@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-format-ustar @kbd{--format=ustar}
-
-@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
from archives.
Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
-2003 Free Software Foundation, Inc.
+2003, 2004 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
* delete::
* compare::
-How to Add Files to Existing Archives: @code{--append}
+How to Add Files to Existing Archives: @option{--append}
* appending files:: Appending Files to an Archive
* multiple::
* how to update::
-Options Used by @code{--create}
+Options Used by @option{--create}
* Ignore Failed Read::
-Options Used by @code{--extract}
+Options Used by @option{--extract}
* Reading:: Options to Help Read Archives
* Writing:: Changing How @command{tar} Writes Files
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
Setting Parameters for Backups and Restoration
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
Choosing Files and Names for @command{tar}
* Day of week items:: Monday and others.
* Relative items in date strings:: next tuesday, 2 years ago.
* Pure numbers in date strings:: 19931219, 1440.
-* Authors of getdate:: Bellovin, Eggert, Salz, Berets, et al.
+* Seconds since the Epoch:: @@1078100502.
+* Authors of get_date:: Bellovin, Eggert, Salz, Berets, et al.
Controlling the Archive Format
* 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.
@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
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
@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.
+@item Revise sparse file handling and multiple volume processing.
+@item Merge with the @acronym{GNU} @code{paxutils} project.
@end itemize
-The following issues need mentioning:
+Some of these aims are already attained, while others are still
+being worked upon. From the point of view of an end user, the
+following issues need special mentioning:
@table @asis
@item Use of short option @option{-o}.
+
Earlier versions of @GNUTAR{} understood @option{-o} command line
option as a synonym for @option{--old-archive}.
old semantics when it is used with one of archive-creation commands.
Users are encouraged to use @value{op-format-oldgnu} instead.
+It is especially important, since versions of @acronym{GNU} Automake
+up to and including 1.8.4 invoke tar with this option to produce
+distribution tarballs. @xref{Formats,v7}, for the detailed discussion
+of this issue and its implications.
+
Future versions of @GNUTAR{} will understand @option{-o} only as a
-synonym for @option{--no-same-owner}.
+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.
+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
@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
+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.
If you find problems or have suggestions about this program or manual,
please report them to @file{bug-tar@@gnu.org}.
+When reporting a bug, please be sure to include as much detail as
+possible, in order to reproduce it. @FIXME{Be more specific, I'd
+like to make this node as detailed as 'Bug reporting' node in Emacs
+manual}.
+
@node Tutorial
@chapter Tutorial Introduction to @command{tar}
This chapter guides you through some basic examples of three @command{tar}
-operations: @samp{--create}, @samp{--list}, and @samp{--extract}. If
+operations: @option{--create}, @option{--list}, and @option{--extract}. If
you already know how to use some other version of @command{tar}, then you
may not need to read this chapter. This chapter omits most complicated
details about how @command{tar} works.
precedes lines you should type; to make this more clear, those lines are
shown in @kbd{this font}, as opposed to lines which represent the
computer's response; those lines are shown in @code{this font}, or
-sometimes @samp{like this}. When we have lines which are too long to be
-displayed in any other way, we will show them like this:
+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
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
+the other two styles of writing options in @ref{Mnemonic Options}, and
@ref{Short Options}.)
In the examples and in the text of this tutorial, we usually use the
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
@item --file=@var{archive-name}
@ref{file}.
@node verbose tutorial
-@unnumberedsubsec The @samp{--verbose} Option
+@unnumberedsubsec The @option{--verbose} Option
@table @kbd
@item --verbose
@value{op-verbose} shows details about the results of running
@command{tar}. This can be especially useful when the results might not be
obvious. For example, if you want to see the progress of @command{tar} as
-it writes files into the archive, you can use the @samp{--verbose}
+it writes files into the archive, you can use the @option{--verbose}
option. In the beginning, you may find it useful to use
-@samp{--verbose} at all times; when you are more accustomed to
+@option{--verbose} at all times; when you are more accustomed to
@command{tar}, you will likely want to use it at certain times but not at
-others. We will use @samp{--verbose} at times to help make something
+others. We will use @option{--verbose} at times to help make something
clear, and we will give many examples both using and not using
-@samp{--verbose} to show the differences.
+@option{--verbose} to show the differences.
-Sometimes, a single instance of @samp{--verbose} on the command line
+Sometimes, a single instance of @option{--verbose} on the command line
will show a full, @samp{ls} style listing of an archive or files,
@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
+@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
@item --help
-The @samp{--help} option to @command{tar} prints out a very brief list of
+The @option{--help} option to @command{tar} prints out a very brief list of
all operations and option available for the current version of
@command{tar} available on your system.
@end table
One of the basic operations of @command{tar} is @value{op-create}, which
you use to create a @command{tar} archive. We will explain
-@samp{--create} first because, in order to learn about the other
+@option{--create} first because, in order to learn about the other
operations, you will find it useful to have an archive available to
practice on.
@file{blues}, @file{folk}, and @file{jazz}. The archive is called
@file{collection.tar}.
-This section will proceed slowly, detailing how to use @samp{--create}
+This section will proceed slowly, detailing how to use @option{--create}
in @code{verbose} mode, and showing examples using both short and long
forms. In the rest of the tutorial, and in the examples in the next
chapter, we will proceed at a slightly quicker pace. This section
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
Use @value{op-append} instead. @xref{append}.
@node create verbose
-@subsection Running @samp{--create} with @samp{--verbose}
+@subsection Running @option{--create} with @option{--verbose}
If you include the @value{op-verbose} option on the command line,
@command{tar} will list the files it is acting on as it is working. In
@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
@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
Be sure to use a @value{op-file} option just as with @value{op-create}
to specify the name of the archive.
-If you use the @value{op-verbose} option with @samp{--list}, then
+If you use the @value{op-verbose} option with @option{--list}, then
@command{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
showing owner, file size, and so forth.
-rw-rw-rw- myself user 62 1990-05-23 10:55 folk
@end smallexample
-@cindex File name arguments, using @code{--list} with
-@cindex @code{--list} with file name arguments
+@cindex File name arguments, using @option{--list} with
+@cindex @option{--list} with file name arguments
You can specify one or more individual member names as arguments when
using @samp{list}. In this case, @command{tar} will only list the
names of members you identify. For example, @w{@kbd{tar --list
with @file{folk}, because @file{folk} is in the archive file
@file{collection.tar}. If you are not sure of the exact file name, try
listing all the files in the archive and searching for the one you
-expect to find; remember that if you use @samp{--list} with no file
+expect to find; remember that if you use @option{--list} with no file
names as arguments, @command{tar} will print the names of all the members
stored in the specified archive.
@node list dir
@unnumberedsubsec Listing the Contents of a Stored Directory
-@UNREVISED
-
-@FIXME{i changed the order of these nodes around and haven't had a
-chance to play around with this node's example, yet. i have to play
-with it and see what it actually does for my own satisfaction, even if
-what it says *is* correct..}
To get information about the contents of an archived directory,
use the directory name as a file name argument in conjunction with
Extracting an archive does not modify the archive in any way; you can
extract it multiple times if you want or need to.
-Using @samp{--extract}, you can extract an entire archive, or specific
+Using @option{--extract}, you can extract an entire archive, or specific
files. The files can be directories containing other files, or not. As
with @value{op-create} and @value{op-list}, you may use the short or the
long form of the operation without affecting the performance.
one of the files you had placed in the archive @file{collection.tar}
earlier (say, @file{blues}), you can extract it from the archive without
changing the archive's structure. It will be identical to the original
-file @file{blues} that you deleted. @FIXME{check this; will the times,
-permissions, owner, etc be the same, also?}
+file @file{blues} that you deleted. @FIXME{At the time of this
+writing, atime and ctime are not restored. Since this is a tutorial
+for a beginnig user, it should hardly be mentioned here. Maybe in
+a footnote? --gray}.
First, make sure you are in the @file{practice} directory, and list the
files in the directory. Now, delete the file, @samp{blues}, and list
(@pxref{list}).
You can extract a file to standard output by combining the above options
-with the @option{--to-stdout} option (@pxref{Writing to Standard
+with the @value{op-to-stdout} option (@pxref{Writing to Standard
Output}).
If you give the @value{op-verbose} option, then @value{op-extract} will
which you extract, the files from the extracted archive will replace
the files already in the working directory (and possible
subdirectories). This will happen regardless of whether or not the
-files in the working directory were more recent than those extracted.
+files in the working directory were more recent than those extracted
+(there exist, however, special options that alter this behavior
+@pxref{Writing}).
However, if a file was stored with a directory name as part of its file
name, and that directory does not exist under the working directory when
the file is extracted, @command{tar} will create the directory.
-We can demonstrate how to use @samp{--extract} to extract a directory
+We can demonstrate how to use @option{--extract} to extract a directory
file with an example. Change to the @file{practice} directory if you
weren't there, and remove the files @file{folk} and @file{jazz}. Then,
go back to the parent directory and extract the archive
@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 @value{op-verbose} options, @command{tar}
+would have displayed more detail about the extracted files, as shown
+in the example below:
+
+@smallexample
+$ @kbd{tar -xvvf music.tar practice/folk practice/jazz}
+-rw-rw-rw- me user 28 1996-10-18 16:31 practice/jazz
+-rw-rw-rw- me user 20 1996-09-23 16:44 practice/folk
+@end smallexample
@noindent
Because you created the directory with @file{practice} as part of the
$ @kbd{tar -xvf ../untrusted.tar}
@end smallexample
+It is also a good practice to examine contents of the archive
+before extracting it, using @value{op-list} option, possibly combined
+with @value{op-verbose}.
+
@node failing commands
@subsection Commands That Will Fail
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}.
only use the option style(s) which makes the most sense to you until you
feel comfortable with the others.
-@FIXME{hag to write a brief paragraph on the option(s) which can
-optionally take an argument}
+Some options @emph{may} take an argument (currently, there are
+two such options: @value{op-backup} and @value{op-occurrence}). Such
+options may have at most long and short forms, they do not have old style
+equivalent. The rules for specifying an argument for such options
+are stricter than those for specifying mandatory arguments. Please,
+pay special attention to them.
@menu
* Mnemonic Options:: Mnemonic Option Style
"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
@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}.
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
@item --catenate
@itemx -A
-Same as @samp{--concatenate}. @xref{concatenate}.
+Same as @option{--concatenate}. @xref{concatenate}.
@item --compare
@itemx -d
@item --diff
@itemx -d
-Same @samp{--compare}. @xref{compare}.
+Same @option{--compare}. @xref{compare}.
@item --extract
@itemx -x
@item --get
@itemx -x
-Same as @samp{--extract}. @xref{extract}.
+Same as @option{--extract}. @xref{extract}.
@item --list
@itemx -t
@item --update
@itemx -u
-@FIXME{It was: A combination of the @samp{--compare} and
-@samp{--append} operations. This is not true and rather misleading,
+@FIXME{It was: A combination of the @option{--compare} and
+@option{--append} operations. This is not true and rather misleading,
as @value{op-compare} does a lot more than @value{op-update} for
ensuring files are identical.} Adds files to the end of the archive,
but only if they are newer than their counterparts already in the
@item --after-date
-(See @samp{--newer}.) @FIXME-pxref{}
+(See @option{--newer}.) @FIXME-pxref{}
@item --anchored
An exclude pattern must match an initial subsequence of the name's components.
This option directs @command{tar} to print periodic checkpoint messages as it
reads through the archive. Its intended for when you want a visual
indication that @command{tar} is still running, but don't want to see
-@samp{--verbose} output. @FIXME-xref{}
+@option{--verbose} output. @FIXME-xref{}
@item --check-links
@itemx -l
@item --confirmation
-(See @samp{--interactive}.) @FIXME-pxref{}
+(See @option{--interactive}.) @FIXME-pxref{}
@item --dereference
@itemx -h
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Similar to @samp{--exclude}, except @command{tar} will use the list of
+Similar to @option{--exclude}, except @command{tar} will use the list of
patterns in the file @var{file}. @FIXME-xref{}
+@item --exclude-caches
+
+Automatically excludes all directories
+containing a cache directory tag. @FIXME-xref{}
+
@item --file=@var{archive}
@itemx -f @var{archive}
@item --force-local
-Forces @command{tar} to interpret the filename given to @samp{--file}
+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{}
numeric fields.
@item ustar
-Creates a POSIX.1-1988 compatible archive.
+Creates a @acronym{POSIX.1-1988} compatible archive.
@item posix
-Creates a POSIX.1-2001 archive.
+Creates a @acronym{POSIX.1-2001 archive}.
@end table
+@xref{Formats}, for a detailed discussion of these formats.
+
@item --group=@var{group}
Files added to the @command{tar} archive will have a group id of @var{group},
performing potentially destructive options, such as overwriting files.
@FIXME-xref{}
+@item --keep-newer-files
+
+Do not replace existing files that are newer than their archive copies
+when extracting files from an archive.
+
@item --keep-old-files
@itemx -k
@item --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
(see --info-script)
+@item -n
+@itemx --seek
+
+Assume that the archive media supports seeks to arbitrary
+locations. Usually @command{tar} determines automatically whether
+the archive can be seeked or not. This option is intended for use
+in cases when such recognition fails.
+
@item --newer=@var{date}
@itemx --after-date=@var{date}
@itemx -N
@item --newer-mtime=@var{date}
-Like @samp{--newer}, but add only files whose
-contents have changed (as opposed to just @samp{--newer}, which will
+Like @option{--newer}, but add only files whose
+contents have changed (as opposed to just @option{--newer}, which will
also back up files for which any status information has changed).
@item --no-anchored
When extracting an archive, do not attempt to preserve the owner
specified in the @command{tar} archive. This the default behavior
-for ordinary users; this option has an effect only for the superuser.
+for ordinary users.
@item --no-same-permissions
When extracting an archive, subtract the user's umask from files from
the permissions specified in the archive. This is the default behavior
-for ordinary users; this option has an effect only for the superuser.
+for ordinary users.
@item --no-wildcards
Do not use wildcards when excluding files.
@item --null
-When @command{tar} is using the @samp{--files-from} option, this option
+When @command{tar} is using the @option{--files-from} option, this option
instructs @command{tar} to expect filenames terminated with @kbd{NUL}, so
@command{tar} can correctly work with file names that contain newlines.
@FIXME-xref{}
@item --pax-option=@var{keyword-list}
-This option is meaningful only with POSIX.1-2001 archives
+This option is meaningful only with @acronym{POSIX.1-2001} archives
(@FIXME-xref{}). It modifies the way @command{tar} handles the
extended header keywords. @var{Keyword-list} is a comma-separated
list of keyword options, each keyword option taking one of
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 POSIX 1003.2, 3.13 (@FIXME-xref{}, see
-man 7 glob). For example:
+matching notation described in @acronym{POSIX 1003.2}, 3.13 @FIXME-xref{see
+man 7 glob}. For example:
@smallexample
--pax-option delete=security.*
@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}. @FIXME-xref{}
@item --preserve-order
-(See @samp{--same-order}; @pxref{Reading}.)
+(See @option{--same-order}; @pxref{Reading}.)
@item --preserve-permissions
@itemx --same-permissions
Directs @command{tar} to remove the source file from the file system after
appending it to an archive. @FIXME-xref{}
+@item --rmt-command=@var{cmd}
+
+Notifies @command{tar} that it should use @var{cmd} instead of
+the default @file{/usr/libexec/rmt} (@pxref{Remote Tape Server}).
+
@item --rsh-command=@var{cmd}
Notifies @command{tar} that is should use @var{cmd} to communicate with remote
@item --same-permissions
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+(See @option{--preserve-permissions}; @pxref{Writing}.)
+
+@item --show-defaults
+
+Displays the default options used by @command{tar} and exits
+successfully. This option is intended for use in shell scripts.
+Here is an example of what you can see using this option:
+
+@smallexample
+$ tar --show-defaults
+--format=gnu -f- -b20
+@end smallexample
@item --show-omitted-dirs
files in the archive until it finds one that matches @var{name}.
@xref{Scarce}.
-@item --strip-path=@var{number}
+@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
@item --uncompress
-(See @samp{--compress}.) @FIXME-pxref{}
+(See @option{--compress}.) @FIXME-pxref{}
@item --ungzip
-(See @samp{--gzip}.) @FIXME-pxref{}
+(See @option{--gzip}.) @FIXME-pxref{}
@item --unlink-first
@itemx -U
Instructs @command{tar} to access the archive through @var{prog}, which is
presumed to be a compression program of some sort. @FIXME-xref{}
+@item --utc
+
+Display file modification dates in @acronym{UTC}. This option implies
+@option{--verbose}.
+
@item --verbose
@itemx -v
@item --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{}
@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.
@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.
+@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
amount written to the archive, after it has been fully created.
The @value{op-checkpoint} option prints an occasional message
-as @command{tar} reads or writes the archive. In fact, it print
-directory names while reading the archive. It is designed for
+as @command{tar} reads or writes the archive. In fact, it prints
+a message each 10 records read or written. It is designed for
those who don't need the more detailed (and voluminous) output of
@value{op-block-number}, but do want visual confirmation that @command{tar}
is actually making forward progress.
if disk or storage space is tight). You can do this by excluding
certain files automatically (@pxref{Choosing}), or by performing
an operation interactively, using the @value{op-interactive} option.
-@command{tar} also accepts @samp{--confirmation} for this option.
+@command{tar} also accepts @option{--confirmation} for this option.
When the @value{op-interactive} option is specified, before
reading, writing, or deleting files, @command{tar} first prints a message
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
@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
If you want to add files to an existing archive, you don't need to
create a new archive; you can use @value{op-append}. The archive must
-already exist in order to use @samp{--append}. (A related operation
-is the @samp{--update} operation; you can use this to add newer
+already exist in order to use @option{--append}. (A related operation
+is the @option{--update} operation; you can use this to add newer
versions of archive members to an existing archive. To learn how to
-do this with @samp{--update}, @pxref{update}.)
-
-@FIXME{Explain in second paragraph whether you can get to the previous
-version -- explain whole situation somewhat more clearly.}
+do this with @option{--update}, @pxref{update}.)
If you use @value{op-append} to add a file that has the same name as an
archive member to an archive containing that archive member, then the
old member is not deleted. What does happen, however, is somewhat
-complex. @command{tar} @emph{allows} you to have infinite numbers of files
+complex. @command{tar} @emph{allows} you to have infinite number of files
with the same name. Some operations treat these same-named members no
differently than any other set of archive members: for example, if you
view an archive with @value{op-list}, you will see all of those members
prefer; if you were to use @value{op-extract} to extract the archive,
only the most recently added copy of a member with the same name as four
other members would end up in the working directory. This is because
-@samp{--extract} extracts an archive in the order the members appeared
+@option{--extract} extracts an archive in the order the members appeared
in the archive; the most recently archived members will be extracted
last. Additionally, an extracted member will @emph{replace} a file of
the same name which existed in the directory already, and @command{tar}
-will not prompt you about this. Thus, only the most recently archived
+will not prompt you about this@footnote{Unless you give it
+@option{--keep-old-files} option, or the disk copy is newer than the
+the one in the archive and you invoke @command{tar} with
+@option{--keep-newer-files} option}. Thus, only the most recently archived
member will end up being extracted, as it will replace the one
extracted before it, and so on.
+There exists a special option that allows you to get around this
+behavior and extract (or list) only a particular copy of the file.
+This is @option{--occurrence} option. If you run @command{tar} with
+this option, it will extract only the first copy of the file. You
+may also give this option an argument specifying the number of
+copy to be extracted. Thus, for example if the archive
+@file{archive.tar} contained three copies of file @file{myfile}, then
+the command
+
+@smallexample
+tar --extract --file archive.tar --occurrence=2 myfile
+@end smallexample
+
+@noindent
+would extract only the second copy. @xref{Option Summary,---occurrence}, for the description of @value{op-occurrence} option.
+
@FIXME{ hag -- you might want to incorporate some of the above into the
-MMwtSN node; not sure. i didn't know how to make it simpler...}
+MMwtSN node; not sure. i didn't know how to make it simpler...
-There are a few ways to get around this. @FIXME-xref{Multiple Members
+There are a few ways to get around this. (maybe xref Multiple Members
with the Same Name.}
@cindex Members, replacing with other members
@cindex Replacing members with other members
If you want to replace an archive member, use @value{op-delete} to
delete the member you want to remove from the archive, , and then use
-@samp{--append} to add the member you want to be in the archive. Note
+@option{--append} to add the member you want to be in the archive. Note
that you can not change the order of the archive; the most recently
added member will still appear last. In this sense, you cannot truly
``replace'' one member with another. (Replacing one member with another
The simplest way to add a file to an already existing archive is the
@value{op-append} operation, which writes specified files into the
archive whether or not they are already among the archived files.
-When you use @samp{--append}, you @emph{must} specify file name
+When you use @option{--append}, you @emph{must} specify file name
arguments, as there is no default. If you specify a file that already
exists in the archive, another copy of the file will be added to the
end of the archive. As with other operations, the member names of the
command line. The @value{op-verbose} option will print out the names
of the files as they are written into the archive.
-@samp{--append} cannot be performed on some tape drives, unfortunately,
+@option{--append} cannot be performed on some tape drives, unfortunately,
due to deficiencies in the formats those tape drives use. The archive
must be a valid @command{tar} archive, or else the results of using this
operation will be unpredictable. @xref{Media}.
-To demonstrate using @samp{--append} to add a file to an archive,
+To demonstrate using @option{--append} to add a file to an archive,
create a file called @file{rock} in the @file{practice} directory.
Make sure you are in the @file{practice} directory. Then, run the
following @command{tar} command to add @file{rock} to
You can use @value{op-append} to add copies of files which have been
updated since the archive was created. (However, we do not recommend
doing this since there is another @command{tar} option called
-@samp{--update}; @pxref{update} for more information. We describe this
-use of @samp{--append} here for the sake of completeness.) @FIXME{is
+@option{--update}; @pxref{update} for more information. We describe this
+use of @option{--append} here for the sake of completeness.) @FIXME{is
this really a good idea, to give this whole description for something
which i believe is basically a Stupid way of doing something? certain
aspects of it show ways in which tar is more broken than i'd personally
like to admit to, specifically the last sentence. On the other hand, i
-don't think it's a good idea to be saying that re explicitly don't
+don't think it's a good idea to be saying that we explicitly don't
recommend using something, but i can't see any better way to deal with
the situation.}When you extract the archive, the older version will be
effectively lost. This works because files are extracted from an
@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:
(note the different creation dates and file sizes). If you extract
the archive, the older version of the file @file{blues} will be
replaced by the newer version. You can confirm this by extracting
-the archive and running @samp{ls} on the directory. @xref{Writing},
-for more information. (@emph{Please note:} This is the case unless
-you employ the @value{op-backup} option. @FIXME-ref{Multiple Members
-with the Same Name}.)
+the archive and running @samp{ls} on the directory.
+
+If you wish to extract the first occurrence of the file @file{blues}
+from the archive, use @value{op-occurrence} option, as shown in
+the following example:
+
+@smallexample
+$ @kbd{tar --extract -vv --occurrence --file=collection.tar blues}
+-rw-rw-rw- me user 21 1996-09-23 16:44 blues
+@end smallexample
+
+@xref{Writing}, for more information on @value{op-extract} and
+@xref{Option Summary, --occurrence}, for the description of
+@value{op-occurrence} option.
@node update
@subsection Updating an Archive
In the previous section, you learned how to use @value{op-append} to add
a file to an existing archive. A related operation is
-@value{op-update}. The @samp{--update} operation updates a @command{tar}
+@value{op-update}. The @option{--update} operation updates a @command{tar}
archive by comparing the date of the specified archive members against
the date of the file with the same name. If the file has been modified
more recently than the archive member, then the newer version of the
file is added to the archive (as with @value{op-append}).
-Unfortunately, you cannot use @samp{--update} with magnetic tape drives.
+Unfortunately, you cannot use @option{--update} with magnetic tape drives.
The operation will fail.
@FIXME{other examples of media on which --update will fail? need to ask
charles and/or mib/thomas/dave shevett..}
-Both @samp{--update} and @samp{--append} work by adding to the end
+Both @option{--update} and @option{--append} work by adding to the end
of the archive. When you extract a file from the archive, only the
version stored last will wind up in the file system, unless you use
the @value{op-backup} option. @FIXME-ref{Multiple Members with the
@end menu
@node how to update
-@subsubsection How to Update an Archive Using @code{--update}
+@subsubsection How to Update an Archive Using @option{--update}
You must use file name arguments with the @value{op-update} operation.
If you don't specify any files, @command{tar} won't act on any files and
@FIXME{note: the above parenthetical added because in fact, this
behavior just confused the author. :-) }
-To see the @samp{--update} option at work, create a new file,
+To see the @option{--update} option at work, create a new file,
@file{classical}, in your practice directory, and some extra text to the
file @file{blues}, using any text editor. Then invoke @command{tar} with
the @samp{update} operation and the @value{op-verbose} option specified,
efficient. If you need to run backups, please consult @ref{Backups}.
@node concatenate
-@subsection Combining Archives with @code{--concatenate}
+@subsection Combining Archives with @option{--concatenate}
@cindex Adding archives to an archive
@cindex Concatenating Archives
one or more archives to the end of another archive, you should use the
@value{op-concatenate} operation.
-To use @samp{--concatenate}, name the archives to be concatenated on the
+To use @option{--concatenate}, name the archives to be concatenated on the
command line. (Nothing happens if you don't list any.) The members,
and their member names, will be copied verbatim from those archives. If
this causes multiple members to have the same name, it does not delete
information on how this affects reading the archive, Multiple
Members with the Same Name.}
-To demonstrate how @samp{--concatenate} works, create two small archives
+To demonstrate how @option{--concatenate} works, create two small archives
called @file{bluesrock.tar} and @file{folkjazz.tar}, using the relevant
files from @file{practice}:
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
@cindex @code{concatenate} vs @command{cat}
@cindex @command{cat} vs @code{concatenate}
It may seem more intuitive to you to want or try to use @command{cat} to
-concatenate two archives instead of using the @samp{--concatenate}
+concatenate two archives instead of using the @option{--concatenate}
operation; after all, @command{cat} is the utility for combining files.
However, @command{tar} archives incorporate an end-of-file marker which
must be removed if the concatenated archives are to be read properly as
-one archive. @samp{--concatenate} removes the end-of-archive marker
+one archive. @option{--concatenate} removes the end-of-archive marker
from the target archive before each new archive is appended. If you use
@command{cat} to combine the archives, the result will not be a valid
@command{tar} format archive. If you need to retrieve files from an
default archive name.
@node delete
-@subsection Removing Archive Members Using @samp{--delete}
+@subsection Removing Archive Members Using @option{--delete}
@UNREVISED
@cindex Deleting files from an archive
@cindex Removing files from an archive
names, nothing will be deleted. The @value{op-verbose} option will
cause @command{tar} to print the names of the members as they are deleted.
As with @value{op-extract}, you must give the exact member names when
-using @samp{tar --delete}. @samp{--delete} will remove all versions of
-the named file from the archive. The @samp{--delete} operation can run
+using @samp{tar --delete}. @option{--delete} will remove all versions of
+the named file from the archive. The @option{--delete} operation can run
very slowly.
-Unlike other operations, @samp{--delete} has no short form.
+Unlike other operations, @option{--delete} has no short form.
-@cindex Tapes, using @code{--delete} and
+@cindex Tapes, using @option{--delete} and
@cindex Deleting from tape archives
This operation will rewrite the archive. You can only use
-@samp{--delete} on an archive if the archive device allows you to
+@option{--delete} on an archive if the archive device allows you to
write to any point on the media, such as a disk; because of this, it
does not work on magnetic tapes. Do not try to delete an archive member
from a magnetic tape; the action will not succeed, and you will be
@cindex Verifying the currency of an archive
@UNREVISED
-The @samp{--compare} (@samp{-d}), or @samp{--diff} operation compares
+The @option{--compare} (@option{-d}), or @option{--diff} operation compares
specified archive members against files with the same names, and then
reports differences in file size, mode, owner, modification date and
contents. You should @emph{only} specify archive member names, not file
the integrity of the archive media. For this later goal, @xref{verify}.
@node create options
-@section Options Used by @code{--create}
+@section Options Used by @option{--create}
The previous chapter described the basics of how to use
@value{op-create} to create an archive from a set of files.
@xref{create}. This section described advanced options to be used with
-@samp{--create}.
+@option{--create}.
@menu
* Ignore Failed Read::
@end table
@node extract options
-@section Options Used by @code{--extract}
+@section Options Used by @option{--extract}
@UNREVISED
@FIXME{i need to get dan to go over these options with me and see if
an archive into the filesystem. Various options cause @command{tar} to
extract more information than just file contents, such as the owner,
the permissions, the modification date, and so forth. This section
-presents options to be used with @samp{--extract} when certain special
+presents options to be used with @option{--extract} when certain special
considerations arise. You may review the information presented in
@ref{extract} for more basic information about the
-@samp{--extract} operation.
+@option{--extract} operation.
@menu
* Reading:: Options to Help Read Archives
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
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
to allow this behavior. In any case, single files are silently
extraction.
@end table
+@node Keep Newer Files
+@unnumberedsubsubsec Keep Newer Files
+
+@table @kbd
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive
+copies. This option is meaningless with @value{op-list}.
+@end table
+
@node Unlink First
@unnumberedsubsubsec Unlink First
@unnumberedsubsubsec Setting Access Permissions
To set the modes (access permissions) of extracted files to those
-recorded for those files in the archive, use @samp{--same-permissions}
+recorded for those files in the archive, use @option{--same-permissions}
in conjunction with the @value{op-extract} operation. @FIXME{Should be
aliased to ignore-umask.}
@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.
@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=-)}}
@end smallexample
@end ifclear
-This chapter documents both the provided FSF scripts and @command{tar}
+This chapter documents both the provided shell scripts and @command{tar}
options which are more specific to usage as a backup tool.
To @dfn{back up} a file system means to create archives that contain
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
+with the @option{--atime-preserve} option), or if you set the clock
backwards.
Despite it should be obvious that a device has a non-volatile value, NFS
to 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-extract} or @value{op-list} are specified, but the
@value{op-listed-incremental} option must still be given. A
placeholder @var{snapshot-file} can be specified, e.g.,
@file{/dev/null}.
@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. @FIXME-xref{Script Syntax} Once the
+backup parameters are set, you can perform backups or restoration by
+running the appropriate script.
+
+The name of the backup script is @code{backup}. The name of the
+restore script is @code{restore}. The following sections describe
+their use in detail.
+
+@emph{Please Note:} The backup and restoration scripts are
designed to be used together. While it is possible to restore files by
hand from an archive which was created using a backup script, and to create
an archive by hand which could then be extracted using the restore script,
-it is easier to use the scripts.@FIXME{There is no such restore script!}
-@value{xref-incremental}, and @value{xref-listed-incremental},
-before making such an attempt.
-
-@FIXME{shorten node names}
+it is easier to use the scripts. @value{xref-incremental}, and
+@value{xref-listed-incremental}, before making such an attempt.
@node Backup Parameters
@section Setting Parameters for Backups and Restoration
-@UNREVISED
The file @file{backup-specs} specifies backup parameters for the
backup and restoration scripts provided with @command{tar}. You must
edit @file{backup-specs} to fit your system configuration and schedule
before using these scripts.
-@FIXME{This about backup scripts needs to be written: BS is a shell
-script .... thus ... @file{backup-specs} is in shell script syntax.}
+Syntactically, @file{backup-specs} is a shell script, containing
+mainly variable assignments. However, any valid shell construct
+is allowed in this file. Particularly, you may wish to define
+functions within that script (e.g. see @code{RESTORE_BEGIN} below).
+For more information about shell script syntax, please refer to
+@url{http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#ta
+g_02, the definition of the Shell Command Language}. See also
+@ref{Top,,Bash Features,bashref,Bash Reference Manual}.
+
+The shell variables controlling behavior of @code{backup} and
+@code{restore} are described in the following subsections.
+
+@menu
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
+* backup-specs example:: An Example Text of @file{Backup-specs}
+@end menu
-@FIXME-xref{Script Syntax, for an explanation of this syntax.}
+@node General-Purpose Variables
+@subsection General-Purpose Variables
-@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:}
+@defvr {Backup variable} ADMINISTRATOR
+The user name of the backup administrator. @code{Backup} scripts
+sends a backup report to this address.
+@end defvr
-@table @samp
-@item ADMINISTRATOR
-The user name of the backup administrator.
+@defvr {Backup variable} BACKUP_HOUR
+The hour at which the backups are done. This can be a number from 0
+to 23, or the time specification in form @var{hours}:@var{minutes},
+or the string @samp{now}.
-@item BACKUP_HOUR
-The hour at which the backups are done. This can be a number from 0
-to 23, 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
+@defvr {Backup variable} 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.
+@end defvr
-@FIXME{examples for all ...}
+@defvr {Backup variable} BLOCKING
-@item TAPE_STATUS
-The command to use to obtain the status of the archive device,
-including error count. On some tape drives there may not be such a
-command; in that case, simply use @samp{TAPE_STATUS=false}.
-
-@item BLOCKING
The blocking factor @command{tar} will use when writing the dump archive.
@value{xref-blocking-factor}.
+@end defvr
+
+@defvr {Backup variable} BACKUP_DIRS
-@item BACKUP_DIRS
-A list of file systems to be dumped. You can include any directory
-name in the list---subdirectories on that file system will be
+A list of file systems to be dumped (for @code{backup}), or restored
+(for @code{restore}). You can include any directory
+name in the list --- subdirectories on that file system will be
included, regardless of how they may look to other networked machines.
Subdirectories on other file systems will be ignored.
the 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
-@FIXME{Same file name, be specific. Through NFS ...}
+@defvr {Backup variable} DIRLIST
+A path to the file containing the list of the filesystems to backup
+or restore. By default it is @file{/etc/backup/dirs}.
+@end defvr
+
+@defvr {Backup variable} BACKUP_FILES
+
+A list of individual files to be dumped (for @code{backup}), or restored
+(for @code{restore}). These should be accessible from the machine on
+which the backup script is run.
+
+If the list of file systems is very long you may wish to store it
+in a separate file. This file is usually named
+@file{/etc/backup/files}, but this name may be overridden in
+@file{backup-specs} using @code{FILELIST} variable.
+@end defvr
+
+@defvr {Backup variable} FILELIST
+
+A path to the file containing the list of the individual files to backup
+or restore. By default it is @file{/etc/backup/files}.
+@end defvr
+
+@defvr {Backup variable} RSH
+
+Path to @code{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
+
+Path to rsh binary on remote mashines. This will be passed via
+@option{--rsh-command} option to the remote invocation of @GNUTAR{}.
+@end defvr
+
+@defvr {Backup variable} VOLNO_FILE
+
+Name of temporary file to hold volume numbers. This needs to be accessible
+by all the machines which have filesystems to be dumped.
+@end defvr
+
+@defvr {Backup variable} XLIST
+
+Name of @dfn{exclude file list}. An @dfn{exclude file list} is a file
+located on the remote machine and containing the list of files to
+be excluded from the backup. Exclude file lists are searched in
+/etc/tar-backup directory. A common use for exclude file lists
+is to exclude files containing security-sensitive information
+(e.g. @file{/etc/shadow} from backups).
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} SLEEP_TIME
+
+Time to sleep between dumps of any two successive filesystems
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} DUMP_REMIND_SCRIPT
+
+Script to be run when it's time to insert a new tape in for the next
+volume. Administrators may want to tailor this script for their site.
+If this variable isn't set, @GNUTAR{} will display its built-in prompt
+@FIXME-xref{describe it somewhere!}, and will expect confirmation from
+the console.
+@end defvr
+
+@defvr {Backup variable} SLEEP_MESSAGE
+
+Message to display on the terminal while waiting for dump time. Usually
+this will just be some literal text.
+@end defvr
+
+@defvr {Backup variable} TAR
+
+Pathname of the @GNUTAR{} executable. If this is not set, backup
+scripts will search @command{tar} in the current shell path.
+@end defvr
+
+@node Magnetic Tape Control
+@subsection Magnetic Tape Control
+
+Backup scripts access tape device using special @dfn{hook functions}.
+These functions take a single argument -- the name of the tape
+device. Their names are kept in the following variables:
+
+@defvr {Backup variable} MT_BEGIN
+The name of @dfn{begin} function. This function is called before
+accessing the drive. By default it retensions the tape:
+
+@smallexample
+MT_BEGIN=mt_begin
+
+mt_begin() @{
+ mt -f "$1" retension
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_REWIND
+The name of @dfn{rewind} function. The default definition is as
+follows:
+
+@smallexample
+MT_REWIND=mt_rewind
+
+mt_rewind() @{
+ mt -f "$1" rewind
+@}
+@end smallexample
+
+@end defvr
+
+@defvr {Backup variable} MT_OFFLINE
+The name of the function switching the tape off line. By default
+it is defined as follows:
+
+@smallexample
+MT_OFFLINE=mt_offline
+
+mt_offline() @{
+ mt -f "$1" offl
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_STATUS
+The name of the function used to obtain the status of the archive device,
+including error count. Default definition:
+
+@smallexample
+MT_STATUS=mt_status
+
+mt_status() @{
+ mt -f "$1" status
+@}
+@end smallexample
+@end defvr
+
+@node User Hooks
+@subsection User Hooks
+
+@dfn{User hooks} are shell functions executed before and after
+each @command{tar} invocation. Thus, there are @dfn{backup
+hooks}, which are executed before and after dumping each file
+system, and @dfn{restore hooks}, executed before and
+after restoring a file system. Each user hook is a shell function
+taking four arguments:
+
+@deffn {User Hook Function} hook @var{level} @var{host} @var{fs} @var{fsname}
+Its arguments are:
+
+@table @var
+@item level
+Current backup or restore level.
+
+@item host
+Name or IP address of the host machine being dumped or restored.
+
+@item fs
+Full path name to the filesystem being dumped or restored.
+
+@item fsname
+Filesystem name with directory separators replaced with colons. This
+is useful e.g. for creating unique files.
@end table
+@end deffn
-@menu
-* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-@end menu
+Following variables keep the names of user hook functions
+
+@defvr {Backup variable} DUMP_BEGIN
+Dump begin function. It is executed before dumping the filesystem.
+@end defvr
+
+@defvr {Backup variable} DUMP_END
+Executed after dumping the filesystem.
+@end defvr
+
+@defvr {Backup variable} RESTORE_BEGIN
+Executed before restoring the filesystem.
+@end defvr
+
+@defvr {Backup variable} RESTORE_END
+Executed after restoring the filesystem.
+@end defvr
@node backup-specs example
@subsection An Example Text of @file{Backup-specs}
-@UNREVISED
-The following is the text of @file{backup-specs} as it appears at FSF:
+The following is an example of @file{backup-specs}:
@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
messages that were generated, as well as how much space was left in
the media volume after the last volume of the archive was written.
You should check this log file after every backup. The file name is
-@file{log-@var{mmm-ddd-yyyy}-level-1} or
-@file{log-@var{mmm-ddd-yyyy}-full}.
+@file{log-@var{mm-dd-yyyy}-level-@var{n}}, where @var{mm-dd-yyyy}
+represents current date, and @var{n} represents current dump level number.
The script also prints the name of each system being dumped to the
standard output.
+Following is the full list of options accepted by @code{backup}
+script:
+
+@table @option
+@item -l @var{level}
+@itemx --level=@var{level}
+Do backup level @var{level} (default 0).
+
+@item -f
+@itemx --force
+Force backup even if today's log file already exists.
+
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
+
+@item -t @var{start-time}
+@itemx --time=@var{start-time}
+Wait till @var{time}, then do backup.
+
+@item -h
+@itemx --help
+Display short help message and exit.
+
+@item -L
+@itemx --license
+Display program license and exit.
+
+@item -V
+@itemx --version
+Display program version and exit.
+@end table
+
+
@node Scripted Restoration
@section Using the Restore Script
-@UNREVISED
-@ifset PUBLISH
+To restore files that were archived using a scripted backup, use the
+@code{restore} script. Its usage is quite straightforward. In the
+simplest form, invoke @code{restore --all}, it will
+then restore all the filesystems and files specified in
+@file{backup-specs} (@pxref{General-Purpose Variables,BACKUP_DIRS}).
-The @command{tar} distribution does not provide restoring scripts.
+You may select the filesystems (and/or files) to restore by
+giving @code{restore} list of @dfn{patterns} in its command
+line. For example, running
-@end ifset
+@smallexample
+restore 'albert:*'
+@end smallexample
-@ifclear PUBLISH
+@noindent
+will restore all filesystems on the machine @samp{albert}. A more
+complicated example:
-@quotation
-@strong{Warning:} The @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 filesystems on the machine @samp{albert}
+as well as @file{/var} filesystem on all machines.
-To restore files that were archived using a scripted backup, use the
-@code{restore} script. The syntax for the script is:
+By default @code{restore} will start restoring files from the lowest
+available dump level (usually zero) and will continue through
+all available dump levels. There may be situations where such a
+thorough restore is not necessary. For example, you may wish to
+restore only files from the recent level one backup. To do so,
+use @option{--level} option, as shown in the example below:
+
+@smallexample
+restore --level=1
+@end smallexample
+
+The full list of options accepted by @code{restore} follows:
+
+@table @option
+@item -a
+@itemx --all
+Restore all filesystems and files specified in @file{backup-specs}
+
+@item -l @var{level}
+@itemx --level=@var{level}
+Start restoring from the given backup level, instead of the default 0.
+
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
+
+@item -h
+@itemx --help
+Display short help message and exit.
-where ***** are the file systems to restore from, and
-***** is a regular expression which specifies which files to
-restore. If you specify --all, the script restores all the files
-in the file system.
+@item -L
+@itemx --license
+Display program license and exit.
+
+@item -V
+@itemx --version
+Display program version and exit.
+@end table
You should start the restore script with the media containing the
first volume of the archive mounted. The script will prompt for other
the tape as needed. @FIXME-xref{Media, for a discussion of tape
positioning.}
-If you specify @samp{--all} as the @var{files} argument, the
-@code{restore} script extracts all the files in the archived file
-system into the active file system.
-
@quotation
@strong{Warning:} The script will delete files from the active file
system if they were not in the file system when the archive was made.
@value{xref-incremental}, and @value{ref-listed-incremental},
for an explanation of how the script makes that determination.
-@FIXME{this may be an option, not a given}
-
-@end ifclear
-
@node Choosing
@chapter Choosing Files and Names for @command{tar}
@UNREVISED
@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
@noindent
@command{tar} will complete the remote connection, if possible, and
prompt you for a username and password. If you use
-@samp{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @command{tar}
+@option{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @command{tar}
will complete the remote connection, if possible, using your username
as the username on the remote machine.
(along with the @samp{@@} sign), then your user name will be used.
(This is the normal @command{rsh} behavior.) It is necessary for the
remote machine, in addition to permitting your @command{rsh} access, to
-have the @file{/usr/ucb/rmt} program installed. If you need to use a
-file whose name includes a colon, then the remote tape drive behavior
+have the @file{rmt} program installed (This command is included in
+the @GNUTAR{} distribution and by default is installed under
+@file{@var{prefix}/libexec/rmt}, were @var{prefix} means your
+installation prefix). If you need to use a file whose name includes a
+colon, then the remote tape drive behavior
can be inhibited by using the @value{op-force-local} option.
@FIXME{i know we went over this yesterday, but bob (and now i do again,
@kbd{tar} @var{operation} [@var{option1} @var{option2} @dots{}] [@var{file name-1} @var{file name-2} @dots{}]
@end smallexample
+If a file name begins with dash (@samp{-}), preceede it with
+@option{--add-file} option to preventit from being treated as an
+option.
+
If you specify a directory name as a file name argument, all the files
in that directory are operated on by @command{tar}.
@node files
@section Reading Names from a File
-@UNREVISED
@cindex Reading file names from a file
@cindex Lists of file names
line, you can put the names into a file, and then use the
@value{op-files-from} option to @command{tar}. Give the name of the file
which contains the list of files to include as the argument to
-@samp{--files-from}. In the list, the file names should be separated by
-newlines. You will frequently use this option when you have generated
+@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
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.)
@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
+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
+
+@cindex @option{--add-file}
+If you happen to have a file whose name starts with @samp{-},
+precede it with @option{--add-file} option to prevent it from
+being recognized as an option. For example: @code{--add-file --my-file}.
@menu
* nul::
@cindex @kbd{NUL} terminated file names
The @value{op-null} option causes @value{op-files-from} to read file
names terminated by a @code{NUL} instead of a newline, so files whose
-names contain newlines can be archived using @samp{--files-from}.
+names contain newlines can be archived using @option{--files-from}.
@table @kbd
@item --null
terminate in a newline.
@end table
-The @samp{--null} option is just like the one in @acronym{GNU}
+The @value{op-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}, @value{op-null} also disables special handling for
+file names that begin with dash.
This example shows how to use @command{find} to generate a list of files
larger than 800K in length and put that list into a file called
-@file{long-files}. The @samp{-print0} option to @command{find} just just
-like @samp{-print}, except that it separates files with a @kbd{NUL}
+@file{long-files}. The @option{-print0} option to @command{find} is just
+like @option{-print}, except that it separates files with a @kbd{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
+@file{big.tgz}. The @option{--null} option to @command{tar} will cause
@command{tar} to recognize the @kbd{NUL} separator between files.
@smallexample
@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
@item --exclude-from=@var{file}
@end table
@findex exclude-from
-Use the @samp{--exclude-from=@var{file-of-patterns}} option to read a
+Use the @option{--exclude-from=@var{file-of-patterns}} option to read a
list of patterns, one per line, from @var{file}; @command{tar} will
ignore files matching those patterns. Thus if @command{tar} is
called as @w{@samp{tar -c -X foo .}} and the file @file{foo} contains a
@FIXME{do the exclude options files need to have stuff separated by
newlines the same as the files-from option does?}
+@table @kbd
+@item --exclude-caches
+Causes @command{tar} to ignore directories containing a cache directory tag.
+@end table
+
+@findex exclude-caches
+When creating an archive,
+the @option{--exclude-caches} option
+causes @command{tar} to exclude all directories
+that contain a @dfn{cache directory tag}.
+A cache directory tag is a short file
+with the well-known name @file{CACHEDIR.TAG}
+and having a standard header
+specified in @url{http://www.brynosaurus.com/cachedir/spec.html}.
+Various applications write cache directory tags
+into directories they use to hold regenerable, non-precious data,
+so that such data can be more easily excluded from backups.
+
@menu
* controlling pattern-patching with exclude::
* problems with exclude::
@table @option
@item --anchored
@itemx --no-anchored
-If anchored (the default), a pattern must match an initial subsequence
-of the name's components. Otherwise, the pattern can match any subsequence.
+If anchored, a pattern must match an initial subsequence
+of the name's components. Otherwise, the pattern can match any
+subsequence. Default is @option{--no-anchored}.
@item --ignore-case
@itemx --no-ignore-case
You can sometimes confuse the meanings of @value{op-exclude} and
@value{op-exclude-from}. Be careful: use @value{op-exclude} when files
to be excluded are given as a pattern on the command line. Use
-@samp{--exclude-from=@var{file-of-patterns}} to introduce the name of a
+@option{--exclude-from=@var{file-of-patterns}} to introduce the name of a
file which contains a list of patterns, one per line; each of these
patterns can exclude zero, one, or many files.
@item
In earlier versions of @command{tar}, what is now the
-@samp{--exclude-from=@var{file-of-patterns}} option was called
-@samp{--exclude=@var{pattern}} instead. Now,
-@samp{--exclude=@var{pattern}} applies to patterns listed on the command
-line and @samp{--exclude-from=@var{file-of-patterns}} applies to
+@option{--exclude-from=@var{file-of-patterns}} option was called
+@option{--exclude=@var{pattern}} instead. Now,
+@option{--exclude=@var{pattern}} applies to patterns listed on the command
+line and @option{--exclude-from=@var{file-of-patterns}} applies to
patterns listed in a file.
@end itemize
given. If @var{date} starts with @samp{/} or @samp{.}, it is taken to
be a file name; the last-modified time of that file is used as the date.
If you use this option when creating or appending to an archive,
-the archive will only include new files. If you use @samp{--after-date}
+the archive will only include new files. If you use @option{--after-date}
when extracting an archive, @command{tar} will only extract files newer
than the @var{date} you specify.
want @command{tar} to act this way.
The @value{op-no-recursion} option inhibits @command{tar}'s recursive descent
-into specified directories. If you specify @samp{--no-recursion}, you can
+into specified directories. If you specify @option{--no-recursion}, you can
use the @command{find} utility for hunting through levels of directories to
construct a list of file names which you could then pass to @command{tar}.
@command{find} allows you to be more selective when choosing which files to
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
archiving. Use in conjunction with any write operation.
@end table
-The @samp{--one-file-system} option causes @command{tar} to modify its
+The @option{--one-file-system} option causes @command{tar} to modify its
normal behavior in archiving the contents of directories. If a file in
a directory is not on the same filesystem as the directory itself, then
@command{tar} will not archive that file. If the file is a directory
@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.
-@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?}
+For instance, the file list for the above example will be:
-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.)
+@smallexample
+@group
+-C
+/etc
+passwd
+hosts
+-C
+/lib
+libc.a
+@end group
+@end smallexample
+
+@noindent
+To use it, you would invoke @command{tar} as follows:
+
+@smallexample
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end smallexample
+
+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 @value{op-directory} is disabled by
+@value{op-null} option.
@node absolute
@subsection Absolute File Names
@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
+@item 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
* 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
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
+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.
+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
able to read old format archives, so it might be safer for you to
always use @value{op-format-v7} for your distributions.
+@node ustar
+@subsection Ustar Archive Format
+
+Archive format defined by @acronym{POSIX}.1-1988 specification is called
+@code{ustar}. Although it is more flexible than the V7 format, it
+still has many restrictions (@xref{Formats,ustar}, for the detailed
+description of @code{ustar} format). Along with V7 format,
+@code{ustar} format is a good choice for archives intended to be read
+with other implementations of @command{tar}.
+
+To create archive in @code{ustar} format, use @value{op-format-ustar}
+option in conjunction with the @value{op-create}.
+
@node gnu
@subsection @acronym{GNU} and old @GNUTAR{} format
@GNUTAR{} was based on an early draft of the
-@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}.
@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.
@node posix
-@subsection @GNUTAR{} and @sc{posix} @command{tar}
+@subsection @GNUTAR{} and @acronym{POSIX} @command{tar}
The version @value{VERSION} of @GNUTAR{} is able
-to read and create archives conforming to @sc{posix.1-2001} standard.
+to read and create archives conforming to @acronym{POSIX.1-2001} standard.
-A @sc{posix} conformant archive will be created if @command{tar}
+A @acronym{POSIX} conformant archive will be created if @command{tar}
was given @value{op-format-posix} option.
Notice, that currently @acronym{GNU} extensions are not
allowed with this format. Following is the list of options that
@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
This restriction will disappear in the future versions.
@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 future time stamps
@cindex negative time stamps
-@sc{posix} @command{tar} format uses fixed-sized unsigned octal strings
+@acronym{POSIX} @command{tar} format uses fixed-sized unsigned octal strings
to represent numeric values. User and group IDs and device major and
minor numbers have unsigned 21-bit representations, and file sizes and
times have unsigned 33-bit representations. @GNUTAR{}
-generates @sc{posix} representations when possible, but for values
-outside the @sc{posix} range it generates two's-complement base-256
+generates @acronym{POSIX} representations when possible, but for values
+outside the @acronym{POSIX} range it generates two's-complement base-256
strings: uids, gids, and device numbers have signed 57-bit
representations, and file sizes and times have signed 89-bit
-representations. These representations are an extension to @sc{posix}
+representations. These representations are an extension to @acronym{POSIX}
@command{tar} format, so they are not universally portable.
The most common portability problems with out-of-range numeric values
are large files and future or negative time stamps.
-Portable archives should avoid members of 8 GB or larger, as @sc{posix}
+Portable archives should avoid members of 8 GB or larger, as @acronym{POSIX}
@command{tar} format cannot represent them.
-Portable archives should avoid time stamps from the future. @sc{posix}
+Portable archives should avoid time stamps from the future. @acronym{POSIX}
@command{tar} format can represent time stamps in the range 1970-01-01
00:00:00 through 2242-03-16 12:56:31 @sc{utc}. However, many current
hosts use a signed 32-bit @code{time_t}, or internal time stamp format,
portable archives must avoid these time stamps for many years to come.
Portable archives should also avoid time stamps before 1970. These time
-stamps are a common @sc{posix} extension but their @code{time_t}
+stamps are a common @acronym{POSIX} extension but their @code{time_t}
representations are negative. Many traditional @command{tar}
implementations generate a two's complement representation for negative
time stamps that assumes a signed 32-bit @code{time_t}; hence they
@subsection Creating and Reading Compressed Archives
@cindex Compressed archives
@cindex Storing archives in compressed format
-@UNREVISED
+
+@GNUTAR{} is able to create and read compressed archives. It supports
+@command{gzip} and @command{bzip2} compression programms. For backward
+compatibilty, it also supports @command{compress} command, although
+we strongly recommend against using it, since there is a patent
+covering the algorithm it uses and you could be sued for patent
+infringement merely by running @command{compress}! Besides, it is less
+effective than @command{gzip} and @command{bzip2}.
+
+Creating a compressed archive is simple: you just specify a
+@dfn{compression option} along with the usual archive creation
+commands. The compression option is @option{-z} (@option{--gzip}) to
+create a @command{gzip} compressed archive, @option{-j}
+(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
+@option{-Z} (@option{--compress}) to use @command{compress} program.
+For example:
+
+@smallexample
+$ @kbd{tar cfz archive.tar.gz .}
+@end smallexample
+
+Reading compressed archive is even simpler: you don't need to specify
+any additional options as @GNUTAR{} recognizes its format
+automatically. Thus, the following commands will list and extract the
+archive created in previous example:
+
+@smallexample
+# List the compressed archive
+$ @kbd{tar tf archive.tar.gz}
+# Extract the compressed archive
+$ @kbd{tar xf archive.tar.gz}
+@end smallexample
+
+The only case when you have to specify a decompression option while
+reading the archive is when reading from a pipe or from a tape drive
+that does not support random access. However, in this case @GNUTAR{}
+will indicate which option you should use. For example:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tf -}
+tar: Archive is compressed. Use -z option
+tar: Error is not recoverable: exiting now
+@end smallexample
+
+If you see such diagnostics, just add the suggested option to the
+invocation of @GNUTAR{}:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tfz -}
+@end smallexample
+
+Notice also, that there are several restrictions on operations on
+compressed archives. First of all, compressed archives cannot be
+modified, i.e. you cannot update (@value{op-update}) them or delete
+(@value{op-delete}) members from them. Likewise, you cannot append
+another @command{tar} archive to a compressed archive using
+@value{op-append}). Secondly, multi-volume archives cannot be
+compressed.
+
+The following table summarizes compression options used by @GNUTAR{}.
@table @kbd
@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 @value{op-gzip} 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
@item -j
@itemx --bzip2
Filter the archive through @code{bzip2}. Otherwise like @value{op-gzip}.
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.
-
-To perform compression and uncompression on the archive, @command{tar}
-runs the @command{compress} utility. @command{tar} uses the default
-compression parameters; if you need to override them, avoid the
-@value{op-compress} option and run the @command{compress} utility
-explicitly. It is useful to be able to call the @command{compress}
-utility from within @command{tar} because the @command{compress} utility by
-itself cannot access remote tape drives.
-
-The @value{op-compress} option will not work in conjunction with the
-@value{op-multi-volume} option or the @value{op-append}, @value{op-update}
-and @value{op-delete} operations. @xref{Operations}, for
-more information on these operations.
+The @acronym{GNU} Project recommends you not use
+@command{compress}, because there is a patent covering the algorithm it
+uses. You could be sued for patent infringement merely by running
+@command{compress}.
-If there is no compress utility available, @command{tar} will report an error.
-@strong{Please note} that the @command{compress} program may be covered by
-a patent, and therefore we recommend you stop using it.
+@item --use-compress-program=@var{prog}
+Use external compression program @var{prog}. Use this option if you
+have a compression program that @GNUTAR{} does not support. There
+are two requirements to which @var{prog} should comply:
-@value{op-bzip2} acts like @value{op-compress}, except that it uses
-the @code{bzip2} utility.
+First, when called without options, it should read data from standard
+input, compress it and output it on standard output.
-@table @kbd
-@item --compress
-@itemx --uncompress
-@itemx -z
-@itemx -Z
-When this option is specified, @command{tar} will compress (when
-writing an archive), or uncompress (when reading an archive). Used in
-conjunction with the @value{op-create}, @value{op-extract},
-@value{op-list} and @value{op-compare} operations.
+Secondly, if called with @option{-d} argument, it should do exactly
+the opposite, i.e. read the compressed data from the standard input
+and produce uncompressed data on the standard output.
@end table
-You can have archives be compressed by using the @value{op-gzip} option.
-This will arrange for @command{tar} to use the @command{gzip} program to be
-used to compress or uncompress the archive wren writing or reading it.
-
-To use the older, obsolete, @command{compress} program, use the
-@value{op-compress} option. The @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
+@FIXME{I have one question, or maybe it's a suggestion if there isn't a way
to do it now. I would like to use @value{op-gzip}, but I'd also like
the output to be fed through a program like @acronym{GNU}
@command{ecc} (actually, right now that's @samp{exactly} what I'd like
Isn't that exactly the role of the @value{op-use-compress-prog} option?
I never tried it myself, but I suspect you may want to write a
@var{prog} script or program able to filter stdin to stdout to
-way you want. It should recognize the @samp{-d} option, for when
+way you want. It should recognize the @option{-d} option, for when
extraction is needed rather than creation.
It has been reported that if one writes compressed data (through the
@value{op-gzip} or @value{op-compress} options) to a DLT and tries to use
the DLT compression mode, the data will actually get bigger and one will
-end up with less space on the tape.
+end up with less space on the tape.}
@node sparse
@subsection Archiving Sparse Files
Extract all protection information.
This option causes @command{tar} to set the modes (access permissions) of
-extracted files exactly as recorded in the archive. If this option
+extracted files exactly as recorded in the archive. If this option
is not used, the current @code{umask} setting limits the permissions
-on extracted files.
+on extracted files. This option is by default enabled when
+@command{tar} is executed by a superuser.
+
This option is meaningless with @value{op-list}.
@end table
@node Standard
-@section The Standard Format
+@section Basic Tar Format
@UNREVISED
While an archive may contain many files, the archive itself is a
@acronym{GNU} Emacs.
Physically, an archive consists of a series of file entries terminated
-by an end-of-archive entry, which consists of 512 zero bytes. A file
+by an end-of-archive entry, which consists of two 512 blocks of zero
+bytes. A file
entry usually describes one of the files in the archive (an
@dfn{archive member}), and consists of a file header and the contents
of the file. File headers contain file names and statistics, checksum
Each file archived is represented by a header block which describes
the file, followed by zero or more blocks which give the contents
-of the file. At the end of the archive file there may be a block
+of the file. At the end of the archive file there are two 512-byte blocks
filled with binary zeros as an end-of-file marker. A reasonable system
-should write a block of zeros at the end, but must not assume that
-such a block exists when reading an archive.
+should write such end-of-file marker at the end of an archive, but
+must not assume that such a block exists when reading an archive. In
+particular @GNUTAR{} always issues a warning if it does not encounter it.
The blocks may be @dfn{blocked} for physical I/O operations.
Each record of @var{n} blocks (where @var{n} is set by the
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.
@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
sign (@kbd{@@}), it is treated as @samp{user@@hostname:file name}. In
either case, @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 @value{op-rmt-command} option (@xref{Option Summary,
+---rmt-command}, for detailed description of this option. @xref{Remote
+Tape Server}, for the description of @command{rmt} command).
If this option is not given, but the environment variable @env{TAPE}
is set, its value is used; otherwise, old versions of @command{tar}
@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{}
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
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
data on the tape will be overwritten (unless it is no longer needed).
Before reading an archive, you should make sure the tape head is at
the beginning of the archive you want to read. (The @code{restore}
-script will find the archive automatically. @FIXME{There is no such
-restore script!}@FIXME-xref{Scripted Restoration}@xref{mt}, for
+script will find the archive automatically. @FIXME-xref{Scripted Restoration}@xref{mt}, for
an explanation of the tape moving utility.
If you want to add new archive file entries to a tape, you should
archive, complete in itself. For example, you can list or extract any
volume alone; just don't specify @value{op-multi-volume}. However, if one
file in the archive is split across volumes, the only way to extract
-it successfully is with a multi-volume extract command @samp{--extract
---multi-volume} (@samp{-xM}) starting on or before the volume where
+it successfully is with a multi-volume extract command @option{--extract
+--multi-volume} (@option{-xM}) starting on or before the volume where
the file begins.
For example, let's presume someone has two tape drives on a system
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
+The @value{op-label} was once called @option{--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
projects / chaz / tar / blobdiff