means that everything went well, besides
-maybe innocuous warnings. Nonzero means that something went wrong.
-Right now, as of today, ``nonzero'' is almost always 2, except for
-remote operations, where it may be 128.
+@option{--compare} @option{--diff}, @option{-d}) option, zero means
+that everything went well, besides maybe innocuous warnings. Nonzero
+means that something went wrong. Right now, as of today, ``nonzero''
+is almost always 2, except for remote operations, where it may be
+128.
@node using tar options
@section Using @command{tar} Options
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
-we used in the tutorial). As we said in the tutorial, @dfn{options} are
-arguments to @command{tar} which are (as their name suggests) optional.
-Depending on the operating mode, you may specify one or more options.
-Different options will have different effects, but in general they all
-change details of the operation, such as archive format, archive name,
-or level of user interaction. Some options make sense with all
-operating modes, while others are meaningful only with particular modes.
-You will likely use some options frequently, while you will only use
-others infrequently, or not at all. (A full list of options is
-available in @pxref{All Options}.)
-
+@command{tar} with one or more options (such as @option{--verbose}
+(@option{-v}), which we used in the tutorial). As we said in the
+tutorial, @dfn{options} are arguments to @command{tar} which are (as
+their name suggests) optional. Depending on the operating mode, you
+may specify one or more options. Different options will have different
+effects, but in general they all change details of the operation, such
+as archive format, archive name, or level of user interaction. Some
+options make sense with all operating modes, while others are
+meaningful only with particular modes. You will likely use some
+options frequently, while you will only use others infrequently, or
+not at all. (A full list of options is available in @pxref{All Options}.)
+
+@vrindex TAR_OPTIONS, environment variable
+@anchor{TAR_OPTIONS}
The @env{TAR_OPTIONS} environment variable specifies default options to
be placed in front of any explicit options. For example, if
@code{TAR_OPTIONS} is @samp{-v --unlink-first}, @command{tar} behaves as
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}.
+write @option{--list} (@option{-t}).
In addition to the eight operations, there are many options to
@command{tar}, and three different styles for writing both: long (mnemonic)
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
different times during the history of @command{tar}. These styles will be
presented below, from the most recent to the oldest.
-Some options must take an argument. (For example, @value{op-file} takes
-the name of an archive file as an argument. If you do not supply an
-archive file name, @command{tar} will use a default, but this can be
-confusing; thus, we recommend that you always supply a specific archive
-file name.) Where you @emph{place} the arguments generally depends on
-which style of options you choose. We will detail specific information
-relevant to each option style in the sections on the different option
-styles, below. The differences are subtle, yet can often be very
-important; incorrect option placement can cause you to overwrite a
-number of important files. We urge you to note these differences, and
-only use the option style(s) which makes the most sense to you until you
-feel comfortable with the others.
-
-@FIXME{hag to write a brief paragraph on the option(s) which can
-optionally take an argument}
+Some options must take an argument. (For example, @option{--file}
+(@option{-f})) takes the name of an archive file as an argument. If
+you do not supply an archive file name, @command{tar} will use a
+default, but this can be confusing; thus, we recommend that you always
+supply a specific archive file name.) Where you @emph{place} the
+arguments generally depends on which style of options you choose. We
+will detail specific information relevant to each option style in the
+sections on the different option styles, below. The differences are
+subtle, yet can often be very important; incorrect option placement
+can cause you to overwrite a number of important files. We urge you
+to note these differences, and only use the option style(s) which
+makes the most sense to you until you feel comfortable with the others.
+
+Some options @emph{may} take an argument (currently, there are
+two such options: @option{--backup} and @option{--occurrence}). Such
+options may have at most long and short forms, they do not have old style
+equivalent. The rules for specifying an argument for such options
+are stricter than those for specifying mandatory arguments. Please,
+pay special attention to them.
@menu
* Mnemonic Options:: Mnemonic Option Style
"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
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
+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
@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. :-) }
@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.
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}.
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.
+@option{--create} (@option{-c}) command to create an archive.
@node Mixing
@subsection Mixing Option Styles
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
+@opindex append, summary
@item --append
@itemx -r
Appends files to the end of the archive. @xref{append}.
+@opindex catenate, summary
@item --catenate
@itemx -A
-Same as @samp{--concatenate}. @xref{concatenate}.
+Same as @option{--concatenate}. @xref{concatenate}.
+@opindex compare, summary
@item --compare
@itemx -d
system, and reports differences in file size, mode, owner,
modification date and contents. @xref{compare}.
+@opindex concatenate, summary
@item --concatenate
@itemx -A
Appends other @command{tar} archives to the end of the archive.
@xref{concatenate}.
+@opindex create, summary
@item --create
@itemx -c
Creates a new @command{tar} archive. @xref{create}.
+@opindex delete, summary
@item --delete
Deletes members from the archive. Don't try this on a archive on a
tape! @xref{delete}.
+@opindex diff, summary
@item --diff
@itemx -d
-Same @samp{--compare}. @xref{compare}.
+Same @option{--compare}. @xref{compare}.
+@opindex extract, summary
@item --extract
@itemx -x
Extracts members from the archive into the file system. @xref{extract}.
+@opindex get, summary
@item --get
@itemx -x
-Same as @samp{--extract}. @xref{extract}.
+Same as @option{--extract}. @xref{extract}.
+@opindex list, summary
@item --list
@itemx -t
Lists the members in an archive. @xref{list}.
+@opindex update, summary
@item --update
@itemx -u
-@FIXME{It was: A combination of the @samp{--compare} and
-@samp{--append} operations. This is not true and rather misleading,
-as @value{op-compare} does a lot more than @value{op-update} for
+@FIXME{It was: A combination of the @option{--compare} and
+@option{--append} operations. This is not true and rather misleading,
+as @option{--compare} (@option{--diff}, @option{-d}) does a lot more than @option{--update} (@option{-u}) for
ensuring files are identical.} Adds files to the end of the archive,
but only if they are newer than their counterparts already in the
archive, or if they do not already exist in the archive.
@node Option Summary
@subsection @command{tar} Options
-@table @kbd
+@table @option
+@opindex absolute-names, summary
@item --absolute-names
@itemx -P
Normally when creating an archive, @command{tar} strips an initial
@samp{/} from member names. This option disables that behavior.
-@FIXME-xref{}
+@xref{absolute}.
+@opindex after-date, summary
@item --after-date
-(See @samp{--newer}.) @FIXME-pxref{}
+(See @option{--newer}, @pxref{after})
+@opindex anchored, summary
@item --anchored
An exclude pattern must match an initial subsequence of the name's components.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
+@opindex atime-preserve, summary
@item --atime-preserve
-
-Tells @command{tar} to preserve the access time field in a file's inode when
-reading it. Due to limitations in the @code{utimes} system call, the
-modification time field is also preserved, which may cause problems if
-the file is simultaneously being modified by another program.
-This option is incompatible with incremental backups, because
-preserving the access time involves updating the last-changed time.
-Also, this option does not work on files that you do not own,
-unless you're root.
-@FIXME-xref{}
-
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+
+Attempt to preserve the access time of files when reading them. This
+option currently is effective only on files that you own, unless you
+have superuser privileges.
+
+@option{--atime-preserve=replace} remembers the access time of a file
+before reading it, and then restores the access time afterwards. This
+may cause problems if other programs are reading the file at the same
+time, as the times of their accesses will be lost. On most platforms
+restoring the access time also requires @command{tar} to restore the
+data modification time too, so this option may also cause problems if
+other programs are writing the file at the same time. (Tar attempts
+to detect this situation, but cannot do so reliably due to race
+conditions.) Worse, on most platforms restoring the access time also
+updates the status change time, which means that this option is
+incompatible with incremental backups.
+
+@option{--atime-preserve=system} avoids changing time stamps on files,
+without interfering with time stamp updates
+caused by other programs, so it works better with incremental backups.
+However, it requires a special @code{O_NOATIME} option from the
+underlying operating and file system implementation, and it also requires
+that searching directories does not update their access times. As of
+this writing (November 2005) this works only with Linux, and only with
+Linux kernels 2.6.8 and later. Worse, there is currently no reliable
+way to know whether this feature actually works. Sometimes
+@command{tar} knows that it does not work, and if you use
+@option{--atime-preserve=system} then @command{tar} complains and
+exits right away. But other times @command{tar} might think that the
+option works when it actually does not.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@option{--atime-preserve=replace}, but this may change in the future
+as support for @option{--atime-preserve=system} improves.
+
+If your operating system does not support
+@option{--atime-preserve=system}, you might be able to preserve access
+times reliably by by using the @command{mount} command. For example,
+you can mount the file system read-only, or access the file system via
+a read-only loopback mount, or use the @samp{noatime} mount option
+available on some systems. However, mounting typically requires
+superuser privileges and can be a pain to manage.
+
+@opindex backup, summary
@item --backup=@var{backup-type}
Rather than deleting files from the file system, @command{tar} will
back them up using simple or numbered backups, depending upon
-@var{backup-type}. @FIXME-xref{}
+@var{backup-type}. @xref{backup}.
+@opindex block-number, summary
@item --block-number
@itemx -R
With this option present, @command{tar} prints error messages for read errors
-with the block number in the archive file. @FIXME-xref{}
+with the block number in the archive file. @xref{block-number}.
+@opindex blocking-factor, summary
@item --blocking-factor=@var{blocking}
@itemx -b @var{blocking}
Sets the blocking factor @command{tar} uses to @var{blocking} x 512 bytes per
-record. @FIXME-xref{}
+record. @xref{Blocking Factor}.
+@opindex bzip2, summary
@item --bzip2
@itemx -j
This option tells @command{tar} to read or write archives through
-@code{bzip2}. @FIXME-xref{}
+@code{bzip2}. @xref{gzip}.
+@opindex checkpoint, summary
@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{}
+@opindex check-links, summary
@item --check-links
@itemx -l
If this option was given, @command{tar} will check the number of links
-dumped for each processed file. If this number does not match the
+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
+@option{--check-links}. However, current release still retains the old
semantics for @option{-l}.
-@xref{Current status}, for more information.
+@xref{Changes}, for more information.
+@opindex compress, summary
+@opindex uncompress, summary
@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{}
+while saving space. @xref{gzip}.
+@opindex confirmation, summary
@item --confirmation
-(See @samp{--interactive}.) @FIXME-pxref{}
+(See @option{--interactive}.) @xref{interactive}.
+@opindex delay-directory-restore, summary
+@item --delay-directory-restore
+
+Delay setting modification times and permissions of extracted
+directories until the end of extraction. @xref{Directory Modification Times and Permissions}.
+
+@opindex dereference, summary
@item --dereference
@itemx -h
When creating a @command{tar} archive, @command{tar} will archive the
file that a symbolic link points to, rather than archiving the
-symlink. @FIXME-xref{}
+symlink. @xref{dereference}.
+@opindex directory, summary
@item --directory=@var{dir}
@itemx -C @var{dir}
When this option is specified, @command{tar} will change its current directory
to @var{dir} before performing any operations. When this option is used
-during archive creation, it is order sensitive. @FIXME-xref{}
+during archive creation, it is order sensitive. @xref{directory}.
+@opindex exclude, summary
@item --exclude=@var{pattern}
When performing operations, @command{tar} will skip files that match
-@var{pattern}. @FIXME-xref{}
+@var{pattern}. @xref{exclude}.
+@opindex exclude-from, summary
@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}. @xref{exclude}.
+
+@opindex exclude-caches, summary
+@item --exclude-caches
+
+Automatically excludes all directories
+containing a cache directory tag. @xref{exclude}.
+@opindex file, summary
@item --file=@var{archive}
@itemx -f @var{archive}
@command{tar} will use the file @var{archive} as the @command{tar} archive it
performs operations on, rather than @command{tar}'s compilation dependent
-default. @FIXME-xref{}
+default. @xref{file tutorial}.
+@opindex files-from, summary
@item --files-from=@var{file}
@itemx -T @var{file}
@command{tar} will use the contents of @var{file} as a list of archive members
or files to operate on, in addition to those specified on the
-command-line. @FIXME-xref{}
+command-line. @xref{files}.
+@opindex force-local, summary
@item --force-local
-Forces @command{tar} to interpret the filename given to @samp{--file}
+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{}
+@xref{local and remote archives}.
+@opindex format, summary
@item --format=@var{format}
-Selects output archive format. @var{Format} may be one of the
+Selects output archive format. @var{Format} may be one of the
following:
@table @samp
@item v7
-Tells @command{tar} to create an archive that is compatible with Unix V7
-@command{tar}.
+Creates an archive that is compatible with Unix V7 @command{tar}.
@item oldgnu
-Tells @command{tar} to create an archive that is compatible with GNU
-@command{tar} version 1.12 or earlier.
+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
-Tells @command{tar} to create POSIX.1-2001 archive.
+Creates a @acronym{POSIX.1-2001 archive}.
-@item gnu
-Tells @command{tar} to create archive in GNU format.
@end table
+@xref{Formats}, for a detailed discussion of these formats.
+
+@opindex group, summary
@item --group=@var{group}
Files added to the @command{tar} archive will have a group id of @var{group},
as a group symbolic name, but if this interpretation fails, it has to be
a decimal numeric group ID. @FIXME-xref{}
-Also see the comments for the @value{op-owner} option.
+Also see the comments for the @option{--owner=@var{user}} option.
+@opindex gzip, summary
+@opindex gunzip, summary
+@opindex ungzip, summary
@item --gzip
@itemx --gunzip
@itemx --ungzip
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{}
+kinds of compressed archives transparently. @xref{gzip}.
+@opindex help, summary
@item --help
@command{tar} will print out a short message summarizing the operations and
-options to @command{tar} and exit. @FIXME-xref{}
+options to @command{tar} and exit. @xref{help}.
+@opindex ignore-case, summary
@item --ignore-case
-Ignore case when excluding files.
-@FIXME-xref{}
+Ignore case when excluding files. @xref{controlling pattern-matching
+with exclude}.
+
+@opindex ignore-command-error, summary
+@item --ignore-command-error
+Ignore exit codes of subprocesses. @xref{Writing to an External Program}.
+@opindex ignore-failed-read, summary
@item --ignore-failed-read
Do not exit unsuccessfully merely because an unreadable file was encountered.
@xref{Reading}.
+@opindex ignore-zeros, summary
@item --ignore-zeros
@itemx -i
With this option, @command{tar} will ignore zeroed blocks in the
archive, which normally signals EOF. @xref{Reading}.
+@opindex incremental, summary
@item --incremental
@itemx -G
Used to inform @command{tar} that it is working with an old
@acronym{GNU}-format incremental backup archive. It is intended
-primarily for backwards compatibility only. @FIXME-xref{}
+primarily for backwards compatibility only. @FIXME{incremental and
+listed-incremental}.
+@opindex index-file, summary
@item --index-file=@var{file}
Send verbose output to @var{file} instead of to standard output.
+@opindex info-script, summary
+@opindex new-volume-script, summary
@item --info-script=@var{script-file}
@itemx --new-volume-script=@var{script-file}
@itemx -F @var{script-file}
When @command{tar} is performing multi-tape backups, @var{script-file} is run
at the end of each tape. If @var{script-file} exits with nonzero status,
-@command{tar} fails immediately. @FIXME-xref{}
+@command{tar} fails immediately. @xref{info-script}, for a detailed
+discussion of @var{script-file}.
+@opindex interactive, summary
@item --interactive
@itemx --confirmation
@itemx -w
Specifies that @command{tar} should ask the user for confirmation before
performing potentially destructive options, such as overwriting files.
-@FIXME-xref{}
+@xref{interactive}.
+
+@opindex keep-newer-files, summary
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive copies
+when extracting files from an archive.
+
+@opindex keep-old-files, summary
@item --keep-old-files
@itemx -k
Do not overwrite existing files when extracting files from an archive.
-@xref{Writing}.
+@xref{Keep Old Files}.
+@opindex label, summary
@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{}
+the pattern specified in @var{name}. @xref{Tape Files}.
+@opindex listed-incremental, summary
@item --listed-incremental=@var{snapshot-file}
@itemx -g @var{snapshot-file}
-During a @samp{--create} operation, specifies that the archive that
+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-xref{}
+incremental format. @FIXME{incremental and listed-incremental}.
+@opindex mode, summary
@item --mode=@var{permissions}
When adding files to an archive, @command{tar} will use
permissions for everybody, while retaining executable bits on directories
or on any other file already marked as executable.
+@opindex multi-volume, summary
@item --multi-volume
@itemx -M
Informs @command{tar} that it should create or otherwise operate on a
-multi-volume @command{tar} archive. @FIXME-xref{}
+multi-volume @command{tar} archive. @xref{Using Multiple Tapes}.
+@opindex new-volume-script, summary
@item --new-volume-script
(see --info-script)
+@opindex seek, summary
+@item --seek
+@itemx -n
+
+Assume that the archive media supports seeks to arbitrary
+locations. Usually @command{tar} determines automatically whether
+the archive can be seeked or not. This option is intended for use
+in cases when such recognition fails.
+
+@opindex newer, summary
@item --newer=@var{date}
@itemx --after-date=@var{date}
@itemx -N
When creating an archive, @command{tar} will only add files that have changed
since @var{date}. If @var{date} begins with @samp{/} or @samp{.}, it
-is taken to be the name of a file whose last-modified time specifies
-the date. @FIXME-xref{}
+is taken to be the name of a file whose data modification time specifies
+the date. @xref{after}.
+@opindex newer-mtime, summary
@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).
+@opindex no-anchored, summary
@item --no-anchored
An exclude pattern can match any subsequence of the name's components.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
+
+@opindex no-delay-directory-restore, summary
+@item --no-delay-directory-restore
+
+Setting modification times and permissions of extracted
+directories when all files from this directory has been
+extracted. This is the default. @xref{Directory Modification Times and Permissions}.
+@opindex no-ignore-case, summary
@item --no-ignore-case
Use case-sensitive matching when excluding files.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
+
+@opindex no-ignore-command-error, summary
+@item --no-ignore-command-error
+Print warnings about subprocesses terminated with a non-zero exit
+code. @xref{Writing to an External Program}.
+@opindex no-quote-chars, summary
+@item --no-quote-chars=@var{string}
+Do not quote characters from @var{string}, even if the selected
+quoting style implies they should be quoted (@FIXME-pxref{Quoting Styles}).
+
+@opindex no-recursion, summary
@item --no-recursion
With this option, @command{tar} will not recurse into directories.
-@FIXME-xref{}
+@xref{recurse}.
+@opindex no-same-owner, summary
@item --no-same-owner
@itemx -o
When extracting an archive, do not attempt to preserve the owner
specified in the @command{tar} archive. This the default behavior
-for ordinary users; this option has an effect only for the superuser.
+for ordinary users.
+@opindex no-same-permissions, summary
@item --no-same-permissions
When extracting an archive, subtract the user's umask from files from
the permissions specified in the archive. This is the default behavior
-for ordinary users; this option has an effect only for the superuser.
+for ordinary users.
+@opindex no-wildcards, summary
@item --no-wildcards
Do not use wildcards when excluding files.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
+@opindex no-wildcards-match-slash, summary
@item --no-wildcards-match-slash
Wildcards do not match @samp{/} when excluding files.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
+@opindex null, summary
@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{}
+@xref{nul}.
+@opindex numeric-owner, summary
@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{}
+@xref{Attributes}.
@item -o
When extracting files, this option is a synonym for
-@option{--no-same-owner}, i.e. it prevents @command{tar} from
+@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
+@option{--old-archive}. This behavior is for compatibility
with previous versions of @GNUTAR{}, and will be
removed in the future releases.
-@xref{Current status}, for more information.
+@xref{Changes}, for more information.
+@opindex occurrence, summary
@item --occurrence[=@var{number}]
This option can be used in conjunction with one of the subcommands
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
+occurrence of each named file. @var{Number} defaults to 1, so
@smallexample
tar -x -f archive.tar --occurrence filename
will extract the first occurrence of @file{filename} from @file{archive.tar}
and will terminate without scanning to the end of the archive.
+@opindex old-archive, summary
@item --old-archive
Synonym for @option{--format=v7}.
+@opindex one-file-system, summary
@item --one-file-system
@itemx -l
Used when creating an archive. Prevents @command{tar} from recursing into
directory.
Earlier versions of @GNUTAR{} understood @option{-l} as a
-synonym for @option{--one-file-system}. Although such usage is still
+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.
+@xref{Changes}, for more information.
+@opindex overwrite, summary
@item --overwrite
Overwrite existing files and directory metadata when extracting files
from an archive. @xref{Overwrite Old Files}.
+@opindex overwrite-dir, summary
@item --overwrite-dir
Overwrite the metadata of existing directories when extracting files
from an archive. @xref{Overwrite Old Files}.
+@opindex owner, summary
@item --owner=@var{user}
Specifies that @command{tar} should use @var{user} as the owner of members
This option does not affect extraction from archives.
+@opindex quote-chars, summary
+@item --quote-chars=@var{string}
+Always quote characters from @var{string}, even if the selected
+quoting style would not quote them (@FIXME-pxref{Quoting Styles}).
+
+@opindex quoting-style, summary
+@item --quoting-style=@var{style}
+Set quoting style to use when printing member and file names
+(@FIXME-pxref{Quoting Styles}). Valid @var{style} values are:
+@code{literal}, @code{shell}, @code{shell-always}, @code{c},
+@code{escape}, @code{locale}, and @code{clocale}. Default quoting
+style is @code{escape}, unless overridden while configuring the
+package.
+
+@opindex pax-option, summary
+@item --pax-option=@var{keyword-list}
+@FIXME{Such a detailed description does not belong there, move it elsewhere.}
+This option is meaningful only with @acronym{POSIX.1-2001} archives
+(@pxref{posix}). It modifies the way @command{tar} handles the
+extended header keywords. @var{Keyword-list} is a comma-separated
+list of keyword options, each keyword option taking one of
+the following forms:
+
+@table @asis
+@item delete=@var{pattern}
+When used with one of archive-creation commands,
+this option instructs @command{tar} to omit from extended header records
+that it produces any keywords matching the string @var{pattern}.
+
+When used in extract or list mode, this option instructs tar
+to ignore any keywords matching the given @var{pattern} in the extended
+header records. In both cases, matching is performed using the pattern
+matching notation described in @acronym{POSIX 1003.2}, 3.13
+(See @cite{glob(7)}). For example:
+
+@smallexample
+--pax-option delete=security.*
+@end smallexample
+
+would suppress security-related information.
+
+@item exthdr.name=@var{string}
+
+This keyword allows user control over the name that is written into the
+ustar header blocks for the extended headers. The name is obtained
+from @var{string} after substituting the following meta-characters:
+
+@multitable @columnfractions .30 .70
+@headitem Meta-character @tab Replaced By
+@item %d @tab The directory name of the file, equivalent to the
+result of the @command{dirname} utility on the translated pathname.
+@item %f @tab The filename of the file, equivalent to the result
+of the @command{basename} utility on the translated pathname.
+@item %p @tab The process ID of the @command{tar} process.
+@item %% @tab A @samp{%} character.
+@end multitable
+
+Any other @samp{%} characters in @var{string} produce undefined
+results.
+
+If no option @samp{exthdr.name=string} is specified, @command{tar}
+will use the following default value:
+
+@smallexample
+%d/PaxHeaders.%p/%f
+@end smallexample
+
+@item globexthdr.name=@var{string}
+This keyword allows user control over the name that is written into
+the ustar header blocks for global extended header records. The name
+shall will be obtained from the contents of @var{string}, after the
+following character substitutions have been made:
+
+@multitable @columnfractions .30 .70
+@headitem Meta-character @tab Replaced By
+@item %n @tab An integer that represents the
+sequence number of the global extended header record in the archive,
+starting at 1.
+@item %p @tab The process ID of the @command{tar} process.
+@item %% @tab A @samp{%} character.
+@end multitable
+
+Any other @samp{%} characters in string produce undefined results.
+
+If no option @samp{globexthdr.name=string} is specified, @command{tar}
+will use the following default value:
+
+@smallexample
+$TMPDIR/GlobalHead.%p.%n
+@end smallexample
+
+@noindent
+where @samp{$TMPDIR} represents the value of the @var{TMPDIR}
+environment variable. If @var{TMPDIR} is not set, @command{tar}
+uses @samp{/tmp}.
+
+@item @var{keyword}=@var{value}
+When used with one of archive-creation commands, these keyword/value pairs
+will be included at the beginning of the archive in a global extended
+header record. When used with one of archive-reading commands,
+@command{tar} will behave as if it has encountered these keyword/value
+pairs at the beginning of the archive in a global extended header
+record.
+
+@item @var{keyword}:=@var{value}
+When used with one of archive-creation commands, these keyword/value pairs
+will be included as records at the beginning of an extended header for
+each file. This is effectively equivalent to @var{keyword}=@var{value}
+form except that it creates no global extended header records.
+
+When used with one of archive-reading commands, @command{tar} will
+behave as if these keyword/value pairs were included as records at the
+end of each extended header; thus, they will override any global or
+file-specific extended header record keywords of the same names.
+For example, in the command:
+
+@smallexample
+tar --format=posix --create \
+ --file archive --pax-option gname:=user .
+@end smallexample
+
+the group name will be forced to a new value for all files
+stored in the archive.
+@end table
+
+@opindex portability, summary
@item --portability
@itemx --old-archive
Synonym for @option{--format=v7}.
+@opindex posix, summary
@item --posix
Same as @option{--format=posix}.
+@opindex preserve, summary
@item --preserve
-Synonymous with specifying both @samp{--preserve-permissions} and
-@samp{--same-order}. @FIXME-xref{}
+Synonymous with specifying both @option{--preserve-permissions} and
+@option{--same-order}. @xref{Setting Access Permissions}.
+@opindex preserve-order, summary
@item --preserve-order
-(See @samp{--same-order}; @pxref{Reading}.)
+(See @option{--same-order}; @pxref{Reading}.)
+@opindex preserve-permissions, summary
+@opindex same-permissions, summary
@item --preserve-permissions
@itemx --same-permissions
@itemx -p
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}.
+permissions directly from the archive. @xref{Setting Access Permissions}.
+@opindex read-full-records, summary
@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}.
+@opindex record-size, summary
@item --record-size=@var{size}
Instructs @command{tar} to use @var{size} bytes per record when accessing the
-archive. @FIXME-xref{}
+archive. @xref{Blocking Factor}.
+@opindex recursion, summary
@item --recursion
With this option, @command{tar} recurses into directories.
-@FIXME-xref{}
+@xref{recurse}.
+@opindex recursive-unlink, summary
@item --recursive-unlink
Remove existing
directory hierarchies before extracting directories of the same name
-from the archive. @xref{Writing}.
+from the archive. @xref{Recursive Unlink}.
+@opindex remove-files, summary
@item --remove-files
Directs @command{tar} to remove the source file from the file system after
-appending it to an archive. @FIXME-xref{}
+appending it to an archive. @xref{remove files}.
+
+@opindex restrict, summary
+@item --restrict
+
+Disable use of some potentially harmful @command{tar} options.
+Currently this option disables shell invocaton from multi-volume menu
+(@pxref{Using Multiple Tapes}).
+@opindex rmt-command, summary
+@item --rmt-command=@var{cmd}
+
+Notifies @command{tar} that it should use @var{cmd} instead of
+the default @file{/usr/libexec/rmt} (@pxref{Remote Tape Server}).
+
+@opindex rsh-command, summary
@item --rsh-command=@var{cmd}
Notifies @command{tar} that is should use @var{cmd} to communicate with remote
-devices. @FIXME-xref{}
+devices. @xref{Device}.
+@opindex same-order, summary
@item --same-order
@itemx --preserve-order
@itemx -s
arguments has already been sorted to match the order of files in the
archive. @xref{Reading}.
+@opindex same-owner, summary
@item --same-owner
When extracting an archive, @command{tar} will attempt to preserve the owner
specified in the @command{tar} archive with this option present.
This is the default behavior for the superuser; this option has an
-effect only for ordinary users. @FIXME-xref{}
+effect only for ordinary users. @xref{Attributes}.
+@opindex same-permissions, summary
@item --same-permissions
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+(See @option{--preserve-permissions}; @pxref{Setting Access Permissions}.)
+
+@opindex show-defaults, summary
+@item --show-defaults
+
+Displays the default options used by @command{tar} and exits
+successfully. This option is intended for use in shell scripts.
+Here is an example of what you can see using this option:
+@smallexample
+$ tar --show-defaults
+--format=gnu -f- -b20 --quoting-style=escape \
+--rmt-command=/usr/libexec/rmt --rsh-command=/usr/bin/rsh
+@end smallexample
+
+@opindex show-omitted-dirs, summary
@item --show-omitted-dirs
Instructs @command{tar} to mention directories its skipping over when
-operating on a @command{tar} archive. @FIXME-xref{}
+operating on a @command{tar} archive. @xref{show-omitted-dirs}.
+
+@opindex show-stored-names, summary
+@item --show-stored-names
+This option has effect only when used in conjunction with one of
+archive creation operations. It instructs tar to list the member names
+stored in the archive, as opposed to the actual file
+names. @xref{listing member and file names}.
+
+@opindex sparse, summary
@item --sparse
@itemx -S
Invokes a @acronym{GNU} extension when adding files to an archive that handles
-sparse files efficiently. @FIXME-xref{}
+sparse files efficiently. @xref{sparse}.
+@opindex starting-file, summary
@item --starting-file=@var{name}
@itemx -K @var{name}
files in the archive until it finds one that matches @var{name}.
@xref{Scarce}.
-@item --strip-path=@var{number}
+@opindex strip-components, summary
+@item --strip-components=@var{number}
Strip given @var{number} of leading components from file names before
-extraction. For example, if archive @file{archive.tar} contained
+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-path=2
+tar --extract --file archive.tar --strip-components=2
@end smallexample
@noindent
would extracted this file to file @file{name}.
+@opindex suffix, summary
@item --suffix=@var{suffix}
Alters the suffix @command{tar} uses when backing up files from the default
-@samp{~}. @FIXME-xref{}
+@samp{~}. @xref{backup}.
+@opindex tape-length, summary
@item --tape-length=@var{num}
@itemx -L @var{num}
Specifies the length of tapes that @command{tar} is writing as being
-@w{@var{num} x 1024} bytes long. @FIXME-xref{}
+@w{@var{num} x 1024} bytes long. @xref{Using Multiple Tapes}.
+
+@opindex test-label, summary
+@item --test-label
+
+Reads the volume label. If an argument is specified, test whether it
+matches the volume label. @xref{--test-label option}.
+
+@opindex to-command, summary
+@item --to-command=@var{command}
+During extraction @command{tar} will pipe extracted files to the
+standard input of @var{command}. @xref{Writing to an External Program}.
+
+@opindex to-stdout, summary
@item --to-stdout
@itemx -O
During extraction, @command{tar} will extract files to stdout rather
-than to the file system. @xref{Writing}.
+than to the file system. @xref{Writing to Standard Output}.
+@opindex totals, summary
@item --totals
Displays the total number of bytes written after creating an archive.
-@FIXME-xref{}
+@xref{verbose}.
+@opindex touch, summary
@item --touch
@itemx -m
-Sets the modification time of extracted files to the extraction time,
-rather than the modification time stored in the archive.
-@xref{Writing}.
+Sets the data modification time of extracted files to the extraction time,
+rather than the data modification time stored in the archive.
+@xref{Data Modification Times}.
+@opindex uncompress, summary
@item --uncompress
-(See @samp{--compress}.) @FIXME-pxref{}
+(See @option{--compress}. @pxref{gzip})
+@opindex ungzip, summary
@item --ungzip
-(See @samp{--gzip}.) @FIXME-pxref{}
+(See @option{--gzip}. @pxref{gzip})
+@opindex unlink-first, summary
@item --unlink-first
@itemx -U
Directs @command{tar} to remove the corresponding file from the file
-system before extracting it from the archive. @xref{Writing}.
+system before extracting it from the archive. @xref{Unlink First}.
+@opindex use-compress-program, summary
@item --use-compress-program=@var{prog}
Instructs @command{tar} to access the archive through @var{prog}, which is
-presumed to be a compression program of some sort. @FIXME-xref{}
+presumed to be a compression program of some sort. @xref{gzip}.
+
+@opindex utc, summary
+@item --utc
+
+Display file modification dates in @acronym{UTC}. This option implies
+@option{--verbose}.
+@opindex verbose, summary
@item --verbose
@itemx -v
Specifies that @command{tar} should be more verbose about the operations its
performing. This option can be specified multiple times for some
-operations to increase the amount of information displayed. @FIXME-xref{}
+operations to increase the amount of information displayed.
+@xref{verbose}.
+@opindex verify, summary
@item --verify
@itemx -W
Verifies that the archive was correctly written when creating an
-archive. @FIXME-xref{}
+archive. @xref{verify}.
+@opindex version, summary
@item --version
-@command{tar} will print an informational message about what version
-it is and a copyright message, some credits, and then exit.
-@FIXME-xref{}
+Print information about the program's name, version, origin and legal
+status, all on standard output, and then exit successfully.
+@xref{help}.
+@opindex volno-file, summary
@item --volno-file=@var{file}
-Used in conjunction with @samp{--multi-volume}. @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{}
+@xref{volno-file}.
+@opindex wildcards, summary
@item --wildcards
Use wildcards when excluding files.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
+@opindex wildcards-match-slash, summary
@item --wildcards-match-slash
Wildcards match @samp{/} when excluding files.
-@FIXME-xref{}
+@xref{controlling pattern-matching with exclude}.
@end table
@node Short Option Summary
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
-@samp{--bzip2}
+@option{--bzip2}
@item -k
-@samp{--keep-old-files}
+@option{--keep-old-files}
@item -l
-@samp{--one-file-system}. Use of this short option is deprecated. It
+@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.
+@xref{Changes}, for more information.
@item -m
-@samp{--touch}
+@option{--touch}
@item -o
-When creating --- @samp{--no-same-owner}, when extracting ---
-@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 @samp{--no-same-owner} only.
+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 @GNUTAR{} documentation
+@cindex Getting program version number
+@opindex version
+@cindex Version of the @command{tar} program
Being careful, the first thing is really checking that you are using
-@GNUTAR{}, indeed. The @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:
+@GNUTAR{}, indeed. The @option{--version} option
+causes @command{tar} to print information about its name, version,
+origin and legal status, all on standard output, and then exit
+successfully. For example, @w{@samp{tar --version}} might print:
@smallexample
-tar (@acronym{GNU} tar) @value{VERSION}
+tar (GNU tar) 1.15.2
+Copyright (C) 2006 Free Software Foundation, Inc.
+This is free software. You may redistribute copies of it under the terms of
+the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
+There is NO WARRANTY, to the extent permitted by law.
+
+Written by John Gilmore and Jay Fenlason.
@end smallexample
@noindent
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}
+@option{--version} would not output @w{@samp{tar (@acronym{GNU}
paxutils) 3.2}}}.
+@cindex Obtaining help
+@cindex Listing all @command{tar} options
+@opindex help, introduction
Another thing you might want to do is checking the spelling or meaning
of some particular @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
+@option{--help} option. By using this option, @command{tar} will
print a usage message listing all available options on standard
output, then exit successfully, without doing anything else and
ignoring all other options. Even if this is only a brief summary, it
presuming, here, that you like using @command{less} for a pager. Other
popular pagers are @command{more} and @command{pg}. If you know about some
@var{keyword} which interests you and do not want to read all the
-@value{op-help} output, another common idiom is doing:
+@option{--help} output, another common idiom is doing:
@smallexample
tar --help | grep @var{keyword}
@end smallexample
@noindent
-for getting only the pertinent lines.
+for getting only the pertinent lines. Notice, however, that some
+@command{tar} options have long description lines and the above
+command will list only the first of them.
-The perceptive reader would have noticed some contradiction in the
-previous paragraphs. It is written that both @value{op-version} and
-@value{op-help} print something, and have all other options ignored. In
-fact, they cannot ignore each other, and one of them has to win. We do
-not specify which is stronger, here; experiment if you really wonder!
+The exact look of the option summary displayed by @kbd{tar --help} is
+configurable. @xref{Configuring Help Summary}, for a detailed description.
+
+@opindex usage
+If you only wish to check the spelling of an option, running @kbd{tar
+--usage} may be a better choice. This will display a terse list of
+@command{tar} option without accompanying explanations.
The short help output is quite succinct, and you might have to get
back to the full documentation for precise points. If you are reading
this paragraph, you already have the @command{tar} manual in some
-form. This manual is available in printed form, as a kind of small
-book. It may printed out of the @GNUTAR{}
+form. This manual is available in a variety of forms from
+@url{http://www.gnu.org/software/tar/manual}. It may printed out of the @GNUTAR{}
distribution, provided you have @TeX{} already installed somewhere,
and a laser printer around. Just configure the distribution, execute
the command @w{@samp{make dvi}}, then print @file{doc/tar.dvi} the
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}.
+either it does not belong to @GNUTAR{}, or it has not
+been produced by @acronym{GNU}. Some package maintainers convert
+@kbd{tar --help} output to a man page, using @command{help2man}. In
+any case, please bear in mind that the authoritative source of
+information about @GNUTAR{} is this Texinfo documentation.
-@node verbose
-@section Checking @command{tar} progress
+@node defaults
+@section Obtaining @GNUTAR{} default values
-@cindex Progress information
-@cindex Status information
-@cindex Information on progress and status of operations
-@cindex Verbose operation
-@cindex Block number where error occurred
-@cindex Error message, block number of
-@cindex Version of the @command{tar} program
+@opindex show-defaults
+@GNUTAR{} has some predefined defaults that are used when you do not
+explicitely specify another values. To obtain a list of such
+defaults, use @option{--show-defaults} option. This will output the
+values in the form of @command{tar} command line options:
+
+@smallexample
+@group
+@kbd{tar --show-defaults}
+--format=gnu -f- -b20 --rmt-command=/etc/rmt --rsh-command=/usr/bin/rsh
+@end group
+@end smallexample
+
+@noindent
+The above output shows that this version of @GNUTAR{} defaults to
+using @samp{gnu} archive format (@pxref{Formats}), it uses standard
+output as the archive, if no @option{--file} option has been given
+(@pxref{file tutorial}), the default blocking factor is 20
+(@pxref{Blocking Factor}). It also shows the default locations where
+@command{tar} will look for @command{rmt} and @command{rsh} binaries.
-@cindex Getting more information during the operation
-@cindex Information during operation
-@cindex Feedback from @command{tar}
+@node verbose
+@section Checking @command{tar} progress
Typically, @command{tar} performs most operations without reporting any
information to the user except error messages. When using @command{tar}
message in order to solve the problem. The following options can be
helpful diagnostic tools.
-Normally, the @value{op-list} command to list an archive prints just
-the file names (one per line) and the other commands are silent.
-When used with most operations, the @value{op-verbose} option causes
-@command{tar} to print the name of each file or archive member as it
-is processed. This and the other options which make @command{tar} print
-status information can be useful in monitoring @command{tar}.
-
-With @value{op-create} or @value{op-extract}, @value{op-verbose} used once
-just prints the names of the files or members as they are processed.
-Using it twice causes @command{tar} to print a longer listing (reminiscent
-of @samp{ls -l}) for each member. Since @value{op-list} already prints
-the names of the members, @value{op-verbose} used once with @value{op-list}
-causes @command{tar} to print an @samp{ls -l} type listing of the files
-in the archive. The following examples both extract members with
-long list output:
+@cindex Verbose operation
+@opindex verbose
+Normally, the @option{--list} (@option{-t}) command to list an archive
+prints just the file names (one per line) and the other commands are
+silent. When used with most operations, the @option{--verbose}
+(@option{-v}) option causes @command{tar} to print the name of each
+file or archive member as it is processed. This and the other options
+which make @command{tar} print status information can be useful in
+monitoring @command{tar}.
+
+With @option{--create} or @option{--extract}, @option{--verbose} used
+once just prints the names of the files or members as they are processed.
+Using it twice causes @command{tar} to print a longer listing
+(reminiscent of @samp{ls -l}) for each member. Since @option{--list}
+already prints the names of the members, @option{--verbose} used once
+with @option{--list} causes @command{tar} to print an @samp{ls -l}
+type listing of the files in the archive. The following examples both
+extract members with long list output:
@smallexample
$ @kbd{tar --extract --file=archive.tar --verbose --verbose}
-$ @kbd{tar xvv archive.tar}
+$ @kbd{tar xvvf archive.tar}
@end smallexample
Verbose output appears on the standard output except when an archive is
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
+@cindex Obtaining total status information
+@opindex totals
+The @option{--totals} option---which is only meaningful when used with
+@option{--create} (@option{-c})---causes @command{tar} to print the total
amount written to the archive, after it has been fully created.
-The @value{op-checkpoint} option prints an occasional message
-as @command{tar} reads or writes the archive. In fact, it print
-directory names while reading the archive. It is designed for
+@cindex Progress information
+@opindex checkpoint
+The @option{--checkpoint} option prints an occasional message
+as @command{tar} reads or writes the archive. In fact, it prints
+a message each 10 records read or written. It is designed for
those who don't need the more detailed (and voluminous) output of
-@value{op-block-number}, but do want visual confirmation that @command{tar}
+@option{--block-number} (@option{-R}), but do want visual confirmation that @command{tar}
is actually making forward progress.
@FIXME{There is some confusion here. It seems that -R once wrote a
message at @samp{every} record read or written.}
-The @value{op-show-omitted-dirs} option, when reading an archive---with
-@value{op-list} or @value{op-extract}, for example---causes a message
+@opindex show-omitted-dirs
+@anchor{show-omitted-dirs}
+The @option{--show-omitted-dirs} option, when reading an archive---with
+@option{--list} or @option{--extract}, for example---causes a message
to be printed for each directory in the archive which is skipped.
This happens regardless of the reason for skipping: the directory might
not have been named on the command line (implicitly or explicitly),
-it might be excluded by the use of the @value{op-exclude} option, or
+it might be excluded by the use of the @option{--exclude=@var{pattern}} option, or
some other reason.
-If @value{op-block-number} is used, @command{tar} prints, along with
+@opindex block-number
+@cindex Block number where error occurred
+@anchor{block-number}
+If @option{--block-number} (@option{-R}) is used, @command{tar} prints, along with
every message it would normally produce, the block number within the
archive where the message was triggered. Also, supplementary messages
are triggered when reading blocks full of NULs, or when hitting end of
file on the archive. As of now, if the archive if properly terminated
with a NUL block, the reading of the file may stop before end of file
is met, so the position of end of file will not usually show when
-@value{op-block-number} is used. Note that @GNUTAR{}
+@option{--block-number} (@option{-R}) is used. Note that @GNUTAR{}
drains the archive before exiting when reading the
archive from a pipe.
+@cindex Error message, block number of
This option is especially useful when reading damaged archives, since
it helps pinpoint the damaged sections. It can also be used with
-@value{op-list} when listing a file-system backup tape, allowing you to
+@option{--list} (@option{-t}) when listing a file-system backup tape, allowing you to
choose among several backup tapes when retrieving a file later, in
favor of the tape where the file appears earliest (closest to the
-front of the tape). @FIXME-xref{when the node name is set and the
-backup section written.}
+front of the tape). @xref{backup}.
@node interactive
@section Asking for Confirmation During Operations
exclude some files and archive members from the operation (for instance
if disk or storage space is tight). You can do this by excluding
certain files automatically (@pxref{Choosing}), or by performing
-an operation interactively, using the @value{op-interactive} option.
-@command{tar} also accepts @samp{--confirmation} for this option.
+an operation interactively, using the @option{--interactive} (@option{-w}) option.
+@command{tar} also accepts @option{--confirmation} for this option.
-When the @value{op-interactive} option is specified, before
+@opindex interactive
+When the @option{--interactive} (@option{-w}) option is specified, before
reading, writing, or deleting files, @command{tar} first prints a message
for each such file, telling what operation it intends to take, then asks
for confirmation on the terminal. The actions which require
@node Basic tar
@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
+The basic @command{tar} operations, @option{--create} (@option{-c}),
+@option{--list} (@option{-t}) and @option{--extract} (@option{--get},
+@option{-x}), are currently presented and described in the tutorial
chapter of this manual. This section provides some complementary notes
for these operations.
-@table @asis
-@item @value{op-create}
+@table @option
+@opindex create, complementary notes
+@item --create
+@itemx -c
Creating an empty archive would have some kind of elegance. One can
-initialize an empty archive and later use @value{op-append} for adding
-all members. Some applications would not welcome making an exception
-in the way of adding the first archive member. On the other hand,
-many people reported that it is dangerously too easy for @command{tar}
-to destroy a magnetic tape with an empty archive@footnote{This is well
-described in @cite{Unix-haters Handbook}, by Simson Garfinkel, Daniel
-Weise & Steven Strassmann, IDG Books, ISBN 1-56884-203-1.}. The two most
-common errors are:
+initialize an empty archive and later use @option{--append}
+(@option{-r}) for adding all members. Some applications would not
+welcome making an exception in the way of adding the first archive
+member. On the other hand, many people reported that it is
+dangerously too easy for @command{tar} to destroy a magnetic tape with
+an empty archive@footnote{This is well described in @cite{Unix-haters
+Handbook}, by Simson Garfinkel, Daniel Weise & Steven Strassmann, IDG
+Books, ISBN 1-56884-203-1.}. The two most common errors are:
@enumerate
@item
So, recognizing the likelihood and the catastrophical nature of these
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 @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:
+cowardly refuses to create an archive when @option{--create} option is
+given, there are no arguments besides options, and
+@option{--files-from} (@option{-T}) option is @emph{not} used. To get
+around the cautiousness of @GNUTAR{} and nevertheless create an
+archive with nothing in it, one may still use, as the value for the
+@option{--files-from} option, a file with no names in it, as shown in
+the following commands:
@smallexample
@kbd{tar --create --file=empty-archive.tar --files-from=/dev/null}
@kbd{tar cfT empty-archive.tar /dev/null}
@end smallexample
-@item @value{op-extract}
+@opindex extract, complementary notes
+@item --extract
+@itemx --get
+@itemx -x
A socket is stored, within a @GNUTAR{} archive, as a pipe.
-@item @value{op-list}
+@item @option{--list} (@option{-t})
@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.
+while it used to show them as @samp{Aug 30 1996}. Preferably,
+people should get used to ISO 8601 dates. Local American dates should
+be made available again with full date localization support, once
+ready. In the meantime, programs not being localizable for dates
+should prefer international dates, that's really the way to go.
Look up @url{http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html} if you
are curious, it contains a detailed explanation of the ISO 8601 standard.
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.
@end table
@node append
-@subsection How to Add Files to Existing Archives: @code{--append}
+@subsection How to Add Files to Existing Archives: @option{--append}
@UNREVISED
+@opindex append
If you want to add files to an existing archive, you don't need to
-create a new archive; you can use @value{op-append}. The archive must
-already exist in order to use @samp{--append}. (A related operation
-is the @samp{--update} operation; you can use this to add newer
-versions of archive members to an existing archive. To learn how to
-do this with @samp{--update}, @pxref{update}.)
+create a new archive; you can use @option{--append} (@option{-r}).
+The archive must already exist in order to use @option{--append}. (A
+related operation is the @option{--update} operation; you can use this
+to add newer versions of archive members to an existing archive. To learn how to
+do this with @option{--update}, @pxref{update}.)
-@FIXME{Explain in second paragraph whether you can get to the previous
-version -- explain whole situation somewhat more clearly.}
-
-If you use @value{op-append} to add a file that has the same name as an
+If you use @option{--append} to add a file that has the same name as an
archive member to an archive containing that archive member, then the
old member is not deleted. What does happen, however, is somewhat
-complex. @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
-listed, with their modification times, owners, etc.
+view an archive with @option{--list} (@option{-t}), you will see all
+of those members listed, with their data modification times, owners, etc.
Other operations don't deal with these members as perfectly as you might
-prefer; if you were to use @value{op-extract} to extract the archive,
+prefer; if you were to use @option{--extract} to extract the archive,
only the most recently added copy of a member with the same name as four
other members would end up in the working directory. This is because
-@samp{--extract} extracts an archive in the order the members appeared
+@option{--extract} extracts an archive in the order the members appeared
in the archive; the most recently archived members will be extracted
last. Additionally, an extracted member will @emph{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 @option{--occurrence}
+option.
+
@FIXME{ hag -- you might want to incorporate some of the above into the
-MMwtSN node; not sure. i didn't know how to make it simpler...}
+MMwtSN node; not sure. i didn't know how to make it simpler...
-There are a few ways to get around this. @FIXME-xref{Multiple Members
+There are a few ways to get around this. (maybe xref Multiple Members
with the Same Name.}
@cindex Members, replacing with other members
@cindex Replacing members with other members
-If you want to replace an archive member, use @value{op-delete} to
+If you want to replace an archive member, use @option{--delete} to
delete the member you want to remove from the archive, , and then use
-@samp{--append} to add the member you want to be in the archive. Note
+@option{--append} to add the member you want to be in the archive. Note
that you can not change the order of the archive; the most recently
added member will still appear last. In this sense, you cannot truly
``replace'' one member with another. (Replacing one member with another
@cindex Archives, Appending files to
The simplest way to add a file to an already existing archive is the
-@value{op-append} operation, which writes specified files into the
+@option{--append} (@option{-r}) operation, which writes specified files into the
archive whether or not they are already among the archived files.
-When you use @samp{--append}, you @emph{must} specify file name
+When you use @option{--append}, you @emph{must} specify file name
arguments, as there is no default. If you specify a file that already
exists in the archive, another copy of the file will be added to the
end of the archive. As with other operations, the member names of the
newly added files will be exactly the same as their names given on the
-command line. The @value{op-verbose} option will print out the names
-of the files as they are written into the archive.
+command line. The @option{--verbose} (@option{-v}) option will print
+out the names of the files as they are written into the archive.
-@samp{--append} cannot be performed on some tape drives, unfortunately,
+@option{--append} cannot be performed on some tape drives, unfortunately,
due to deficiencies in the formats those tape drives use. The archive
must be a valid @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
@end smallexample
@noindent
-If you now use the @value{op-list} operation, you will see that
+If you now use the @option{--list} (@option{-t}) operation, you will see that
@file{rock} has been added to the archive:
@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
+-rw-r--r-- me user 28 1996-10-18 16:31 jazz
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+-rw-r--r-- me user 20 1996-09-23 16:44 folk
+-rw-r--r-- me user 20 1996-09-23 16:44 rock
@end smallexample
@FIXME{in theory, dan will (soon) try to turn this node into what it's
@node multiple
@subsubsection Multiple Files with the Same Name
-You can use @value{op-append} to add copies of files which have been
+You can use @option{--append} (@option{-r}) to add copies of files which have been
updated since the archive was created. (However, we do not recommend
doing this since there is another @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
@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:
@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
+-rw-r--r-- me user 28 1996-10-18 16:31 jazz
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+-rw-r--r-- me user 20 1996-09-23 16:44 folk
+-rw-r--r-- me user 20 1996-09-23 16:44 rock
+-rw-r--r-- me user 58 1996-10-24 18:30 blues
@end smallexample
@noindent
(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 @option{--occurrence} option, as shown in
+the following example:
+
+@smallexample
+$ @kbd{tar --extract -vv --occurrence --file=collection.tar blues}
+-rw-r--r-- me user 21 1996-09-23 16:44 blues
+@end smallexample
+
+@xref{Writing}, for more information on @option{--extract} and
+@xref{Option Summary, --occurrence}, for the description of
+@option{--occurrence} option.
@node update
@subsection Updating an Archive
@UNREVISED
@cindex Updating an archive
-In the previous section, you learned how to use @value{op-append} to add
-a file to an existing archive. A related operation is
-@value{op-update}. The @samp{--update} operation updates a @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.
+@opindex update
+In the previous section, you learned how to use @option{--append} to
+add a file to an existing archive. A related operation is
+@option{--update} (@option{-u}). The @option{--update} operation
+updates a @command{tar} archive by comparing the date of the specified
+archive members against the date of the file with the same name. If
+the file has been modified more recently than the archive member, then
+the newer version of the file is added to the archive (as with
+@option{--append}).
+
+Unfortunately, you cannot use @option{--update} with magnetic tape drives.
The operation will fail.
@FIXME{other examples of media on which --update will fail? need to ask
charles and/or mib/thomas/dave shevett..}
-Both @samp{--update} and @samp{--append} work by adding to the end
+Both @option{--update} and @option{--append} work by adding to the end
of the archive. When you extract a file from the archive, only the
version stored last will wind up in the file system, unless you use
-the @value{op-backup} option. @FIXME-ref{Multiple Members with the
+the @option{--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.
+You must use file name arguments with the @option{--update} (@option{-u}) operation.
If you don't specify any files, @command{tar} won't act on any files and
won't tell you that it didn't do anything (which may end up confusing
you).
@FIXME{note: the above parenthetical added because in fact, this
behavior just confused the author. :-) }
-To see the @samp{--update} option at work, create a new file,
+To see the @option{--update} option at work, create a new file,
@file{classical}, in your practice directory, and some extra text to the
file @file{blues}, using any text editor. Then invoke @command{tar} with
-the @samp{update} operation and the @value{op-verbose} option specified,
+the @samp{update} operation and the @option{--verbose} (@option{-v}) option specified,
using the names of all the files in the practice directory as file name
arguments:
process. Tapes are not designed to go backward. @xref{Media}, for more
information about tapes.
-@value{op-update} is not suitable for performing backups for two
+@option{--update} (@option{-u}) is not suitable for performing backups for two
reasons: it does not change directory content entries, and it
lengthens the archive every time it is used. The @GNUTAR{}
options intended specifically for backups are more
efficient. If you need to run backups, please consult @ref{Backups}.
@node concatenate
-@subsection Combining Archives with @code{--concatenate}
+@subsection Combining Archives with @option{--concatenate}
@cindex Adding archives to an archive
@cindex Concatenating Archives
+@opindex concatenate
+@opindex catenate
+@c @cindex @option{-A} described
Sometimes it may be convenient to add a second archive onto the end of
an archive rather than adding individual files to the archive. To add
one or more archives to the end of another archive, you should use the
-@value{op-concatenate} operation.
+@option{--concatenate} (@option{--catenate}, @option{-A}) operation.
-To use @samp{--concatenate}, name the archives to be concatenated on the
-command line. (Nothing happens if you don't list any.) The members,
-and their member names, will be copied verbatim from those archives. If
-this causes multiple members to have the same name, it does not delete
-any members; all the members with the same name coexist. @FIXME-ref{For
+To use @option{--concatenate}, give the first archive with
+@option{--file} option and name the rest of archives to be
+concatenated on the command line. The members, and their member
+names, will be copied verbatim from those archives to the first one.
+@FIXME-ref{This can cause multiple members to have the same name, for
information on how this affects reading the archive, Multiple
Members with the Same Name.}
+The new, concatenated archive will be called by the same name as the
+one given with the @option{--file} option. As usual, if you omit
+@option{--file}, @command{tar} will use the value of the environment
+variable @env{TAPE}, or, if this has not been set, the default archive name.
+
+@FIXME{There is no way to specify a new name...}
-To demonstrate how @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}:
@smallexample
$ @kbd{tar -tvf bluesrock.tar}
--rw-rw-rw- melissa user 105 1997-01-21 19:42 blues
--rw-rw-rw- melissa user 33 1997-01-20 15:34 rock
+-rw-r--r-- melissa user 105 1997-01-21 19:42 blues
+-rw-r--r-- melissa user 33 1997-01-20 15:34 rock
$ @kbd{tar -tvf folkjazz.tar}
--rw-rw-rw- melissa user 20 1996-09-23 16:44 folk
--rw-rw-rw- melissa user 65 1997-01-30 14:15 jazz
+-rw-r--r-- melissa user 20 1996-09-23 16:44 folk
+-rw-r--r-- melissa user 65 1997-01-30 14:15 jazz
@end smallexample
We can concatenate these two archives with @command{tar}:
folk
@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
-new name?}
+parameters. Notice, that @command{tar} does not check whether the
+archives it concatenates have compatible formats, it does not
+even check if the files are really tar archives.
-Like @value{op-append}, this operation cannot be performed on some
+Like @option{--append} (@option{-r}), this operation cannot be performed on some
tape drives, due to deficiencies in the formats those tape drives use.
@cindex @code{concatenate} vs @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
archive that was added to using the @command{cat} utility, use the
-@value{op-ignore-zeros} option. @xref{Ignore Zeros}, for further
+@option{--ignore-zeros} (@option{-i}) option. @xref{Ignore Zeros}, for further
information on dealing with archives improperly combined using the
@command{cat} shell utility.
-@FIXME{this shouldn't go here. where should it go?} You must specify
-the source archives using @value{op-file} (@value{pxref-file}). If you
-do not specify the target archive, @command{tar} uses the value of the
-environment variable @env{TAPE}, or, if this has not been set, the
-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
-You can remove members from an archive by using the @value{op-delete}
-option. Specify the name of the archive with @value{op-file} and then
-specify the names of the members to be deleted; if you list no member
-names, nothing will be deleted. The @value{op-verbose} option will
-cause @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
-very slowly.
+@opindex delete
+You can remove members from an archive by using the @option{--delete}
+option. Specify the name of the archive with @option{--file}
+(@option{-f}) and then specify the names of the members to be deleted;
+if you list no member names, nothing will be deleted. The
+@option{--verbose} option will cause @command{tar} to print the names
+of the members as they are deleted. As with @option{--extract}, you
+must give the exact member names when using @samp{tar --delete}.
+@option{--delete} will remove all versions of the named file from the
+archive. The @option{--delete} operation can run very slowly.
-Unlike other operations, @samp{--delete} has no short form.
+Unlike other operations, @option{--delete} has no short form.
-@cindex Tapes, using @code{--delete} and
+@cindex Tapes, using @option{--delete} and
@cindex Deleting from tape archives
This operation will rewrite the archive. You can only use
-@samp{--delete} on an archive if the archive device allows you to
+@option{--delete} on an archive if the archive device allows you to
write to any point on the media, such as a disk; because of this, it
does not work on magnetic tapes. Do not try to delete an archive member
from a magnetic tape; the action will not succeed, and you will be
to fix the above example's results, yet. I have to play with this and
follow it and see what it actually does!}
-The @value{op-delete} option has been reported to work properly when
+The @option{--delete} option has been reported to work properly when
@command{tar} acts as a filter from @code{stdin} to @code{stdout}.
@node compare
@cindex Verifying the currency of an archive
@UNREVISED
-The @samp{--compare} (@samp{-d}), or @samp{--diff} operation compares
+@opindex compare
+The @option{--compare} (@option{-d}), or @option{--diff} operation compares
specified archive members against files with the same names, and then
reports differences in file size, mode, owner, modification date and
contents. You should @emph{only} specify archive member names, not file
tar: funk not found in archive
@end smallexample
-@noindent
-@FIXME{what does this actually depend on? i'm making a guess,
-here.}Depending on the system where you are running @command{tar} and the
-version you are running, @command{tar} may have a different error message,
-such as:
-
-@smallexample
-funk: does not exist
-@end smallexample
-
-@FIXME-xref{somewhere, for more information about format parameters.
-Melissa says: such as "format variations"? But why? Clearly I don't
-get it yet; I'll deal when I get to that section.}
-
-The spirit behind the @value{op-compare} option is to check whether the
+The spirit behind the @option{--compare} (@option{--diff}, @option{-d}) option is to check whether the
archive represents the current state of files on disk, more than validating
the integrity of the archive media. For this later goal, @xref{verify}.
@node create options
-@section Options Used by @code{--create}
+@section Options Used by @option{--create}
+@opindex create, additional options
The previous chapter described the basics of how to use
-@value{op-create} to create an archive from a set of files.
+@option{--create} (@option{-c}) 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
there's a better way of organizing them.}
-The previous chapter showed how to use @value{op-extract} to extract
-an archive into the filesystem. Various options cause @command{tar} to
+@opindex extract, additional options
+The previous chapter showed how to use @option{--extract} to extract
+an archive into the file system. Various options cause @command{tar} to
extract more information than just file contents, such as the owner,
the permissions, the modification date, and so forth. This section
-presents options to be used with @samp{--extract} when certain special
+presents options to be used with @option{--extract} when certain special
considerations arise. You may review the information presented in
@ref{extract} for more basic information about the
-@samp{--extract} operation.
+@option{--extract} operation.
@menu
* Reading:: Options to Help Read Archives
@node Reading
@subsection Options to Help Read Archives
@cindex Options when reading archives
-@cindex Reading incomplete records
-@cindex Records, incomplete
-@cindex End-of-archive entries, ignoring
-@cindex Ignoring end-of-archive entries
-@cindex Large lists of file names on small machines
-@cindex Small memory
-@cindex Running out of space
@UNREVISED
+@cindex Reading incomplete records
+@cindex Records, incomplete
+@opindex read-full-records
Normally, @command{tar} will request data in full record increments from
an archive storage device. If the device cannot return a full record,
@command{tar} will report an error. However, some devices do not always
return full records, or do not require the last record of an archive to
be padded out to the next record boundary. To keep reading until you
obtain a full record, or to accept an incomplete record if it contains
-an end-of-archive marker, specify the @value{op-read-full-records} option
-in conjunction with the @value{op-extract} or @value{op-list} operations.
-@value{xref-read-full-records}.
+an end-of-archive marker, specify the @option{--read-full-records} (@option{-B}) option
+in conjunction with the @option{--extract} or @option{--list} operations.
+@xref{Blocking}.
-The @value{op-read-full-records} option is turned on by default when
+The @option{--read-full-records} (@option{-B}) option is turned on by default when
@command{tar} reads an archive from standard input, or from a remote
machine. This is because on BSD Unix systems, attempting to read a
pipe returns however much happens to be in the pipe, even if it is
would fail as soon as it read an incomplete record from the pipe.
If you're not sure of the blocking factor of an archive, you can
-read the archive by specifying @value{op-read-full-records} and
-@value{op-blocking-factor}, using a blocking factor larger than what the
-archive uses. This lets you avoid having to determine the blocking factor
-of an archive. @value{xref-blocking-factor}.
+read the archive by specifying @option{--read-full-records} (@option{-B}) and
+@option{--blocking-factor=@var{512-size}} (@option{-b
+@var{512-size}}), using a blocking factor larger than what the archive
+uses. This lets you avoid having to determine the blocking factor
+of an archive. @xref{Blocking Factor}.
@menu
* read full records::
@FIXME{need sentence or so of intro here}
-@table @kbd
+@table @option
+@opindex read-full-records
@item --read-full-records
@item -B
-Use in conjunction with @value{op-extract} to read an archive which
-contains incomplete records, or one which has a blocking factor less
-than the one specified.
+Use in conjunction with @option{--extract} (@option{--get},
+@option{-x}) to read an archive which contains incomplete records, or
+one which has a blocking factor less than the one specified.
@end table
@node Ignore Zeros
@unnumberedsubsubsec Ignoring Blocks of Zeros
+@cindex End-of-archive blocks, ignoring
+@cindex Ignoring end-of-archive blocks
+@opindex ignore-zeros
Normally, @command{tar} stops reading when it encounters a block of zeros
between file entries (which usually indicates the end of the archive).
-@value{op-ignore-zeros} allows @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
-together).
+@option{--ignore-zeros} (@option{-i}) allows @command{tar} to
+completely read an archive which contains a block of zeros before the
+end (i.e., a damaged archive, or one that was created by concatenating
+several archives together).
-The @value{op-ignore-zeros} option is turned off by default because many
+The @option{--ignore-zeros} (@option{-i}) option is turned off by default because many
versions of @command{tar} write garbage after the end-of-archive entry,
since that part of the media is never supposed to be read. @GNUTAR{}
does not write after the end of an archive, but seeks to
maintain compatiblity among archiving utilities.
-@table @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}.
+@option{--extract} or @option{--list}.
@end table
@node Writing
@subsection Changing How @command{tar} Writes Files
-@cindex Overwriting old files, prevention
-@cindex Protecting old files
-@cindex Modification times of extracted files
-@cindex Permissions of extracted files
-@cindex Modes of extracted files
-@cindex Writing extracted files to standard output
-@cindex Standard output, writing extracted files to
@UNREVISED
-@FIXME{need to mention the brand new option, --backup}
+@FIXME{Introductory paragraph}
@menu
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
+* Directory Modification Times and Permissions::
* Writing to Standard Output::
+* Writing to an External Program::
* remove files::
@end menu
@node Dealing with Old Files
@unnumberedsubsubsec Options Controlling the Overwriting of Existing Files
+@opindex overwrite-dir, introduced
When extracting files, if @command{tar} discovers that the extracted
file already exists, it normally replaces the file by removing it before
extracting it, to prevent confusion in the presence of hard or symbolic
default behavior. To be more cautious and preserve the metadata of
such a directory, use the @option{--no-overwrite-dir} option.
+@cindex Overwriting old files, prevention
+@opindex keep-old-files, introduced
To be even more cautious and prevent existing files from being replaced, use
-the @value{op-keep-old-files} option. It causes @command{tar} to refuse
+the @option{--keep-old-files} (@option{-k}) option. It causes @command{tar} to refuse
to replace or update a file that already exists, i.e., a file with the
same name as an archive member prevents extraction of that archive
member. Instead, it reports an error.
+@opindex overwrite, introduced
To be more aggressive about altering existing files, use the
-@value{op-overwrite} option. It causes @command{tar} to overwrite
+@option{--overwrite} option. It causes @command{tar} to overwrite
existing files and to follow existing symbolic links when extracting.
+@cindex Protecting old files
Some people argue that @GNUTAR{} should not hesitate
to overwrite files with other files when extracting. When extracting
a @command{tar} archive, they expect to see a faithful copy of the
-state of the filesystem when the archive was created. It is debatable
+state of the file system when the archive was created. It is debatable
that this would always be a proper behavior. For example, suppose one
has an archive in which @file{usr/local} is a link to
@file{usr/local2}. Since then, maybe the site removed the link and
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
+@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
+example, but @emph{only if} @option{--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
+@opindex unlink-first, introduced
+Finally, the @option{--unlink-first} (@option{-U}) option can improve performance in
some cases by causing @command{tar} to remove files unconditionally
before extracting them.
@node Overwrite Old Files
@unnumberedsubsubsec Overwrite Old Files
-@table @kbd
+@table @option
+@opindex overwrite
@item --overwrite
Overwrite existing files and directory metadata when extracting files
from an archive.
-This
-causes @command{tar} to write extracted files into the file system without
+This causes @command{tar} to write extracted files into the file system without
regard to the files already on the system; i.e., files with the same
names as archive members are overwritten when the archive is extracted.
It also causes @command{tar} to extract the ownership, permissions,
empty directories and even symbolic links are automatically removed if
they are in the way of extraction.
-Be careful when using the @value{op-overwrite} option, particularly when
-combined with the @value{op-absolute-names} option, as this combination
+Be careful when using the @option{--overwrite} option, particularly when
+combined with the @option{--absolute-names} (@option{-P}) option, as this combination
can change the contents, ownership or permissions of any file on your
system. Also, many systems do not take kindly to overwriting files that
are currently being executed.
+@opindex overwrite-dir
@item --overwrite-dir
Overwrite the metadata of directories when extracting files from an
archive, but remove other files before extracting.
@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
-@table @kbd
+@table @option
+@opindex keep-old-files
@item --keep-old-files
@itemx -k
Do not replace existing files from archive. The
-@value{op-keep-old-files} option prevents @command{tar} from replacing
-existing files with files with the same name from the archive.
-The @value{op-keep-old-files} option is meaningless with @value{op-list}.
-Prevents @command{tar} from replacing files in the file system during
-extraction.
+@option{--keep-old-files} (@option{-k}) option prevents @command{tar}
+from replacing existing files with files with the same name from the
+archive. The @option{--keep-old-files} option is meaningless with
+@option{--list} (@option{-t}). Prevents @command{tar} from replacing
+files in the file system during extraction.
@end table
-@node Unlink First
+@node Keep Newer Files
+@unnumberedsubsubsec Keep Newer Files
+
+@table @option
+@opindex keep-newer-files
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive
+copies. This option is meaningless with @option{--list} (@option{-t}).
+@end table
+
+@node Unlink First
@unnumberedsubsubsec Unlink First
-@table @kbd
+@table @option
+@opindex unlink-first
@item --unlink-first
@itemx -U
Remove files before extracting over them.
@node Recursive Unlink
@unnumberedsubsubsec Recursive Unlink
-@table @kbd
+@table @option
+@opindex recursive-unlink
@item --recursive-unlink
When this option is specified, try removing files and directory hierarchies
before extracting over them. @emph{This is a dangerous option!}
@end table
-If you specify the @value{op-recursive-unlink} option,
+If you specify the @option{--recursive-unlink} option,
@command{tar} removes @emph{anything} that keeps you from extracting a file
as far as current permissions will allow it. This could include removal
of the contents of a full directory hierarchy.
-@node Modification Times
-@unnumberedsubsubsec Setting Modification Times
+@node Data Modification Times
+@unnumberedsubsubsec Setting Data Modification Times
-Normally, @command{tar} sets the modification times of extracted files to
-the modification times recorded for the files in the archive, but
+@cindex Data modification times of extracted files
+@cindex Modification times of extracted files
+Normally, @command{tar} sets the data modification times of extracted
+files to the corresponding times recorded for the files in the archive, but
limits the permissions of extracted files by the current @code{umask}
setting.
-To set the modification times of extracted files to the time when
-the files were extracted, use the @value{op-touch} option in
-conjunction with @value{op-extract}.
+To set the data modification times of extracted files to the time when
+the files were extracted, use the @option{--touch} (@option{-m}) option in
+conjunction with @option{--extract} (@option{--get}, @option{-x}).
-@table @kbd
+@table @option
+@opindex touch
@item --touch
@itemx -m
-Sets the modification time of extracted archive members to the time
+Sets the data modification time of extracted archive members to the time
they were extracted, not the time recorded for them in the archive.
-Use in conjunction with @value{op-extract}.
+Use in conjunction with @option{--extract} (@option{--get}, @option{-x}).
@end table
@node Setting Access Permissions
@unnumberedsubsubsec Setting Access Permissions
+@cindex Permissions of extracted files
+@cindex Modes of extracted files
To set the modes (access permissions) of extracted files to those
-recorded for those files in the archive, use @samp{--same-permissions}
-in conjunction with the @value{op-extract} operation. @FIXME{Should be
-aliased to ignore-umask.}
+recorded for those files in the archive, use @option{--same-permissions}
+in conjunction with the @option{--extract} (@option{--get},
+@option{-x}) operation. @FIXME{Should be aliased to ignore-umask.}
-@table @kbd
+@table @option
+@opindex preserve-permission
+@opindex same-permission
@item --preserve-permission
@itemx --same-permission
-@itemx --ignore-umask
+@c @itemx --ignore-umask
@itemx -p
Set modes of extracted archive members to those recorded in the
archive, instead of current umask settings. Use in conjunction with
-@value{op-extract}.
+@option{--extract} (@option{--get}, @option{-x}).
@end table
-@FIXME{Following paragraph needs to be rewritten: why doesn't this cat
-files together, why is this useful. is it really useful with
-more than one file?}
+@node Directory Modification Times and Permissions
+@unnumberedsubsubsec Directory Modification Times and Permissions
+
+After sucessfully extracting a file member, @GNUTAR{} normally
+restores its permissions and modification times, as described in the
+previous sections. This cannot be done for directories, because
+after extracting a directory @command{tar} will almost certainly
+extract files into that directory and this will cause the directory
+modification time to be updated. Moreover, restoring that directory
+permissions may not permit file creation within it. Thus, restoring
+directory permissions and modification times must be delayed at least
+until all files have been extracted into that directory. @GNUTAR{}
+restores directories using the following approach.
+
+The extracted directories are created with the mode specified in the
+archive, as modified by the umask of the user, which gives sufficient
+permissions to allow file creation. The meta-information about the
+directory is recorded in the temporary list of directories. When
+preparing to extract next archive member, @GNUTAR{} checks if the
+directory prefix of this file contains the remembered directory. If
+it does not, the program assumes that all files have been extracted
+into that directory, restores its modification time and permissions
+and removes its entry from the internal list. This approach allows
+to correctly restore directory meta-information in the majority of
+cases, while keeping memory requirements sufficiently small. It is
+based on the fact, that most @command{tar} archives use the predefined
+order of members: first the directory, then all the files and
+subdirectories in that directory.
+
+However, this is not always true. The most important exception are
+incremental archives (@pxref{Incremental Dumps}). The member order in
+an incremental archive is reversed: first all directory members are
+stored, followed by other (non-directory) members. So, when extracting
+from incremental archives, @GNUTAR{} alters the above procedure. It
+remebers all restored directories, and restores their meta-data
+only after the entire archive has been processed. Notice, that you do
+not need to specity any special options for that, as @GNUTAR{}
+automatically detects archives in incremental format.
+
+There may be cases, when such processing is required for normal archives
+too. Consider the following example:
+
+@smallexample
+@group
+$ @kbd{tar --no-recursion -cvf archive \
+ foo foo/file1 bar bar/file foo/file2}
+foo/
+foo/file1
+bar/
+bar/file
+foo/file2
+@end group
+@end smallexample
+
+During the normal operation, after encountering @file{bar}
+@GNUTAR{} will assume that all files from the directory @file{foo}
+were already extracted and will therefore restore its timestamp and
+permission bits. However, after extracting @file{foo/file2} the
+directory timestamp will be offset again.
+
+To correctly restore directory meta-information in such cases, use
+@option{delay-directory-restore} command line option:
+
+@table @option
+@opindex delay-directory-restore
+@item --delay-directory-restore
+Delays restoring of the modification times and permissions of extracted
+directories until the end of extraction. This way, correct
+meta-information is restored even if the archive has unusual member
+ordering.
+
+@opindex no-delay-directory-restore
+@item --no-delay-directory-restore
+Cancel the effect of the previous @option{--delay-directory-restore}.
+Use this option if you have used @option{--delay-directory-restore} in
+@env{TAR_OPTIONS} variable (@pxref{TAR_OPTIONS}) and wish to
+temporarily disable it.
+@end table
@node Writing to Standard Output
@unnumberedsubsubsec Writing to Standard Output
+@cindex Writing extracted files to standard output
+@cindex Standard output, writing extracted files to
To write the extracted files to the standard output, instead of
-creating the files on the file system, use @value{op-to-stdout} in
-conjunction with @value{op-extract}. This option is useful if you are
+creating the files on the file system, use @option{--to-stdout} (@option{-O}) in
+conjunction with @option{--extract} (@option{--get}, @option{-x}). This option is useful if you are
extracting files to send them through a pipe, and do not need to
preserve them in the file system. If you extract multiple members,
they appear on standard output concatenated, in the order they are
found in the archive.
-@table @kbd
+@table @option
+@opindex to-stdout
@item --to-stdout
@itemx -O
-Writes files to the standard output. Used in conjunction with
-@value{op-extract}. Extract files to standard output. When this option
-is used, instead of creating the files specified, @command{tar} writes
+Writes files to the standard output. Use only in conjunction with
+@option{--extract} (@option{--get}, @option{-x}). When this option is
+used, instead of creating the files specified, @command{tar} writes
the contents of the files extracted to its standard output. This may
be useful if you are only extracting the files in order to send them
-through a pipe. This option is meaningless with @value{op-list}.
+through a pipe. This option is meaningless with @option{--list}
+(@option{-t}).
@end table
This can be useful, for example, if you have a tar archive containing
tar -xOzf foo.tgz bigfile1 bigfile2 | process
@end smallexample
+Hovewer, @option{--to-command} may be more convenient for use with
+multiple files. See the next section.
+
+@node Writing to an External Program
+@unnumberedsubsubsec Writing to an External Program
+
+You can instruct @command{tar} to send the contents of each extracted
+file to the standard input of an external program:
+
+@table @option
+@opindex to-program
+@item --to-program=@var{command}
+Extract files and pipe their contents to the standard input of
+@var{command}. When this option is used, instead of creating the
+files specified, @command{tar} invokes @var{command} and pipes the
+contents of the files to its standard output. @var{Command} may
+contain command line arguments. The program is executed via
+@code{sh -c}. Notice, that @var{command} is executed once for each regular file
+extracted. Non-regular files (directories, etc.) are ignored when this
+option is used.
+@end table
+
+The command can obtain the information about the file it processes
+from the following environment variables:
+
+@table @var
+@vrindex TAR_FILETYPE, to-command environment
+@item TAR_FILETYPE
+Type of the file. It is a single letter with the following meaning:
+
+@multitable @columnfractions 0.10 0.90
+@item f @tab Regular file
+@item d @tab Directory
+@item l @tab Symbolic link
+@item h @tab Hard link
+@item b @tab Block device
+@item c @tab Character device
+@end multitable
+
+Currently only regular files are supported.
+
+@vrindex TAR_MODE, to-command environment
+@item TAR_MODE
+File mode, an octal number.
+
+@vrindex TAR_FILENAME, to-command environment
+@item TAR_FILENAME
+The name of the file.
+
+@vrindex TAR_REALNAME, to-command environment
+@item TAR_REALNAME
+Name of the file as stored in the archive.
+
+@vrindex TAR_UNAME, to-command environment
+@item TAR_UNAME
+Name of the file owner.
+
+@vrindex TAR_GNAME, to-command environment
+@item TAR_GNAME
+Name of the file owner group.
+
+@vrindex TAR_ATIME, to-command environment
+@item TAR_ATIME
+Time of last access. It is a decimal number, representing seconds
+since the epoch. If the archive provides times with nanosecond
+precision, the nanoseconds are appended to the timestamp after a
+decimal point.
+
+@vrindex TAR_MTIME, to-command environment
+@item TAR_MTIME
+Time of last modification.
+
+@vrindex TAR_CTIME, to-command environment
+@item TAR_CTIME
+Time of last status change.
+
+@vrindex TAR_SIZE, to-command environment
+@item TAR_SIZE
+Size of the file.
+
+@vrindex TAR_UID, to-command environment
+@item TAR_UID
+UID of the file owner.
+
+@vrindex TAR_GID, to-command environment
+@item TAR_GID
+GID of the file owner.
+@end table
+
+In addition to these variables, @env{TAR_VERSION} contains the
+@GNUTAR{} version number.
+
+If @var{command} exits with a non-0 status, @command{tar} will print
+an error message similar to the following:
+
+@smallexample
+tar: 2345: Child returned status 1
+@end smallexample
+
+Here, @samp{2345} is the PID of the finished process.
+
+If this behavior is not wanted, use @option{--ignore-command-error}:
+
+@table @option
+@opindex ignore-command-error
+@item --ignore-command-error
+Ignore exit codes of subprocesses. Notice that if the program
+exits on signal or otherwise terminates abnormally, the error message
+will be printed even if this option is used.
+
+@opindex no-ignore-command-error
+@item --no-ignore-command-error
+Cancel the effect of any previous @option{--ignore-command-error}
+option. This option is useful if you have set
+@option{--ignore-command-error} in @env{TAR_OPTIONS}
+(@pxref{TAR_OPTIONS}) and wish to temporarily cancel it.
+@end table
+
@node remove files
@unnumberedsubsubsec Removing Files
option goes in this section. i have no idea; i only know it's nowhere
else in the book...}
-@table @kbd
+@table @option
+@opindex remove-files
@item --remove-files
Remove files after adding them to the archive.
@end table
@node Scarce
@subsection Coping with Scarce Resources
-@cindex Middle of the archive, starting in the
-@cindex Running out of space during extraction
-@cindex Disk space, running out of
-@cindex Space on the disk, recovering from lack of
@UNREVISED
+@cindex Small memory
+@cindex Running out of space
+
@menu
* Starting File::
* Same Order::
@node Starting File
@unnumberedsubsubsec Starting File
-@table @kbd
+@table @option
+@opindex starting-file
@item --starting-file=@var{name}
@itemx -K @var{name}
Starts an operation in the middle of an archive. Use in conjunction
-with @value{op-extract} or @value{op-list}.
+with @option{--extract} (@option{--get}, @option{-x}) or @option{--list} (@option{-t}).
@end table
+@cindex Middle of the archive, starting in the
If a previous attempt to extract files failed due to lack of disk
-space, you can use @value{op-starting-file} to start extracting only
-after member @var{name} of the archive. This assumes, of course, that
-there is now free space, or that you are now extracting into a
-different file system. (You could also choose to suspend @command{tar},
-remove unnecessary files from the file system, and then restart the
-same @command{tar} operation. In this case, @value{op-starting-file} is
-not necessary. @value{xref-incremental}, @value{xref-interactive},
-and @value{ref-exclude}.)
+space, you can use @option{--starting-file=@var{name}} (@option{-K
+@var{name}}) to start extracting only after member @var{name} of the
+archive. This assumes, of course, that there is now free space, or
+that you are now extracting into a different file system. (You could
+also choose to suspend @command{tar}, remove unnecessary files from
+the file system, and then restart the same @command{tar} operation.
+In this case, @option{--starting-file} is not necessary.
+@xref{Incremental Dumps}, @xref{interactive}, and @ref{exclude}.)
@node Same Order
@unnumberedsubsubsec Same Order
-@table @kbd
+@table @option
+@cindex Large lists of file names on small machines
+@opindex same-order
+@opindex preserve-order
@item --same-order
@itemx --preserve-order
@itemx -s
To process large lists of file names on machines with small amounts of
-memory. Use in conjunction with @value{op-compare},
-@value{op-list}
-or @value{op-extract}.
+memory. Use in conjunction with @option{--compare} (@option{--diff},
+@option{-d}), @option{--list} (@option{-t}) or @option{--extract}
+(@option{--get}, @option{-x}).
@end table
-@FIXME{we don't need/want --preserve to exist any more (from melissa:
-ie, don't want that *version* of the option to exist, or don't want
-the option to exist in either version?}
-
-@FIXME{i think this explanation is lacking.}
-
-The @value{op-same-order} option tells @command{tar} that the list of file
+The @option{--same-order} (@option{--preserve-order}, @option{-s}) option tells @command{tar} that the list of file
names to be listed or extracted is sorted in the same order as the
files in the archive. This allows a large list of names to be used,
even on a small machine that would not otherwise be able to hold all
file are kept.
@table @samp
-
@item --backup[=@var{method}]
-@opindex --backup
+@opindex backup
@vindex VERSION_CONTROL
@cindex backups
Back up files that are about to be overwritten or removed.
@table @samp
@item t
@itemx numbered
-@opindex numbered @r{backup method}
+@cindex numbered @r{backup method}
Always make numbered backups.
@item nil
@itemx existing
-@opindex existing @r{backup method}
+@cindex existing @r{backup method}
Make numbered backups of files that already have them, simple backups
of the others.
@item never
@itemx simple
-@opindex simple @r{backup method}
+@cindex simple @r{backup method}
Always make simple backups.
@end table
@item --suffix=@var{suffix}
-@opindex --suffix
+@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.
@end table
-Some people express the desire to @emph{always} use the @value{op-backup}
+Some people express the desire to @emph{always} use the @option{--backup}
option, by defining some kind of alias or script. This is not as easy
as one may think, due to the fact that old style options should appear first
and consume arguments a bit unpredictably for an alias or script. But,
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
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.
-@value{xref-files-from}.
+@xref{files}.
There are various ways of causing @command{tar} to skip over some files,
and not archive them. @xref{Choosing}.
ftp://ftp.cs.umd.edu/pub/amanda
@end smallexample
-@ifclear PUBLISH
+@FIXME{
Here is a possible plan for a future documentation about the backuping
scripts which are provided within the @GNUTAR{}
distribution.
-@smallexample
-.* dumps
-. + what are dumps
-
-. + different levels of dumps
-. - full dump = dump everything
-. - level 1, level 2 dumps etc, -
- A level n dump dumps everything changed since the last level
- n-1 dump (?)
-
-. + how to use scripts for dumps (ie, the concept)
-. - scripts to run after editing backup specs (details)
-
-. + Backup Specs, what is it.
-. - how to customize
-. - actual text of script [/sp/dump/backup-specs]
-
-. + Problems
-. - rsh doesn't work
-. - rtape isn't installed
-. - (others?)
-
-. + the --incremental option of tar
-
-. + tapes
-. - write protection
-. - types of media
-. : different sizes and types, useful for different things
-. - files and tape marks
+@itemize @bullet
+@item dumps
+ @itemize @minus
+ @item what are dumps
+ @item different levels of dumps
+ @itemize +
+ @item full dump = dump everything
+ @item level 1, level 2 dumps etc
+ A level @var{n} dump dumps everything changed since the last level
+ @var{n}-1 dump (?)
+ @end itemize
+ @item how to use scripts for dumps (ie, the concept)
+ @itemize +
+ @item scripts to run after editing backup specs (details)
+ @end itemize
+ @item Backup Specs, what is it.
+ @itemize +
+ @item how to customize
+ @item actual text of script [/sp/dump/backup-specs]
+ @end itemize
+ @item Problems
+ @itemize +
+ @item rsh doesn't work
+ @item rtape isn't installed
+ @item (others?)
+ @end itemize
+ @item the @option{--incremental} option of tar
+ @item tapes
+ @itemize +
+ @item write protection
+ @item types of media, different sizes and types, useful for different things
+ @item files and tape marks
one tape mark between files, two at end.
-. - positioning the tape
+ @item positioning the tape
MT writes two at end of write,
- backspaces over one when writing again.
-@end smallexample
-
-@end ifclear
+ backspaces over one when writing again.
+ @end itemize
+ @end itemize
+@end itemize
+}
-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
@menu
* Full Dumps:: Using @command{tar} to Perform Full Dumps
-* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
@cindex corrupted archives
Full dumps should only be made when no other people or programs
-are modifying files in the filesystem. If files are modified while
+are modifying files in the file system. If files are modified while
@command{tar} is making the backup, they may not be stored properly in
the archive, in which case you won't be able to restore them if you
have to. (Files not being modified are written with no trouble, and do
not corrupt the entire archive.)
-You will want to use the @value{op-label} option to give the archive a
+You will want to use the @option{--label=@var{archive-label}}
+(@option{-V @var{archive-label}}) option to give the archive a
volume label, so you can tell what this archive is even if the label
falls off the tape, or anything like that.
-Unless the filesystem you are dumping is guaranteed to fit on
-one volume, you will need to use the @value{op-multi-volume} option.
+Unless the file system you are dumping is guaranteed to fit on
+one volume, you will need to use the @option{--multi-volume} (@option{-M}) option.
Make sure you have enough tapes on hand to complete the backup.
-If you want to dump each filesystem separately you will need to use
-the @value{op-one-file-system} option to prevent @command{tar} from crossing
-filesystem boundaries when storing (sub)directories.
+If you want to dump each file system separately you will need to use
+the @option{--one-file-system} (@option{-l}) option to prevent
+@command{tar} from crossing file system boundaries when storing
+(sub)directories.
-The @value{op-incremental} option is not needed, since this is a complete
-copy of everything in the filesystem, and a full restore from this
-backup would only be done onto a completely empty disk.
+The @option{--incremental} (@option{-G}) (@pxref{Incremental Dumps})
+option is not needed, since this is a complete copy of everything in
+the file system, and a full restore from this backup would only be
+done onto a completely
+empty disk.
Unless you are in a hurry, and trust the @command{tar} program (and your
-tapes), it is a good idea to use the @value{op-verify} option, to make
-sure your files really made it onto the dump properly. This will
-also detect cases where the file was modified while (or just after)
-it was being archived. Not all media (notably cartridge tapes) are
-capable of being verified, unfortunately.
-
-@value{op-listed-incremental} take a file name argument always. If the
-file doesn't exist, run a level zero dump, creating the file. If the
-file exists, uses that file to see what has changed.
-
-@value{op-incremental} @FIXME{look it up}
-
-@value{op-incremental} handle old @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}
-writes, at the beginning of the archive, an entry for each of the
-directories that will be operated on. The entry for a directory
-includes a list of all the files in the directory at the time the
-dump was done, and a flag for each file indicating whether the file
-is going to be put in the archive. This information is used when
-doing a complete incremental restore.
-
-Note that this option causes @command{tar} to create a non-standard
-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-extract}, then
-when the entry for a directory is found, all files that currently
-exist in that directory but are not listed in the archive @emph{are
-deleted from the directory}.
-
-This behavior is convenient when you are restoring a damaged file
-system from a succession of incremental backups: it restores the
-entire state of the file system to that which obtained when the backup
-was made. If you don't use @value{op-incremental}, the file system will
-probably fill up with files that shouldn't exist any more.
-
-@value{op-listed-incremental} handle new @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
-used in conjunction with @value{op-create} will also cause @command{tar} to
-use the file @var{file}, which contains information about the state
-of the filesystem at the time of the last backup, to decide which
-files to include in the archive being created. That file will then
-be updated by @command{tar}. If the file @var{file} does not exist when
-this option is specified, @command{tar} will create it, and include all
-appropriate files in the archive.
-
-The file, which is archive independent, contains the date it was last
-modified and a list of devices, inode numbers and directory names.
-@command{tar} will archive files with newer mod dates or inode change
-times, and directories with an unchanged inode number and device but
-a changed directory name. The file is updated after the files to
-be archived are determined, but before the new archive is actually
-created.
-
-@node Inc Dumps
+tapes), it is a good idea to use the @option{--verify} (@option{-W})
+option, to make sure your files really made it onto the dump properly.
+This will also detect cases where the file was modified while (or just
+after) it was being archived. Not all media (notably cartridge tapes)
+are capable of being verified, unfortunately.
+
+@node Incremental Dumps
@section Using @command{tar} to Perform Incremental Dumps
-@UNREVISED
-@cindex incremental dumps
-@cindex dumps, incremental
+@dfn{Incremental backup} is a special form of @GNUTAR{} archive that
+stores additional metadata so that exact state of the file system
+can be restored when extracting the archive.
-Performing incremental dumps is similar to performing full dumps,
-although a few more options will usually be needed.
+@GNUTAR{} currently offers two options for handling incremental
+backups: @option{--listed-incremental=@var{snapshot-file}} (@option{-g
+@var{snapshot-file}}) and @option{--incremental} (@option{-G}).
-A standard scheme is to do a @emph{monthly} (full) dump once a month,
-a @emph{weekly} dump once a week of everything since the last monthly
-and a @emph{daily} every day of everything since the last (weekly or
-monthly) dump.
+@opindex listed-incremental
+The option @option{--listed-incremental} instructs tar to operate on
+an incremental archive with additional metadata stored in a standalone
+file, called a @dfn{snapshot file}. The purpose of this file is to help
+determine which files have been changed, added or deleted since the
+last backup, so that the next incremental backup will contain only
+modified files. The name of the snapshot file is given as an argument
+to the option:
-Here is a sample script to dump the directory hierarchies @samp{/usr}
-and @samp{/var}.
+@table @option
+@item --listed-incremental=@var{file}
+@itemx -g @var{file}
+ Handle incremental backups with snapshot data in @var{file}.
+@end table
+
+To create an incremental backup, you would use
+@option{--listed-incremental} together with @option{--create}
+(@pxref{create}). For example:
@smallexample
-#! /bin/sh
-tar --create \
- --blocking-factor=126 \
- --file=/dev/rmt/0 \
- --label="`hostname` /usr /var `date +%Y-%m-%d`" \
- --listed-incremental=/var/log/usr-var.snar \
- --verbose \
- /usr /var
+$ @kbd{tar --create \
+ --file=archive.1.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
@end smallexample
-This script uses the file @file{/var/log/usr-var.snar} as a snapshot to
-store information about the previous tar dump.
+This will create in @file{archive.1.tar} an incremental backup of
+the @file{/usr} file system, storing additional metadata in the file
+@file{/var/log/usr.snar}. If this file does not exist, it will be
+created. The created archive will then be a @dfn{level 0 backup};
+please see the next section for more on backup levels.
-The blocking factor 126 is an attempt to make the tape drive stream.
-Some tape devices cannot handle 64 kB blocks or larger, and require the
-block size to be a multiple of 1 kB; for these devices, 126 is the
-largest blocking factor that can be used.
+Otherwise, if the file @file{/var/log/usr.snar} exists, it
+determines which files are modified. In this case only these files will be
+stored in the archive. Suppose, for example, that after running the
+above command, you delete file @file{/usr/doc/old} and create
+directory @file{/usr/local/db} with the following contents:
-@node incremental and listed-incremental
-@section The Incremental Options
-@UNREVISED
+@smallexample
+$ @kbd{ls /usr/local/db}
+/usr/local/db/data
+/usr/local/db/index
+@end smallexample
+
+Some time later you create another incremental backup. You will
+then see:
-@value{op-incremental} is used in conjunction with @value{op-create},
-@value{op-extract} or @value{op-list} when backing up and restoring file
-systems. An archive cannot be extracted or listed with the
-@value{op-incremental} option specified unless it was created with the
-option specified. This option should only be used by a script, not by
-the user, and is usually disregarded in favor of
-@value{op-listed-incremental}, which is described below.
-
-@value{op-incremental} in conjunction with @value{op-create} causes
-@command{tar} to write, at the beginning of the archive, an entry for
-each of the directories that will be archived. The entry for a
-directory includes a list of all the files in the directory at the
-time the archive was created and a flag for each file indicating
-whether or not the file is going to be put in the archive.
-
-Note that this option causes @command{tar} to create a non-standard
-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
-in the archive, @emph{delete} files in the file system that did not
-exist in their directories when the archive was created, and then
-extract the files in the archive.
-
-This behavior is convenient when restoring a damaged file system from
-a succession of incremental backups: it restores the entire state of
-the file system to that which obtained when the backup was made. If
-@value{op-incremental} isn't specified, the file system will probably
-fill up with files that shouldn't exist any more.
-
-@value{op-incremental} in conjunction with @value{op-list} causes
-@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-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @command{tar}
-to use the file @var{snapshot-file}, which contains information about
-the state of the file system at the time of the last backup, to decide
-which files to include in the archive being created. That file will
-then be updated by @command{tar}. If the file @var{file} does not exist
-when this option is specified, @command{tar} will create it, and include
-all appropriate files in the archive.
-
-The file @var{file}, which is archive independent, contains the date
-it was last modified and a list of devices, inode numbers and
-directory names. @command{tar} will archive files with newer mod dates
-or inode change times, and directories with an unchanged inode number
-and device but a changed directory name. The file is updated after
-the files to be archived are determined, but before the new archive is
-actually created.
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+tar: usr/local/db: Directory is new
+usr/local/db/
+usr/local/db/data
+usr/local/db/index
+@end smallexample
+
+@noindent
+The created archive @file{archive.2.tar} will contain only these
+three members. This archive is called a @dfn{level 1 backup}. Notice
+that @file{/var/log/usr.snar} will be updated with the new data, so if
+you plan to create more @samp{level 1} backups, it is necessary to
+create a working copy of the snapshot file before running
+@command{tar}. The above example will then be modified as follows:
+
+@smallexample
+$ @kbd{cp /var/log/usr.snar /var/log/usr.snar-1}
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar-1 \
+ /usr}
+@end smallexample
Incremental dumps depend crucially on time stamps, so the results are
-unreliable if you modify a file's time stamps during dumping (e.g.@:
-with the @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=replace} option), or if you set the clock
backwards.
-Despite it should be obvious that a device has a non-volatile value, NFS
-devices have non-dependable values when an automounter gets in the picture.
-This led to a great deal of spurious redumping in incremental dumps,
-so it is somewhat useless to compare two NFS devices numbers over time.
-So @command{tar} now considers all NFS devices as being equal when it comes
-to comparing directories; this is fairly gross, but there does not seem
+Metadata stored in snapshot files include device numbers, which,
+obviously is supposed to be a non-volatile value. However, it turns
+out that NFS devices have undependable values when an automounter
+gets in the picture. This can lead to a great deal of spurious
+redumping in incremental dumps, so it is somewhat useless to compare
+two NFS devices numbers over time. The solution implemented currently
+is to considers all NFS devices as being equal when it comes to
+comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
-@command{tar} doesn't access @var{snapshot-file} when
-@value{op-create} 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}.
+Note that incremental archives use @command{tar} extensions and may
+not be readable by non-@acronym{GNU} versions of the @command{tar} program.
+
+@opindex listed-incremental, using with @option{--extract}
+@opindex extract, using with @option{--listed-incremental}
+To extract from the incremental dumps, use
+@option{--listed-incremental} together with @option{--extract}
+option (@pxref{extracting files}). In this case, @command{tar} does
+not need to access snapshot file, since all the data necessary for
+extraction are stored in the archive itself. So, when extracting, you
+can give whatever argument to @option{--listed-incremental}, the usual
+practice is to use @option{--listed-incremental=/dev/null}.
+Alternatively, you can use @option{--incremental}, which needs no
+arguments. In general, @option{--incremental} (@option{-G}) can be
+used as a shortcut for @option{--listed-incremental} when listing or
+extracting incremental backups (for more information, regarding this
+option, @pxref{incremental-op}).
+
+When extracting from the incremental backup @GNUTAR{} attempts to
+restore the exact state the file system had when the archive was
+created. In particular, it will @emph{delete} those files in the file
+system that did not exist in their directories when the archive was
+created. If you have created several levels of incremental files,
+then in order to restore the exact contents the file system had when
+the last level was created, you will need to restore from all backups
+in turn. Continuing our example, to restore the state of @file{/usr}
+file system, one would do@footnote{Notice, that since both archives
+were created withouth @option{-P} option (@pxref{absolute}), these
+commands should be run from the root file system.}:
-@FIXME{this section needs to be written}
+@smallexample
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.1.tar}
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.2.tar}
+@end smallexample
+
+To list the contents of an incremental archive, use @option{--list}
+(@pxref{list}), as usual. To obtain more information about the
+archive, use @option{--listed-incremental} or @option{--incremental}
+combined with two @option{--verbose} options@footnote{Two
+@option{--verbose} options were selected to avoid breaking usual
+verbose listing output (@option{--list --verbose}) when using in
+scripts.
+
+@opindex incremental, using with @option{--list}
+@opindex listed-incremental, using with @option{--list}
+@opindex list, using with @option{--incremental}
+@opindex list, using with @option{--listed-incremental}
+Versions of @GNUTAR{} up to 1.15.1 used to dump verbatim binary
+contents of the DUMPDIR header (with terminating nulls) when
+@option{--incremental} or @option{--listed-incremental} option was
+given, no matter what the verbosity level. This behavior, and,
+especially, the binary output it produced were considered incovenient
+and were changed in version 1.16}:
+
+@smallexample
+@kbd{tar --list --incremental --verbose --verbose archive.tar}
+@end smallexample
+
+This command will print, for each directory in the archive, the list
+of files in that directory at the time the archive was created. This
+information is put out in a format which is both human-readable and
+unambiguous for a program: each file name is printed as
+
+@smallexample
+@var{x} @var{file}
+@end smallexample
+
+@noindent
+where @var{x} is a letter describing the status of the file: @samp{Y}
+if the file is present in the archive, @samp{N} if the file is not
+included in the archive, or a @samp{D} if the file is a directory (and
+is included in the archive).@FIXME-xref{dumpdir format}. Each such
+line is terminated by a newline character. The last line is followed
+by an additional newline to indicate the end of the data.
+
+@anchor{incremental-op}The option @option{--incremental} (@option{-G})
+gives the same behavior as @option{--listed-incremental} when used
+with @option{--list} and @option{--extract} options. When used with
+@option{--create} option, it creates an incremental archive without
+creating snapshot file. Thus, it is impossible to create several
+levels of incremental backups with @option{--incremental} option.
@node Backup Levels
@section Levels of Backups
-@UNREVISED
An archive containing all the files in the file system is called a
@dfn{full backup} or @dfn{full dump}. You could insure your data by
are daily re-archived.
It is more efficient to do a full dump only occasionally. To back up
-files between full dumps, you can a incremental dump. A @dfn{level
+files between full dumps, you can use @dfn{incremental dumps}. A @dfn{level
one} dump archives all the files that have changed since the last full
dump.
more than once a day is usually not worth the trouble).
@GNUTAR{} 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.
+and level-one (actually, even level-two and so on) dumps. Using
+scripts (shell programs) to perform backups and restoration is a
+convenient and reliable alternative to typing out file name lists
+and @command{tar} commands by hand.
Before you use these scripts, you need to edit the file
@file{backup-specs}, which specifies parameters used by the backup
-scripts and by the restore script. @FIXME{There is no such restore
-script!}@FIXME-xref{Script Syntax}Once the backup parameters
-are set, you can perform backups or restoration by running the
-appropriate script.
-
-The name of the restore script is @code{restore}. @FIXME{There is
-no such restore script!}The names of the level one and full backup
-scripts are, respectively, @code{level-1} and @code{level-0}.
-The @code{level-0} script also exists under the name @code{weekly}, and
-the @code{level-1} under the name @code{daily}---these additional names
-can be changed according to your backup schedule. @FIXME-xref{Scripted
-Restoration, for more information on running the restoration script.}
-@FIXME-xref{Scripted Backups, for more information on running the
-backup scripts.}
-
-@emph{Please Note:} The backup scripts and the restoration scripts are
+scripts and by the restore script. This file is usually located
+in @file{/etc/backup} directory. @xref{Backup Parameters}, for its
+detailed description. Once the backup parameters are set, you can
+perform backups or restoration by running the appropriate script.
+
+The name of the backup script is @code{backup}. The name of the
+restore script is @code{restore}. The following sections describe
+their use in detail.
+
+@emph{Please Note:} The backup and restoration scripts are
designed to be used together. While it is possible to restore files by
hand from an archive which was created using a backup script, and to create
an archive by hand which could then be extracted using the restore script,
-it is easier to use the scripts.@FIXME{There is no such restore script!}
-@value{xref-incremental}, and @value{xref-listed-incremental},
-before making such an attempt.
-
-@FIXME{shorten node names}
+it is easier to use the scripts. @xref{Incremental Dumps}, before
+making such an attempt.
@node Backup Parameters
@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}.
+
+The shell variables controlling behavior of @code{backup} and
+@code{restore} are described in the following subsections.
-@FIXME-xref{Script Syntax, for an explanation of this syntax.}
+@menu
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
+* backup-specs example:: An Example Text of @file{Backup-specs}
+@end menu
-@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:}
+@node General-Purpose Variables
+@subsection General-Purpose Variables
-@table @samp
-@item ADMINISTRATOR
-The user name of the backup administrator.
+@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}.
+@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 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
+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.
-@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.
+If the list of file systems is very long you may wish to put it
+in a separate file. This file is usually named
+@file{/etc/backup/dirs}, but this name may be overridden in
+@file{backup-specs} using @code{DIRLIST} variable.
+@end defvr
+
+@defvr {Backup variable} DIRLIST
+
+A path to the file containing the list of the file systems to backup
+or restore. By default it is @file{/etc/backup/dirs}.
+@end defvr
+
+@defvr {Backup variable} BACKUP_FILES
+
+A list of individual files to be dumped (for @code{backup}), or restored
+(for @code{restore}). These should be accessible from the machine on
+which the backup script is run.
+
+If the list of file systems is very long you may wish to store it
+in a separate file. This file is usually named
+@file{/etc/backup/files}, but this name may be overridden in
+@file{backup-specs} using @code{FILELIST} variable.
+@end defvr
+
+@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 file systems to be dumped.
+@end defvr
+
+@defvr {Backup variable} XLIST
+
+Name of @dfn{exclude file list}. An @dfn{exclude file list} is a file
+located on the remote machine and containing the list of files to
+be excluded from the backup. Exclude file lists are searched in
+/etc/tar-backup directory. A common use for exclude file lists
+is to exclude files containing security-sensitive information
+(e.g., @file{/etc/shadow} from backups).
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} SLEEP_TIME
+
+Time to sleep between dumps of any two successive file systems
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} DUMP_REMIND_SCRIPT
+
+Script to be run when it's time to insert a new tape in for the next
+volume. Administrators may want to tailor this script for their site.
+If this variable isn't set, @GNUTAR{} will display its built-in prompt
+@FIXME-xref{describe it somewhere!}, and will expect confirmation from
+the console.
+@end defvr
+
+@defvr {Backup variable} SLEEP_MESSAGE
+
+Message to display on the terminal while waiting for dump time. Usually
+this will just be some literal text.
+@end defvr
+
+@defvr {Backup variable} TAR
+
+Full file name of the @GNUTAR{} executable. If this is not set, backup
+scripts will search @command{tar} in the current shell path.
+@end defvr
+
+@node Magnetic Tape Control
+@subsection Magnetic Tape Control
+
+Backup scripts access tape device using special @dfn{hook functions}.
+These functions take a single argument -- the name of the tape
+device. Their names are kept in the following variables:
+
+@defvr {Backup variable} MT_BEGIN
+The name of @dfn{begin} function. This function is called before
+accessing the drive. By default it retensions the tape:
+
+@smallexample
+MT_BEGIN=mt_begin
+
+mt_begin() @{
+ mt -f "$1" retension
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_REWIND
+The name of @dfn{rewind} function. The default definition is as
+follows:
+
+@smallexample
+MT_REWIND=mt_rewind
+
+mt_rewind() @{
+ mt -f "$1" rewind
+@}
+@end smallexample
+
+@end defvr
+
+@defvr {Backup variable} MT_OFFLINE
+The name of the function switching the tape off line. By default
+it is defined as follows:
+
+@smallexample
+MT_OFFLINE=mt_offline
+
+mt_offline() @{
+ mt -f "$1" offl
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_STATUS
+The name of the function used to obtain the status of the archive device,
+including error count. Default definition:
+
+@smallexample
+MT_STATUS=mt_status
+
+mt_status() @{
+ mt -f "$1" status
+@}
+@end smallexample
+@end defvr
+
+@node User Hooks
+@subsection User Hooks
+
+@dfn{User hooks} are shell functions executed before and after
+each @command{tar} invocation. Thus, there are @dfn{backup
+hooks}, which are executed before and after dumping each file
+system, and @dfn{restore hooks}, executed before and
+after restoring a file system. Each user hook is a shell function
+taking four arguments:
+
+@deffn {User Hook Function} hook @var{level} @var{host} @var{fs} @var{fsname}
+Its arguments are:
+
+@table @var
+@item level
+Current backup or restore level.
-@FIXME{Same file name, be specific. Through NFS ...}
+@item host
+Name or IP address of the host machine being dumped or restored.
+@item fs
+Full path name to the file system being dumped or restored.
+
+@item fsname
+File system name with directory separators replaced with colons. This
+is useful, e.g., for creating unique files.
@end table
+@end deffn
-@menu
-* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-@end menu
+Following variables keep the names of user hook functions
+
+@defvr {Backup variable} DUMP_BEGIN
+Dump begin function. It is executed before dumping the file system.
+@end defvr
+
+@defvr {Backup variable} DUMP_END
+Executed after dumping the file system.
+@end defvr
+
+@defvr {Backup variable} RESTORE_BEGIN
+Executed before restoring the file system.
+@end defvr
+
+@defvr {Backup variable} RESTORE_END
+Executed after restoring the file system.
+@end defvr
@node backup-specs example
@subsection An Example Text of @file{Backup-specs}
-@UNREVISED
-The following is the text of @file{backup-specs} as it appears at FSF:
+The following is an example of @file{backup-specs}:
@smallexample
# site-specific parameters for file system backup.
ADMINISTRATOR=friedman
BACKUP_HOUR=1
TAPE_FILE=/dev/nrsmt0
-TAPE_STATUS="mts -t $TAPE_FILE"
+
+# Use @code{ssh} instead of the less secure @code{rsh}
+RSH=/usr/bin/ssh
+RSH_COMMAND=/usr/bin/ssh
+
+# Override MT_STATUS function:
+my_status() @{
+ mts -t $TAPE_FILE
+@}
+MT_STATUS=my_status
+
+# Disable MT_OFFLINE function
+MT_OFFLINE=:
+
BLOCKING=124
BACKUP_DIRS="
albert:/fs/fsf
@end smallexample
-@node Script Syntax
-@subsection Syntax for @file{Backup-specs}
-@UNREVISED
-
-@file{backup-specs} is in shell script syntax. The following
-conventions should be considered when editing the script:
-@FIXME{"conventions?"}
-
-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.
-
-A quoted string typically cannot contain wildcards. In
-@file{backup-specs}, however, the parameters BACKUP_DIRS and
-BACKUP_FILES can contain wildcards.
-
@node Scripted Backups
@section Using the Backup Scripts
-@UNREVISED
The syntax for running a backup script is:
@smallexample
-@file{script-name} [@var{time-to-be-run}]
+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
to store and retrieve information about which files were dumped. This
file is not meant to be read by humans, and should not be deleted by
-them. @FIXME-xref{incremental and listed-incremental, for a more
-detailed explanation of this file.}
+them. @xref{Snapshot Files}, for a more detailed explanation of this
+file.
The second file is a log file containing the names of the file systems
and files dumped, what time the backup was made, and any error
messages that were generated, as well as how much space was left in
the media volume after the last volume of the archive was written.
You should check this log file after every backup. The file name is
-@file{log-@var{mmm-ddd-yyyy}-level-1} or
-@file{log-@var{mmm-ddd-yyyy}-full}.
+@file{log-@var{mm-dd-yyyy}-level-@var{n}}, where @var{mm-dd-yyyy}
+represents current date, and @var{n} represents current dump level number.
The script also prints the name of each system being dumped to the
standard output.
+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 -V
+@itemx --version
+Display information about the program's name, version, origin and legal
+status, all on standard output, and then exit successfully.
+@end table
+
+
@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 file systems 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 file systems (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 file systems on the machine @samp{albert}. A more
+complicated example:
-@quotation
-@strong{Warning:} The @GNUTAR{} 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 file systems on the machine @samp{albert}
+as well as @file{/var} file system 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
-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.
+The full list of options accepted by @code{restore} follows:
+
+@table @option
+@item -a
+@itemx --all
+Restore all file systems and files specified in @file{backup-specs}
+
+@item -l @var{level}
+@itemx --level=@var{level}
+Start restoring from the given backup level, instead of the default 0.
+
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
+
+@item -h
+@itemx --help
+Display short help message and exit.
+
+@item -V
+@itemx --version
+Display information about the program's name, version, origin and legal
+status, all on standard output, and then exit successfully.
+@end table
You should start the restore script with the media containing the
first volume of the archive mounted. The script will prompt for other
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.
@end quotation
-@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
+@xref{Incremental Dumps}, for an explanation of how the script makes
+that determination.
@node Choosing
@chapter Choosing Files and Names for @command{tar}
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
@end menu
@node file
@section Choosing and Naming Archive Files
-@cindex Naming an archive
-@cindex Archive Name
-@cindex Directing output
-@cindex Choosing an archive file
-@cindex Where is the archive?
@UNREVISED
@FIXME{should the title of this section actually be, "naming an
archive"?}
+@cindex Naming an archive
+@cindex Archive Name
+@cindex Choosing an archive file
+@cindex Where is the archive?
By default, @command{tar} uses an archive file name that was compiled when
it was built on the system; usually this name refers to some physical
tape drive on the machine. However, the person who installed @command{tar}
on the system may not set the default to a meaningful value as far as
most users are concerned. As a result, you will usually want to tell
-@command{tar} where to find (or create) the archive. The @value{op-file}
+@command{tar} where to find (or create) the archive. The @option{--file=@var{archive-name}} (@option{-f @var{archive-name}})
option allows you to either specify or name a file to use as the archive
instead of the default archive file location.
-@table @kbd
+@table @option
+@opindex file, short description
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Name the archive to create or operate on. Use in conjunction with
@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
"notable tar usages".}
@smallexample
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+$ @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:
@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.
+@cindex Local and remote archives
+@anchor{local and remote archives}
If the archive file name includes a colon (@samp{:}), then it is assumed
to be a file on another machine. If the archive file is
@samp{@var{user}@@@var{host}:@var{file}}, then @var{file} is used on the
(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
-can be inhibited by using the @value{op-force-local} option.
+have the @file{rmt} program installed (This command is included in
+the @GNUTAR{} distribution and by default is installed under
+@file{@var{prefix}/libexec/rmt}, were @var{prefix} means your
+installation prefix). If you need to use a file whose name includes a
+colon, then the remote tape drive behavior
+can be inhibited by using the @option{--force-local} option.
@FIXME{i know we went over this yesterday, but bob (and now i do again,
too) thinks it's out of the middle of nowhere. it doesn't seem to tie
@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}.
If you do not specify files when @command{tar} is invoked with
-@value{op-create}, @command{tar} operates on all the non-directory files in
-the working directory. If you specify either @value{op-list} or
-@value{op-extract}, @command{tar} operates on all the archive members in the
+@option{--create} (@option{-c}), @command{tar} operates on all the non-directory files in
+the working directory. If you specify either @option{--list} (@option{-t}) or
+@option{--extract} (@option{--get}, @option{-x}), @command{tar} operates on all the archive members in the
archive. If you specify any operation other than one of these three,
@command{tar} does nothing.
@node files
@section Reading Names from a File
-@UNREVISED
@cindex Reading file names from a file
@cindex Lists of file names
@cindex File Name arguments, alternatives
Instead of giving the names of files or archive members on the command
line, you can put the names into a file, and then use the
-@value{op-files-from} option to @command{tar}. Give the name of the file
+@option{--files-from=@var{file-of-names}} (@option{-T @var{file-of-names}}) option to @command{tar}. Give the name of the file
which contains the list of files to include as the argument to
-@samp{--files-from}. In the list, the file names should be separated by
+@option{--files-from}. In the list, the file names should be separated by
newlines. You will frequently use this option when you have generated
the list of files to archive with the @command{find} utility.
-@table @kbd
+@table @option
+@opindex files-from
@item --files-from=@var{file name}
@itemx -T @var{file name}
Get names to extract or create from file @var{file name}.
@end table
-If you give a single dash as a file name for @samp{--files-from}, (i.e.,
-you specify either @samp{--files-from=-} or @samp{-T -}), then the file
+If you give a single dash as a file name for @option{--files-from}, (i.e.,
+you specify either @code{--files-from=-} or @code{-T -}), then the file
names are read from standard input.
-Unless you are running @command{tar} with @samp{--create}, you can not use
-both @samp{--files-from=-} and @samp{--file=-} (@samp{-f -}) in the same
+Unless you are running @command{tar} with @option{--create}, you can not use
+both @code{--files-from=-} and @code{--file=-} (@code{-f -}) in the same
command.
+Any number of @option{-T} options can be given in the command line.
+
@FIXME{add bob's example, from his message on 2-10-97}
The following example shows how to use @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
+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 @samp{-z} option 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{find . -size -400 -print > small-files}
$ @kbd{tar -c -v -z -T small-files -f little.tgz}
@end smallexample
@noindent
-@FIXME{say more here to conclude the example/section?}
+In the file list given by @option{-T} option, any file name beginning
+with @samp{-} character is considered a @command{tar} option and is
+processed accordingly.@footnote{Versions of @GNUTAR{} up to 1.15.1
+recognized only @option{-C} option in file lists, and only if the
+option and its argument occupied two consecutive lines.} For example,
+the common use of this feature is to change to another directory by
+specifying @option{-C} option:
+
+@smallexample
+@group
+$ @kbd{cat list}
+-C/etc
+passwd
+hosts
+-C/lib
+libc.a
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end group
+@end smallexample
+
+@noindent
+In this example, @command{tar} will first switch to @file{/etc}
+directory and add files @file{passwd} and @file{hosts} to the
+archive. Then it will change to @file{/lib} directory and will archive
+the file @file{libc.a}. Thus, the resulting archive @file{foo.tar} will
+contain:
+
+@smallexample
+@group
+$ @kbd{tar tf foo.tar}
+passwd
+hosts
+libc.a
+@end group
+@end smallexample
+
+@noindent
+@opindex directory, using in @option{--files-from} argument
+Notice that the option parsing algorithm used with @option{-T} is
+stricter than the one used by shell. Namely, when specifying option
+arguments, you should observe the following rules:
+
+@itemize @bullet
+@item
+When using short (single-letter) option form, its argument must
+immediately follow the option letter, without any intervening
+whitespace. For example: @code{-Cdir}.
+
+@item
+When using long option form, the option argument must be separated
+from the option by a single equal sign. No whitespace is allowed on
+any side of the equal sign. For example: @code{--directory=dir}.
+
+@item
+For both short and long option forms, the option argument can be given
+on the next line after the option name, e.g.:
+
+@smallexample
+@group
+--directory
+dir
+@end group
+@end smallexample
+
+@noindent
+and
+
+@smallexample
+@group
+-C
+dir
+@end group
+@end smallexample
+@end itemize
+
+@opindex add-file
+If you happen to have a file whose name starts with @samp{-},
+precede it with @option{--add-file} option to prevent it from
+being recognized as an option. For example: @code{--add-file --my-file}.
@menu
* nul::
@end menu
@node nul
-@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
-The @value{op-null} option causes @value{op-files-from} to read file
+@cindex File names, terminated by @code{NUL}
+@cindex @code{NUL} terminated file names
+The @option{--null} option causes @option{--files-from=@var{file-of-names}} (@option{-T @var{file-of-names}}) to read file
names terminated by a @code{NUL} instead of a newline, so files whose
-names contain newlines can be archived using @samp{--files-from}.
+names contain newlines can be archived using @option{--files-from}.
-@table @kbd
+@table @option
+@opindex null
@item --null
-Only consider @kbd{NUL} terminated file names, instead of files that
+Only consider @code{NUL} terminated file names, instead of files that
terminate in a newline.
@end table
-The @samp{--null} option is just like the one in @acronym{GNU}
+The @option{--null} option is just like the one in @acronym{GNU}
@command{xargs} and @command{cpio}, and is useful with the
-@samp{-print0} predicate of @acronym{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}.
+@option{-print0} predicate of @acronym{GNU} @command{find}. In
+@command{tar}, @option{--null} also disables special handling for
+file names that begin with dash.
This example shows how to use @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.
@smallexample
-$ @kbd{find . -size +800 -print0 > long-files}
+$ @kbd{find . -size +800 -print0 > long-files}
$ @kbd{tar -c -v --null --files-from=long-files --file=big.tar}
@end smallexample
@node exclude
@section Excluding Some Files
+@UNREVISED
+
@cindex File names, excluding files by
@cindex Excluding files by name and pattern
@cindex Excluding files by file system
-@UNREVISED
-
To avoid operating on files whose names match a particular pattern,
-use the @value{op-exclude} or @value{op-exclude-from} options.
+use the @option{--exclude} or @option{--exclude-from} options.
-@table @kbd
+@table @option
+@opindex exclude
@item --exclude=@var{pattern}
Causes @command{tar} to ignore files that match the @var{pattern}.
@end table
@findex exclude
-The @value{op-exclude} option prevents any file or member whose name
+The @option{--exclude=@var{pattern}} option prevents any file or member whose name
matches the shell wildcard (@var{pattern}) from being operated on.
For example, to create an archive with all the contents of the directory
@file{src} except for files whose names end in @file{.o}, use the
command @samp{tar -cf src.tar --exclude='*.o' src}.
-You may give multiple @samp{--exclude} options.
+You may give multiple @option{--exclude} options.
-@table @kbd
+@table @option
+@opindex exclude-from
@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} 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
+@opindex exclude-caches
+@item --exclude-caches
+Causes @command{tar} to ignore directories containing a cache directory tag.
+@end table
+
+@findex exclude-caches
+When creating an archive, the @option{--exclude-caches} option causes
+@command{tar} to exclude all directories that contain a @dfn{cache
+directory tag}. A cache directory tag is a short file with the
+well-known name @file{CACHEDIR.TAG} and having a standard header
+specified in @url{http://www.brynosaurus.com/cachedir/spec.html}.
+Various applications write cache directory tags into directories they
+use to hold regenerable, non-precious data, so that such data can be
+more easily excluded from backups.
+
@menu
-* controlling pattern-patching with exclude::
+* controlling pattern-matching with exclude::
* problems with exclude::
@end menu
-@node controlling pattern-patching with exclude
+@node controlling pattern-matching with exclude
@unnumberedsubsec Controlling Pattern-Matching with the @code{exclude} Options
Normally, a pattern matches a name if an initial subsequence of the
@samp{readme}.
@table @option
+@opindex anchored
+@opindex no-anchored
@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}.
+@opindex ignore-case
+@opindex no-ignore-case
@item --ignore-case
@itemx --no-ignore-case
When ignoring case, upper-case patterns match lower-case names and vice versa.
When not ignoring case (the default), matching is case-sensitive.
+@opindex wildcards
+@opindex no-wildcards
@item --wildcards
@itemx --no-wildcards
When using wildcards (the default), @samp{*}, @samp{?}, and @samp{[...]}
Otherwise, none of these characters are special, and patterns must match
names literally.
+@opindex wildcards-match-slash
+@opindex no-wildcards-match-slash
@item --wildcards-match-slash
@itemx --no-wildcards-match-slash
When wildcards match slash (the default), a wildcard like @samp{*} in
@node problems with exclude
@unnumberedsubsec Problems with Using the @code{exclude} Options
+@opindex exclude, potential problems with
Some users find @samp{exclude} options confusing. Here are some common
pitfalls:
listed, @samp{dir.o/foo} will be excluded from the archive.
@item
-You can sometimes confuse the meanings of @value{op-exclude} and
-@value{op-exclude-from}. Be careful: use @value{op-exclude} when files
+You can sometimes confuse the meanings of @option{--exclude} and
+@option{--exclude-from}. Be careful: use @option{--exclude} when files
to be excluded are given as a pattern on the command line. Use
-@samp{--exclude-from=@var{file-of-patterns}} to introduce the name of a
-file which contains a list of patterns, one per line; each of these
-patterns can exclude zero, one, or many files.
+@option{--exclude-from} to introduce the name of a file which contains
+a list of patterns, one per line; each of these patterns can exclude
+zero, one, or many files.
@item
-When you use @value{op-exclude}, be sure to quote the @var{pattern}
+When you use @option{--exclude=@var{pattern}}, be sure to quote the @var{pattern}
parameter, so @GNUTAR{} sees wildcard characters
like @samp{*}. If you do not do this, the shell might expand the
@samp{*} itself using files at hand, so @command{tar} might receive a
@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
-patterns listed in a file.
+@option{--exclude-from} option was called @option{--exclude} instead.
+Now, @option{--exclude} applies to patterns listed on the command
+line and @option{--exclude-from} applies to patterns listed in a
+file.
@end itemize
@samp{*} or @samp{?} for example, are replaced and expanded into all
existing files matching the given pattern. However, @command{tar} often
uses wildcard patterns for matching (or globbing) archive members instead
-of actual files in the filesystem. Wildcard patterns are also used for
+of actual files in the file system. Wildcard patterns are also used for
verifying volume labels of @command{tar} archives. This section has the
purpose of explaining wildcard syntax for @command{tar}.
@node after
@section Operating Only on New Files
+@UNREVISED
+
@cindex Excluding file by age
+@cindex Data Modification time, excluding files by
@cindex Modification time, excluding files by
@cindex Age, excluding files by
-@UNREVISED
-
-The @value{op-after-date} option causes @command{tar} to only work on files
-whose modification or inode-changed times are newer than the @var{date}
-given. If @var{date} starts with @samp{/} or @samp{.}, it is taken to
-be a file name; the 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}
-when extracting an archive, @command{tar} will only extract files newer
-than the @var{date} you specify.
+The @option{--after-date=@var{date}} (@option{--newer=@var{date}},
+@option{-N @var{date}}) option causes @command{tar} to only work on
+files whose data modification or status change times are newer than
+the @var{date} given. If @var{date} starts with @samp{/} or @samp{.},
+it is taken to be a file name; the data modification time of that file
+is used as the date. If you use this option when creating or appending
+to an archive, the archive will only include new files. If you use
+@option{--after-date} when extracting an archive, @command{tar} will
+only extract files newer than the @var{date} you specify.
If you only want @command{tar} to make the date comparison based on
-modification of the actual contents of the file (rather than inode
-changes), then use the @value{op-newer-mtime} option.
+modification of the file's data (rather than status
+changes), then use the @option{--newer-mtime=@var{date}} option.
You may use these options with any operation. Note that these options
-differ from the @value{op-update} operation in that they allow you to
-specify a particular date against which @command{tar} can compare when
-deciding whether or not to archive the files.
+differ from the @option{--update} (@option{-u}) operation in that they
+allow you to specify a particular date against which @command{tar} can
+compare when deciding whether or not to archive the files.
-@table @kbd
+@table @option
+@opindex after-date
+@opindex newer
@item --after-date=@var{date}
@itemx --newer=@var{date}
@itemx -N @var{date}
Only store files newer than @var{date}.
-Acts on files only if their modification or inode-changed times are
+Acts on files only if their data modification or status change times are
later than @var{date}. Use in conjunction with any operation.
If @var{date} starts with @samp{/} or @samp{.}, it is taken to be a file
-name; the last-modified time of that file is used as the date.
+name; the data modification time of that file is used as the date.
+@opindex newer-mtime
@item --newer-mtime=@var{date}
-Acts like @value{op-after-date}, but only looks at modification times.
+Acts like @option{--after-date}, but only looks at data modification times.
@end table
-These options limit @command{tar} to only operating on files which have
-been modified after the date specified. A file is considered to have
-changed if the contents have been modified, or if the owner,
+These options limit @command{tar} to operate only on files which have
+been modified after the date specified. A file's status is considered to have
+changed if its contents have been modified, or if its owner,
permissions, and so forth, have been changed. (For more information on
how to specify a date, see @ref{Date input formats}; remember that the
entire date argument must be quoted if it contains any spaces.)
-Gurus would say that @value{op-after-date} tests both the @code{mtime}
-(time the contents of the file were last modified) and @code{ctime}
-(time the file's status was last changed: owner, permissions, etc)
-fields, while @value{op-newer-mtime} tests only @code{mtime} field.
+Gurus would say that @option{--after-date} tests both the data
+modification time (@code{mtime}, the time the contents of the file
+were last modified) and the status change time (@code{ctime}, the time
+the file's status was last changed: owner, permissions, etc.@:)
+fields, while @option{--newer-mtime} tests only the @code{mtime}
+field.
-To be precise, @value{op-after-date} checks @emph{both} @code{mtime} and
+To be precise, @option{--after-date} checks @emph{both} @code{mtime} and
@code{ctime} and processes the file if either one is more recent than
-@var{date}, while @value{op-newer-mtime} only checks @code{mtime} and
-disregards @code{ctime}. Neither uses @code{atime} (the last time the
+@var{date}, while @option{--newer-mtime} only checks @code{mtime} and
+disregards @code{ctime}. Neither does it use @code{atime} (the last time the
contents of the file were looked at).
Date specifiers can have embedded spaces. Because of this, you may need
@FIXME{Need example of --newer-mtime with quoted argument.}
@quotation
-@strong{Please Note:} @value{op-after-date} and @value{op-newer-mtime}
+@strong{Please Note:} @option{--after-date} and @option{--newer-mtime}
should not be used for incremental backups. Some files (such as those
in renamed directories) are not selected properly by these options.
-@xref{incremental and listed-incremental}.
+@xref{Incremental Dumps}.
@end quotation
@noindent
@node recurse
@section Descending into Directories
+@UNREVISED
@cindex Avoiding recursion in directories
@cindex Descending directories, avoiding
@cindex Directories, avoiding recursion
@cindex Recursion in directories, avoiding
-@UNREVISED
@FIXME{arrggh! this is still somewhat confusing to me. :-< }
@FIXME{show dan bob's comments, from 2-10-97}
Usually, @command{tar} will recursively explore all directories (either
-those given on the command line or through the @value{op-files-from}
+those given on the command line or through the @option{--files-from}
option) for the various files they contain. However, you may not always
want @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
+@opindex no-recursion
+The @option{--no-recursion} option inhibits @command{tar}'s recursive descent
+into specified directories. If you specify @option{--no-recursion}, you can
use the @command{find} utility for hunting through levels of directories to
construct a list of file names which you could then pass to @command{tar}.
@command{find} allows you to be more selective when choosing which files to
archive; see @ref{files} for more information on using @command{find} with
@command{tar}, or look.
-@table @kbd
+@table @option
@item --no-recursion
Prevents @command{tar} from recursively descending directories.
+@opindex recursion
@item --recursion
Requires @command{tar} to recursively descend directories.
This is the default.
@end table
-When you use @samp{--no-recursion}, @GNUTAR{} grabs
+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
+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
+They then use the @option{--files-from} option to archive the files
located via @command{find}.
The problem when restoring files archived in this manner is that the
directories themselves are not in the archive; so the
-@value{op-same-permissions} option does not affect them---while users
-might really like it to. Specifying @value{op-no-recursion} is a way to
-tell @command{tar} to grab only the directory entries given to it, adding
+@option{--same-permissions} (@option{--preserve-permissions},
+@option{-p}) option does not affect them---while users might really
+like it to. Specifying @option{--no-recursion} is a way to tell
+@command{tar} to grab only the directory entries given to it, adding
no new files on its own.
-The @value{op-no-recursion} option also applies when extracting: it
+The @option{--no-recursion} option also applies when extracting: it
causes @command{tar} to extract only the matched directory entries, not
the files under those directories.
-The @value{op-no-recursion} option also affects how exclude patterns
-are interpreted (@pxref{controlling pattern-patching with exclude}).
+The @option{--no-recursion} option also affects how exclude patterns
+are interpreted (@pxref{controlling pattern-matching with exclude}).
The @option{--no-recursion} and @option{--recursion} options apply to
later options and operands, and can be overridden by later occurrences
of @option{--no-recursion} and @option{--recursion}. For example:
@smallexample
-$ @kbd{tar -cf jams.tar --norecursion grape --recursion grape/concord}
+$ @kbd{tar -cf jams.tar --no-recursion grape --recursion grape/concord}
@end smallexample
@noindent
other than @file{grape/concord}.
@node one
-@section Crossing Filesystem Boundaries
+@section Crossing File System Boundaries
@cindex File system boundaries, not crossing
@UNREVISED
@command{tar} will normally automatically cross file system boundaries in
order to archive files which are part of a directory tree. You can
change this behavior by running @command{tar} and specifying
-@value{op-one-file-system}. This option only affects files that are
+@option{--one-file-system} (@option{-l}). This option only affects files that are
archived because they are in a directory that is being archived;
@command{tar} will still archive files explicitly named on the command line
-or through @value{op-files-from}, regardless of where they reside.
+or through @option{--files-from}, regardless of where they reside.
-@table @kbd
+@table @option
+@opindex one-file-system
@item --one-file-system
@itemx -l
Prevents @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
+a directory is not on the same file system as the directory itself, then
@command{tar} will not archive that file. If the file is a directory
itself, @command{tar} will not archive anything beneath it; in other words,
@command{tar} will not cross mount points.
This option is useful for making full or incremental archival backups of
a file system. If this option is used in conjunction with
-@value{op-verbose}, files that are excluded are mentioned by name on the
+@option{--verbose} (@option{-v}), files that are excluded are mentioned by name on the
standard error.
@menu
@node directory
@subsection Changing the Working Directory
+@UNREVISED
@FIXME{need to read over this node now for continuity; i've switched
things around some.}
@cindex Changing directory mid-stream
@cindex Directory, changing mid-stream
@cindex Working directory, specifying
-@UNREVISED
-
To change the working directory in the middle of a list of file names,
either on the command line or in a file specified using
-@value{op-files-from}, use @value{op-directory}. This will change the
-working directory to the directory @var{directory} after that point in
-the list.
+@option{--files-from} (@option{-T}), use @option{--directory} (@option{-C}).
+This will change the working directory to the specified directory
+after that point in the list.
-@table @kbd
+@table @option
+@opindex directory
@item --directory=@var{directory}
@itemx -C @var{directory}
Changes the working directory in the middle of a command line.
@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
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:
-@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?}
+@smallexample
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end smallexample
-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.)
+Notice also that you can only use the short option variant in the file
+list, i.e., always use @option{-C}, not @option{--directory}.
+
+The interpretation of @option{--directory} is disabled by
+@option{--null} option.
@node absolute
@subsection Absolute File Names
@UNREVISED
-@table @kbd
-@item -P
-@itemx --absolute-names
+@table @option
+@opindex absolute-names
+@item --absolute-names
+@itemx -P
Do not strip leading slashes from file names, and permit file names
containing a @file{..} file name component.
@end table
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}.
+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.
+If you use the @option{--absolute-names} (@option{-P}) option,
+@command{tar} will do none of these transformations.
To archive or extract files relative to the root directory, specify
-the @value{op-absolute-names} option.
+the @option{--absolute-names} (@option{-P}) option.
Normally, @command{tar} acts on files relative to the working
directory---ignoring superior directory names when archiving, and
ignoring leading slashes when extracting.
-When you specify @value{op-absolute-names}, @command{tar} stores file names
-including all superior directory names, and preserves leading slashes.
-If you only invoked @command{tar} from the root directory you would never
-need the @value{op-absolute-names} option, but using this option may be
-more convenient than switching to root.
+When you specify @option{--absolute-names} (@option{-P}),
+@command{tar} stores file names including all superior directory
+names, and preserves leading slashes. If you only invoked
+@command{tar} from the root directory you would never need the
+@option{--absolute-names} option, but using this option
+may be more convenient than switching to root.
@FIXME{Should be an example in the tutorial/wizardry section using this
to transfer files between systems.}
@FIXME{Is write access an issue?}
-@table @kbd
+@table @option
@item --absolute-names
Preserves full file names (including superior directory names) when
archiving files. Preserves leading slash when extracting files.
@node Formats
@chapter Controlling the Archive Format
+@cindex Tar archive formats
Due to historical reasons, there are several formats of tar archives.
All of them are based on the same principles, but have some subtle
differences that often make them incompatible with each other.
@table @asis
@item gnu
-Format used by @GNUTAR{}.
+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.
-@item v7
-Archive format, compatible with the V7 implementation of tar.
+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 posix
-Archive format defined by POSIX.1-2001 specification.
+@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.
+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
-@GNUTAR{} is able to create archives in any of these formats,
-except @samp{star}. It is able to read archives in any of these
-formats.
+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
+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}.
other kind of special files. Do not attempt to save sparse files or
contiguous files as such. Let's discuss a few more problems, in turn.
+@FIXME{Discuss GNU extensions (incremental backups, multi-volume
+archives and archive labels) in GNU and PAX formats.}
+
@menu
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
+* ustar:: Ustar Archives
* gnu:: GNU and old GNU format archives.
-* posix:: @sc{posix} archives
+* posix:: @acronym{POSIX} archives
* Checksumming:: Checksumming Problems
* Large or Negative Values:: Large files, negative time stamps, etc.
@end menu
@cindex File names, using symbolic links
@cindex Symbolic link as file name
+@opindex dereference
Normally, when @command{tar} archives a symbolic link, it writes a
block to the archive naming the target of the link. In that way, the
-@command{tar} archive is a faithful record of the filesystem contents.
-@value{op-dereference} is used with @value{op-create}, and causes
+@command{tar} archive is a faithful record of the file system contents.
+@option{--dereference} (@option{-h}) is used with @option{--create} (@option{-c}), and causes
@command{tar} to archive the files symbolic links point to, instead of
the links themselves. When this option is used, when @command{tar}
encounters a symbolic link, it will archive the linked-to file,
@emph{might} be considered a bug.)
So, for portable archives, do not archive symbolic links as such,
-and use @value{op-dereference}: many systems do not support
+and use @option{--dereference} (@option{-h}): many systems do not support
symbolic links, and moreover, your distribution might be unusable if
it contains unresolved symbolic links.
@cindex Format, old style
@cindex Old style format
@cindex Old style archives
+@cindex v7 archive format
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-format-v7} option in
-conjunction with the @value{op-create} (@command{tar} also
-accepts @samp{--portability} or @samp{op-old-archive} for this
-option). When you specify it,
+versions, specify the @option{--format=v7} option in
+conjunction with the @option{--create} (@option{-c}) (@command{tar} also
+accepts @option{--portability} or @samp{op-old-archive} for this
+option). When you specify it,
@command{tar} leaves out information about directories, pipes, fifos,
contiguous files, and device files, and specifies file ownership by
group and user IDs instead of group and user names.
-When updating an archive, do not use @value{op-format-v7}
-unless the archive was created with using this option.
+When updating an archive, do not use @option{--format=v7}
+unless the archive was created using this option.
In most cases, a @emph{new} format archive can be read by an @emph{old}
@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-format-v7} for your distributions.
+always use @option{--format=v7} for your distributions.
+
+@node ustar
+@subsection Ustar Archive Format
+
+@cindex ustar archive format
+Archive format defined by @acronym{POSIX}.1-1988 specification is called
+@code{ustar}. Although it is more flexible than the V7 format, it
+still has many restrictions (@xref{Formats,ustar}, for the detailed
+description of @code{ustar} format). Along with V7 format,
+@code{ustar} format is a good choice for archives intended to be read
+with other implementations of @command{tar}.
+
+To create archive in @code{ustar} format, use @option{--format=ustar}
+option in conjunction with the @option{--create} (@option{-c}).
@node gnu
@subsection @acronym{GNU} and old @GNUTAR{} format
+@cindex GNU archive format
+@cindex Old GNU archive format
@GNUTAR{} was based on an early draft of the
-@sc{posix} 1003.1 @code{ustar} standard. @acronym{GNU} extensions to
+@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 @sc{posix} draft as unused. Subsequent changes in
-@sc{posix} have allocated the same parts of the header record for
+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 @sc{posix} specification, and with
+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 may change in the future, since we plan
-to make @samp{posix} format the default.
+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}
-@item @value{op-sparse}
-@end itemize
-
-These options will be re-implemented for the @samp{posix} archive
-format in the future.
+@option{--format=gnu}.
@node posix
-@subsection @GNUTAR{} and @sc{posix} @command{tar}
+@subsection @GNUTAR{} and @acronym{POSIX} @command{tar}
+@cindex POSIX archive format
+@cindex PAX archive format
The version @value{VERSION} of @GNUTAR{} is able
-to read and create archives conforming to @sc{posix.1-2001} standard.
-
-A @sc{posix} conformant archive will be created if @command{tar}
-was given @value{op-format-posix} option, or if it was given
-@value{op-format-gnu} option and the environment variable
-@env{POSIXLY_CORRECT} is set. The later usage is retained for
-compatibility with previous versions of @GNUTAR{}
-and is discouraged.
-
-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}
-@item @value{op-sparse}
-@end itemize
+to read and create archives conforming to @acronym{POSIX.1-2001} standard.
-This restriction will disappear in the future versions.
+A @acronym{POSIX} conformant archive will be created if @command{tar}
+was given @option{--format=posix} option.
@node Checksumming
@subsection Checksumming Problems
@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 @sc{posix} standards. On
+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
@cindex large values
@cindex future time stamps
@cindex negative time stamps
-
-@sc{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. @GNUTAR{}
-generates @sc{posix} representations when possible, but for values
-outside the @sc{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}
-@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}
-@command{tar} format cannot represent them.
-
-Portable archives should avoid time stamps from the future. @sc{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,
-and cannot represent time stamps after 2038-01-19 03:14:07 @sc{utc}; so
-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}
-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. @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.
+@UNREVISED{}
+
+The above sections suggest to use @samp{oldest possible} archive
+format if in doubt. However, sometimes it is not possible. If you
+attempt to archive a file whose metadata cannot be represented using
+required format, @GNUTAR{} will print error message and ignore such a
+file. You will than have to switch to a format that is able to
+handle such values. The format summary table (@pxref{Formats}) will
+help you to do so.
+
+In particular, when trying to archive files larger than 8GB or with
+timestamps not in the range 1970-01-01 00:00:00 through 2242-03-16
+12:56:31 @sc{utc}, you will have to chose between @acronym{GNU} and
+@acronym{POSIX} archive formats. When considering which format to
+choose, bear in mind that the @acronym{GNU} format uses
+two's-complement base-256 notation to store values that do not fit
+into standard @acronym{ustar} range. Such archives can generally be
+read only by a @GNUTAR{} implementation. Moreover, they sometimes
+cannot be correctly restored on another hosts even by @GNUTAR{}. For
+example, using two's complement representation for negative time
+stamps that assumes a signed 32-bit @code{time_t} generates archives
+that are not portable to hosts with differing @code{time_t}
+representations.
+
+On the other hand, @acronym{POSIX} archives, generally speaking, can
+be extracted by any tar implementation that understands older
+@acronym{ustar} format. The only exception are files larger than 8GB.
+
+@FIXME{Describe how @acronym{POSIX} archives are extracted by non
+POSIX-aware tars.}
@node Compression
@section Using Less Space through Compression
@subsection Creating and Reading Compressed Archives
@cindex Compressed archives
@cindex Storing archives in compressed format
-@UNREVISED
-@table @kbd
+@GNUTAR{} is able to create and read compressed archives. It supports
+@command{gzip} and @command{bzip2} compression programs. For backward
+compatibilty, it also supports @command{compress} command, although
+we strongly recommend against using it, since there is a patent
+covering the algorithm it uses and you could be sued for patent
+infringement merely by running @command{compress}! Besides, it is less
+effective than @command{gzip} and @command{bzip2}.
+
+Creating a compressed archive is simple: you just specify a
+@dfn{compression option} along with the usual archive creation
+commands. The compression option is @option{-z} (@option{--gzip}) to
+create a @command{gzip} compressed archive, @option{-j}
+(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
+@option{-Z} (@option{--compress}) to use @command{compress} program.
+For example:
+
+@smallexample
+$ @kbd{tar cfz archive.tar.gz .}
+@end smallexample
+
+Reading compressed archive is even simpler: you don't need to specify
+any additional options as @GNUTAR{} recognizes its format
+automatically. Thus, the following commands will list and extract the
+archive created in previous example:
+
+@smallexample
+# List the compressed archive
+$ @kbd{tar tf archive.tar.gz}
+# Extract the compressed archive
+$ @kbd{tar xf archive.tar.gz}
+@end smallexample
+
+The only case when you have to specify a decompression option while
+reading the archive is when reading from a pipe or from a tape drive
+that does not support random access. However, in this case @GNUTAR{}
+will indicate which option you should use. For example:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tf -}
+tar: Archive is compressed. Use -z option
+tar: Error is not recoverable: exiting now
+@end smallexample
+
+If you see such diagnostics, just add the suggested option to the
+invocation of @GNUTAR{}:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tfz -}
+@end smallexample
+
+Notice also, that there are several restrictions on operations on
+compressed archives. First of all, compressed archives cannot be
+modified, i.e., you cannot update (@option{--update} (@option{-u})) them or delete
+(@option{--delete}) members from them. Likewise, you cannot append
+another @command{tar} archive to a compressed archive using
+@option{--append} (@option{-r})). Secondly, multi-volume archives cannot be
+compressed.
+
+The following table summarizes compression options used by @GNUTAR{}.
+
+@table @option
+@opindex gzip
+@opindex ungzip
@item -z
@itemx --gzip
@itemx --ungzip
Filter the archive through @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 @GNUTAR{} 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:
-
-@smallexample
-$ @kbd{tar cfz archive.tar.gz subdir}
-@end smallexample
-
-@noindent
-to save all of @samp{subdir} into a @code{gzip}'ed archive. Later you
-can do:
+override them, set @env{GZIP} environment variable, e.g.:
@smallexample
-$ @kbd{tar xfz archive.tar.gz}
+$ @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 @option{--gzip} (@option{--gunzip}, @option{--ungzip}, @option{-z}) option and run
+@command{gzip} explicitly:
@smallexample
-$ @kbd{tar tfz archive.tar.gz}
+$ @kbd{tar cf - subdir | gzip --best -c - > archive.tar.gz}
@end smallexample
@cindex corrupted archives
lose some compressibility. But this would have make recovering easier.
So, there are pros and cons. We'll see!
-@table @kbd
+@opindex bzip2
@item -j
@itemx --bzip2
-Filter the archive through @code{bzip2}. Otherwise like @value{op-gzip}.
+Filter the archive through @code{bzip2}. Otherwise like @option{--gzip}.
+@opindex compress
+@opindex uncompress
@item -Z
@itemx --compress
@itemx --uncompress
-Filter the archive through @command{compress}. Otherwise like
-@value{op-gzip}.
-
-@item --use-compress-program=@var{prog}
-Filter through @var{prog} (must accept @samp{-d}).
-@end table
-
-@value{op-compress} stores an archive in compressed format. This
-option is useful in saving time over networks and space in pipes, and
-when storage space is at a premium. @value{op-compress} causes
-@command{tar} to compress when writing the archive, or to uncompress when
-reading the archive.
+Filter the archive through @command{compress}. Otherwise like @option{--gzip}.
-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.
+@opindex use-compress-program
+@item --use-compress-program=@var{prog}
+Use external compression program @var{prog}. Use this option if you
+have a compression program that @GNUTAR{} does not support. There
+are two requirements to which @var{prog} should comply:
-@value{op-bzip2} acts like @value{op-compress}, except that it uses
-the @code{bzip2} utility.
+First, when called without options, it should read data from standard
+input, compress it and output it on standard output.
-@table @kbd
-@item --compress
-@itemx --uncompress
-@itemx -z
-@itemx -Z
-When this option is specified, @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 @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}.
-
-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
+@FIXME{I have one question, or maybe it's a suggestion if there isn't a way
+to do it now. I would like to use @option{--gzip}, but I'd also like
the output to be fed through a program like @acronym{GNU}
@command{ecc} (actually, right now that's @samp{exactly} what I'd like
to use :-)), basically adding ECC protection on top of compression.
get it (apparently) working, do you accept contributed changes to
utilities like that? (Leigh Clayton @file{loc@@soliton.com}, May 1995).
-Isn't that exactly the role of the @value{op-use-compress-prog} option?
+Isn't that exactly the role of the @option{--use-compress-prog=@var{program}} option?
I never tried it myself, but I suspect you may want to write a
@var{prog} script or program able to filter stdin to stdout to
-way you want. It should recognize the @samp{-d} option, for when
+way you want. It should recognize the @option{-d} option, for when
extraction is needed rather than creation.
It has been reported that if one writes compressed data (through the
-@value{op-gzip} or @value{op-compress} options) to a DLT and tries to use
+@option{--gzip} or @option{--compress} options) to a DLT and tries to use
the DLT compression mode, the data will actually get bigger and one will
-end up with less space on the tape.
+end up with less space on the tape.}
@node sparse
@subsection Archiving Sparse Files
@cindex Sparse Files
@UNREVISED
-@table @kbd
+@table @option
+@opindex sparse
@item -S
@itemx --sparse
Handle sparse files efficiently.
@end table
This option causes all files to be put in the archive to be tested for
-sparseness, and handled specially if they are. The @value{op-sparse}
-option is useful when many @code{dbm} files, for example, are being
+sparseness, and handled specially if they are. The @option{--sparse}
+(@option{-S}) option is useful when many @code{dbm} files, for example, are being
backed up. Using this option dramatically decreases the amount of
space needed to store such a file.
@acronym{GNU} options. For now, it is an option needing to be specified on
the command line with the creation or updating of an archive.
-Files in the filesystem occasionally have ``holes.'' A hole in a file
+Files in the file system occasionally have ``holes.'' A hole in a file
is a section of the file's contents which was never written. The
contents of a hole read as all zeros. On many operating systems,
actual disk storage is not allocated for holes, but they are counted
in the length of the file. If you archive such a file, @command{tar}
could create an archive longer than the original. To have @command{tar}
-attempt to recognize the holes in a file, use @value{op-sparse}. When
-you use the @value{op-sparse} option, then, for any file using less
-disk space than would be expected from its length, @command{tar} searches
-the file for consecutive stretches of zeros. It then records in the
-archive for the file where the consecutive stretches of zeros are, and
-only archives the ``real contents'' of the file. On extraction (using
-@value{op-sparse} is not needed on extraction) any such files have
-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.
+attempt to recognize the holes in a file, use @option{--sparse} (@option{-S}). When
+you use this option, then, for any file using less disk space than
+would be expected from its length, @command{tar} searches the file for
+consecutive stretches of zeros. It then records in the archive for
+the file where the consecutive stretches of zeros are, and only
+archives the ``real contents'' of the file. On extraction (using
+@option{--sparse} is not needed on extraction) any such
+files have holes created wherever the continuous stretches of zeros
+were found. Thus, if you use @option{--sparse}, @command{tar} archives
+won't take more space than the original.
A file is sparse if it contains blocks of zeros whose existence is
recorded, but that have no space allocated on disk. When you specify
-the @value{op-sparse} option in conjunction with the @value{op-create}
-operation, @command{tar} tests all files for sparseness while archiving.
-If @command{tar} finds a file to be sparse, it uses a sparse representation of
-the file in the archive. @value{xref-create}, for more information
-about creating archives.
+the @option{--sparse} option in conjunction with the @option{--create}
+(@option{-c}) operation, @command{tar} tests all files for sparseness
+while archiving. If @command{tar} finds a file to be sparse, it uses a
+sparse representation of the file in the archive. @xref{create}, for
+more information about creating archives.
-@value{op-sparse} is useful when archiving files, such as dbm files,
+@option{--sparse} is useful when archiving files, such as dbm files,
likely to contain many nulls. This option dramatically
decreases the amount of space needed to store such an archive.
@quotation
-@strong{Please Note:} Always use @value{op-sparse} when performing file
+@strong{Please Note:} Always use @option{--sparse} when performing file
system backups, to avoid archiving the expanded forms of files stored
sparsely in the system.
Even if your system has no sparse files currently, some may be
-created in the future. If you use @value{op-sparse} while making file
+created in the future. If you use @option{--sparse} while making file
system backups as a matter of course, you can be assured the archive
will never take more space on the media than the files take on disk
(otherwise, archiving a disk filled with sparse files might take
hundreds of tapes). @FIXME-xref{incremental when node name is set.}
@end quotation
-@command{tar} ignores the @value{op-sparse} option when reading an archive.
+@command{tar} ignores the @option{--sparse} option when reading an archive.
-@table @kbd
+@table @option
@item --sparse
@itemx -S
Files stored sparsely in the file system are represented sparsely in
ELC, with full CPU utilization.)
This reading is required in all cases and is not related to the fact
-the @value{op-sparse} option is used or not, so by merely @emph{not}
+the @option{--sparse} option is used or not, so by merely @emph{not}
using the option, you are not saving time@footnote{Well! We should say
-the whole truth, here. When @value{op-sparse} is selected while creating
+the whole truth, here. When @option{--sparse} is selected while creating
an archive, the current @command{tar} algorithm requires sparse files to be
read twice, not once. We hope to develop a new archive format for saving
sparse files in which one pass will be sufficient.}.
@section Handling File Attributes
@UNREVISED
-When @command{tar} reads files, this causes them to have the access
-times updated. To have @command{tar} attempt to set the access times
-back to what they were before they were read, use the
-@value{op-atime-preserve} option.
+When @command{tar} reads files, it updates their access times. To
+avoid this, use the @option{--atime-preserve[=METHOD]} option, which can either
+reset the access time retroactively or avoid changing it in the first
+place.
Handling of file attributes
-@table @kbd
+@table @option
+@opindex atime-preserve
@item --atime-preserve
-Preserve access times on files that are read.
-This doesn't work for files that
-you don't own, unless you're root, and it doesn't interact with
-incremental dumps nicely (@pxref{Backups}), and it can set access or
-modification times incorrectly if other programs access the file while
-@command{tar} is running; but it is good enough for some purposes.
-
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+Preserve the access times of files that are read. This works only for
+files that you own, unless you have superuser privileges.
+
+@option{--atime-preserve=replace} works on most systems, but it also
+restores the data modification time and updates the status change
+time. Hence it doesn't interact with incremental dumps nicely
+(@pxref{Backups}), and it can set access or data modification times
+incorrectly if other programs access the file while @command{tar} is
+running.
+
+@option{--atime-preserve=system} avoids changing the access time in
+the first place, if the operating system supports this.
+Unfortunately, this may or may not work on any given operating system
+or file system. If @command{tar} knows for sure it won't work, it
+complains right away.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@option{--atime-preserve=replace}, but this is intended to change to
+@option{--atime-preserve=system} when the latter is better-supported.
+
+@opindex touch
@item -m
@itemx --touch
-Do not extract file modified time.
+Do not extract data modification time.
-When this option is used, @command{tar} leaves the modification times
-of the files it extracts as the time when the files were extracted,
-instead of setting it to the time recorded in the archive.
+When this option is used, @command{tar} leaves the data modification times
+of the files it extracts as the times when the files were extracted,
+instead of setting it to the times recorded in the archive.
-This option is meaningless with @value{op-list}.
+This option is meaningless with @option{--list} (@option{-t}).
+@opindex same-owner
@item --same-owner
Create extracted files with the same ownership they have in the
archive.
When writing an archive, @command{tar} writes the user id and user name
separately. If it can't find a user name (because the user id is not
in @file{/etc/passwd}), then it does not write one. When restoring,
-and doing a @code{chmod} like when you use @value{op-same-permissions},
+and doing a @code{chmod} like when you use @option{--same-permissions},
@FIXME{same-owner?}it tries to look the name (if one was written)
up in @file{/etc/passwd}. If it fails, then it uses the user id
stored in the archive instead.
+@opindex no-same-owner
@item --no-same-owner
@itemx -o
Do not attempt to restore ownership when extracting. This is the
default behavior for ordinary users, so this option has an effect
only for the superuser.
+@opindex numeric-owner
@item --numeric-owner
-The @value{op-numeric-owner} option allows (ANSI) archives to be written
+The @option{--numeric-owner} option allows (ANSI) archives to be written
without user/group name information or such information to be ignored
when extracting. It effectively disables the generation and/or use
of user/group name information. This option forces extraction using
an emergency floppy with different passwd/group files for example.
It is otherwise impossible to extract files with the right ownerships
if the password file in use during the extraction does not match the
-one belonging to the filesystem(s) being extracted. This occurs,
+one belonging to the file system(s) being extracted. This occurs,
for example, if you are restoring your files after a major crash and
had booted from an emergency floppy with no password file or put your
disk into another machine to do the restore.
The numeric ids are @emph{always} saved into @command{tar} archives.
The identifying names are added at create time when provided by the
-system, unless @value{op-old-archive} is used. Numeric ids could be
+system, unless @option{--old-archive} (@option{-o}) is used. Numeric ids could be
used when moving archives between a collection of machines using
a centralized management for attribution of numeric ids to users
and groups. This is often made through using the NIS capabilities.
already crowded with options and moreover, the approach just explained
gives you a great deal of control already.
+@opindex same-permissions, short description
+@opindex preserve-permissions, short description
@item -p
@itemx --same-permissions
@itemx --preserve-permissions
This option causes @command{tar} to set the modes (access permissions) of
extracted files exactly as recorded in the archive. If this option
is not used, the current @code{umask} setting limits the permissions
-on extracted files.
+on extracted files. This option is by default enabled when
+@command{tar} is executed by a superuser.
-This option is meaningless with @value{op-list}.
+This option is meaningless with @option{--list} (@option{-t}).
+
+@opindex preserve
@item --preserve
-Same as both @value{op-same-permissions} and @value{op-same-order}.
+Same as both @option{--same-permissions} and @option{--same-order}.
-The @value{op-preserve} option has no equivalent short option name.
-It is equivalent to @value{op-same-permissions} plus @value{op-same-order}.
+The @option{--preserve} option has no equivalent short option name.
+It is equivalent to @option{--same-permissions} plus @option{--same-order}.
@FIXME{I do not see the purpose of such an option. (Neither I. FP.)}
@end table
@node Standard
-@section The Standard Format
+@section Basic Tar Format
@UNREVISED
While an archive may contain many files, the archive itself is a
@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
In addition to entries describing archive members, an archive may
contain entries which @command{tar} itself uses to store information.
-@value{xref-label}, for an example of such an archive entry.
+@xref{label}, for an example of such an archive entry.
A @command{tar} archive file contains a series of blocks. Each block
contains @code{BLOCKSIZE} bytes. Although this format may be thought
Each file archived is represented by a header block which describes
the file, followed by zero or more blocks which give the contents
-of the file. At the end of the archive file there may be a block
+of the file. At the end of the archive file there are two 512-byte blocks
filled with binary zeros as an end-of-file marker. A reasonable system
-should write a block of zeros at the end, but must not assume that
-such a block exists when reading an archive.
+should write such end-of-file marker at the end of an archive, but
+must not assume that such a block exists when reading an archive. In
+particular @GNUTAR{} always issues a warning if it does not encounter it.
The blocks may be @dfn{blocked} for physical I/O operations.
Each record of @var{n} blocks (where @var{n} is set by the
-@value{op-blocking-factor} option to @command{tar}) is written with a single
+@option{--blocking-factor=@var{512-size}} (@option{-b @var{512-size}}) option to @command{tar}) is written with a single
@w{@samp{write ()}} operation. On magnetic tapes, the result of
such a write is a single record. When writing an archive,
the last record of blocks should be written at the full size, with
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
The @code{size} field is the size of the file in bytes; linked files
are archived with this field specified as zero. @FIXME-xref{Modifiers, in
-particular the @value{op-incremental} option.}
+particular the @option{--incremental} (@option{-G}) option.}
-The @code{mtime} field is the modification time of the file at the time
-it was archived. It is the ASCII representation of the octal value of
-the last time the file was modified, represented as an integer number of
+The @code{mtime} field is the data modification time of the file at
+the time it was archived. It is the ASCII representation of the octal
+value of the last time the file's contents were modified, represented
+as an integer number of
seconds since January 1, 1970, 00:00 Coordinated Universal Time.
The @code{chksum} field is the ASCII representation of the octal value
action occurs, @command{tar} issues a warning to the standard error.
The @code{atime} and @code{ctime} fields are used in making incremental
-backups; they store, respectively, the particular file's access time
-and last inode-change time.
+backups; they store, respectively, the particular file's access and
+status change times.
-The @code{offset} is used by the @value{op-multi-volume} option, when
+The @code{offset} is used by the @option{--multi-volume} (@option{-M}) option, when
making a multi-volume archive. The offset is number of bytes into
the file that we need to restart at to continue the file on the next
tape, i.e., where we store the location that a continued file is
@item GNUTYPE_DUMPDIR
@itemx 'D'
This represents a directory and a list of files created by the
-@value{op-incremental} option. The @code{size} field gives the total
+@option{--incremental} (@option{-G}) option. The @code{size} field gives the total
size of the associated list of files. Each file name is preceded by
either a @samp{Y} (the file should be in this archive) or an @samp{N}.
(The file is a directory, or is not stored in the archive.) Each file
@item GNUTYPE_MULTIVOL
@itemx 'M'
This represents a file continued from another volume of a multi-volume
-archive created with the @value{op-multi-volume} option. The original
+archive created with the @option{--multi-volume} (@option{-M}) option. The original
type of the file is not given here. The @code{size} field gives the
maximum size of this piece of the file (assuming the volume does
not end before the file is written out). The @code{offset} field
@item GNUTYPE_VOLHDR
@itemx 'V'
This file type is used to mark the volume header that was given with
-the @value{op-label} option when the archive was created. The @code{name}
-field contains the @code{name} given after the @value{op-label} option.
+the @option{--label=@var{archive-label}} (@option{-V @var{archive-label}}) option when the archive was created. The @code{name}
+field contains the @code{name} given after the @option{--label=@var{archive-label}} (@option{-V @var{archive-label}}) option.
The @code{size} field is zero. Only the first file in each volume
of an archive should have this type.
@end table
You may have trouble reading a @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
+non-@acronym{GNU} system if the options @option{--incremental} (@option{-G}),
+@option{--multi-volume} (@option{-M}), @option{--sparse} (@option{-S}), or @option{--label=@var{archive-label}} (@option{-V @var{archive-label}}) were
used when writing the archive. In general, if @command{tar} does not
use the @acronym{GNU}-added fields of the header, other versions of
@command{tar} should be able to read the archive. Otherwise, the
@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
@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.
+@command{remsh}) to start up an @command{/usr/libexec/rmt} on the remote
+machine. If you give an alternate login name, it will be given to the
+@command{rsh}.
+Naturally, the remote machine must have an executable
+@command{/usr/libexec/rmt}. This program is free software from the
+University of California, and a copy of the source code can be found
+with the sources for @command{tar}; it's compiled and installed by default.
+The exact path to this utility is determined when configuring the package.
+It is @file{@var{prefix}/libexec/rmt}, where @var{prefix} stands for
+your installation prefix. This location may also be overridden at
+runtime by using @option{rmt-command=@var{command}} option (@xref{Option Summary,
+---rmt-command}, for detailed description of this option. @xref{Remote
+Tape Server}, for the description of @command{rmt} command).
If this option is not given, but the environment variable @env{TAPE}
is set, its value is used; otherwise, old versions of @command{tar}
too. The installer could also check for @samp{DEFTAPE} in
@file{<sys/mtio.h>}.
-@table @kbd
+@table @option
+@opindex force-local, short description
@item --force-local
Archive file is local even if it contains a colon.
+@opindex rsh-command
@item --rsh-command=@var{command}
Use remote @var{command} instead of @command{rsh}. This option exists
so that people who use something other than the standard @command{rsh}
@item -[0-7][lmh]
Specify drive and density.
+@opindex multi-volume, short description
@item -M
@itemx --multi-volume
Create/list/extract multi-volume archive.
that may be larger than will fit on the medium used to hold it.
@xref{Multi-Volume Archives}.
+@opindex tape-length, short description
@item -L @var{num}
@itemx --tape-length=@var{num}
Change tape after writing @var{num} x 1024 bytes.
detect end of physical tapes. By being slightly conservative on the
maximum tape length, you might avoid the problem entirely.
+@opindex info-script, short description
+@opindex new-volume-script, short description
@item -F @var{file}
@itemx --info-script=@var{file}
@itemx --new-volume-script=@var{file}
-Execute @file{file} at end of each tape. If @file{file} exits with
-nonzero status, exit. This implies @value{op-multi-volume}.
+Execute @file{file} at end of each tape. This implies
+@option{--multi-volume} (@option{-M}). @xref{info-script}, for a detailed
+description of this option.
@end table
@node Remote Tape Server
@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, @GNUTAR{}
-will not allow you to create an archive that contains
+Unless you use the @option{--absolute-names} (@option{-P}) option,
+@GNUTAR{} will not allow you to create an archive that contains
absolute file names (a file name beginning with @samp{/}.) If you try,
@command{tar} will automatically remove the leading @samp{/} from the
file names it stores in the archive. It will also type a warning
relative to the current directory. If you want to extract the files in
an archive to the same absolute names that they had when the archive
was created, you should do a @samp{cd /} before extracting the files
-from the archive, or you should either use the @value{op-absolute-names}
+from the archive, or you should either use the @option{--absolute-names}
option, or use the command @samp{tar -C / @dots{}}.
@cindex Ultrix 3.1 and write failure
and industry-standard 9-track magnetic tape (or any other kind of tape
that can be backspaced with the @code{MTIOCTOP} @code{ioctl}.
-This means that the @value{op-append}, @value{op-update},
-@value{op-concatenate}, and @value{op-delete} commands will not work on any
-other kind of file. Some media simply cannot be backspaced, which
-means these commands and options will never be able to work on them.
-These non-backspacing media include pipes and cartridge tape drives.
+This means that the @option{--append}, @option{--concatenate}, and
+@option{--delete} commands will not work on any other kind of file.
+Some media simply cannot be backspaced, which means these commands and
+options will never be able to work on them. These non-backspacing
+media include pipes and cartridge tape drives.
Some other media can be backspaced, and @command{tar} will work on them
once @command{tar} is modified to do so.
-Archives created with the @value{op-multi-volume}, @value{op-label}, and
-@value{op-incremental} options may not be readable by other version
+Archives created with the @option{--multi-volume}, @option{--label}, and
+@option{--incremental} (@option{-G}) options may not be readable by other version
of @command{tar}. In particular, restoring a file that was split over
a volume boundary will require some careful work with @command{dd}, if
it can be done at all. Other versions of @command{tar} may also create
an empty file whose name is that of the volume header. Some versions
of @command{tar} may create normal files instead of directories archived
-with the @value{op-incremental} option.
+with the @option{--incremental} (@option{-G}) option.
@node Common Problems and Solutions
@section Some Common Problems and their Solutions
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
When writing to tapes, @command{tar} writes the contents of the archive
in chunks known as @dfn{records}. To change the default blocking
-factor, use the @value{op-blocking-factor} option. Each record will
-then be composed of @var{512-size} blocks. (Each @command{tar} block is
-512 bytes. @xref{Standard}.) Each file written to the archive uses
-at least one full record. As a result, using a larger record size
-can result in more wasted space for small files. On the other hand, a
-larger record size can often be read and written much more efficiently.
+factor, use the @option{--blocking-factor=@var{512-size}} (@option{-b
+@var{512-size}}) option. Each record will then be composed of
+@var{512-size} blocks. (Each @command{tar} block is 512 bytes.
+@xref{Standard}.) Each file written to the archive uses at least one
+full record. As a result, using a larger record size can result in
+more wasted space for small files. On the other hand, a larger record
+size can often be read and written much more efficiently.
Further complicating the problem is that some tape drives ignore the
blocking entirely. For these, a larger record size can still improve
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
+blocking factor (with @option{--blocking-factor}) larger than the
+actual blocking factor, and then use the @option{--read-full-records}
+(@option{-B}) option. (If you specify a blocking factor with
+@option{--blocking-factor} and don't use the
+@option{--read-full-records} option, then @command{tar} will not
attempt to figure out the recording size itself.) On some devices,
you must always specify the record size exactly with
-@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
+@option{--blocking-factor} when reading, because @command{tar} cannot
+figure it out. In any case, use @option{--list} (@option{-t}) before
+doing any extractions to see whether @command{tar} is reading the archive
correctly.
@command{tar} blocks are all fixed size (512 bytes), and its scheme for
In a standard @command{tar} file (no options), the block size is 512
and the record size is 10240, for a blocking factor of 20. What the
-@value{op-blocking-factor} option does is sets the blocking factor,
+@option{--blocking-factor} option does is sets the blocking factor,
changing the record size while leaving the block size at 512 bytes.
20 was fine for ancient 800 or 1600 bpi reel-to-reel tape drives;
most tape drives these days prefer much bigger records in order to
you can use the options described in the following sections.
If you do not specify any format parameters, @command{tar} uses
default parameters. You cannot modify a compressed archive.
-If you create an archive with the @value{op-blocking-factor} option
-specified (@value{pxref-blocking-factor}), you must specify that
+If you create an archive with the @option{--blocking-factor} option
+specified (@pxref{Blocking Factor}), you must specify that
blocking-factor when operating on the archive. @xref{Formats}, for other
examples of format parameter considerations.
@cindex Blocks per record
@UNREVISED
+@opindex blocking-factor
The data in an archive is grouped into blocks, which are 512 bytes.
Blocks are read and written in whole number multiples called
-@dfn{records}. The number of blocks in a record (ie. the size of a
+@dfn{records}. The number of blocks in a record (ie. the size of a
record in units of 512 bytes) is called the @dfn{blocking factor}.
-The @value{op-blocking-factor} option specifies the blocking factor of
-an archive. The default blocking factor is typically 20 (ie.@:
-10240 bytes), but can be specified at installation. To find out
-the blocking factor of an existing archive, use @samp{tar --list
---file=@var{archive-name}}. This may not work on some devices.
+The @option{--blocking-factor=@var{512-size}} (@option{-b
+@var{512-size}}) option specifies the blocking factor of an archive.
+The default blocking factor is typically 20 (i.e., 10240 bytes), but
+can be specified at installation. To find out the blocking factor of
+an existing archive, use @samp{tar --list --file=@var{archive-name}}.
+This may not work on some devices.
Records are separated by gaps, which waste space on the archive media.
If you are archiving on magnetic tape, using a larger blocking factor
(and therefore larger records) provides faster throughput and allows you
-to fit more data on a tape (because there are fewer gaps). If you are
+to fit more data on a tape (because there are fewer gaps). If you are
archiving on cartridge, a very large blocking factor (say 126 or more)
-greatly increases performance. A smaller blocking factor, on the other
+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
must specify the same blocking factor when you modify that archive. Some
archive devices will also require you to specify the blocking factor when
reading that archive, however this is not typically the case. Usually, you
-can use @value{op-list} without specifying a blocking factor---@command{tar}
+can use @option{--list} (@option{-t}) without specifying a blocking factor---@command{tar}
reports a non-default record size and then lists the archive members as
it would normally. To extract files from an archive with a non-standard
blocking factor (particularly if you're not sure what the blocking factor
-is), you can usually use the @value{op-read-full-records} option while
+is), you can usually use the @option{--read-full-records} (@option{-B}) option while
specifying a blocking factor larger then the blocking factor of the archive
-(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
-@xref{list}, for more information on the @value{op-list}
+(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
+@xref{list}, for more information on the @option{--list} (@option{-t})
operation. @xref{Reading}, for a more detailed explanation of that option.
-@table @kbd
+@table @option
@item --blocking-factor=@var{number}
@itemx -b @var{number}
Specifies the blocking factor of an archive. Can be used with any
-operation, but is usually not necessary with @value{op-list}.
+operation, but is usually not necessary with @option{--list} (@option{-t}).
@end table
Device blocking
-@table @kbd
+@table @option
@item -b @var{blocks}
@itemx --blocking-factor=@var{blocks}
Set record size to @math{@var{blocks} * 512} bytes.
the archive is directly handled to a local disk, instead of any special
device,
@item
-@value{op-blocking-factor} is not explicitly specified on the @command{tar}
+@option{--blocking-factor} is not explicitly specified on the @command{tar}
invocation.
@end itemize
@command{tar} should rather drain the pipe out before exiting itself.
@end itemize
+@opindex ignore-zeros, short description
@item -i
@itemx --ignore-zeros
Ignore blocks of zeros in archive (means EOF).
-The @value{op-ignore-zeros} option causes @command{tar} to ignore blocks
+The @option{--ignore-zeros} (@option{-i}) option causes @command{tar} to ignore blocks
of zeros in the archive. Normally a block of zeros indicates the
end of the archive, but when reading a damaged archive, or one which
was created by concatenating several archives together, this option
archive file, which may sometimes avoid problems when multiple files
are stored on a single physical tape.
+@opindex read-full-records, short description
@item -B
@itemx --read-full-records
Reblock as we read (for reading 4.2BSD pipes).
-If @value{op-read-full-records} is used, @command{tar} will not panic if an
-attempt to read a record from the archive does not return a full record.
-Instead, @command{tar} will keep reading until it has obtained a full
+If @option{--read-full-records} is used, @command{tar}
+will not panic if an attempt to read a record from the archive does
+not return a full record. Instead, @command{tar} will keep reading
+until it has obtained a full
record.
This option is turned on by default when @command{tar} is reading
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
head is on. Before writing an archive, you should make sure that no
data on the tape will be overwritten (unless it is no longer needed).
Before reading an archive, you should make sure the tape head is at
-the beginning of the archive you want to read. (The @code{restore}
-script will find the archive automatically. @FIXME{There is no such
-restore script!}@FIXME-xref{Scripted Restoration}@xref{mt}, for
-an explanation of the tape moving utility.
+the beginning of the archive you want to read. You can do it manually
+via @code{mt} utility (@pxref{mt}). The @code{restore} script does
+that automatically (@pxref{Scripted Restoration}).
If you want to add new archive file entries to a tape, you should
advance the tape to the end of the existing file entries, backspace
@FIXME{Is it true that this only works on non-block devices?
should explain the difference, (fixed or variable).}
-@value{xref-blocking-factor}.
+@xref{Blocking Factor}.
You can use the @command{mt} utility to advance or rewind a tape past a
specified number of archive files on the tape. This will allow you
@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
Often you might want to write a large archive, one larger than will fit
on the actual tape you are using. In such a case, you can run multiple
@command{tar} commands, but this can be inconvenient, particularly if you
-are using options like @value{op-exclude} or dumping entire filesystems.
+are using options like @option{--exclude=@var{pattern}} or dumping entire file systems.
Therefore, @command{tar} supports multiple tapes automatically.
-Use @value{op-multi-volume} on the command line, and then @command{tar} will,
-when it reaches the end of the tape, prompt for another tape, and
-continue the archive. Each tape will have an independent archive, and
-can be read without needing the other. (As an exception to this, the
-file that @command{tar} was archiving when it ran out of tape will usually
-be split between the two archives; in this case you need to extract from
-the first archive, using @value{op-multi-volume}, and then put in the
-second tape when prompted, so @command{tar} can restore both halves of the
-file.)
+Use @option{--multi-volume} (@option{-M}) on the command line, and
+then @command{tar} will, when it reaches the end of the tape, prompt
+for another tape, and continue the archive. Each tape will have an
+independent archive, and can be read without needing the other. (As
+an exception to this, the file that @command{tar} was archiving when
+it ran out of tape will usually be split between the two archives; in
+this case you need to extract from the first archive, using
+@option{--multi-volume}, and then put in the second tape when
+prompted, so @command{tar} can restore both halves of the file.)
-@GNUTAR{} multi-volume archives do not use a truly
-portable format. You need @GNUTAR{} at both end to
-process them properly.
+@GNUTAR{} multi-volume archives do not use a truly portable format.
+You need @GNUTAR{} at both ends to process them properly.
When prompting for a new tape, @command{tar} accepts any of the following
responses:
@item n @var{file name}
Request @command{tar} to write the next volume on the file @var{file name}.
@item !
-Request @command{tar} to run a subshell.
+Request @command{tar} to run a subshell. This option can be disabled
+by giving @option{--restrict} command line option to @command{tar}.
@item y
Request @command{tar} to begin writing the next volume.
@end table
(You should only type @samp{y} after you have changed the tape;
otherwise @command{tar} will write over the volume it just finished.)
+@cindex End-of-archive info script
+@cindex Info script
+@anchor{info-script}
+@opindex info-script
+@opindex new-volume-script
If you want more elaborate behavior than this, give @command{tar} the
-@value{op-info-script} option. The file @var{script-name} is expected
-to be a program (or shell script) to be run instead of the normal
-prompting procedure. If the program fails, @command{tar} exits;
-otherwise, @command{tar} begins writing the next volume. The behavior
-of the
-@samp{n} response to the normal tape-change prompt is not available
-if you use @value{op-info-script}.
+@option{--info-script=@var{script-name}}
+(@option{--new-volume-script=@var{script-name}}, @option{-F
+@var{script-name}}) option. The file @var{script-name} is expected to
+be a program (or shell script) to be run instead of the normal
+prompting procedure. It is executed without any command line
+arguments. Additional data is passed to it via the following
+environment variables:
+
+@table @env
+@vrindex TAR_VERSION, info script environment variable
+@item TAR_VERSION
+@GNUTAR{} version number.
+
+@vrindex TAR_ARCHIVE, info script environment variable
+@item TAR_ARCHIVE
+The name of the archive @command{tar} is processing.
+
+@vrindex TAR_VOLUME, info script environment variable
+@item TAR_VOLUME
+Ordinal number of the volume @command{tar} is about to start.
+
+@vrindex TAR_SUBCOMMAND, info script environment variable
+@item TAR_SUBCOMMAND
+Short option describing the operation @command{tar} is executed.
+@xref{Operations}, for a complete list of subcommand options.
+
+@vrindex TAR_FORMAT, info script environment variable
+@item TAR_FORMAT
+Format of the archive being processed. @xref{Formats}, for a complete
+list of archive format names.
+@end table
+
+The info script can instruct @command{tar} to use new archive name,
+by writing in to file descriptor 3 (see below for an
+example).
+
+If the info script fails, @command{tar} exits; otherwise, it begins
+writing the next volume.
The method @command{tar} uses to detect end of tape is not perfect, and
fails on some operating systems or on some devices. You can use the
-@value{op-tape-length} option if @command{tar} can't detect the end of the
-tape itself. This option selects @value{op-multi-volume} automatically.
-The @var{size} argument should then be the usable size of the tape.
-But for many devices, and floppy disks in particular, this option is
-never required for real, as far as we know.
-
+@option{--tape-length=@var{size}} (@option{-L @var{size}}) option if
+@command{tar} can't detect the end of the tape itself. This option
+selects @option{--multi-volume} (@option{-M}) automatically. The
+@var{size} argument should then be the usable size of the tape in
+units of 1024 bytes. But for many devices, and floppy disks in
+particular, this option is never required for real, as far as we know.
+
+@cindex Volume number file
+@cindex volno file
+@anchor{volno-file}
+@opindex volno-file
The volume number used by @command{tar} in its tape-change prompt
-can be changed; if you give the @value{op-volno-file} option, then
-@var{file-of-number} should be an unexisting file to be created, or else,
-a file already containing a decimal number. That number will be used
-as the volume number of the first volume written. When @command{tar} is
-finished, it will rewrite the file with the now-current volume number.
-(This does not change the volume number written on a tape label, as
-per @value{ref-label}, it @emph{only} affects the number used in
-the prompt.)
-
-If you want @command{tar} to cycle through a series of tape drives, then
-you can use the @samp{n} response to the tape-change prompt. This is
-error prone, however, and doesn't work at all with @value{op-info-script}.
-Therefore, if you give @command{tar} multiple @value{op-file} options, then
-the specified files will be used, in sequence, as the successive volumes
-of the archive. Only when the first one in the sequence needs to be
-used again will @command{tar} prompt for a tape change (or run the info
-script).
-
-Multi-volume archives
-
-With @value{op-multi-volume}, @command{tar} will not abort when it cannot
-read or write any more data. Instead, it will ask you to prepare a new
-volume. If the archive is on a magnetic tape, you should change tapes
-now; if the archive is on a floppy disk, you should change disks, etc.
+can be changed; if you give the
+@option{--volno-file=@var{file-of-number}} option, then
+@var{file-of-number} should be an unexisting file to be created, or
+else, a file already containing a decimal number. That number will be
+used as the volume number of the first volume written. When
+@command{tar} is finished, it will rewrite the file with the
+now-current volume number. (This does not change the volume number
+written on a tape label, as per @ref{label}, it @emph{only} affects
+the number used in the prompt.)
+
+If you want @command{tar} to cycle through a series of files or tape
+drives, there are three approaches to choose from. First of all, you
+can give @command{tar} multiple @option{--file} options. In this case
+the specified files will be used, in sequence, as the successive
+volumes of the archive. Only when the first one in the sequence needs
+to be used again will @command{tar} prompt for a tape change (or run
+the info script). Secondly, you can use the @samp{n} response to the
+tape-change prompt, and, finally, you can use an info script, that
+writes new archive name to file descriptor. The following example
+illustrates this approach:
+
+@smallexample
+@group
+#! /bin/sh
+echo Preparing volume $TAR_VOLUME of $TAR_ARCHIVE.
+
+name=`expr $TAR_ARCHIVE : '\(.*\)-.*'`
+case $TAR_SUBCOMMAND in
+-c) ;;
+-d|-x|-t) test -r $@{name:-$TAR_ARCHIVE@}-$TAR_VOLUME || exit 1
+ ;;
+*) exit 1
+esac
+
+echo $@{name:-$TAR_ARCHIVE@}-$TAR_VOLUME >&3
+@end group
+@end smallexample
Each volume of a multi-volume archive is an independent @command{tar}
archive, complete in itself. For example, you can list or extract any
-volume alone; just don't specify @value{op-multi-volume}. However, if one
-file in the archive is split across volumes, the only way to extract
-it successfully is with a multi-volume extract command @samp{--extract
---multi-volume} (@samp{-xM}) starting on or before the volume where
-the file begins.
+volume alone; just don't specify @option{--multi-volume}
+(@option{-M}). However, if one file in the archive is split across
+volumes, the only way to extract it successfully is with a
+multi-volume extract command @option{--extract --multi-volume}
+(@option{-xM}) starting on or before the volume where the file begins.
For example, let's presume someone has two tape drives on a system
named @file{/dev/tape0} and @file{/dev/tape1}. For having @GNUTAR{}
@menu
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
+
@end menu
@node Multi-Volume Archives
@cindex Multi-volume archives
@UNREVISED
+@opindex multi-volume
To create an archive that is larger than will fit on a single unit of
-the media, use the @value{op-multi-volume} option in conjunction with
-the @value{op-create} option (@pxref{create}). A
-@dfn{multi-volume} archive can be manipulated like any other archive
-(provided the @value{op-multi-volume} option is specified), but is
-stored on more than one tape or disk.
+the media, use the @option{--multi-volume} (@option{-M}) option in conjunction with
+the @option{--create} option (@pxref{create}). A @dfn{multi-volume}
+archive can be manipulated like any other archive (provided the
+@option{--multi-volume} option is specified), but is stored on more
+than one tape or disk.
-When you specify @value{op-multi-volume}, @command{tar} does not report an
+When you specify @option{--multi-volume}, @command{tar} does not report an
error when it comes to the end of an archive volume (when reading), or
the end of the media (when writing). Instead, it prompts you to load
a new storage volume. If the archive is on a magnetic tape, you
You can read each individual volume of a multi-volume archive as if it
were an archive by itself. For example, to list the contents of one
-volume, use @value{op-list}, without @value{op-multi-volume} specified.
+volume, use @option{--list}, without @option{--multi-volume} specified.
To extract an archive member from one volume (assuming it is described
-that volume), use @value{op-extract}, again without
-@value{op-multi-volume}.
+that volume), use @option{--extract}, again without
+@option{--multi-volume}.
-If an archive member is split across volumes (ie. its entry begins on
+If an archive member is split across volumes (ie. its entry begins on
one volume of the media and ends on another), you need to specify
-@value{op-multi-volume} to extract it successfully. In this case, you
+@option{--multi-volume} to extract it successfully. In this case, you
should load the volume where the archive member starts, and use
@samp{tar --extract --multi-volume}---@command{tar} will prompt for later
volumes as it needs them. @xref{extracting archives}, for more
information about extracting archives.
-@value{op-info-script} is like @value{op-multi-volume}, except that
-@command{tar} does not prompt you directly to change media volumes when
-a volume is full---instead, @command{tar} runs commands you have stored
-in @var{script-name}. For example, this option can be used to eject
+@option{--info-script=@var{script-name}}
+(@option{--new-volume-script=@var{script-name}}, @option{-F
+@var{script-name}}) (@pxref{info-script}) is like
+@option{--multi-volume} (@option{-M}), except that @command{tar} does
+not prompt you directly to change media volumes when a volume is
+full---instead, @command{tar} runs commands you have stored in
+@var{script-name}. For example, this option can be used to eject
cassettes, or to broadcast messages such as @samp{Someone please come
-change my tape} when performing unattended backups. When @var{script-name}
-is done, @command{tar} will assume that the media has been changed.
+change my tape} when performing unattended backups. When
+@var{script-name} is done, @command{tar} will assume that the media
+has been changed.
Multi-volume archives can be modified like any other archive. To add
files to a multi-volume archive, you need to only mount the last
volume of the archive media (and new volumes, if needed). For all
other operations, you need to use the entire archive.
-If a multi-volume archive was labeled using @value{op-label}
-(@value{pxref-label}) when it was created, @command{tar} will not
-automatically label volumes which are added later. To label subsequent
-volumes, specify @value{op-label} again in conjunction with the
-@value{op-append}, @value{op-update} or @value{op-concatenate} operation.
+If a multi-volume archive was labeled using
+@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
+(@pxref{label}) when it was created, @command{tar} will not
+automatically label volumes which are added later. To label
+subsequent volumes, specify @option{--label=@var{archive-label}} again
+in conjunction with the @option{--append}, @option{--update} or
+@option{--concatenate} operation.
@cindex Labeling multi-volume archives
@FIXME{example}
@FIXME{There should be a sample program here, including an exit
-before end. Is the exit status even checked in tar? :-(}
+before end. Is the exit status even checked in tar? :-(}
-@table @kbd
+@table @option
@item --multi-volume
@itemx -M
Creates a multi-volume archive, when used in conjunction with
-@value{op-create}. To perform any other operation on a multi-volume
-archive, specify @value{op-multi-volume} in conjunction with that
+@option{--create} (@option{-c}). To perform any other operation on a multi-volume
+archive, specify @option{--multi-volume} in conjunction with that
operation.
@item --info-script=@var{program-file}
+@itemx --new-volume-script=@var{program-file}
@itemx -F @var{program-file}
Creates a multi-volume archive via a script. Used in conjunction with
-@value{op-create}.
+@option{--create} (@option{-c}). @xref{info-script}, dor a detailed discussion.
@end table
Beware that there is @emph{no} real standard about the proper way, for
@UNREVISED
To give the archive a name which will be recorded in it, use the
-@value{op-label} option. This will write a special block identifying
-@var{volume-label} as the name of the archive to the front of the archive
-which will be displayed when the archive is listed with @value{op-list}.
-If you are creating a multi-volume archive with
-@value{op-multi-volume}@FIXME-pxref{Using Multiple Tapes}, then the
-volume label will have
-@samp{Volume @var{nnn}} appended to the name you give, where @var{nnn} is
-the number of the volume of the archive. (If you use the @value{op-label}
-option when reading an archive, it checks to make sure the label on the
-tape matches the one you give. @value{xref-label}.
+@option{--label=@var{volume-label}} (@option{-V @var{volume-label}})
+option. This will write a special block identifying
+@var{volume-label} as the name of the archive to the front of the
+archive which will be displayed when the archive is listed with
+@option{--list}. If you are creating a multi-volume archive with
+@option{--multi-volume} (@pxref{Using Multiple Tapes}), then the
+volume label will have @samp{Volume @var{nnn}} appended to the name
+you give, where @var{nnn} is the number of the volume of the archive.
+(If you use the @option{--label=@var{volume-label}}) option when
+reading an archive, it checks to make sure the label on the tape
+matches the one you give. @xref{label}.
When @command{tar} writes an archive to tape, it creates a single
tape file. If multiple archives are written to the same tape, one
or such, for pushing a common date in all volumes or an archive set.
+@node Tarcat
+@subsection Concatenate Volumes into a Single Archive
+
+@pindex tarcat
+ Sometimes it is necessary to convert existing @GNUTAR{} multi-volume
+archive to a single @command{tar} archive. Simply concatenating all
+volumes into one will not work, since each volume carries an additional
+information at the beginning. @GNUTAR{} is shipped with the shell
+script @command{tarcat} designed for this purpose.
+
+ The script takes a list of files comprising a multi-volume archive
+and creates the resulting archive at the standard output. For example:
+
+@smallexample
+@kbd{tarcat vol.1 vol.2 vol.3 | tar tf -}
+@end smallexample
+
+ The script implements a simple heuristics to determine the format of
+the first volume file and to decide how to process the rest of the
+files. However, it makes no attempt to verify whether the files are
+given in order or even if they are valid @command{tar} archives.
+It uses @command{dd} and does not filter its standard error, so you
+will usually see lots of spurious messages.
+
+@FIXME{The script is not installed. Should we install it?}
+
@node label
@section Including a Label in the Archive
@cindex Labeling an archive
@cindex Labels on the archive media
@UNREVISED
-@table @kbd
-@item -V @var{name}
-@itemx --label=@var{name}
-Create archive with volume name @var{name}.
+@opindex label
+ To avoid problems caused by misplaced paper labels on the archive
+media, you can include a @dfn{label} entry---an archive member which
+contains the name of the archive---in the archive itself. Use the
+@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
+option in conjunction with the @option{--create} operation to include
+a label entry in the archive as it is being created.
+
+@table @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
+@option{--create} operation. Checks to make sure the archive label
+matches the one specified (when used in conjunction with any other
+operation.
@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}
+ If you create an archive using both
+@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
+and @option{--multi-volume} (@option{-M}), each volume of the archive
+will have an archive label of the form @samp{@var{archive-label}
Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
-next, and so on.
-
-@FIXME{Should the arg to --label be a quoted string?? No.}
+next, and so on. @xref{Using Multiple Tapes}, for information on
+creating multiple volume archives.
-To avoid problems caused by misplaced paper labels on the archive
-media, you can include a @dfn{label} entry---an archive member which
-contains the name of the archive---in the archive itself. Use the
-@value{op-label} option in conjunction with the @value{op-create} operation
-to include a label entry in the archive as it is being created.
-
-If you create an archive using both @value{op-label} and
-@value{op-multi-volume}, each volume of the archive will have an
-archive label of the form @samp{@var{archive-label} Volume @var{n}},
-where @var{n} is 1 for the first volume, 2 for the next, and so on.
-@FIXME-xref{Multi-Volume Archives, for information on creating multiple
-volume archives.}
-
-If you list or extract an archive using @value{op-label}, @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:
@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
+-rw-r--r-- ringo user 40 1990-05-21 13:30 iamafilename
+@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
+@opindex test-label
+@anchor{--test-label option}
+ However, @option{--list} option will cause listing entire
+contents of the archive, which may be undesirable (for example, if the
+archive is stored on a tape). You can request checking only the volume
+by specifying @option{--test-label} option. This option reads only the
+first block of an archive, so it can be used with slow storage
+devices. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive}
+iamalabel
+@end group
+@end smallexample
+
+ If @option{--test-label} is used with a single command line
+argument, @command{tar} compares the volume label with the
+argument. It exits with code 0 if the two strings match, and with code
+2 otherwise. In this case no output is displayed. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable'}
+@result{} 0
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable' alabel}
+@result{} 1
+@end group
+@end smallexample
-To get a common information on all tapes of a series, use the
-@value{op-label} option. For having this information different in each
+ If you request any operation, other than @option{--create}, along
+with using @option{--label} option, @command{tar} will first check if
+the archive label matches the one specified and will refuse to proceed
+if it does not. Use this as a safety precaution to avoid accidentally
+overwriting existing archives. For example, if you wish to add files
+to @file{archive}, presumably labelled with string @samp{My volume},
+you will get:
+
+@smallexample
+@group
+$ @kbd{tar -rf archive --label 'My volume' .}
+tar: Archive not labeled to match `My volume'
+@end group
+@end smallexample
+
+@noindent
+in case its label does not match. This will work even if
+@file{archive} is not labelled at all.
+
+ Similarly, @command{tar} will refuse to list or extract the
+archive if its label doesn't match the @var{archive-label}
+specified. In those cases, @var{archive-label} argument is interpreted
+as a globbing-style pattern which must match the actual magnetic
+volume label. @xref{exclude}, for a precise description of how match
+is attempted@footnote{Previous versions of @command{tar} used full
+regular expression matching, or before that, only exact string
+matching, instead of wildcard matchers. We decided for the sake of
+simplicity to use a uniform matching device through
+@command{tar}.}. If the switch @option{--multi-volume} (@option{-M}) is being used,
+the volume label matcher will also suffix @var{archive-label} by
+@w{@samp{ Volume [1-9]*}} if the initial match fails, before giving
+up. Since the volume numbering is automatically added in labels at
+creation time, it sounded logical to equally help the user taking care
+of it when the archive is being read.
+
+ The @option{--label} was once called @option{--volume}, but is not
+available under that name anymore.
+
+ You can also use @option{--label} to get a common information on
+all tapes of a series. For having this information different in each
series created through a single script used on a regular basis, just
manage to get some date string as part of the label. For example:
@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 group
@end smallexample
-Also note that each label has its own date and time, which corresponds
+ 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
rewinding tapes and the operator switching them were negligible, which
is usually not the case.
-@FIXME{was --volume}
-
@node verify
@section Verifying Data as It is Stored
@cindex Verifying a write operation
@cindex Double-checking a write operation
-@table @kbd
+@table @option
@item -W
@itemx --verify
+@opindex verify, short description
Attempt to verify the archive after writing.
@end table
operation, or can compare a previously written archive, to insure that
it is up to date.
+@opindex verify, using with @option{--create}
+@opindex create, using with @option{--verify}
To check for discrepancies in an archive immediately after it is
-written, use the @value{op-verify} option in conjunction with
-the @value{op-create} operation. When this option is
+written, use the @option{--verify} (@option{-W}) option in conjunction with
+the @option{--create} operation. When this option is
specified, @command{tar} checks archive members against their counterparts
in the file system, and reports discrepancies on the standard error.
errors on some tapes. Archives written to pipes, some cartridge tape
drives, and some other devices cannot be verified.
-One can explicitly compare an already made archive with the file system
-by using the @value{op-compare} option, instead of using the more automatic
-@value{op-verify} option. @value{xref-compare}.
+One can explicitly compare an already made archive with the file
+system by using the @option{--compare} (@option{--diff}, @option{-d})
+option, instead of using the more automatic @option{--verify} option.
+@xref{compare}.
Note that these two options have a slightly different intent. The
-@value{op-compare} option how identical are the logical contents of some
-archive with what is on your disks, while the @value{op-verify} option is
+@option{--compare} option checks how identical are the logical contents of some
+archive with what is on your disks, while the @option{--verify} option is
really for checking if the physical contents agree and if the recording
-media itself is of dependable quality. So, for the @value{op-verify}
+media itself is of dependable quality. So, for the @option{--verify}
operation, @command{tar} tries to defeat all in-memory cache pertaining to
the archive, while it lets the speed optimization undisturbed for the
-@value{op-compare} option. If you nevertheless use @value{op-compare} for
+@option{--compare} option. If you nevertheless use @option{--compare} for
media verification, you may have to defeat the in-memory cache yourself,
maybe by opening and reclosing the door latch of your recording unit,
forcing some doubt in your operating system about the fact this is really
the same volume as the one just written or read.
-The @value{op-verify} option would not be necessary if drivers were indeed
+The @option{--verify} option would not be necessary if drivers were indeed
able to detect dependably all write failures. This sometimes require many
magnetic heads, some able to read after the writes occurred. One would
not say that drivers unable to detect all cases are necessarily flawed,
as long as programming is concerned.
-The @value{op-verify} 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 @option{--verify} (@option{-W}) option will not work in
+conjunction with the @option{--multi-volume} (@option{-M}) option or
+the @option{--append} (@option{-r}), @option{--update} (@option{-u})
+and @option{--delete} operations. @xref{Operations}, for more
+information on these operations.
Also, since @command{tar} normally strips leading @samp{/} from file
names (@pxref{absolute}), a command like @samp{tar --verify -cf
which can be removed from the center of a tape reel, or some other
changeable feature.
+@node Changes
+@appendix Changes
+
+This appendix lists some important user-visible changes between
+version @GNUTAR{} @value{VERSION} and previous versions. An up-to-date
+version of this document is available at
+@uref{http://www.gnu.org/@/software/@/tar/manual/changes.html,the
+@GNUTAR{} documentation page}.
+
+@table @asis
+@item Use of short option @option{-o}.
+
+Earlier versions of @GNUTAR{} understood @option{-o} command line
+option as a synonym for @option{--old-archive}.
+
+@GNUTAR{} starting from version 1.13.90 understands this option as
+a synonym for @option{--no-same-owner}. This is compatible with
+UNIX98 @command{tar} implementations.
+
+However, to facilitate transition, @option{-o} option retains its
+old semantics when it is used with one of archive-creation commands.
+Users are encouraged to use @option{--format=oldgnu} instead.
+
+It is especially important, since versions of @acronym{GNU} Automake
+up to and including 1.8.4 invoke tar with this option to produce
+distribution tarballs. @xref{Formats,v7}, for the detailed discussion
+of this issue and its implications.
+
+Future versions of @GNUTAR{} will understand @option{-o} only as a
+synonym for @option{--no-same-owner}.
+
+@item Use of short option @option{-l}
+
+Earlier versions of @GNUTAR{} understood @option{-l} option as a
+synonym for @option{--one-file-system}. Such usage is deprecated.
+For compatibility with other implementations future versions of
+@GNUTAR{} will understand this option as a synonym for
+@option{--check-links}.
+
+@item Use of options @option{--portability} and @option{--old-archive}
+
+These options are deprecated. Please use @option{--format=v7} instead.
+
+@item Use of option @option{--posix}
+
+This option is deprecated. Please use @option{--format=posix} instead.
+@end table
+
+@node Configuring Help Summary
+@appendix Configuring Help Summary
+
+Running @kbd{tar --help} displays the short @command{tar} option
+summary (@pxref{help}). This summary is organised by @dfn{groups} of
+semantically close options. The options within each group are printed
+in the following order: a short option, eventually followed by a list
+of corresponding long option names, followed by a short description of
+the option. For example, here is an excerpt from the actual @kbd{tar
+--help} output:
+
+@verbatim
+ Main operation mode:
+
+ -A, --catenate, --concatenate append tar files to an archive
+ -c, --create create a new archive
+ -d, --diff, --compare find differences between archive and
+ file system
+ --delete delete from the archive
+@end verbatim
+
+@vrindex ARGP_HELP_FMT, environment variable
+The exact visual representation of the help output is configurable via
+@env{ARGP_HELP_FMT} environment variable. The value of this variable
+is a comma-separated list of @dfn{format variable} assignments. There
+are two kinds of format variables. An @dfn{offset variable} keeps the
+offset of some part of help output text from the leftmost column on
+the screen. A @dfn{boolean} variable is a flag that toggles some
+output feature on or off. Depending on the type of the corresponding
+variable, there are two kinds of assignments:
+
+@table @asis
+@item Offset assignment
+
+The assignment to an offset variable has the following syntax:
+
+@smallexample
+@var{variable}=@var{value}
+@end smallexample
+
+@noindent
+where @var{variable} is the variable name, and @var{value} is a
+numeric value to be assigned to the variable.
+
+@item Boolean assignment
+
+To assign @code{true} value to a variable, simply put this variable name. To
+assign @code{false} value, prefix the variable name with @samp{no-}. For
+example:
+
+@smallexample
+@group
+# Assign @code{true} value:
+dup-args
+# Assign @code{false} value:
+no-dup-args
+@end group
+@end smallexample
+@end table
+
+Following variables are declared:
+
+@deftypevr {Help Output} boolean dup-args
+If true, arguments for an option are shown with both short and long
+options, even when a given option has both forms, for example:
+
+@smallexample
+ -f ARCHIVE, --file=ARCHIVE use archive file or device ARCHIVE
+@end smallexample
+
+If false, then if an option has both short and long forms, the
+argument is only shown with the long one, for example:
+
+@smallexample
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+@end smallexample
+
+@noindent
+and a message indicating that the argument is applicable to both
+forms is printed below the options. This message can be disabled
+using @code{dup-args-note} (see below).
+
+The default is false.
+@end deftypevr
+
+@deftypevr {Help Output} boolean dup-args-note
+If this variable is true, which is the default, the following notice
+is displayed at the end of the help output:
+
+@quotation
+Mandatory or optional arguments to long options are also mandatory or
+optional for any corresponding short options.
+@end quotation
+
+Setting @code{no-dup-args-note} inhibits this message. Normally, only one of
+variables @code{dup-args} or @code{dup-args-note} should be set.
+@end deftypevr
+
+@deftypevr {Help Output} offset short-opt-col
+Column in which short options start. Default is 2.
+
+@smallexample
+@group
+$ @kbd{tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=short-opt-col=6 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+@end group
+@end smallexample
+@end deftypevr
+
+@deftypevr {Help Output} offset long-opt-col
+Column in which long options start. Default is 6. For example:
+
+@smallexample
+@group
+$ @kbd{tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=long-opt-col=16 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+@end group
+@end smallexample
+@end deftypevr
+
+@deftypevr {Help Output} offset doc-opt-col
+Column in which @dfn{doc options} start. A doc option isn't actually
+an option, but rather an arbitrary piece of documentation that is
+displayed in much the same manner as the options. For example, in
+the description of @option{--format} option:
+
+@smallexample
+@group
+ -H, --format=FORMAT create archive of the given format.
+
+ FORMAT is one of the following:
+
+ gnu GNU tar 1.13.x format
+ oldgnu GNU format as per tar <= 1.12
+ pax POSIX 1003.1-2001 (pax) format
+ posix same as pax
+ ustar POSIX 1003.1-1988 (ustar) format
+ v7 old V7 tar format
+@end group
+@end smallexample
+
+@noindent
+the format names are doc options. Thus, if you set
+@kbd{ARGP_HELP_FMT=doc-opt-col=6} the above part of the help output
+will look as follows:
+
+@smallexample
+@group
+ -H, --format=FORMAT create archive of the given format.
+
+ FORMAT is one of the following:
+
+ gnu GNU tar 1.13.x format
+ oldgnu GNU format as per tar <= 1.12
+ pax POSIX 1003.1-2001 (pax) format
+ posix same as pax
+ ustar POSIX 1003.1-1988 (ustar) format
+ v7 old V7 tar format
+@end group
+@end smallexample
+@end deftypevr
+
+@deftypevr {Help Output} offset opt-doc-col
+Column in which option description starts. Default is 29.
+
+@smallexample
+@group
+$ @kbd{tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=opt-doc-col=19 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE use archive file or device ARCHIVE
+$ @kbd{ARGP_HELP_FMT=opt-doc-col=9 tar --help|grep ARCHIVE}
+ -f, --file=ARCHIVE
+ use archive file or device ARCHIVE
+@end group
+@end smallexample
+
+@noindent
+Notice, that the description starts on a separate line if
+@code{opt-doc-col} value is too small.
+@end deftypevr
+
+@deftypevr {Help Output} offset header-col
+Column in which @dfn{group headers} are printed. A group header is a
+descriptive text preceding an option group. For example, in the
+following text:
+
+@verbatim
+ Main operation mode:
+
+ -A, --catenate, --concatenate append tar files to
+ an archive
+ -c, --create create a new archive
+@end verbatim
+@noindent
+@samp{Main operation mode:} is the group header.
+
+The default value is 1.
+@end deftypevr
+
+@deftypevr {Help Output} offset usage-indent
+Indentation of wrapped usage lines. Affects @option{--usage}
+output. Default is 12.
+@end deftypevr
+
+@deftypevr {Help Output} offset rmargin
+Right margin of the text output. Used for wrapping.
+@end deftypevr
+
+@node Genfile
+@appendix Genfile
+@include genfile.texi
+
+@node Snapshot Files
+@appendix Format of the Incremental Snapshot Files
+@include snapshot.texi
+
@node Free Software Needs Free Documentation
@appendix Free Software Needs Free Documentation
@include freemanuals.texi
@include fdl.texi
+@node Index of Command Line Options
+@appendix Index of Command Line Options
+
+This appendix contains an index of all @GNUTAR{} long command line
+options. The options are listed without the preceeding double-dash.
+
+@FIXME{@itemize
+@item Make sure @emph{all} options are indexed.
+@item Provide an index of short options
+@end itemize}
+
+@printindex op
+
@node Index
@appendix Index
projects / chaz / tar / blobdiff