-\input texinfo @c -*-texinfo-*-
+\input texinfo
@c %**start of header
@setfilename tar.info
-@settitle The Tar Manual: DRAFT
-@setchapternewpage odd
+@settitle GNU tar
+@finalout
+@smallbook
@c %**end of header
-@c Note: the edition number and date is listed in *two* places; please update.
-@c subtitle and top node; search for !!set
-
-@c Search for comments marked with !! or <<< (or >>>)
-
-@smallbook
+@c ======================================================================
+@c This document has three levels of rendition: PUBLISH, DISTRIB or PROOF,
+@c as decided by @set symbols. The PUBLISH rendition does not show
+@c notes or marks asking for revision. Most users will prefer having more
+@c information, even if this information is not fully revised for adequacy,
+@c so DISTRIB is the default for tar distributions. The PROOF rendition
+@c show all marks to the point of ugliness, but is nevertheless useful to
+@c those working on the manual itself.
+@c ======================================================================
+
+@ifclear PUBLISH
+@ifclear DISTRIB
+@ifclear PROOF
+@set DISTRIB
+@end ifclear
+@end ifclear
+@end ifclear
+
+@ifset PUBLISH
+@set RENDITION The book, version
+@end ifset
+
+@ifset DISTRIB
+@set RENDITION FTP release, version
+@end ifset
+
+@ifset PROOF
+@set RENDITION Proof reading version
+@end ifset
+
+@c ---------------------------------------------------------------------
+@c The @FIXME's, @UNREVISED and @c comments are part Fran@,{c}ois's work
+@c plan. These annotations are somewhat precious to him; he asks that I
+@c do not alter them inconsiderately. Much work is needed for GNU tar
+@c internals (the sources, the programs themselves). Revising the
+@c adequacy of the manual while revising the sources, and cleaning them
+@c both at the same time, seems to him like a good way to proceed.
+@c ---------------------------------------------------------------------
+
+@c Output marks for nodes needing revision, but not in PUBLISH rendition.
+
+@macro UNREVISED
+@ifclear PUBLISH
+@quotation
+@emph{(This message will disappear, once this node revised.)}
+@end quotation
+@end ifclear
+@end macro
+
+@c Output various FIXME information only in PROOF rendition.
+
+@macro FIXME{string}
+@allow-recursion
+@quote-arg
+@ifset PROOF
+@strong{<FIXME>} \string\ @strong{</>}
+@end ifset
+
+@end macro
+
+@macro FIXME-ref{string}
+@quote-arg
+@ifset PROOF
+@strong{<REF>} \string\ @strong{</>}
+@end ifset
+
+@end macro
+
+@macro FIXME-pxref{string}
+@quote-arg
+@ifset PROOF
+@strong{<PXREF>} \string\ @strong{</>}
+@end ifset
+
+@end macro
+
+@macro FIXME-xref{string}
+@quote-arg
+@ifset PROOF
+@strong{<XREF>} \string\ @strong{</>}
+@end ifset
+
+@end macro
+
+@c @macro option{entry}
+@c @quote-arg
+@c @opindex{--\entry\}
+@c @value{\entry\}
+@c @end macro
+
+@set op-absolute-names @kbd{--absolute-names} (@kbd{-P})
+@set ref-absolute-names @ref{absolute}
+@set xref-absolute-names @xref{absolute}
+@set pxref-absolute-names @pxref{absolute}
+
+@set op-after-date @kbd{--after-date=@var{date}} (@kbd{--newer=@var{date}}, @kbd{-N @var{date}})
+@set ref-after-date @ref{after}
+@set xref-after-date @xref{after}
+@set pxref-after-date @pxref{after}
+
+@set op-append @kbd{--append} (@kbd{-r})
+@set ref-append @ref{add}
+@set xref-append @xref{add}
+@set pxref-append @pxref{add}
+
+@set op-atime-preserve @kbd{--atime-preserve}
+@set ref-atime-preserve @ref{Attributes}
+@set xref-atime-preserve @xref{Attributes}
+@set pxref-atime-preserve @pxref{Attributes}
+
+@set op-backup @kbd{--backup}
+@set ref-backup @ref{Backup options}
+@set xref-backup @xref{Backup options}
+@set pxref-backup @pxref{Backup options}
+
+@set op-block-number @kbd{--block-number} (@kbd{-R})
+@set ref-block-number @ref{verbose}
+@set xref-block-number @xref{verbose}
+@set pxref-block-number @pxref{verbose}
+
+@set op-blocking-factor @kbd{--blocking-factor=@var{512-size}} (@kbd{-b @var{512-size}})
+@set ref-blocking-factor @ref{Blocking Factor}
+@set xref-blocking-factor @xref{Blocking Factor}
+@set pxref-blocking-factor @pxref{Blocking Factor}
+
+@set op-checkpoint @kbd{--checkpoint}
+@set ref-checkpoint @ref{verbose}
+@set xref-checkpoint @xref{verbose}
+@set pxref-checkpoint @pxref{verbose}
+
+@set op-compare @kbd{--compare} (@kbd{--diff}, @kbd{-d})
+@set ref-compare @ref{compare}
+@set xref-compare @xref{compare}
+@set pxref-compare @pxref{compare}
+
+@set op-compress @kbd{--compress} (@kbd{--uncompress}, @kbd{-Z})
+@set ref-compress @ref{gzip}
+@set xref-compress @xref{gzip}
+@set pxref-compress @pxref{gzip}
+
+@set op-concatenate @kbd{--concatenate} (@kbd{--catenate}, @kbd{-A})
+@set ref-concatenate @ref{concatenate}
+@set xref-concatenate @xref{concatenate}
+@set pxref-concatenate @pxref{concatenate}
+
+@set op-create @kbd{--create} (@kbd{-c})
+@set ref-create @ref{create}
+@set xref-create @xref{create}
+@set pxref-create @pxref{create}
+
+@set op-delete @kbd{--delete}
+@set ref-delete @ref{delete}
+@set xref-delete @xref{delete}
+@set pxref-delete @pxref{delete}
+
+@set op-dereference @kbd{--dereference} (@kbd{-h})
+@set ref-dereference @ref{dereference}
+@set xref-dereference @xref{dereference}
+@set pxref-dereference @pxref{dereference}
+
+@set op-directory @kbd{--directory=@var{directory}} (@kbd{-C @var{directory}})
+@set ref-directory @ref{directory}
+@set xref-directory @xref{directory}
+@set pxref-directory @pxref{directory}
+
+@set op-exclude @kbd{--exclude=@var{pattern}}
+@set ref-exclude @ref{exclude}
+@set xref-exclude @xref{exclude}
+@set pxref-exclude @pxref{exclude}
+
+@set op-exclude-from @kbd{--exclude-from=@var{file-of-patterns}} (@kbd{-X @var{file-of-patterns}})
+@set ref-exclude-from @ref{exclude}
+@set xref-exclude-from @xref{exclude}
+@set pxref-exclude-from @pxref{exclude}
+
+@set op-extract @kbd{--extract} (@kbd{--get}, @kbd{-x})
+@set ref-extract @ref{extract}
+@set xref-extract @xref{extract}
+@set pxref-extract @pxref{extract}
+
+@set op-file @kbd{--file=@var{archive-name}} (@kbd{-f @var{archive-name}})
+@set ref-file @ref{file}
+@set xref-file @xref{file}
+@set pxref-file @pxref{file}
+
+@set op-files-from @kbd{--files-from=@var{file-of-names}} (@kbd{-T @var{file-of-names}})
+@set ref-files-from @ref{files}
+@set xref-files-from @xref{files}
+@set pxref-files-from @pxref{files}
+
+@set op-force-local @kbd{--force-local}
+@set ref-force-local @ref{file}
+@set xref-force-local @xref{file}
+@set pxref-force-local @pxref{file}
+
+@set op-group @kbd{--group=@var{group}}
+@set ref-group @ref{Option Summary}
+@set xref-group @xref{Option Summary}
+@set pxref-group @pxref{Option Summary}
+
+@set op-gzip @kbd{--gzip} (@kbd{--gunzip}, @kbd{--ungzip}, @kbd{-z})
+@set ref-gzip @ref{gzip}
+@set xref-gzip @xref{gzip}
+@set pxref-gzip @pxref{gzip}
+
+@set op-help @kbd{--help}
+@set ref-help @ref{help}
+@set xref-help @xref{help}
+@set pxref-help @pxref{help}
+
+@set op-ignore-failed-read @kbd{--ignore-failed-read}
+@set ref-ignore-failed-read @ref{Reading}
+@set xref-ignore-failed-read @xref{Reading}
+@set pxref-ignore-failed-read @pxref{Reading}
+
+@set op-ignore-zeros @kbd{--ignore-zeros} (@kbd{-i})
+@set ref-ignore-zeros @ref{Reading}
+@set xref-ignore-zeros @xref{Reading}
+@set pxref-ignore-zeros @pxref{Reading}
+
+@set op-incremental @kbd{--incremental} (@kbd{-G})
+@set ref-incremental @ref{Inc Dumps}
+@set xref-incremental @xref{Inc Dumps}
+@set pxref-incremental @pxref{Inc Dumps}
+
+@set op-info-script @kbd{--info-script=@var{script-name}} (@kbd{--new-volume-script=@var{script-name}}, @kbd{-F @var{script-name}})
+@set ref-info-script @ref{Multi-Volume Archives}
+@set xref-info-script @xref{Multi-Volume Archives}
+@set pxref-info-script @pxref{Multi-Volume Archives}
+
+@set op-interactive @kbd{--interactive} (@kbd{-w})
+@set ref-interactive @ref{interactive}
+@set xref-interactive @xref{interactive}
+@set pxref-interactive @pxref{interactive}
+
+@set op-keep-old-files @kbd{--keep-old-files} (@kbd{-k})
+@set ref-keep-old-files @ref{Writing}
+@set xref-keep-old-files @xref{Writing}
+@set pxref-keep-old-files @pxref{Writing}
+
+@set op-label @kbd{--label=@var{archive-label}} (@kbd{-V @var{archive-label}})
+@set ref-label @ref{label}
+@set xref-label @xref{label}
+@set pxref-label @pxref{label}
+
+@set op-list @kbd{--list} (@kbd{-t})
+@set ref-list @ref{list}
+@set xref-list @xref{list}
+@set pxref-list @pxref{list}
+
+@set op-listed-incremental @kbd{--listed-incremental=@var{snapshot-file}} (@kbd{-g @var{snapshot-file}})
+@set ref-listed-incremental @ref{Inc Dumps}
+@set xref-listed-incremental @xref{Inc Dumps}
+@set pxref-listed-incremental @pxref{Inc Dumps}
+
+@set op-mode @kbd{--mode=@var{permissions}}
+@set ref-mode @ref{Option Summary}
+@set xref-mode @xref{Option Summary}
+@set pxref-mode @pxref{Option Summary}
+
+@set op-multi-volume @kbd{--multi-volume} (@kbd{-M})
+@set ref-multi-volume @ref{Multi-Volume Archives}
+@set xref-multi-volume @xref{Multi-Volume Archives}
+@set pxref-multi-volume @pxref{Multi-Volume Archives}
+
+@set op-newer-mtime @kbd{--newer-mtime=@var{date}}
+@set ref-newer-mtime @ref{after}
+@set xref-newer-mtime @xref{after}
+@set pxref-newer-mtime @pxref{after}
+
+@set op-no-recursion @kbd{--no-recursion}
+@set ref-no-recursion @ref{recurse}
+@set xref-no-recursion @xref{recurse}
+@set pxref-no-recursion @pxref{recurse}
+
+@set op-null @kbd{--null}
+@set ref-null @ref{files}
+@set xref-null @xref{files}
+@set pxref-null @pxref{files}
+
+@set op-numeric-owner @kbd{--numeric-owner}
+@set ref-numeric-owner @ref{Attributes}
+@set xref-numeric-owner @xref{Attributes}
+@set pxref-numeric-owner @pxref{Attributes}
+
+@set op-old-archive @kbd{--old-archive} (@kbd{-o})
+@set ref-old-archive @ref{old}
+@set xref-old-archive @xref{old}
+@set pxref-old-archive @pxref{old}
+
+@set op-one-file-system @kbd{--one-file-system} (@kbd{-l})
+@set ref-one-file-system @ref{one}
+@set xref-one-file-system @xref{one}
+@set pxref-one-file-system @pxref{one}
+
+@set op-owner @kbd{--owner=@var{user}}
+@set ref-owner @ref{Option Summary}
+@set xref-owner @xref{Option Summary}
+@set pxref-owner @pxref{Option Summary}
+
+@set op-posix @kbd{--posix}
+@set ref-posix @ref{posix}
+@set xref-posix @xref{posix}
+@set pxref-posix @pxref{posix}
+
+@set op-preserve @kbd{--preserve}
+@set ref-preserve @ref{Attributes}
+@set xref-preserve @xref{Attributes}
+@set pxref-preserve @pxref{Attributes}
+
+@set op-record-size @kbd{--record-size=@var{size}}
+@set ref-record-size @ref{Blocking}
+@set xref-record-size @xref{Blocking}
+@set pxref-record-size @pxref{Blocking}
+
+@set op-recursive-unlink @kbd{--recursive-unlink}
+@set ref-recursive-unlink @ref{Writing}
+@set xref-recursive-unlink @xref{Writing}
+@set pxref-recursive-unlink @pxref{Writing}
+
+@set op-read-full-records @kbd{--read-full-records} (@kbd{-B})
+@set ref-read-full-records @ref{Blocking}
+@set xref-read-full-records @xref{Blocking}
+@set pxref-read-full-records @pxref{Blocking}
+@c FIXME: or should it be Reading, or Blocking Factor
+
+@set op-remove-files @kbd{--remove-files}
+@set ref-remove-files @ref{Writing}
+@set xref-remove-files @xref{Writing}
+@set pxref-remove-files @pxref{Writing}
+
+@set op-rsh-command @kbd{rsh-command=@var{command}}
+
+@set op-same-order @kbd{--same-order} (@kbd{--preserve-order}, @kbd{-s})
+@set ref-same-order @ref{Scarce}
+@set xref-same-order @xref{Scarce}
+@set pxref-same-order @pxref{Scarce}
+@c FIXME: or should it be Reading, or Attributes?
+
+@set op-same-owner @kbd{--same-owner}
+@set ref-same-owner @ref{Attributes}
+@set xref-same-owner @xref{Attributes}
+@set pxref-same-owner @pxref{Attributes}
+
+@set op-same-permissions @kbd{--same-permissions} (@kbd{--preserve-permissions}, @kbd{-p})
+@set ref-same-permissions @ref{Attributes}
+@set xref-same-permissions @xref{Attributes}
+@set pxref-same-permissions @pxref{Attributes}
+@c FIXME: or should it be Writing?
+
+@set op-show-omitted-dirs @kbd{--show-omitted-dirs}
+@set ref-show-omitted-dirs @ref{verbose}
+@set xref-show-omitted-dirs @xref{verbose}
+@set pxref-show-omitted-dirs @pxref{verbose}
+
+@set op-sparse @kbd{--sparse} (@kbd{-S})
+@set ref-sparse @ref{sparse}
+@set xref-sparse @xref{sparse}
+@set pxref-sparse @pxref{sparse}
+
+@set op-starting-file @kbd{--starting-file=@var{name}} (@kbd{-K @var{name}})
+@set ref-starting-file @ref{Scarce}
+@set xref-starting-file @xref{Scarce}
+@set pxref-starting-file @pxref{Scarce}
+
+@set op-suffix @kbd{--suffix=@var{suffix}}
+@set ref-suffix @ref{Backup options}
+@set xref-suffix @xref{Backup options}
+@set pxref-suffix @pxref{Backup options}
+
+@set op-tape-length @kbd{--tape-length=@var{1024-size}} (@kbd{-L @var{1024-size}})
+@set ref-tape-length @ref{Using Multiple Tapes}
+@set xref-tape-length @xref{Using Multiple Tapes}
+@set pxref-tape-length @pxref{Using Multiple Tapes}
+
+@set op-to-stdout @kbd{--to-stdout} (@kbd{-O})
+@set ref-to-stdout @ref{Writing}
+@set xref-to-stdout @xref{Writing}
+@set pxref-to-stdout @pxref{Writing}
+
+@set op-totals @kbd{--totals}
+@set ref-totals @ref{verbose}
+@set xref-totals @xref{verbose}
+@set pxref-totals @pxref{verbose}
+
+@set op-touch @kbd{--touch} (@kbd{-m})
+@set ref-touch @ref{Writing}
+@set xref-touch @xref{Writing}
+@set pxref-touch @pxref{Writing}
+
+@set op-unlink-first @kbd{--unlink-first} (@kbd{-U})
+@set ref-unlink-first @ref{Writing}
+@set xref-unlink-first @xref{Writing}
+@set pxref-unlink-first @pxref{Writing}
+
+@set op-update @kbd{--update} (@kbd{-u})
+@set ref-update @ref{update}
+@set xref-update @xref{update}
+@set pxref-update @pxref{update}
+
+@set op-use-compress-prog @kbd{--use-compress-prog=@var{program}}
+@set ref-use-compress-prog @ref{gzip}
+@set xref-use-compress-prog @xref{gzip}
+@set pxref-use-compress-prog @pxref{gzip}
+
+@set op-verbose @kbd{--verbose} (@kbd{-v})
+@set ref-verbose @ref{verbose}
+@set xref-verbose @xref{verbose}
+@set pxref-verbose @pxref{verbose}
+
+@set op-verify @kbd{--verify} (@kbd{-W})
+@set ref-verify @ref{verify}
+@set xref-verify @xref{verify}
+@set pxref-verify @pxref{verify}
+
+@set op-version @kbd{--version}
+@set ref-version @ref{help}
+@set xref-version @xref{help}
+@set pxref-version @pxref{help}
+
+@set op-version-control @kbd{--version-control=@var{method}}
+@set ref-version-control @ref{Backup options}
+@set xref-version-control @xref{Backup options}
+@set pxref-version-control @pxref{Backup options}
+
+@set op-volno-file @kbd{--volno-file=@var{file-of-number}}
+@set ref-volno-file @ref{Using Multiple Tapes}
+@set xref-volno-file @xref{Using Multiple Tapes}
+@set pxref-volno-file @pxref{Using Multiple Tapes}
+
+@include version.texi
+
+@c Put everything in one index (arbitrarily chosen to be the concept index).
+@syncodeindex fn cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex vr cp
+
+@defindex op
+@syncodeindex op cp
-@iftex
-@c finalout
-@end iftex
+@ifinfo
+@format
+START-INFO-DIR-ENTRY
+* tar: (tar). Making tape (or disk) archives.
+END-INFO-DIR-ENTRY
+@end format
+@end ifinfo
@ifinfo
-This file documents @code{tar}, a utility used to store, backup, and
+This file documents GNU @code{tar}, a utility used to store, backup, and
transport files.
-Copyright (C) 1992 Free Software Foundation, Inc. DRAFT!
-@c Need to put distribution information here when ready.
+Copyright (C) 1992, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+@ignore
+Permission is granted to process this file through TeX and print the
+results, provided the printed document carries copying permission
+notice identical to this one except for the removal of this paragraph
+(this paragraph not being relevant to the printed manual).
+
+@end ignore
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided that the entire
+resulting derived work is distributed under the terms of a permission
+notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions,
+except that this permission notice may be stated in a translation approved
+by the Foundation.
@end ifinfo
-@c !!set edition number and date here
-@titlepage
-@title @code{tar}
-@subtitle The GNU Tape Archiver
-@subtitle Edition 0.01, for @code{tar} Version 1.10
-@subtitle @today{}
-@c remove preceding today line when ready
-@sp 1
-@subtitle DRAFT
-@c subtitle insert month here when ready
+@setchapternewpage odd
-@author Michael I. Bushnell and Amy Gorin
+@shorttitlepage GNU @code{tar}
+
+@titlepage
+@title GNU tar: an archiver tool
+@subtitle @value{RENDITION} @value{VERSION}, @value{UPDATED}
+@author Melissa Weisshaus, Jay Fenlason,
+@author Thomas Bushnell, n/BSG, Amy Gorin
+@c he said to remove it: Fran@,{c}ois Pinard
+@c i'm thinking about how the author page *should* look. -mew 2may96
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1992 Free Software Foundation, Inc.
-
-@sp 2
-This draft is not yet ready for distribution.
+Copyright @copyright{} 1992, 1994, 1995, 1996, 1997 Free Software
+Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided that the entire
+resulting derived work is distributed under the terms of a permission
+notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions,
+except that this permission notice may be stated in a translation approved
+by the Foundation.
@end titlepage
@ifinfo
-@node Top, Introduction, (dir), (dir)
-@top @code{tar}
-This file documents @code{tar}, a utility used to store, backup, and
-transport files.
+This file documents GNU @code{tar}, which is a utility used to store,
+backup, and transport files. @code{tar} is a tape (or disk) archiver.
+This manual documents the release @value{VERSION}.
-@c !!set edition number and date here
-This is DRAFT Edition 0.01 of the @code{tar} documentation, @today{}, for @code{tar}
-version 1.12.
@end ifinfo
-@c <<< The menus need to be gone over, and node names fixed.
+@node Top, Introduction, (dir), (dir)
+
@menu
-* Introduction:: @code{tar}: The GNU Tape Archiver
-* Invoking @code{tar}:: How to invoke @code{tar}
-* Tutorial:: Getting started
-* Wizardry:: Some More Advanced Uses for @code{tar}
-* Archive Structure:: The structure of an archive
-* Reading and Writing:: Reading and writing archives
-* Insuring Accuracy:: How to insure the accuracy of an archive
-* Selecting Archive Members:: How to select archive members
-* User Interaction:: How @code{tar} interacts with people.
-* Backups and Restoration:: How to restore files and perform backups
-* Media:: Using tapes and other archive media
-* Quick Reference:: A quick reference guide to
- @code{tar} operations and options
-* Data Format Details:: Details of the archive data format
-* Concept Index:: Concept Index
-@end menu
+* Introduction::
+* Tutorial::
+* tar invocation::
+* operations::
+* Backups::
+* Choosing::
+* Date input formats::
+* Formats::
+* Media::
+* Index::
-@chapter Tutorial Introduction to @code{tar}
+ --- The Detailed Node Listing ---
-This chapter guides you through some basic examples of @code{tar}
-operations. If you already know how to use some other version of
-@code{tar}, then you probably don't need to read this chapter. This
-chapter omits complicated details about many of the ways @code{tar}
-works. See later chapters for full information.
+Introduction
-@menu
-* Creating Archives:: Creating Archives
-* Extracting Files:: Extracting Files from an Archive
-* Listing Archive Contents:: Listing the Contents of an Archive
-* Comparing Files:: Comparing Archives with the File System
-* Adding to Archives:: Adding Files to Existing Archives
-* Concatenate:: Concatenating Archives
-* Deleting Files:: Deleting Files From an Archive
-@end menu
+* Book Contents:: What this Book Contains
+* Definitions:: Some Definitions
+* What tar Does:: What @code{tar} Does
+* Naming tar Archives:: How @code{tar} Archives are Named
+* posix compliance::
+* Authors:: GNU @code{tar} Authors
+* Reports:: Reporting bugs or suggestions
-@section What @code{tar} Does
+Tutorial Introduction to @code{tar}
-The @code{tar} program is used to create and manipulate @code{tar}
-archives. An @dfn{archive} is a single file which contains within it
-the contents of many files. In addition, the archive identifies the
-names of the files, their owner, and so forth.
+* assumptions::
+* stylistic conventions::
+* basic tar options:: Basic @code{tar} Operations and Options
+* frequent operations::
+* Two Frequent Options::
+* create:: How to Create Archives
+* list:: How to List Archives
+* extract:: How to Extract Members from an Archive
+* going further::
-You can use @code{tar} archives in many ways. Initially, @code{tar}
-archives were used to store files conveniently on magnetic tape. The
-name @samp{tar} comes from this use; it stands for Tape ARchiver.
-Often, @code{tar} archives are used to store related files for
-convenient file transfer over a network. For example, the GNU Project
-distributes its software bundled into @code{tar} archives, so that all
-the files relating to a particular program (or set of related programs)
-can be transferred as a single unit.
+Two Frequently Used Options
-The files inside an archive are called @dfn{members}. Within this
-manual, we use the term @dfn{file} to refer only to files accessible in
-the normal ways (by @code{ls}, @code{cat}, and so forth), and the term
-@dfn{members} to refer only to the members of an archive. Similarly, a
-@dfn{file name} is the name of a file, as it resides in the filesystem,
-and a @dfn{member name} is the name of an archive member within the
-archive.
+* file tutorial::
+* verbose tutorial::
+* help tutorial::
-The @code{tar} program provides the ability to create @code{tar}
-archives, as well as for various other kinds of manipulation. The term
-@dfn{extraction} is used to refer to the process of copying an archive
-member into a file in the filesystem. One might speak of extracting a
-single member. Extracting all the members of an archive is often called
-extracting the archive. Often the term @dfn{unpack} is used to refer to
-the extraction of many or all the members of an archive.
+How to Create Archives
-Conventionally, @code{tar} archives are given names ending with
-@samp{.tar}. This is not necessary for @code{tar} to operate properly,
-but this manual follows the convention in order to get the reader used
-to seeing it.
+* prepare for examples::
+* Creating the archive::
+* create verbose::
+* short create::
+* create dir::
-Occasionally archive members are referred to as files. For people
-familiar with the operation of @code{tar}, this causes no difficulty.
-However, this manual consistently uses the terminology above in
-referring to files and archive members, to make it easier to learn how
-to use @code{tar}.
+How to List Archives
-@section How to Create Archives
+* list dir::
-To create a new archive, use @samp{tar --create}. You should generally
-use the @samp{--file} option to specify the name the tar archive will
-have. Then specify the names of the files you wish to place in the new
-archive. For example, to place the files @file{apple}, @file{angst},
-and @file{asparagus} into an archive named @file{afiles.tar}, use the
-following command:
+How to Extract Members from an Archive
-@example
-tar --create --file=afiles.tar apple angst asparagus
-@end example
+* extracting archives::
+* extracting files::
+* extract dir::
+* failing commands::
-The order of the arguments is not important. You could also say:
+Invoking GNU @code{tar}
-@example
-tar apple --create angst --file=afiles.tar asparagus
-@end example
+* Synopsis::
+* using tar options::
+* Styles::
+* All Options::
+* help::
+* verbose::
+* interactive::
-This order is harder to understand however. In this manual, we will
-list the arguments in a reasonable order to make the commands easier to
-understand, but you can type them in any order you wish.
+The Three Option Styles
-If you don't specify the names of any files to put in the archive, then
-tar will create an empty archive. So, the following command will create
-an archive with nothing in it:
+* Mnemonic Options:: Mnemonic Option Style
+* Short Options:: Short Option Style
+* Old Options:: Old Option Style
+* Mixing:: Mixing Option Styles
-@example
-tar --create --file=empty-archive.tar
-@end example
+All @code{tar} Options
-Whenever you use @samp{tar --create}, @code{tar} will erase the current
-contents of the file named by @samp{--file} if it exists. To add files
-to an existing archive, you need to use a different option.
-@xref{Adding to Archives} for information on how to do this.
+* Operation Summary::
+* Option Summary::
+* Short Option Summary::
-When @samp{tar --create} creates an archive, the member names of the
-members of the archive are exactly the same as the file names as you
-typed them in the @code{tar} command. So, the member names of
-@file{afiles} (as created by the first example above) are @file{apple},
-@file{angst}, and @file{asparagus}. However, suppose an archive were
-created with this command:
+GNU @code{tar} Operations
-@example
-tar --create --file=bfiles.tar ./balloons baboon ./bodacious
-@end example
+* Basic tar::
+* Advanced tar::
+* extract options::
+* backup::
+* Applications::
+* looking ahead::
-Then, the three files @file{balloons}, @file{baboon}, and
-@file{bodacious} would get placed in the archive (because @file{./} is a
-synonym for the current directory), but their member names would be
-@file{./balloons}, @file{baboon}, and @file{./bodacious}.
+Advanced GNU @code{tar} Operations
-If you want to see the progress of tar as it writes files into the
-archive, you can use the @samp{--verbose} option.
+* Operations::
+* current state::
+* append::
+* update::
+* concatenate::
+* delete::
+* compare::
-If one of the files named to @samp{tar --create} is a directory, then
-the operation of tar is more complicated. @xref{Tar and Directories},
-the last section of this tutorial, for more information.
+How to Add Files to Existing Archives: @code{--append}
-If you don't specify the @samp{--file} option, then @code{tar} will use
-a default. Usually this default is some physical tape drive attached to
-your machine. If there is no tape drive attached, or the default is not
-meaningful, then tar will print an error message. This error message
-might look roughly like one of the following:
+* appending files:: Appending Files to an Archive
+* multiple::
-@example
-tar: can't open /dev/rmt8 : No such device or address
-tar: can't open /dev/rsmt0 : I/O error
-@end example
+Updating an Archive
-If you get an error like this, mentioning a file you didn't specify
-(@file{/dev/rmt8} or @file{/dev/rsmt0} in the examples above), then @code{tar}
-is using a default value for @samp{--file}. You should generally specify a
-@samp{--file} argument whenever you use @code{tar}, rather than relying
-on a default.
+* how to update::
-@section How to List Archives
+Options Used by @code{--extract}
-Use @samp{tar --list} to print the names of members stored in an
-archive. Use a @samp{--file} option just as with @samp{tar --create} to
-specify the name of the archive. For example, the archive
-@file{afiles.tar} created in the last section could be examined with the
-command @samp{tar --list --file=afiles.tar}. The output of tar would
-then be:
+* Reading:: Options to Help Read Archives
+* Writing:: Changing How @code{tar} Writes Files
+* Scarce:: Coping with Scarce Resources
-@example
-apple
-angst
-asparagus
-@end example
+Options to Help Read Archives
-The archive @file{bfiles.tar} would list as follows:
+* read full records::
+* Ignore Zeros::
+* Ignore Failed Read::
-@example
-./baloons
-baboon
-./bodacious
-@end example
+Changing How @code{tar} Writes Files
-(Of course, @samp{tar --list --file=empty-archive.tar} would produce no
-output.)
+* Prevention Overwriting::
+* Keep Old Files::
+* Unlink First::
+* Recursive Unlink::
+* Modification Times::
+* Setting Access Permissions::
+* Writing to Standard Output::
+* remove files::
-If you use the @samp{--verbose} option with @samp{tar --list}, then tar
-will print out a listing reminiscent of @samp{ls -l}, showing owner,
-file size, and so forth.
+Options to Prevent Overwriting Files
-You can also specify member names when using @samp{tar --list}. In this
-case, tar will only list the names of members you identify. For
-example, @samp{tar --list --file=afiles.tar apple} would only print
-@samp{apple}. It is essential when specifying member names to tar that
-you give the exact member names. For example, @samp{tar --list
---file=bfiles baloons} would produce no output, because there is no
-member named @file{baloons}, only one named @file{./baloons}. While the
-file names @file{baloons} and @file{./baloons} name the same file,
-member names are compared using a simplistic name comparison, in which
-an exact match is necessary.
+* Keep Old Files::
+* Unlink First::
+* Recursive Unlink::
-@section How to Extract Members from an Archive
+Coping with Scarce Resources
-In order to extract members from an archive, use @samp{tar --extract}.
-Specify the name of the archive with @samp{--file}. To extract specific
-archive members, give their member names as arguments. It essential to
-give their exact member name, as printed by @samp{tar --list}. This
-will create a copy of the archive member, with a file name the same as
-its name in the archive.
-
-Keeping the example of the two archives created at the beginning of this
-tutorial, @samp{tar --extract --file=afiles.tar apple} would create a
-file @file{apple} in the current directory with the contents of the
-archive member @file{apple}. It would remove any file named
-@file{apple} already present in the directory, but it would not change
-the archive in any way.
-
-Remember that specifying the exact member name is important. @samp{tar
---extract --file=bfiles.tar baloons} will fail, because there is no
-member named @file{baloons}. To extract the member named
-@file{./baloons} you would need to specify @samp{tar --extract
---file=bfiles.tar ./baloons}. To find the exact member names of the
-members of an archive, use @samp{tar --list} (@pxref{Listing
-Archives}).
-
-If you do not list any archive member names, then @samp{tar --extract}
-will extract all the members of the archive.
-
-If you give the @samp{--verbose} option, then @samp{tar --extract} will
-print the names of the archive members as it extracts them.
+* Starting File::
+* Same Order::
-@section How to Add Files to Existing Archives
+Performing Backups and Restoring Files
-If you want to add files to an existing archive, then don't use
-@samp{tar --create}. That will erase the archive and create a new one
-in its place. Instead, use @samp{tar --append}. The command @samp{tar
---append --file=afiles.tar arbalest} would add the file @file{arbalest}
-to the existing archive @file{afiles.tar}. The archive must already
-exist in order to use @samp{tar --append}.
+* Full Dumps:: Using @code{tar} to Perform Full Dumps
+* Inc Dumps:: Using @code{tar} to Perform Incremental Dumps
+* incremental and listed-incremental:: The Incremental Options
+* Backup Levels:: Levels of Backups
+* Backup Parameters:: Setting Parameters for Backups and Restoration
+* Scripted Backups:: Using the Backup Scripts
+* Scripted Restoration:: Using the Restore Script
-As with @samp{tar --create}, the member names of the newly added files
-will be the exact same as their names given on the command line. The
-@samp{--verbose} option will print out the names of the files as they
-are written into the archive.
+Setting Parameters for Backups and Restoration
-If you add a file to an archive using @samp{tar --append} with the
-same name as an archive member already present in the archive, then the
-old member is not deleted. What does happen, however, is somewhat
-complex. @xref{Multiple Members with the Same Name}. If you want to
-replace an archive member, use @samp{tar --delete} first, and then use
-@samp{tar --append}.
-
-@section How to Delete Members from Archives
-
-You can delete members from an archive using @samp{tar --delete}.
-Specify the name of the archive with @samp{--file}. List the member
-names of the members to be deleted. (If you list no member names, then
-nothing will be deleted.) The @samp{--verbose} option will cause
-@code{tar} to print the names of the members as they are deleted. As
-with @samp{tar --extract}, it is important that you give the exact
-member names when using @samp{tar --delete}. Use @samp{tar --list} to
-find out the exact member names in an archive (@pxref{Listing
-Archives}).
-
-The @samp{tar --delete} command only works with archives stored on disk.
-You cannot delete members from an archive stored on a tape.
-
-@section How to Archive Directories
-
-When the names of files or members specify directories, the operation of
-@code{tar} is more complex. Generally, when a directory is named,
-@code{tar} also operates on all the contents of the directory,
-recursively. Thus, to @code{tar}, the file name @file{/} names the
-entire file system.
-
-To archive the entire contents of a directory, use @samp{tar --create}
-(or @samp{tar --append}) as usual, and specify the name of the
-directory. For example, to archive all the contents of the current
-directory, use @samp{tar --create --file=@var{archive-name} .}. Doing
-this will give the archive members names starting with @samp{./}. To
-archive the contents of a directory named @file{foodir}, use @samp{tar
---create --file=@var{archive-name} foodir}. In this case, the member
-names will all start with @samp{foodir/}.
-
-If you give @code{tar} a command such as @samp{tar --create
---file=foo.tar .}, it will report @samp{tar: foo.tar is the archive; not
-dumped}. This happens because the archive @file{foo.tar} is created
-before putting any files into it. Then, when @code{tar} attempts to add
-all the files in the directory @file{.} to the archive, it notices that
-the file @file{foo.tar} is the same as the archive, and skips it. (It
-makes no sense to put an archive into itself.) GNU @code{tar} will
-continue in this case, and create the archive as normal, except for the
-exclusion of that one file. Other versions of @code{tar}, however, are
-not so clever, and will enter an infinite loop when this happens, so you
-should not depend on this behavior. In general, make sure that the
-archive is not inside a directory being dumped.
-
-When extracting files, you can also name directory archive members on
-the command line. In this case, @code{tar} extracts all the archive
-members whose names begin with the name of the directory. As usual,
-@code{tar} is not particularly clever about interpreting member names.
-The command @samp{tar --extract --file=@var{archive-name} .} will not
-extract all the contents of the archive, but only those members whose
-member names begin with @samp{./}.
-
-@section Shorthand Names
-
-Most of the options to @code{tar} come in both long forms and short
-forms. The options described in this tutorial have the following
-abbreviations (except @samp{--delete}, which has no shorthand form):
+* backup-specs example:: An Example Text of @file{Backup-specs}
+* Script Syntax:: Syntax for @file{Backup-specs}
-@table @samp
-@item --create
-@samp{-c}
-@item --list
-@samp{-t}
-@item --extract
-@samp{-x}
-@item --append
-@samp{-r}
-@item --verbose
-@samp{-v}
-@item --file=@var{archive-name}
-@samp{-f @var{archive-name}}
-@end table
+Choosing Files and Names for @code{tar}
-These options make typing long @code{tar} commands easier. For example,
-instead of typing
-@example
-tar --create --file=/tmp/afiles.tar --verbose apple angst asparagus
-@end example
-you can type
-@example
-tar -c -f /tmp/afiles.tar -v apple angst asparagus
-@end example
+* file:: Choosing the Archive's Name
+* Selecting Archive Members::
+* files:: Reading Names from a File
+* exclude:: Excluding Some Files
+* Wildcards::
+* after:: Operating Only on New Files
+* recurse:: Descending into Directories
+* one:: Crossing Filesystem Boundaries
-For more information on option syntax, @ref{Invoking @code{tar}}. In
-the remainder of this manual, short forms and long forms are given
-together when an option is discussed.
+Reading Names from a File
-@chapter Invoking @code{tar}
+* nul::
-The usual way to invoke tar is
+Excluding Some Files
-@example
-@code{tar} @var{options}... [@var{file-or-member-names}...]
-@end example
+* problems with exclude::
-All the options start with @samp{-}. You can actually type in arguments
-in any order, but in this manual the options always precede the other
-arguments, to make examples easier to understand.
+Crossing Filesystem Boundaries
-@menu
-* Option Form:: The Forms of Arguments
-* Argument Functions:: The Functions of Arguments
-* Old Syntax for Commands:: An Old, but Still Supported, Syntax
- for @code{tar} Commands
-@end menu
+* directory:: Changing Directory
+* absolute:: Absolute File Names
-@section The Forms of Arguments
-
-Most options of @code{tar} have a single letter form (a single letter
-preceded by @samp{-}), and at least one mnemonic form (a word or
-abbreviation preceded by @samp{--}). The forms are absolutely
-identical in function. For example, you can use either @samp{tar -t}
-or @samp{tar --list} to list the contents of an archive. In addition,
-mnemonic names can be given unique abbreviations. For example,
-@samp{--cre} can be used in place of @samp{--create} because there is
-no other option which begins with @samp{cre}.
-
-Some options require an additional argument. Single letter options
-which require arguments use the immediately following argument.
-Mnemonic options are separated from their arguments by an @samp{=}
-sign. For example, to create an an archive file named
-@file{george.tar}, use either @samp{tar --create --file=george.tar} or
-@samp{tar --create -f george.tar}. Both
-@samp{--file=@var{archive-name}} and @samp{-f @var{archive-name}} denote
-the option to give the archive a non-default name, which in the example
-is @file{george.tar}.
-
-You can mix single letter and mnemonic forms in the same command. You
-could type the above example as @samp{tar -c --file=george} or
-@samp{tar --create -f george}. However, @code{tar} operations and
-options are case sensitive. You would not type the above example as
-@samp{tar -C --file=george}, because @samp{-C} is an option that
-causes @code{tar} to change directories, not an operation that creates
-an archive. In fact, @samp{-C} requires a further argument (the name
-of the directory which to change to). In this case, tar would think
-it needs to change to a directory named @samp{--file=george}, and
-wouldn't interpret @samp{--file-george} as an option at all!
-
-@section The Functions of Arguments
-
-You must give exactly one option from the following list to tar. This
-option specifies the basic operation for @code{tar} to perform.
-
-@table samp
-@item --help
-Print a summary of the options to @code{tar} and do nothing else
+Date input formats
-@item --create
-@item -c
-Create a new archive
+* General date syntax:: Common rules.
+* Calendar date item:: 19 Dec 1994.
+* Time of day item:: 9:20pm.
+* Timezone item:: EST, DST, BST, UCT, AHST, ...
+* Day of week item:: Monday and others.
+* Relative item in date strings:: next tuesday, 2 years ago.
+* Pure numbers in date strings:: 19931219, 1440.
+* Authors of getdate:: Bellovin, Salz, Berets, et al.
-@item --catenate
-@item --concatenate
-@item -A
-Add the contents of one or more archives to another archive
+Controlling the Archive Format
-@item --append
-@item -a
-Add files to an existing archive
+* Portability:: Making @code{tar} Archives More Portable
+* Compression:: Using Less Space through Compression
+* Attributes:: Handling File Attributes
+* Standard:: The Standard Format
+* Extensions:: GNU Extensions to the Archive Format
+* cpio:: Comparison of @code{tar} and @code{cpio}
-@item --list
-@item -t
-List the members in an archive
+Making @code{tar} Archives More Portable
-@item --delete
-Delete members from an archive
+* Portable Names:: Portable Names
+* dereference:: Symbolic Links
+* old:: Old V7 Archives
+* posix:: POSIX archives
+* Checksumming:: Checksumming Problems
-@item --extract
-@item --get
-@item -x
-Extract members from an archive
+Using Less Space through Compression
-@item --compare
-@item --diff
-@item -d
-Compare members in an archive with files in the file system
+* gzip:: Creating and Reading Compressed Archives
+* sparse:: Archiving Sparse Files
-@item --update
-@item -u
-Update an archive by appending newer versions of already stored files
-@end itemize
+Tapes and Other Archive Media
-The remaining options to @code{tar} change details of the operation,
-such as archive format, archive name, or level of user interaction.
-You can specify more than one option.
-
-The remaining arguments are interpreted either as file names or as
-member names, depending on the basic operation @code{tar} is
-performing. For @samp{--append} and @samp{--create} these arguments
-specify the names of files (which must already exist) to place in the
-archive. For the remaining operation types, the additional arguments
-specify archive members to compare, delete, extract, list, or update.
-When naming archive members, you must give the exact name of the member
-in the archive, as it is printed by @code{tar --list}. When naming
-files, the normal file name rules apply.
-
-If you don't use any additional arguments, @samp{--append},
-@samp{--catenate}, and @samp{--delete} will do nothing. Naturally,
-@samp{--create} will make an empty archive if given no files to add.
-The other operations of @code{tar} (@samp{--list}, @samp{--extract},
-@samp{--compare}, and @samp{--update}) will act on the entire contents
-of the archive.
+* Device:: Device selection and switching
+* Remote Tape Server::
+* Common Problems and Solutions::
+* Blocking:: Blocking
+* Many:: Many archives on one tape
+* Using Multiple Tapes:: Using Multiple Tapes
+* label:: Including a Label in the Archive
+* verify::
+* Write Protection::
-If you give the name of a directory as either a file name or a member
-name, then @code{tar} acts recursively on all the files and directories
-beneath that directory. For example, the name @file{/} identifies all
-the files in the filesystem to @code{tar}.
+Blocking
-@section An Old, but Still Supported, Syntax for @code{tar} Commands
+* Format Variations:: Format Variations
+* Blocking Factor:: The Blocking Factor of an Archive
-For historical reasons, GNU @code{tar} also accepts a syntax for
-commands which splits options that require additional arguments into
-two parts. That syntax is of the form:
+Many Archives on One Tape
-@example
-@code{tar} @var{option-letters}... [@var{option-arguments}...] [@var{file-names}...]@refill
-@end example
+* Tape Positioning:: Tape Positions and Tape Marks
+* mt:: The @code{mt} Utility
-@noindent
-where arguments to the options appear in the same order as the letters
-to which they correspond, and the operation and all the option letters
-appear as a single argument, without separating spaces.
+Using Multiple Tapes
-This command syntax is useful because it lets you type the single
-letter forms of the operation and options as a single argument to
-@code{tar}, without writing preceding @samp{-}s or inserting spaces
-between letters. @samp{tar cv} or @samp{tar -cv} are equivalent to
-@samp{tar -c -v}.
+* Multi-Volume Archives:: Archives Longer than One Tape or Disk
+* Tape Files:: Tape Files
+@end menu
-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 @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
-argument. The modern syntax---@samp{tar -c -v -b 20 -f
-/dev/rmt0}---is clearer.
+@node Introduction, Tutorial, Top, Top
+@chapter Introduction
-@chapter Basic @code{tar} Operations
+Welcome to the GNU @code{tar} manual. GNU @code{tar} is used to create
+and manipulate files (@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.
+
+@menu
+* Book Contents:: What this Book Contains
+* Definitions:: Some Definitions
+* What tar Does:: What @code{tar} Does
+* Naming tar Archives:: How @code{tar} Archives are Named
+* posix compliance::
+* Authors:: GNU @code{tar} Authors
+* Reports:: Reporting bugs or suggestions
+@end menu
-This chapter describes the basic operations supported by the @code{tar}
-program. A given invocation of @code{tar} will do exactly one of these
-operations.
+@node Book Contents, Definitions, Introduction, Introduction
+@ifinfo
+@heading What this Book Contains
+@end ifinfo
-@section Creating a New Archive
+The first part of this chapter introduces you to various terms that will
+recur throughout the book. It also tells you who has worked on GNU
+@code{tar} and its documentation, and where you should send bug reports
+or comments.
+
+The second chapter is a tutorial (@pxref{Tutorial}) which provides a
+gentle introduction for people who are new to using @code{tar}. It is
+meant to be self contained, not requiring any reading from subsequent
+chapters to make sense. It moves from topic to topic in a logical,
+progressive order, building on information already explained.
+
+Although the tutorial is paced and structured to allow beginners to
+learn how to use @code{tar}, it is not intended solely for beginners.
+The tutorial explains how to use the three most frequently used
+operations (@samp{create}, @samp{list}, and @samp{extract}) as well as
+two frequently used options (@samp{file} and @samp{verbose}). The other
+chapters do not refer to the tutorial frequently; however, if a section
+discusses something which is a complex variant of a basic concept, there
+may be a cross reference to that basic concept. (The entire book,
+including the tutorial, assumes that the reader understands some basic
+concepts of using a Unix-type operating system; @pxref{Tutorial}.)
+
+The third chapter presents the remaining five operations, and
+information about using @code{tar} options and option syntax.
+
+@FIXME{this sounds more like a GNU Project Manuals Concept [tm] more
+than the reality. should think about whether this makes sense to say
+here, or not.} The other chapters are meant to be used as a
+reference. Each chapter presents everything that needs to be said
+about a specific topic.
+
+One of the chapters (@pxref{Date input formats}) exists in its entirety
+in other GNU manuals, and is mostly self-contained. In addition, one
+section of this manual (@pxref{Standard}) contains a big quote which is
+taken directly from @code{tar} sources.
+
+In general, we give both the long and short (abbreviated) option names
+at least once in each section where the relevant option is covered, so
+that novice readers will become familiar with both styles. (A few
+options have no short versions, and the relevant sections will
+indicate this.)
+
+@node Definitions, What tar Does, Book Contents, Introduction
+@section Some Definitions
+
+@cindex archive
+@cindex tar archive
+The @code{tar} program is used to create and manipulate @code{tar}
+archives. An @dfn{archive} is a single file which contains the contents
+of many files, while still identifying the names of the files, their
+owner(s), and so forth. (In addition, archives record access
+permissions, user and group, size in bytes, and last modification time.
+Some archives also record the file names in each archived directory, as
+well as other file and directory information.) You can use @code{tar}
+to @dfn{create} a new archive in a specified directory.
+
+@cindex member
+@cindex archive member
+@cindex file name
+@cindex member name
+The files inside an archive are called @dfn{members}. Within this
+manual, we use the term @dfn{file} to refer only to files accessible in
+the normal ways (by @code{ls}, @code{cat}, and so forth), and the term
+@dfn{member} to refer only to the members of an archive. Similarly, a
+@dfn{file name} is the name of a file, as it resides in the filesystem,
+and a @dfn{member name} is the name of an archive member within the
+archive.
-The @samp{--create} (@code{-c}) option causes @code{tar} to create a new
-archive. The files to be archived are then named on the command line.
-Each file will be added to the archive with a member name exactly the
-same as the name given on the command line. (When you give an absolute
-file name @code{tar} actually modifies it slightly, @ref{Absolute
-Paths}.) If you list no files to be archived, then an empty archive is
-created.
+@cindex extraction
+@cindex unpacking
+The term @dfn{extraction} refers to the process of copying an archive
+member (or multiple members) into a file in the filesystem. Extracting
+all the members of an archive is often called @dfn{extracting the
+archive}. The term @dfn{unpack} can also be used to refer to the
+extraction of many or all the members of an archive. Extracting an
+archive does not destroy the archive's structure, just as creating an
+archive does not destroy the copies of the files that exist outside of
+the archive. You may also @dfn{list} the members in a given archive
+(this is often thought of as ``printing'' them to the standard output,
+or the command line), or @dfn{append} members to a pre-existing archive.
+All of these operations can be peformed using @code{tar}.
+
+@node What tar Does, Naming tar Archives, Definitions, Introduction
+@section What @code{tar} Does
-If there are two many files to conveniently list on the command line,
-you can list the names in a file, and @code{tar} will read that file.
-@xref{Reading Names from a File}.
+@cindex tar
+The @code{tar} program provides the ability to create @code{tar}
+archives, as well as various other kinds of manipulation. For example,
+you can use @code{tar} on previously created archives to extract files,
+to store additional files, or to update or list files which were already
+stored.
-If you name a directory, then @code{tar} will archive not only the
-directory, but all its contents, recursively. For example, if you name
-@file{/}, then @code{tar} will archive the entire filesystem.
+Initially, @code{tar} archives were used to store files conveniently on
+magnetic tape. The name @samp{tar} comes from this use; it stands for
+@code{t}ape @code{ar}chiver. Despite the utility's name, @code{tar} can
+direct its output to available devices, files, or other programs (using
+pipes). @code{tar} may even access remote devices or files (as archives).
-Do not use the option to add files to an existing archive; it will
-delete the archive and write a new one. Use @samp{--append} instead.
-(@xref{Adding to an Existing Archive}.)
+@FIXME{the following table entries need a bit of work..}
-There are various ways of causing @code{tar} to skip over some files,
-and not archive them. @xref{Specifying Names to @code{tar}}.
+You can use @code{tar} archives in many ways. We want to stress a few
+of them: storage, backup, and transportation.
-@section Adding to an Existing Archive
+@table @asis
+@item Storage
+Often, @code{tar} archives are used to store related files for
+convenient file transfer over a network. For example, the GNU Project
+distributes its software bundled into @code{tar} archives, so that
+all the files relating to a particular program (or set of related
+programs) can be transferred as a single unit.
+
+A magnetic tape can store several files in sequence. However, the tape
+has no names for these files; it only knows their relative position on
+the tape. One way to store several files on one tape and retain their
+names is by creating a @code{tar} archive. Even when the basic transfer
+mechanism can keep track of names, as FTP can, the nuisance of handling
+multiple files, directories, and multiple links makes @code{tar}
+archives useful.
+
+Archive files are also used for long-term storage. You can think of
+this as transportation from the present into the future. (It is a
+science-fiction idiom that you can move through time as well as in
+space; the idea here is that @code{tar} can be used to move archives in
+all dimensions, even time!)
+
+@item Backup
+Because the archive created by @code{tar} is capable of preserving file
+information and directory structure, @code{tar} is commonly used for
+performing full and incremental backups of disks. A backup puts a
+collection of files (possibly pertaining to many users and
+projects) together on a disk or a tape. This guards against accidental
+destruction of the information in those files. GNU @code{tar} has
+special features that allow it to be used to make incremental and full
+dumps of all the files in a filesystem.
+
+@item Transportation
+You can create an archive on one system, transfer it to another system,
+and extract the contents there. This allows you to transport a group of
+files from one system to another.
+@end table
-The @samp{--append} (@code{-r}) option will case @code{tar} to add new
-files to an existing archive. It interprets file names and member names
-in exactly the same manner as @samp{--create}. Nothing happens if you
-don't list any names.
+@node Naming tar Archives, posix compliance, What tar Does, Introduction
+@section How @code{tar} Archives are Named
-This option never deletes members. If a new member is added under the
-same name as an existing member, then both will be in the archive, with
-the new member after the old one. For information on how this affects
-reading the archive, @ref{Multiple Members with the Same Name}.
+Conventionally, @code{tar} archives are given names ending with
+@samp{.tar}. This is not necessary for @code{tar} to operate properly,
+but this manual follows that convention in order to accustom readers to
+it and to make examples more clear.
-This operation cannot be performed on some tape drives, unfortunately,
-due to deficiencies in the formats thoes tape drives use.
+@cindex tar file
+@cindex entry
+@cindex tar entry
+Often, people refer to @code{tar} archives as ``@code{tar} files,'' and
+archive members as ``files'' or ``entries''. For people familiar with
+the operation of @code{tar}, this causes no difficulty. However, in
+this manual, we consistently refer to ``archives'' and ``archive
+members'' to make learning to use @code{tar} easier for novice users.
-@section Combining Archives
+@node posix compliance, Authors, Naming tar Archives, Introduction
+@section POSIX Compliance
-The @samp{--catenate} (or @code{--concatenate}, or @code{-A}) causes
-@code{tar} to add the contents of several archives to an existing
-archive.
+@noindent
+@FIXME{must ask franc,ois about this. dan hagerty thinks this might
+be an issue, but we're not really sure at this time. dan just tried a
+test case of mixing up options' orders while the variable was set, and
+there was no problem...}
+
+We make some of our recommendations throughout this book for one
+reason in addition to what we think of as ``good sense''. The main
+additional reason for a recommendation is to be compliant with the
+POSIX standards. If you set the shell environment variable
+@code{POSIXLY_CORRECT}, GNU @code{tar} will force you to adhere to
+these standards. Therefore, if this variable is set and you violate
+one of the POSIX standards in the way you phrase a command, for
+example, GNU @code{tar} will not allow the command and will signal an
+error message. You would then have to reorder the options or rephrase
+the command to comply with the POSIX standards.
+
+There is a chance in the future that, if you set this environment
+variable, your archives will be forced to comply with POSIX standards,
+also. No GNU @code{tar} extensions will be allowed.
+
+@node Authors, Reports, posix compliance, Introduction
+@section GNU @code{tar} Authors
+
+GNU @code{tar} was originally written by John Gilmore, and modified by
+many people. The GNU enhancements were written by Jay Fenlason, then
+Joy Kendall, and the whole package has been further maintained by
+Thomas Bushnell, n/BSG, and finally Fran@,{c}ois Pinard, with
+the help of numerous and kind users.
+
+We wish to stress that @code{tar} is a collective work, and owes much to
+all those people who reported problems, offered solutions and other
+insights, or shared their thoughts and suggestions. An impressive, yet
+partial list of those contributors can be found in the @file{THANKS}
+file from the GNU @code{tar} distribution.
+
+@FIXME{i want all of these names mentioned, Absolutely. BUT, i'm not
+sure i want to spell out the history in this detail, at least not for
+the printed book. i'm just not sure it needs to be said this way.
+i'll think about it.}
+
+@FIXME{History is more important, and surely more interesting, than
+actual names. Quoting names without history would be meaningless. FP}
+
+Jay Fenlason put together a draft of a GNU @code{tar} manual,
+borrowing notes from the original man page from John Gilmore. This
+draft has been distributed in @code{tar} versions 1.04 (or even
+before?) @FIXME{huh? IMO, either we know or we don't; the
+parenthetical is confusing.} through 1.10, then withdrawn in version
+1.11. Thomas Bushnell, n/BSG and Amy Gorin worked on a tutorial and
+manual for GNU @code{tar}. Fran@,{c}ois Pinard put version 1.11.8
+of the manual together by taking information from all these sources
+and merging them. Melissa Weisshaus finally edited and redesigned the
+book to create version 1.12. @FIXME{update version number as
+necessary; i'm being optimistic!} @FIXME{Someone [maybe karl berry?
+maybe bob chassell? maybe melissa? maybe julie sussman?] needs to
+properly index the thing.}
+
+For version 1.12, Daniel Hagerty contributed a great deal of technical
+consulting. In particular, he is the primary author of @ref{Backups}.
+
+@node Reports, , Authors, Introduction
+@section Reporting bugs or suggestions
+
+@cindex bug reports
+@cindex reporting bugs
+If you find problems or have suggestions about this program or manual,
+please report them to @file{bug-gnu-utils@@prep.ai.mit.edu}.
+
+@node Tutorial, tar invocation, Introduction, Top
+@chapter Tutorial Introduction to @code{tar}
-Name the archives to be catenated 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 either; all the members with the
-same name coexist. For information on how this affects reading the
-archive, @ref{Multiple Members with the Same Name}.
+This chapter guides you through some basic examples of three @code{tar}
+operations: @samp{--create}, @samp{--list}, and @samp{--extract}. If
+you already know how to use some other version of @code{tar}, then you
+may not need to read this chapter. This chapter omits most complicated
+details about how @code{tar} works.
-You must use this option to concatenate archives. If you just combine
-them with @code{cat}, the result will not be a valid @code{tar} format
-archive.
+@menu
+* assumptions::
+* stylistic conventions::
+* basic tar options:: Basic @code{tar} Operations and Options
+* frequent operations::
+* Two Frequent Options::
+* create:: How to Create Archives
+* list:: How to List Archives
+* extract:: How to Extract Members from an Archive
+* going further::
+@end menu
-This operation cannot be performed on some tape drives, unfortunately,
-due to deficiencies in the formats thoes tape drives use.
+@node assumptions, stylistic conventions, Tutorial, Tutorial
+@ifinfo
+@heading Assumptions this Tutorial Makes
+@end ifinfo
-@section Removing Archive Members
+This chapter is paced to allow beginners to learn about @code{tar}
+slowly. At the same time, we will try to cover all the basic aspects of
+these three operations. In order to accomplish both of these tasks, we
+have made certain assumptions about your knowledge before reading this
+manual, and the hardware you will be using:
+
+@itemize @bullet
+@item
+Before you start to work through this tutorial, you should understand
+what the terms ``archive'' and ``archive member'' mean
+(@pxref{Definitions}). In addition, you should understand something
+about how Unix-type operating systems work, and you should know how to
+use some basic utilities. For example, you should know how to create,
+list, copy, rename, edit, and delete files and directories; how to
+change between directories; and how to figure out where you are in the
+filesystem. You should have some basic understanding of directory
+structure and how files are named according to which directory they are
+in. You should understand concepts such as standard output and standard
+input, what various definitions of the term ``argument'' mean, the
+differences between relative and absolute path names, and @FIXME{what
+else?}.
+
+@item
+This manual assumes that you are working from your own home directory
+(unless we state otherwise). In this tutorial, you will create a
+directory to practice @code{tar} commands in. When we show path names,
+we will assume that those paths are relative to your home directory.
+For example, my home directory path is @file{/home/fsf/melissa}. All of
+my examples are in a subdirectory of the directory named by that path
+name; the subdirectory is called @file{practice}.
+
+@item
+In general, we show examples of archives which exist on (or can be
+written to, or worked with from) a directory on a hard disk. In most
+cases, you could write those archives to, or work with them on any other
+device, such as a tape drive. However, some of the later examples in
+the tutorial and next chapter will not work on tape drives.
+Additionally, working with tapes is much more complicated than working
+with hard disks. For these reasons, the tutorial does not cover working
+with tape drives. @xref{Media} for complete information on using
+@code{tar} archives with tape drives.
+
+@FIXME{this is a cop out. need to add some simple tape drive info.}
+@end itemize
-You can use the @samp{--delete} option to remove members from an
-archive. Name the members on the command line to be deleted. This
-option will rewrite the archive; because of this, it does not work on
-tape drives. If you list no members to be deleted, nothing happens.
+@node stylistic conventions, basic tar options, assumptions, Tutorial
+@ifinfo
+@heading Stylistic Conventions
+@end ifinfo
-@section Listing Archive Members
+In the examples, @samp{$} represents a typical shell prompt. It
+precedes lines you should type; to make this more clear, those lines are
+shown in @kbd{this font}, as opposed to lines which represent the
+computer's response; those lines are shown in @code{this font}, or
+sometimes @samp{like this}. When we have lines which are too long to be
+displayed in any other way, we will show them like this:
+
+@smallexample
+This is an example of a line which would otherwise not fit in this space.
+@end smallexample
+
+@FIXME{how often do we use smallexample?}
+
+@node basic tar options, frequent operations, stylistic conventions, Tutorial
+@section Basic @code{tar} Operations and Options
+
+@code{tar} can take a wide variety of arguments which specify and define
+the actions it will have on the particular set of files or the archive.
+The main types of arguments to @code{tar} fall into one of two classes:
+operations, and options.
+
+Some arguments fall into a class called @dfn{operations}; exactly one of
+these is both allowed and required for any instance of using @code{tar};
+you may @emph{not} specify more than one. People sometimes speak of
+@dfn{operating modes}. You are in a particular operating mode when you
+have specified the operation which specifies it; there are eight
+operations in total, and thus there are eight operating modes.
+
+The other arguments fall into the class known as @dfn{options}. You are
+not required to specify any options, and you are allowed to specify more
+than one at a time (depending on the way you are using @code{tar} at
+that time). Some options are used so frequently, and are so useful for
+helping you type commands more carefully that they are effectively
+``required''. We will discuss them in this chapter.
+
+You can write most of the @code{tar} operations and options in any of
+three forms: long (mnemonic) form, short form, and old style. Some of
+the operations and options have no short or ``old'' forms; however, the
+operations and options which we will cover in this tutorial have
+corresponding abbreviations. @FIXME{make sure this is still the case,
+at the end} We will indicate those abbreviations appropriately to get
+you used to seeing them. (Note that the ``old style'' option forms
+exist in GNU @code{tar} for compatibility with Unix @code{tar}. We
+present a full discussion of this way of writing options and operations
+appears in @ref{Old Options}, and we discuss the other two styles of
+writing options in @ref{Mnemonic Options} and @ref{Short Options}.)
+
+In the examples and in the text of this tutorial, we usually use the
+long forms of operations and options; but the ``short'' forms produce
+the same result and can make typing long @code{tar} commands easier.
+For example, instead of typing
-The @samp{--list} (@samp{-t}) option will list the names of members of
-the archive. Name the members to be listed on the command line (to
-modify the way these names are interpreted, @pxref{Specifying Names to
-@code{tar}}). If you name no members, then @samp{--list} will list the
-names of all the members of the archive.
+@example
+@kbd{tar --create --verbose --file=afiles.tar apple angst aspic}
+@end example
-To see more than just the names of the members, use the @samp{--verbose}
-option to cause @code{tar} to print out a listing similar to that of
-@samp{ls -l}.
+@noindent
+you can type
+@example
+@kbd{tar -c -v -f afiles.tar apple angst aspic}
+@end example
-@section Extracting Archive Members
+@noindent
+or even
+@example
+@kbd{tar -cvf afiles.tar apple angst aspic}
+@end example
-Use @samp{--extract} (or @samp{--get}, or @samp{-x}) to extract members
-from an archive. For each member named (or for the entire archive if no
-members are named) on the command line (or with @samp{--files-from}) the
-a file is created with the contents of the archive member. The name of
-the file is the same as the member name.
+@noindent
+For more information on option syntax, see @ref{Advanced tar}. In
+discussions in the text, when we name an option by its long form, we
+also give the corresponding short option in parentheses.
+
+The term, ``option'', can be confusing at times, since ``operations''
+are often lumped in with the actual, @emph{optional} ``options'' in certain
+general class statements. For example, we just talked about ``short and
+long forms of options and operations''. However, experienced @code{tar}
+users often refer to these by shorthand terms such as, ``short and long
+options''. This term assumes that the ``operations'' are included, also.
+Context will help you determine which definition of ``options'' to use.
+
+Similarly, the term ``command'' can be confusing, as it is often used in
+two different ways. People sometimes refer to @code{tar} ``commands''.
+A @code{tar} @dfn{command} is the entire command line of user input
+which tells @code{tar} what to do --- including the operation, options,
+and any arguments (file names, pipes, other commands, etc). However,
+you will also sometimes hear the term ``the @code{tar} command''. When
+the word ``command'' is used specifically like this, a person is usually
+referring to the @code{tar} @emph{operation}, not the whole line.
+Again, use context to figure out which of the meanings the speaker
+intends.
+
+@node frequent operations, Two Frequent Options, basic tar options, Tutorial
+@section The Three Most Frequently Used Operations
+
+Here are the three most frequently used operations (both short and long
+forms), as well as a brief description of their meanings. The rest of
+this chapter will cover how to use these operations in detail. We will
+present the rest of the operations in the next chapter.
+
+@table @kbd
+@item --create
+@itemx -c
+Create a new @code{tar} archive.
+@item --list
+@itemx -t
+List the contents of an archive.
+@item --extract
+@itemx -x
+Extract one or more members from an archive.
+@end table
-Various options cause @code{tar} to extract more than just file
-contents, such as the owner, the permissions, the modification date, and
-so forth.
+@node Two Frequent Options, create, frequent operations, Tutorial
+@section Two Frequently Used Options
-XXX
-The @samp{--same-permissions} (or @samp{--preserve-permissions}, or
-@samp{-p}) options cause @code{tar} to cause the new file to have the
-same permissions as the original file did when it was placed in the
-archive. Without this option, the current @code{umask} is used to
-affect the permissions.
+To understand how to run @code{tar} in the three operating modes listed
+previously, you also need to understand how to use two of the options to
+@code{tar}: @samp{--file} (which takes an archive file as an argument)
+and @samp{--verbose}. (You are usually not @emph{required} to specify
+either of these options when you run @code{tar}, but they can be very
+useful in making things more clear and helping you avoid errors.)
-When extrating, @code{tar} normally sets the modification time of the
-file to the value recorded in the archive. The
-@samp{--modification-time} option causes @code{tar} to omit doing this.
-XXX
+@menu
+* file tutorial::
+* verbose tutorial::
+* help tutorial::
+@end menu
-@section Updating an Archive
+@node file tutorial, verbose tutorial, Two Frequent Options, Two Frequent Options
+@unnumberedsubsec The @samp{--file} Option
-The @samp{--update} (or @samp{-u}) option updates a @code{tar} archive
-by comparing the date of the specified archive members against the date
-of the file with the same name. If the file has been modified more
-recently than the archive member, then the archive member is deleted (as
-with @samp{--delete}) and then the file is added to the archive (as with
-@samp{--append}). On media where the @samp{--delete} option cannot be
-performed (such as magnetic tapes), the @samp{--update} option similarly
-fails.
+@table @kbd
+@item --file=@var{archive-name}
+@itemx -f @var{archive-name}
+Specify the name of an archive file.
+@end table
-If no archive members are named (either on the command line or via
-@samp{--files-from}), then the entire archive is processed in this
-manner.
+You can specify an argument for the @value{op-file} option whenever you
+use @code{tar}; this option determines the name of the archive file
+that @code{tar} will work on.
-@section Comparing Archives Members with Files
+If you don't specify this argument, then @code{tar} will use a
+default, usually some physical tape drive attached to your machine.
+If there is no tape drive attached, or the default is not meaningful,
+then @code{tar} will print an error message. The error message might
+look roughly like one of the following:
-The @samp{--compare} (or @samp{--diff}, or @samp{-d}) option compares
-the contents of the specified archive members against the files with the
-same names, and reports its findings. If no members are named on the
-command line (or through @samp{--files-from}), then the entire archive
-is so compared.
+@example
+tar: can't open /dev/rmt8 : No such device or address
+tar: can't open /dev/rsmt0 : I/O error
+@end example
-@chapter Specifying Names to @code{tar}
+@noindent
+To avoid confusion, we recommend that you always specfiy an archive file
+name by using @value{op-file} when writing your @code{tar} commands.
+For more information on using the @value{op-file} option, see
+@ref{file}.
-When specifying the names of files or members to @code{tar}, it by
-default takes the names of the files from the command line. There are
-other ways, however, to specify file or member names, or to modify the
-manner in which @code{tar} selects the files or members upon which to
-operate. In general, these methods work both for specifying the names
-of files and archive members.
+@node verbose tutorial, help tutorial, file tutorial, Two Frequent Options
+@unnumberedsubsec The @samp{--verbose} Option
-@section Reading Names from a File
+@table @kbd
+@item --verbose
+@itemx -v
+Show the files being worked on as @code{tar} is running.
+@end table
-Instead of giving the names of files or archive members on the command
-line, you can put the names into a file, and then use the
-@samp{--files-from=@var{file-name-list}} (@samp{-T
-@var{file-name-list}}) option to @code{tar}. Give the name of the file
-which contains the list as the argument to @samp{--files-from}. The
-file names should be separated by newlines in the list. If you give a
-single dash as a filename for @samp{--files-from} (that is, you specify
-@samp{--files-from=-} or @samp{-T -}), then the filenames are read from
-standard input.
-
-If you want to specify names that might contain newlines, use the
-@samp{--null} option. Then, the filenames should be separated by NUL
-characters (ASCII 000) instead of newlines. In addition, the
-@samp{--null} option turns off the @samp{-C} option (@pxref{Changing
-Directory}).
+@value{op-verbose} shows details about the results of running
+@code{tar}. This can be especially useful when the results might not be
+obvious. For example, if you want to see the progress of @code{tar} as
+it writes files into the archive, you can use the @samp{--verbose}
+option. In the beginning, you may find it useful to use
+@samp{--verbose} at all times; when you are more accustomed to
+@code{tar}, you will likely want to use it at certain times but not at
+others. We will use @samp{--verbose} at times to help make something
+clear, and we will give many examples both using and not using
+@samp{--verbose} to show the differences.
+
+Sometimes, a single instance of @samp{--verbose} on the command line
+will show a full, @samp{ls} style listing of an archive or files,
+giving sizes, owners, and similar information. Other times,
+@samp{--verbose} will only show files or members that the particular
+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
+in the former case. For example, instead of saying
-@section Excluding Some Files
+@example
+@kbd{tar -cvf afiles.tar apple angst aspic}
+@end example
-The @samp{--exclude=@var{pattern}} option will prevent any file or
-member which matches the regular expression @var{pattern} from being
-operated on. For example, if you want to create an archive with all the
-contents of @file{/tmp} except the file @file{/tmp/foo}, you can use the
-command @samp{tar --create --file=arch.tar --exclude=foo}.
+@noindent
+above, you might say
-If there are many files you want to exclude, you can use the
-@samp{--exclude-from=@var{exclude-list}} (@samp{-X @var{exclude-list}})
-option. This works just like the
-@samp{--files-from=@var{file-name-list}} option: specify the name of a
-file as @var{exclude-list} which contains the list of patterns you want
-to exclude.
+@example
+@kbd{tar -cvvf afiles.tar apple angst aspic}
+@end example
-@xref{Regular Expressions} for more information on the syntax and
-meaning of regular expressions.
+@noindent
+This works equally well using short or long forms of options. Using
+long forms, you would simply write out the mnemonic form of the option
+twice, like this:
-@section Operating Only on New Files
+@example
+$ @kbd{tar --create --verbose --verbose @dots{}}
+@end example
-The @samp{--newer=@var{date}} (@samp{--after-date=@var{date}} or
-@samp{-N @var{date}}) limits @code{tar} to only operating on files which
-have been modified after the date specified. (For more information on
-how to specify a date, @xref{Date Formats}.) A file is considered to
-have changed if the contents have been modified, or if the owner,
-permissions, and so forth, have been changed.
+@noindent
+Note that you must double the hyphens properly each time.
-If you only want @code{tar} make the date comparison on the basis of the
-actual contents of the file's modification, then use the
-@samp{--newer-mtime=@var{date}} option.
+Later in the tutorial, we will give examples using @w{@samp{--verbose
+--verbose}}.
-You should never use this option for making incremental dumps. To learn
-how to use @code{tar} to make backups, @ref{Making Backups}.
+@node help tutorial, , verbose tutorial, Two Frequent Options
+@unnumberedsubsec Getting Help: Using the @code{--help} Option
-@section Crossing Filesystem Boundaries
+@table @kbd
+@item --help
-The @samp{--one-file-system} option causes @code{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
-(because it is a mounted filesystem in its own right), then @code{tar}
-will not archive that file, or (if it is a directory itself) anything
-beneath it.
+The @samp{--help} option to @code{tar} prints out a very brief list of
+all operations and option available for the current version of
+@code{tar} available on your system.
+@end table
-This does not necessarily limit @code{tar} to only archiving the
-contents of a single filesystem, because all files named on the command
-line (or through the @samp{--files-from} option) will always be
-archived.
+@node create, list, Two Frequent Options, Tutorial
+@section How to Create Archives
+@UNREVISED
+
+One of the basic operations of @code{tar} is @value{op-create}, which
+you use to create a @code{tar} archive. We will explain
+@samp{--create} first because, in order to learn about the other
+operations, you will find it useful to have an archive available to
+practice on.
+
+To make this easier, in this section you will first create a directory
+containing three files. Then, we will show you how to create an
+@emph{archive} (inside the new directory). Both the directory, and
+the archive are specifically for you to practice on. The rest of this
+chapter and the next chapter will show many examples using this
+directory and the files you will create: some of those files may be
+other directories and other archives.
+
+The three files you will archive in this example are called
+@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}
+in @code{verbose} mode, and showing examples using both short and long
+forms. In the rest of the tutorial, and in the examples in the next
+chapter, we will proceed at a slightly quicker pace. This section
+moves more slowly to allow beginning users to understand how
+@code{tar} works.
-@chapter Changing the Names of Members when Archiving
+@menu
+* prepare for examples::
+* Creating the archive::
+* create verbose::
+* short create::
+* create dir::
+@end menu
-@section Changing Directory
+@node prepare for examples, Creating the archive, create, create
+@subsection Preparing a Practice Directory for Examples
+
+To follow along with this and future examples, create a new directory
+called @file{practice} containing files called @file{blues}, @file{folk}
+and @file{jazz}. The files can contain any information you like:
+ideally, they should contain information which relates to their names,
+and be of different lengths. Our examples assume that @file{practice}
+is a subdirectory of your home directory.
+
+Now @code{cd} to the directory named @file{practice}; @file{practice}
+is now your @dfn{working directory}. (@emph{Please note}: Although
+the full path name of this directory is
+@file{/@var{homedir}/practice}, in our examples we will refer to
+this directory as @file{practice}; the @var{homedir} is presumed.
+
+In general, you should check that the files to be archived exist where
+you think they do (in the working directory) by running @code{ls}.
+Because you just created the directory and the files and have changed to
+that directory, you probably don't need to do that this time.
+
+It is very important to make sure there isn't already a file in the
+working directory with the archive name you intend to use (in this case,
+@samp{collection.tar}), or that you don't care about its contents.
+Whenever you use @samp{create}, @code{tar} will erase the current
+contents of the file named by @value{op-file} if it exists. @code{tar}
+will not tell you if you are about to overwrite a file unless you
+specify an option which does this @FIXME{xref to the node for
+--backup!}. To add files to an existing archive, you need to use a
+different option, such as @value{op-append}; see @ref{append} for
+information on how to do this.
+
+@node Creating the archive, create verbose, prepare for examples, create
+@subsection Creating the Archive
+
+To place the files @file{blues}, @file{folk}, and @file{jazz} into an
+archive named @file{collection.tar}, use the following command:
-The @samp{--directory=@var{directory}} (@samp{-C @var{directory}})
-option causes @code{tar} to change its current working directory to
-@var{directory}. Unlike most options, this one is processed at the
-point it occurs within the list of files to be processed. Consider the
-following command:
@example
-tar --create --file=foo.tar -C /etc passwd hosts -C /lib libc.a
+$ @kbd{tar --create --file=collection.tar blues folk jazz}
@end example
-This command will place the files @file{/etc/passwd}, @file{/etc/hosts},
-and @file{/lib/libc.a} into the archive. However, the names of the
-archive members will be exactly what they were on the command line:
-@file{passwd}, @file{hosts}, and @file{libc.a}. The @samp{--directory}
-option is frequently used to make the archive independent of the
-original name of the directory holding the files.
+The order of the arguments is not very important, @emph{when using long
+option forms}. You could also say:
-Note that @samp{--directory} options are interpreted consecutively. If
-@samp{--directory} option specifies a relative pathname, it is
-interpreted relative to the then current directory, which might not be
-the same as the original current working directory of @code{tar}, due to
-a previous @samp{--directory} option.
+@example
+$ @kbd{tar blues --create folk --file=collection.tar jazz}
+@end example
-When using @samp{--files-from} (@pxref{Reading Names from a File}), 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 @samp{--null} option.)
+@noindent
+However, you can see that this order is harder to understand; this is
+why we will list the arguments in the order that makes the commands
+easiest to understand (and we encourage you to do the same when you use
+@code{tar}, to avoid errors).
+
+Note that the part of the command which says,
+@w{@kbd{--file=collection.tar}} is considered to be @emph{one} argument.
+If you substituted any other string of characters for
+@kbd{`collection.tar'}, then that string would become the name of the
+archive file you create.
+
+The order of the options becomes more important when you begin to use
+short forms. With short forms, if you type commands in the wrong order
+(even if you type them correctly in all other ways), you may end up with
+results you don't expect. For this reason, it is a good idea to get
+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}
+is the operation which creates the new archive
+(@file{collection.tar}), and @samp{--file} is the option which lets
+you give it the name you chose. The files, @file{blues}, @file{folk},
+and @file{jazz}, are now members of the archive, @file{collection.tar}
+(they are @dfn{file name arguments} to the @samp{--create} operation)
+@FIXME{xref here to the discussion of file name args?}. Now that they
+are are in the archive, they are called @emph{archive members}, not
+files @FIXME{xref to definitions?}.
+
+When you create an archive, you @emph{must} specify which files you want
+placed in the archive. If you do not specify any archive members, GNU
+@code{tar} will complain.
+
+If you now list the contents of the working directory (@kbd{ls}), you will
+find the archive file listed as well as the files you saw previously:
-@section Absolute Path Names
+@example
+blues folk jazz collection.tar
+@end example
-When @code{tar} extracts archive members from an archive, it strips any
-leading slashes (@code{/}) from the member name. This causes absolute
-member names in the archive to be treated as relative file names. This
-allows you to have such members extracted wherever you want, instead of
-being restricted to extracting the member in the exact directory named
-in the archive. For example, if the archive member has the name
-@file{/etc/passwd}, @code{tar} will extract it as if the name were
-really @file{etc/passwd}.
+@noindent
+Creating the archive @samp{collection.tar} did not destroy the copies of
+the files in the directory.
-Other @code{tar} programs do not do this. As a result, if you create an
-archive whose member names start with a slash, they will be difficult
-for other people with an inferior @code{tar} program to use. Therefore,
-GNU @code{tar} also strips leading slashes from member names when
-putting members into the archive. For example, if you ask @code{tar} to
-add the file @file{/bin/ls} to an archive, it will do so, but the member
-name will be @file{bin/ls}.
+Keep in mind that if you don't indicate an operation, @code{tar} will not
+run and will prompt you for one. If you don't name any files, @code{tar}
+will complain. You must have write access to the working directory,
+or else you will not be able to create an archive in that directory.
-If you use the @samp{--absolute-paths} option, @code{tar} will do
-neither of these transformations.
+@emph{Caution}: Do not attempt to use @value{op-create} to add files to
+an existing archive; it will delete the archive and write a new one.
+Use @value{op-append} instead. @xref{append}.
-@section Symbolic Links
+@node create verbose, short create, Creating the archive, create
+@subsection Running @samp{--create} with @samp{--verbose}
-Normally, when @code{tar} archives a symbolic link, it writes a record
-to the archive naming the target of the link. In that way, the
-@code{tar} archive is a faithful record of the filesystem contents.
-However, if you want @code{tar} to actually dump the contents of the
-target of the symbolic link, then use the @samp{--dereference} option.
+If you include the @value{op-verbose} option on the command line,
+@code{tar} will list the files it is acting on as it is working. In
+verbose mode, the @code{create} example above would appear as:
-@chapter Making @code{tar} More Verbose
+@example
+$ @kbd{tar --create --verbose --file=collection.tar blues folk jazz}
+blues
+folk
+jazz
+@end example
-Various options cause @code{tar} to print information as it progresses
-in its job.
+This example is just like the example we showed which did not use
+@samp{--verbose}, except that @code{tar} generated the remaining lines
+@iftex
+(note the different font styles).
+@end iftex
+@ifinfo
+.
+@end ifinfo
-The @samp{--verbose} (or @samp{-v}) option causes @code{tar} to print
-the name of each archive member or file as it is processed. Since
-@samp{--list} already prints the names of the members, @samp{--verbose}
-used with @samp{--list} causes @code{tar} to print a longer listing
-(reminiscent of @samp{ls -l}) for each member.
+In the rest of the examples in this chapter, we will frequently use
+@code{verbose} mode so we can show actions or @code{tar} responses that
+you would otherwise not see, and which are important for you to
+understand.
-To see the progress of @code{tar} through the archive, the
-@samp{--record-number} option prints a message for each record read or
-writted. (@xref{Archive Structure}.) This option can be very helpful
-when trying to figure out where in the archive an error occurs.
+@node short create, create dir, create verbose, create
+@subsection Short Forms with @samp{create}
-The @samp{--totals} option (which is only meaningful when used with
-@samp{--create}) causes @code{tar} to print the total amount written to
-the archive, after it has been fully created.
+As we said before, the @value{op-create} operation is one of the most
+basic uses of @code{tar}, and you will use it countless times.
+Eventually, you will probably want to use abbreviated (or ``short'')
+forms of options. A full discussion of the three different forms that
+options can take appears in @ref{Styles}; for now, here is what the
+previous example (including the @value{op-verbose} option) looks like
+using short option forms:
-The @samp{--checkpoint} option prints an occasional message as
-@code{tar} reads or writes the archive. It is designed for those who
-don't need the more detailed (and voluminous) output of
-@samp{--record-number}, but do want visual confirmation that @code{tar}
-is actually making forward progress.
+@example
+$ @kbd{tar -cvf collection.tar blues folk jazz}
+blues
+folk
+jazz
+@end example
-The @samp{--version} option will generate a message with the version of
-GNU @code{tar} you are using.
+@noindent
+As you can see, the system responds the same no matter whether you use
+long or short option forms.
-@chapter Input and Output
+@FIXME{i don't like how this is worded:} One difference between using
+short and long option forms is that, although the exact placement of
+arguments following options is no more specific when using short forms,
+it is easier to become confused and make a mistake when using short
+forms. For example, suppose you attempted the above example in the
+following way:
-@section Changing the Archive Name
+@example
+$ @kbd{tar -cfv collection.tar blues folk jazz}
+@end example
-By default, @code{tar} uses an archive file name compiled in when
-@code{tar} was built. Usually this refers to some physical tape drive
-on the machine. Often, the installer of @code{tar} didn't set the
-default to anything meaningful at all.
+@noindent
+In this case, @code{tar} will make an archive file called @file{v},
+containing the files @file{blues}, @file{folk}, and @file{jazz}, because
+the @samp{v} is the closest ``file name'' to the @samp{-f} option, and
+is thus taken to be the chosen archive file name. @code{tar} will try
+to add a file called @file{collection.tar} to the @file{v} archive file;
+if the file @file{collection.tar} did not already exist, @code{tar} will
+report an error indicating that this file does not exist. If the file
+@file{collection.tar} does already exist (e.g., from a previous command
+you may have run), then @code{tar} will add this file to the archive.
+Because the @samp{-v} option did not get registered, @code{tar} will not
+run under @samp{verbose} mode, and will not report its progress.
+
+The end result is that you may be quite confused about what happened,
+and possibly overwrite a file. To illustrate this further, we will show
+you how an example we showed previously would look using short forms.
+
+This example,
-As a result, most uses of @code{tar} need to tell @code{tar} where to
-find (or create) the archive. The @samp{--file=@var{archive-name}} (or
-@samp{-f @var{archive-name}} option selects another file to use as the
-archive.
+@example
+$ @kbd{tar blues --create folk --file=collection.tar jazz}
+@end example
-If the archive file name includes a colon (@samp{:}), then it is assumed
-to be a file on another machine. If the archive file is
-@samp{@var{user}@@@var{host}:@var{file}}, then @var{file} is used on the
-host @var{host}. The remote host is accessed using the @code{rsh}
-program, with a username of @var{user}. If the username is omitted
-(along with the @samp{@@} sign), then your user name will be used.
-(This is the normal @code{rsh} behavior.) It is necessary for the
-remote machine, in addition to permitting your @code{rsh} access, to
-have the @code{/usr/ucb/rmt} program installed. If you need to use a
-file whose name includes a colon, then the remote tape drive behavior
-can be inhibited by using the @samp{--force-local} option.
+@noindent
+is confusing as it is. When shown using short forms, however, it
+becomes much more so:
-If the filename you give to @samp{--file} is a single dash (@samp{-}),
-then @code{tar} will read the archive from (or write it to) standard
-input (or standard output).
+@example
+$ @kbd{tar blues -c folk -f collection.tar jazz}
+@end example
-@section Extracting Members to Standard Output
+@noindent
+It would be very easy to put the wrong string of characters
+immediately following the @samp{-f}, but doing that could sacrifice
+valuable data.
+
+For this reason, we recommend that you pay very careful attention to
+the order of options and placement of file and archive names,
+especially when using short option forms. Not having the option name
+written out mnemonically can affect how well you remember which option
+does what, and therefore where different names have to be placed.
+(Placing options in an unusual order can also cause @code{tar} to
+report an error if you have set the shell environment variable,
+@code{POSIXLY_CORRECT}; @pxref{posix compliance} for more information
+on this.)
+
+@node create dir, , short create, create
+@subsection Archiving Directories
+
+@cindex Archiving Directories
+@cindex Directories, Archiving
+You can archive a directory by specifying its directory name as a
+file name argument to @code{tar}. The files in the directory will be
+archived relative to the working directory, and the directory will be
+re-created along with its contents when the archive is extracted.
+
+To archive a directory, first move to its superior directory. If you
+have followed the previous instructions in this tutorial, you should
+type:
-An archive member in normally extracted into a file with the same name
-as the archive member. However, you can use the @samp{--to-stdout} to
-cause @code{tar} to write extracted archive members to standard output.
-If you extract multiple members, they appear on standard output
-concatenated, in the order they are found in the archive.
+@example
+$ @kbd{cd ..}
+$
+@end example
-@section Dealing with Compressed Archives
+@noindent
+This will put you into the directory which contains @file{practice},
+i.e. your home directory. Once in the superior directory, you can
+specify the subdirectory, @file{practice}, as a file name argument. To
+store @file{practice} in the new archive file @file{music.tar}, type:
-You can have archives be compressed by using the @samp{--gzip} (or
-@samp{-z}) option. This will arrange for @code{tar} to use the
-@code{gzip} program to be used to compress or uncompress the archive
-wren writing or reading it.
+@example
+$ @kbd{tar --create --verbose --file=music.tar practice}
+@end example
-To use the older, obsolete, @code{compress} program, use the
-@samp{--compress} (or @samp{-Z}) option. The GNU Project recommends you
-not use @code{compress}, because there is a patent covering the
-algorithm it uses. Merely by running @code{compress} you could be sued
-for patent infringment.
-
-When using either @samp{--gzip} or @samp{--compress}, @code{tar} does
-not do blocking (@pxref{Blocking}) correctly. Use @samp{--gzip-block}
-or @samp{--compress-block} instead when using real tape drives.
-
-@chapter Being More Careful
-
-When using @code{tar} with many options, particularly ones with
-complicated or difficult-to-predict behavior, it is possible to make
-serious mistakes. As a result, @code{tar} provides several options that
-make observing @code{tar} easier.
-
-The @samp{--verbose} option causes @code{tar} to print the name of each
-file or archive member as it is processed. This and the other options
-which make tar print status information can be useful in monitoring
-@code{tar}. @xref{Making @code{tar} More Verbose}.
-
-If you use @samp{--interactive} (or {@samp--confirm}), then @code{tar}
-will ask you for confirmation before each operation. For example, when
-extracting, it will prompt you before each archive member is extracted,
-and you can select that member for extraction or pass over to the next.
-
-The @samp{--verify} option, when using @samp{--create}, causes
-@code{tar}, after having finished creating the archive, to go back over
-it and compare its contents against the files that were placed in the
-archive.
-
-The @samp{--show-omitted-dirs} option, when reading an archive (with
-@samp{--list} or @samp{--extract}, for example), causes a message to be
-printed for each directory in the archive which is skipped. This
-happens regardless of the reason for skipping: the directory might not
-have been named on the command line (implicitly or explicitly), it might
-be excluded by the use of the @samp{--exclude} option, or some other
-reason.
-
-@chapter Using Real Tape Drives
+@noindent
+@code{tar} should output:
-Many complexities surround the use of @code{tar} on tape drives. Since
-the creation and manipulation of archives located on magnetic tape was
-the original purpose of @code{tar}, it contains many features making
-such manipulation easier.
+@example
+practice/
+practice/blues
+practice/folk
+practice/jazz
+practice/collection.tar
+@end example
-@section Blocking
+Note that the archive thus created is not in the subdirectory
+@file{practice}, but rather in the current working directory---the
+directory from which @code{tar} was invoked. Before trying to archive a
+directory from its superior directory, you should make sure you have
+write access to the superior directory itself, not only the directory
+you are trying archive with @code{tar}. For example, you will probably
+not be able to store your home directory in an archive by invoking
+@code{tar} from the root directory; @value{xref-absolute-names}. (Note
+also that @file{collection.tar}, the original archive file, has itself
+been archived. @code{tar} will accept any file as a file to be
+archived, regardless of its content. When @file{music.tar} is
+extracted, the archive file @file{collection.tar} will be re-written
+into the file system).
+
+If you give @code{tar} a command such as
-When writing to tapes, @code{tar} writes the contents of the archive in
-chunks known as @dfn{blocks}. To change the default blocksize, use the
-@samp{--block-size=@var{blocking-factor}} (@samp{-b
-@var{blocking-factor}) option. Each block will then be composed of
-@var{blocking-factor} records. (Each @code{tar} record is 512 bytes.
-@xref{Archive Format}.) Each file written to the archive uses at least
-one full block. As a result, using a larger block size can result in
-more wasted space for small files. On the other hand, a larger block
-size can ofter be read and written much more efficiently.
+@example
+$ @kbd{tar --create --file=foo.tar .}
+@end example
-Further complicating the problem is that some tape drives ignore the
-blocking entirely. For these, a larger block size can still improve
-performance (because the software layers above the tape drive still
-honor the blocking), but not as dramatically as on tape drives that
-honor blocking.
+@noindent
+@code{tar} will report @samp{tar: foo.tar is the archive; not dumped}.
+This happens because @code{tar} creates the archive @file{foo.tar} in
+the current directory before putting any files into it. Then, when
+@code{tar} attempts to add all the files in the directory @file{.} to
+the archive, it notices that the file @file{foo.tar} is the same as the
+archive, and skips it. (It makes no sense to put an archive into
+itself.) GNU @code{tar} will continue in this case, and create the
+archive normally, except for the exclusion of that one file.
+(@emph{Please note:} Other versions of @code{tar} are not so clever;
+they will enter an infinite loop when this happens, so you should not
+depend on this behavior unless you are certain you are running GNU
+@code{tar}. @FIXME{bob doesn't like this sentence, since he does it
+all the time, and we've been doing it in the editing passes for this
+manual: In general, make sure that the archive is not inside a
+directory being dumped.})
+
+@node list, extract, create, Tutorial
+@section How to List Archives
-Wher reading an archive, @code{tar} can usually figure out the block
-size on itself. When this is the case, and a non-standard block size
-was used when the archive was created, @code{tar} will print a message
-about a non-standard blocking factor, and then operate normally. On
-some tape devices, however, @code{tar} cannot figure out the block size
-itself. On most of those, you can specify a blocking factor (with
-@samp{--block-size) larger than the actual blocking factor, and then use
-the @samp{--read-full-blocks} option. (If you specify a blocking factor
-with @samp{--block-size} and don't use the @samp{--read-full-blocks}
-option, then @code{tar} will not attempt to figure out the blocking size
-itself.) On some devices, you must always specify the block size
-exactly with @samp{--block-size} when reading, because @code{tar} cannot
-figure it out. In any case, use @samp{--list} before doing any
-extractions to see whether @code{tar} is reading the archive correctly.
+Frequently, you will find yourself wanting to determine exactly what a
+particular archive contains. You can use the @value{op-list} operation
+to get the member names as they currently appear in the archive, as well
+as various attributes of the files at the time they were archived. For
+example, you can examine the archive @file{collection.tar} that you
+created in the last section with the command,
-If you use a blocking factor larger than 20, older @code{tar} programs
-might not be able to read the archive, so we recommend this as a limit
-to use in practice. GNU @code{tar}, however, will support arbitrarily
-large block sizes, limited only by the amount of virtual memory or the
-physical characteristics of the tape device.
+@example
+$ @kbd{tar --list --file=collection.tar}
+@end example
-If you are writing a compressed archive to tape with @samp{--compress}
-or @samp{--gzip} (@pxref{Input and Output}), @code{tar} will not block
-the archive correctly. This doesn't matter if you are writing the
-archive to a normal file or through a pipe, but if you are writing it to
-a tape drive, then this causes problems. Use @samp{--compress-block} or
-@samp{--gzip-block} instead, to cause @code{tar} to arrange to have
-blocking work correctly.
+@noindent
+The output of @code{tar} would then be:
-@section Using Multiple Tapes
+@example
+blues
+folk
+jazz
+@end example
-Often you might want to write a large archive, one larger than will fit
-on the actual tape you are using. In such a case, you can run multiple
-@code{tar} commands, but this can be inconvenient, particularly if you
-are using options like @samp{--exclude} or dumping entire filesystems.
-Therefore, @code{tar} supports multiple tapes automatically.
+@FIXME{we hope this will change. if it doesn't, need to show the
+creation of bfiles somewhere above!!! : }
-Use @samp{--multi-volume} on the command line, and then @code{tar} will,
-when it reaches the end of the tape, prompt for another tape, and
-continue the archive. Each tape will have an independent archive, and
-can be read without needing the other. (As an exception to this, the
-file that @code{tar} was archiving when it ran out of tape will usually
-be split between the two archives; in this case you need to extract from
-the first archive, using @samp{--multi-volume}, and then put in the
-second tape when prompted, so @code{tar} can restore both halves of the
-file.)
+@noindent
+The archive @file{bfiles.tar} would list as follows:
-When prompting for a new tape, @code{tar} accepts any of the following
-responses:
+@example
+./birds
+baboon
+./box
+@end example
-@table @samp
-@item ?
-Request @code{tar} to explain possible responses
-@item q
-Request @code{tar} to exit immediately.
-@item n @var{file-name}
-Request @code{tar} to write the next volume on the file @var{file-name}.
-@item !
-Request @code{tar} to run a subshell.
-@item y
-Request @code{tar} to begin writing the next volume.
-@end table
+@noindent
+Be sure to use a @value{op-file} option just as with @value{op-create}
+to specify the name of the archive.
-(You should only type @samp{y} after you have changed the tape;
-otherwise @code{tar} will write over the volume it just finished.)
+If you use the @value{op-verbose} option with @samp{--list}, then
+@code{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
+showing owner, file size, and so forth.
-If you want more elaborate behavior than this, give @code{tar} the
-@samp{--info-script=@var{script-name}} option. The file
-@var{script-name} is expected to be a program (or shell script) to be
-run instead of the normal prompting procedure. When the program
-finishes, @code{tar} will immediately begin writing the next volume.
-(The behavior of the @samp{n} response to the normal tape-change prompt
-is not available if you use @samp{--info-script}.)
+If you had used @value{op-verbose} mode, the example above would look
+like:
-The method @code{tar} uses to detect end of tape is not perfect, and
-fails on some operating systems or on some devices. You can use the
-@samp{--tape-length=@var{size}} (or @samp{-L @var{size}}) option if
-@code{tar} can't detect the end of the tape itself. The @var{size}
-argument should be the size of the tape.
-
-The volume number used by @code{tar} in its tape-change prompt can be
-changed; if you give the @samp{--volno-file=@var{file-name}} option,
-then @var{file-name} should contain a decimal number. That number will
-be used as the volume number of the first volume written. When
-@code{tar} is finished, it will rewrite the file with the now--current
-volume number. (This does not change the volume number written on a
-tape label (@pxref{Special Options for Archiving}; it @emph{only}
-affects the number used in the prompt.)
+@example
+$ @kbd{tar --list --verbose --file=collection.tar folk}
+-rw-rw-rw- myself user 62 1990-05-23 10:55 folk
+@end example
-If you want @code{tar} to cycle through a series of tape drives, then
-you can use the @samp{n} response to the tape-change prompt. This is
-error prone, however, and doesn't work at all with @samp{--info-script}.
-Therefore, if you give @code{tar} multiple @samp{--file} options, then
-the specified files will be used, in sequence, as the successive volumes
-of the archive. Only when the first one in the sequence needs to be
-used again will @code{tar} prompt for a tape change (or run the info
-script).
+@cindex File name arguments, using @code{--list} with
+@cindex @code{--list} with file name arguments
+You can specify one or more individual member names as arguments when
+using @samp{list}. In this case, @code{tar} will only list the
+names of members you identify. For example, @w{@kbd{tar --list
+--file=afiles.tar apple}} would only print @file{apple}.
+
+@FIXME{we hope the relevant aspects of this will change:}Because
+@code{tar} preserves paths, file names must be specified as they appear
+in the archive (ie., relative to the directory from which the archive
+was created). Therefore, it is essential when specifying member names
+to @code{tar} that you give the exact member names. For example,
+@w{@kbd{tar --list --file=bfiles birds}} would produce an error message
+something like @samp{tar: birds: Not found in archive}, because there is
+no member named @file{birds}, only one named @file{./birds}. While the
+names @file{birds} and @file{./birds} name the same file, @emph{member}
+names are compared using a simplistic name comparison, in which an exact
+match is necessary. @xref{absolute}.
+
+However, @w{@kbd{tar --list --file=collection.tar folk}} would respond
+with @file{folk}, because @file{folk} is in the archive file
+@file{collection.tar}. If you are not sure of the exact file name, try
+listing all the files in the archive and searching for the one you
+expect to find; remember that if you use @samp{--list} with no file
+names as arguments, @code{tar} will print the names of all the members
+stored in the specified archive.
-@section Tape Files
+@menu
+* list dir::
+@end menu
-When @code{tar} writes an archive to tape, it creates a single tape
-file. If multiple archives are written to the same tape, one after the
-other, they each get written as separate tape files. When extracting,
-it is necessary to position the tape at the right place before running
-@code{tar}. To do this, use the @code{mt} command. For more
-information on the @code{mt} command and on the organization of tapes
-into a sequence of tape files, see XXX.
+@node list dir, , list, list
+@unnumberedsubsec Listing the Contents of a Stored Directory
+@UNREVISED
-@chapter Special Options for Archiving
+@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 give the archive a name which will be recorded in it, use the
-@samp{--label=@var{volume-label}} (or @samp{-V}) option. This will
-write a special record identifying @var{volume-label} as the name of the
-archive to the front of the archive which will be displayed when the
-archive is listed with @samp{--list}. If you are creating a
-multi-volume archive with @samp{--multi-volume} (@pxref{Using Multiple
-Tapes}), then the volume label will have @same{ Volume @var{nnn}}
-appended to the name you give, where @var{nnn} is the number of the
-volume of the archive. (If you use the @samp{--label} option when
-reading an archive, it checks to make sure the label on the tape matches
-the one you give. @xref{Special Options for Archiving}.)
+To get information about the contents of an archived directory,
+use the directory name as a file name argument in conjunction with
+@value{op-list}. To find out file attributes, include the
+@value{op-verbose} option.
-Files in the filesystem occasionally have ``holes.'' A hole in a file
-is a section of the file's contents which was never written. The
-contents of a hole read as all zeros. On many operating systems, actual@c
-disk storage is not allocated for holes, but they are counted in the
-length of the file. If you archive such a file, @code{tar} could create
-an archive longer than the original. To have @code{tar} attempt to
-recognize the holes in a file, use @samp{--sparse}. When you use the
-@samp{--sparse} option, then, for any file using less disk space than
-would be expected from its length, @code{tar} searches the file for
-consecutive stretches of zeros. It then records in the archive for the
-file where the consecutive stretches of zeros are, and only archives the
-``real contents'' of the file. On extraction (using @samp{--sparse} is
-not needed on extraction) any such files have hols created wherever the
-continuous stretches of zeros were found. Thus, if you use
-@samp{--sparse}, @code{tar} archives won't take more space than the
-original.
+For example, to find out about files in the directory @file{practice}, in
+the archive file @file{music.tar}, type:
-When @code{tar} reads files, this causes them to have the access times
-updated. To have @code{tar} attempt to set the access times back to
-what they were before they were read, use the @samp{--atime-preserve}
-option. This doesn't work for files that you don't own, unless you're
-root, and it doesn't interact with incremental dumps nicely
-(@pxref{Making Backups}), but it is good enough for some purposes.
+@example
+$ @kbd{tar --list --verbose --file=music.tar practice}
+@end example
+
+@code{tar} responds:
-@chapter Special Options for Reading Archives
+@example
+drwxrwxrwx myself user 0 1990-05-31 21:49 practice/
+-rw-rw-rw- myself user 42 1990-05-21 13:29 practice/blues
+-rw-rw-rw- myself user 62 1990-05-23 10:55 practice/folk
+-rw-rw-rw- myself user 40 1990-05-21 13:30 practice/jazz
+-rw-rw-rw- myself user 10240 1990-05-31 21:49 practice/collection.tar
+@end example
+When you use a directory name as a file name argument, @code{tar} acts on
+all the files (including sub-directories) in that directory.
+@node extract, going further, list, Tutorial
+@section How to Extract Members from an Archive
+@UNREVISED
+@cindex Extraction
+@cindex Retrieving files from an archive
+@cindex Resurrecting files from an archive
+Creating an archive is only half the job---there is no point in storing
+files in an archive if you can't retrieve them. The act of retrieving
+members from an archive so they can be used and manipulated as
+unarchived files again is called @dfn{extraction}. To extract files
+from an archive, use the @value{op-extract} operation. As with
+@value{op-create}, specify the name of the archive with @value{op-file}.
+Extracting an archive does not modify the archive in any way; you can
+extract it multiple times if you want or need to.
+Using @samp{--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.
+@menu
+* extracting archives::
+* extracting files::
+* extract dir::
+* failing commands::
+@end menu
+@node extracting archives, extracting files, extract, extract
+@subsection Extracting an Entire Archive
+To extract an entire archive, specify the archive file name only, with
+no individual file names as arguments. For example,
+@example
+$ @kbd{tar -xvf collection.tar}
+@end example
-XXXX MIB XXXX
+@noindent
+produces this:
+@example
+-rw-rw-rw- me user 28 1996-10-18 16:31 jazz
+-rw-rw-rw- me user 21 1996-09-23 16:44 blues
+-rw-rw-rw- me user 20 1996-09-23 16:44 folk
+@end example
+@node extracting files, extract dir, extracting archives, extract
+@subsection Extracting Specific Files
-@node Wizardry, Archive Structure, Tutorial, Top
-@chapter Wizardry
+To extract specific archive members, give their exact member names as
+arguments, as printed by @value{op-list}. If you had mistakenly deleted
+one of the files you had placed in the archive @file{collection.tar}
+earlier (say, @file{blues}), you can extract it from the archive without
+changing the archive's structure. It will be identical to the original
+file @file{blues} that you deleted. @FIXME{check this; will the times,
+permissions, owner, etc be the same, also?}
-<<<This section needs to be written -ringo
+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
+the files in the directory again.
-@strong{To come:} using Unix file linking capability to recreate directory
-structures---linking files into one subdirectory and then tarring that
-directory.
+You can now extract the member @file{blues} from the archive file
+@file{collection.tar} like this:
-@strong{to come:} nice hairy example using absolute-paths, newer, etc.
+@example
+$ @kbd{tar --extract --file=collection.tar blues}
+@end example
+@noindent
+If you list the files in the directory again, you will see that the file
+@file{blues} has been restored, with its original permissions, creation
+times, and owner. @FIXME{This is only accidentally true, but not in
+general. In most cases, one has to be root for restoring the owner, and
+use a special option for restoring permissions. Here, it just happens
+that the restoring user is also the owner of the archived members, and
+that the current @code{umask} is compatible with original permissions.}
+(These parameters will be identical to those which
+the file had when you originally placed it in the archive; any changes
+you may have made before deleting the file from the file system,
+however, will @emph{not} have been made to the archive member.) The
+archive file, @samp{collection.tar}, is the same as it was before you
+extracted @samp{blues}. You can confirm this by running @code{tar} with
+@value{op-list}.
+
+@FIXME{we hope this will change:}Remember that as with other operations,
+specifying the exact member name is important. @w{@kbd{tar --extract
+--file=bfiles.tar birds}} will fail, because there is no member named
+@file{birds}. To extract the member named @file{./birds}, you must
+specify @w{@kbd{tar --extract --file=bfiles.tar ./birds}}. To find the
+exact member names of the members of an archive, use @value{op-list}
+(@pxref{list}).
+
+If you give the @value{op-verbose} option, then @value{op-extract} will
+print the names of the archive members as it extracts them.
-Piping one @code{tar} to another is an easy way to copy a directory's
-contents from one disk to another, while preserving the dates, modes, owners
-and link-structure of all the files therein.
+@node extract dir, failing commands, extracting files, extract
+@subsection Extracting Files that are Directories
+
+Extracting directories which are members of an archive is similar to
+extracting other files. The main difference to be aware of is that if
+the extracted directory has the same name as any directory already in
+the working directory, then files in the extracted directory will be
+placed into the directory of the same name. Likewise, if there are
+files in the pre-existing directory with the same names as the members
+which you extract, the files from the extracted archive will overwrite
+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.
+
+However, if a file was stored with a directory name as part of its file
+name, and that directory does not exist under the working directory when
+the file is extracted, @code{tar} will create the directory.
+
+We can demonstrate how to use @samp{--extract} to extract a directory
+file with an example. Change to the @file{practice} directory if you
+weren't there, and remove the files @file{folk} and @file{jazz}. Then,
+go back to the parent directory and extract the archive
+@file{music.tar}. You may either extract the entire archive, or you may
+extract only the files you just deleted. To extract the entire archive,
+don't give any file names as arguments after the archive name
+@file{music.tar}. To extract only the files you deleted, use the
+following command:
@example
-cd sourcedirectory; tar cf - . | (cd targetdir; tar xf -)
+$ @kbd{tar -xvf music.tar practice/folk practice/jazz}
@end example
+@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
-or
+Because you created the directory with @file{practice} as part of the
+file names of each of the files by archiving the @file{practice}
+directory as @file{practice}, you must give @file{practice} as part
+of the file names when you extract those files from the archive.
+
+@FIXME{IMPORTANT! show the final structure, here. figure out what it
+will be.}
+
+@node failing commands, , extract dir, extract
+@subsection Commands That Will Fail
+
+Here are some sample commands you might try which will not work, and why
+they won't work.
+
+If you try to use this command,
-<<< the following using standard input/output correct??
@example
-cd sourcedirectory; tar --create --file=- . | (cd targetdir; tar --extract --file=-)
+$ @kbd{tar -xvf music.tar folk jazz}
@end example
@noindent
+you will get the following response:
-Archive files can be used for transporting a group of files from one system
-to another: put all relevant files into an archive on one computer system,
-transfer the archive to another, and extract the contents there. The basic
-transfer medium might be magnetic tape, Internet FTP, or even electronic
-mail (though you must encode the archive with @code{uuencode} in order to
-transport it properly by mail). Both machines do not have to use the same
-operating system, as long as they both support the @code{tar} program.
-@findex uuencode
-<<< mention uuencode on a paragraph of its own
-
-<<<<<end construction>>>>>
+@example
+tar: folk: Not found in archive
+tar: jazz: Not found in archive
+$
+@end example
-@node Archive Structure, Reading and Writing, Wizardry, Top
-@chapter The Structure of an Archive
+@noindent
+This is because these files were not originally @emph{in} the parent
+directory @file{..}, where the archive is located; they were in the
+@file{practice} directory, and their file names reflect this:
-While an archive may contain many files, the archive itself is a
-single ordinary file. Like any other file, an archive file can be
-written to a storage device such as a tape or disk, sent through a
-pipe or over a network, saved on the active file system, or even
-stored in another archive. An archive file is not easy to read or
-manipulate without using the @code{tar} utility or Tar mode in Emacs.
+@example
+$ @kbd{tar -tvf music.tar}
+practice/folk
+practice/jazz
+practice/rock
+@end example
+@FIXME{make sure the above works when going through the examples in
+order...}
-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
-entry usually describes one of the files in the archive (an
-@dfn{archive member}), and consists of a file header and the contents
-of the file. File headers contain file names and statistics, checksum
-information which @code{tar} uses to detect file corruption, and
-information about file types.
+@noindent
+Likewise, if you try to use this command,
-More than archive member can have the same file name. One way this
-situation can occur is if more than one version of a file has been
-stored in the archive. For information about adding new versions of a
-file to an archive, @pxref{Modifying}.
+@example
+$ @kbd{tar -tvf music.tar folk jazz}
+@end example
-In addition to entries describing archive members, an archive may contain
-entries which @code{tar} itself uses to store information.
-@xref{Archive Label}, for an example of such an archive entry.
+@noindent
+you would get a similar response. Members with those names are not in the
+archive. You must use the correct member names in order to extract the
+files from the archive.
+
+If you have forgotten the correct names of the files in the archive,
+use @w{@kbd{tar --list --verbose}} to list them correctly.
+
+@FIXME{more examples, here? hag thinks it's a good idea.}
+
+@node going further, , extract, Tutorial
+@section Going Further Ahead in this Manual
+
+@FIXME{need to write up a node here about the things that are going to
+be in the rest of the manual.}
+
+@node tar invocation, operations, Tutorial, Top
+@chapter Invoking GNU @code{tar}
+@UNREVISED
+
+This chapter is about how one invokes the GNU @code{tar} command, from
+the command synopsis (@pxref{Synopsis}). There are numerous options,
+and many styles for writing them. One mandatory option specifies
+the operation @code{tar} should perform (@pxref{Operation Summary}),
+other options are meant to detail how this operation should be performed
+(@pxref{Option Summary}). Non-option arguments are not always interpreted
+the same way, depending on what the operation is.
+
+You will find in this chapter everything about option styles and rules for
+writing them (@pxref{Styles}). On the other hand, operations and options
+are fully described elsewhere, in other chapters. Here, you will find
+only synthetic descriptions for operations and options, together with
+pointers to other parts of the @code{tar} manual.
+
+Some options are so special they are fully described right in this
+chapter. They have the effect of inhibiting the normal operation of
+@code{tar} or else, they globally alter the amount of feedback the user
+receives about what is going on. These are the @value{op-help} and
+@value{op-version} (@pxref{help}), @value{op-verbose} (@pxref{verbose})
+and @value{op-interactive} options (@pxref{interactive}).
@menu
-* Old Style File Information:: Old Style File Information
-* Archive Label::
-* Format Variations::
+* Synopsis::
+* using tar options::
+* Styles::
+* All Options::
+* help::
+* verbose::
+* interactive::
@end menu
-@node Old Style File Information, Archive Label, Archive Structure, Archive Structure
-@section Old Style File Information
-@cindex Format, old style
-@cindex Old style format
-@cindex Old style archives
+@node Synopsis, using tar options, tar invocation, tar invocation
+@section General Synopsis of @code{tar}
-Archives record not only an archive member's contents, but also its
-file name or names, its access permissions, user and group, size in
-bytes, and last modification time. Some archives also record the file
-names in each archived directory, as well as other file and directory
-information.
+The GNU @code{tar} program is invoked as either one of:
-Certain old versions of @code{tar} cannot handle additional
-information recorded by newer @code{tar} programs. To create an
-archive which can be read by these old versions, specify the
-@samp{--old-archive} option in conjunction with the @samp{tar --create}
-operation. When you specify this option, @code{tar} leaves out
-information about directories, pipes, fifos, contiguous files, and
-device files, and specifies file ownership by group and user ids
-instead of names.
-
-The @samp{--old-archive} option is needed only if the archive must be
-readable by an older tape archive program which cannot handle the new format.
-Most @code{tar} programs do not have this limitation, so this option
-is seldom needed.
+@example
+@kbd{tar @var{option}@dots{} [@var{name}]@dots{}}
+@kbd{tar @var{letter}@dots{} [@var{argument}]@dots{} [@var{option}]@dots{} [@var{name}]@dots{}}
+@end example
-@table @samp
-@item --old-archive
-@itemx -o
-@itemx --old
-@itemx --portable
-@c has portability been changed to portable?
-Creates an archive that can be read by an old @code{tar} program.
-Used in conjunction with the @samp{tar --create} operation.
-@end table
+The second form is for when old options are being used.
+
+You can use @code{tar} to store files in an archive, to extract them from
+an archive, and to do other types of archive manipulation. The primary
+argument to @code{tar}, which is called the @dfn{operation}, specifies
+which action to take. The other arguments to @code{tar} are either
+@dfn{options}, which change the way @code{tar} performs an operation,
+or file names or archive members, which specify the files or members
+@code{tar} is to act on.
+
+You can actually type in arguments in any order, even if in this manual
+the options always precede the other arguments, to make examples easier
+to understand. Further, the option stating the main operation mode
+(the @code{tar} main command) is usually given first.
+
+Each @var{name} in the synopsis above is interpreted as an archive member
+name when the main command is one of @value{op-compare}, @value{op-delete},
+@value{op-extract}, @value{op-list} or @value{op-update}. When naming
+archive members, you must give the exact name of the member in the
+archive, as it is printed by @value{op-list}. For @value{op-append}
+and @value{op-create}, these @var{name} arguments specify the names
+of either files or directory hierarchies to place in the archive.
+These files or hierarchies should already exist in the file system,
+prior to the execution of the @code{tar} command.
+
+@code{tar} interprets relative file names as being relative to the
+working directory. @code{tar} will make all file names relative
+(by removing leading slashes when archiving or restoring files),
+unless you specify otherwise (using the @value{op-absolute-names}
+option). @value{xref-absolute-names}, for more information about
+@value{op-absolute-names}.
-@node Archive Label, Format Variations, Old Style File Information, Archive Structure
-@section Including a Label in the Archive
-@cindex Labeling an archive
-@cindex Labels on the archive media
+If you give the name of a directory as either a file name or a member
+name, then @code{tar} acts recursively on all the files and directories
+beneath that directory. For example, the name @file{/} identifies all
+the files in the filesystem to @code{tar}.
-@c !! Should the arg to --label be a quoted string?? no - ringo
-To avoid problems caused by misplaced paper labels on the archive
-media, you can include a @dfn{label} entry---an archive member which
-contains the name of the archive---in the archive itself. Use the
-@samp{--label=@var{archive-label}} option in conjunction with the
-@samp{--create} operation to include a label entry in the archive as it
-is being created.
+The distinction between file names and archive member names is especially
+important when shell globbing is used, and sometimes a source of confusion
+for newcomers. @xref{Wildcards}, for more information about globbing.
+The problem is that shells may only glob using existing files in the
+file system. Only @code{tar} itself may glob on archive members, so when
+needed, you must ensure that wildcard characters reach @code{tar} without
+being interpreted by the shell first. Using a backslash before @samp{*}
+or @samp{?}, or putting the whole argument between quotes, is usually
+sufficient for this.
+
+Even if @var{name}s are often specified on the command line, they
+can also be read from a text file in the file system, using the
+@value{op-files-from} option.
+
+If you don't use any file name arguments, @value{op-append},
+@value{op-delete} and @value{op-concatenate} will do nothing, while
+@value{op-create} will usually yield a diagnostic and inhibit @code{tar}
+execution. The other operations of @code{tar} (@value{op-list},
+@value{op-extract}, @value{op-compare}, and @value{op-update}) will act
+on the entire contents of the archive.
+
+@cindex exit status
+@cindex return status
+Besides successful exits, GNU @code{tar} may fail for many reasons.
+Some reasons correspond to bad usage, that is, when the @code{tar}
+command is improperly written.
+Errors may be encountered later, while encountering an error
+processing the archive or the files. Some errors are recoverable,
+in which case the failure is delayed until @code{tar} has completed
+all its work. Some errors are such that it would not meaningful,
+or at least risky, to continue processing: @code{tar} then aborts
+processing immediately. All abnormal exits, whether immediate or
+delayed, should always be clearly diagnosed on @code{stderr}, after
+a line stating the nature of the error.
+
+GNU @code{tar} returns only a few exit statuses. I'm really
+aiming simplicity in that area, for now. If you are not using the
+@value{op-compare} option, zero means that everything went well, besides
+maybe innocuous warnings. Nonzero means that something went wrong.
+Right now, as of today, ``nonzero'' is almost always 2, except for
+remote operations, where it may be 128.
+
+@node using tar options, Styles, Synopsis, tar invocation
+@section Using @code{tar} Options
+
+GNU @code{tar} has a total of eight operating modes which allow you to
+perform a variety of tasks. You are required to choose one operating
+mode each time you employ the @code{tar} program by specifying one, and
+only one operation as an argument to the @code{tar} command (two lists
+of four operations each may be found at @ref{frequent operations} and
+@ref{Operations}). Depending on circumstances, you may also wish to
+customize how the chosen operating mode behaves. For example, you may
+wish to change the way the output looks, or the format of the files that
+you wish to archive may require you to do something special in order to
+make the archive look right.
+
+You can customize and control @code{tar}'s performance by running
+@code{tar} with one or more options (such as @value{op-verbose}, which
+we used in the tutorial). As we said in the tutorial, @dfn{options} are
+arguments to @code{tar} which are (as their name suggests) optional.
+Depending on the operating mode, you may specify one or more options.
+Different options will have different effects, but in general they all
+change details of the operation, such as archive format, archive name,
+or level of user interaction. Some options make sense with all
+operating modes, while others are meaningful only with particular modes.
+You will likely use some options frequently, while you will only use
+others infrequently, or not at all. (A full list of options is
+available in @pxref{All Options}.)
+
+Note that @code{tar} options are case sensitive. For example, the
+options @samp{-T} and @samp{-t} are different; the first requires an
+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}.
+
+In addition to the eight operations, there are many options to
+@code{tar}, and three different styles for writing both: long (mnemonic)
+form, short form, and old style. These styles are discussed below.
+Both the options and the operations can be written in any of these three
+styles.
+
+@FIXME{menu at end of this node. need to think of an actual outline
+for this chapter; probably do that after stuff from chap. 4 is
+incorporated.}
+
+@node Styles, All Options, using tar options, tar invocation
+@section The Three Option Styles
+
+There are three styles for writing operations and options to the command
+line invoking @code{tar}. The different styles were developed at
+different times during the history of @code{tar}. These styles will be
+presented below, from the most recent to the oldest.
+
+Some options must take an argument. (For example, @value{op-file} takes
+the name of an archive file as an argument. If you do not supply an
+archive file name, @code{tar} will use a default, but this can be
+confusing; thus, we recommend that you always supply a specific archive
+file name.) Where you @emph{place} the arguments generally depends on
+which style of options you choose. We will detail specific information
+relevant to each option style in the sections on the different option
+styles, below. The differences are subtle, yet can often be very
+important; incorrect option placement can cause you to overwrite a
+number of important files. We urge you to note these differences, and
+only use the option style(s) which makes the most sense to you until you
+feel comfortable with the others.
+
+@FIXME{hag to write a brief paragraph on the option(s) which can
+optionally take an argument}
-If you create an archive using both @samp{--label=@var{archive-label}}
-and @samp{--multi-volume}, each volume of the archive will have an
-archive label of the form @samp{@var{archive-label} Volume @var{n}},
-where @var{n} is 1 for the first volume, 2 for the next, and so on.
-@xref{Multi-Volume Archives}, for information on creating multiple
-volume archives.
+@menu
+* Mnemonic Options:: Mnemonic Option Style
+* Short Options:: Short Option Style
+* Old Options:: Old Option Style
+* Mixing:: Mixing Option Styles
+@end menu
-If you extract an archive using @samp{--label=@var{archive-label}},
-@code{tar} will print an error if the archive label doesn't match the
-@var{archive-label} specified, and will then not extract the archive.
-You can include a regular expression in @var{archive-label}, in this
-case only.
-@c >>> why is a reg. exp. useful here? (to limit extraction to a
-@c >>>specific group? ie for multi-volume??? -ringo
+@node Mnemonic Options, Short Options, Styles, Styles
+@subsection Mnemonic Option Style
+
+@FIXME{have to decide whether or ot to replace other occurrences of
+"mnemonic" with "long", or *ugh* vice versa.}
+
+Each option has at least one long (or mnemonic) name starting with two
+dashes in a row, e.g. @samp{list}. The long names are more clear than
+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,
+long option names can be given unique abbreviations. For example,
+@samp{--cre} can be used in place of @samp{--create} because there is no
+other mnemonic option which begins with @samp{cre}. (One way to find
+this out is by trying it and seeing what happens; if a particular
+abbreviation could represent more than one option, @code{tar} will tell
+you that that abbreviation is ambiguous and you'll know that that
+abbreviation won't work. You may also choose to run @samp{tar --help}
+to see a list of options. Be aware that if you run @code{tar} with a
+unique abbreviation for the long name of an option you didn't want to
+use, you are stuck; @code{tar} will perform the command as ordered.)
+
+Mnemonic options are meant to be obvious and easy to remember, and their
+meanings are generally easier to discern than those of their
+corresponding short options (see below). For example:
-To find out an archive's label entry (or to find out if an archive has
-a label at all), use @samp{tar --list --verbose}. @code{tar} will print the
-label first, and then print archive member information, as in the
-example below:
+@example
+$ @kbd{tar --create --verbose --blocking-factor=20 --file=/dev/rmt0}
+@end example
+
+@noindent
+gives a fairly good set of hints about what the command does, even
+for those not fully acquainted with @code{tar}.
+
+Mnemonic options which require arguments take those arguments
+immediately following the option name; they are introduced by an equal
+sign. For example, the @samp{--file} option (which tells the name
+of the @code{tar} archive) is given a file such as @file{archive.tar}
+as argument by using the notation @samp{--file=archive.tar} for the
+mnemonic option.
+
+@node Short Options, Old Options, Mnemonic Options, Styles
+@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
+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
+specific archive, here named @file{archive.tar}.
+
+Short options' letters may be clumped together, but you are not
+required to do this (as compared to old options; see below). When short
+options are clumped as a set, use one (single) dash for them all, e.g.
+@w{@samp{@code{tar} -cvf}}. Only the last option in such a set is allowed
+to have an argument@footnote{Clustering many options, the last of which
+has an argument, is a rather opaque way to write options. Some wonder if
+GNU @code{getopt} should not even be made helpful enough for considering
+such usages as invalid.}.
+
+When the options are separated, the argument for each option which requires
+an argument directly follows that option, as is usual for Unix programs.
+For example:
@example
-% tar --verbose --list --file=iamanarchive
-V--------- 0/0 0 Mar 7 12:01 1992 iamalabel--Volume Header--
--rw-rw-rw- ringo/user 40 May 21 13:30 1990 iamafilename
+$ @kbd{tar -c -v -b 20 -f /dev/rmt0}
@end example
-@table @samp
-@item --label=@var{archive-label}
-@itemx -V @var{archive-label}
-Includes an @dfn{archive-label} at the beginning of the archive when
-the archive is being created (when used in conjunction with the
-@samp{tar --create} operation). Checks to make sure the archive label
-matches the one specified (when used in conjunction with the @samp{tar
---extract} operation.
-@end table
-@c was --volume
+If you reorder short options' locations, be sure to move any arguments
+that belong to them. If you do not move the arguments properly, you may
+end up overwriting files.
+
+@node Old Options, Mixing, Short Options, Styles
+@subsection Old Option Style
+@UNREVISED
+
+Like short options, old options are single letters. However, old options
+must be written together as a single clumped set, without spaces separating
+them or dashes preceding them@footnote{Beware that if you precede options
+with a dash, you are announcing the short option style instead of the
+old option style; short options are decoded differently.}. This set
+of letters must be the first to appear on the command line, after the
+@code{tar} program name and some whitespace; old options cannot appear
+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}.
+
+@FIXME{bob suggests having an uglier example. :-) }
+
+When options that need arguments are given together with the command,
+all the associated arguments follow, in the same order as the options.
+Thus, the example given previously could also be written in the old
+style as follows:
-@node Format Variations, , Archive Label, Archive Structure
-@section Format Variations
-@cindex Format Parameters
-@cindex Format Options
-@cindex Options to specify archive format.
+@example
+$ @kbd{tar cvbf 20 /dev/rmt0}
+@end example
-Format parameters specify how an archive is written on the archive
-media. The best choice of format parameters will vary depending on
-the type and number of files being archived, and on the media used to
-store the archive.
+@noindent
+Here, @samp{20} is the argument of @samp{-b} and @samp{/dev/rmt0} is
+the argument of @samp{-f}.
-To specify format parameters when accessing or creating an archive,
-you can use the options described in the following sections. If you
-do not specify any format parameters, @code{tar} uses default
-parameters. You cannot modify a compressed archive. If you create an
-archive with the @samp{--block-size} option specified (@pxref{Blocking
-Factor}), you must specify that block-size when operating on the
-archive. @xref{Matching Format Parameters}, for other examples of
-format parameter considerations.
+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
+argument. Even using short options like in @w{@samp{tar -c -v -b 20 -f
+/dev/rmt0}} is clearer, putting all arguments next to the option they
+pertain to.
+If you want to reorder the letters in the old option argument, be
+sure to reorder any corresponding argument appropriately.
-@menu
-* Multi-Volume Archives::
-* Sparse Files::
-* Blocking Factor::
-* Compressed Archives::
-@end menu
+This old way of writing @code{tar} options can surprise even experienced
+users. For example, the two commands:
-@node Multi-Volume Archives, Sparse Files, Format Variations, Format Variations
-@subsection Archives Longer than One Tape or Disk
-@cindex Multi-volume archives
+@example
+@kbd{tar cfz archive.tar.gz file}
+@kbd{tar -cfz archive.tar.gz file}
+@end example
-To create an archive that is larger than will fit on a single unit of
-the media, use the @samp{--multi-volume} option in conjunction with the
-@samp{tar --create} operation (@pxref{Creating Archives}). A
-@dfn{multi-volume} archive can be manipulated like any other archive
-(provided the @samp{--multi-volume} option is specified), but is stored
-on more than one tape or disk.
+@noindent
+are quite different. The first example uses @file{archive.tar.gz} as
+the value for option @samp{f} and recognizes the option @samp{z}. The
+second example, however, uses @file{z} as the value for option
+@samp{f}---probably not what was intended.
-When you specify @samp{--multi-volume}, @code{tar} does not report an
-error when it comes to the end of an archive volume (when reading), or
-the end of the media (when writing). Instead, it prompts you to load
-a new storage volume. If the archive is on a magnetic tape, you
-should change tapes when you see the prompt; if the archive is on a
-floppy disk, you should change disks; etc.
+Old options are kept for compatibility with old versions of @code{tar}.
-You can read each individual volume of a multi-volume archive as if it
-were an archive by itself. For example, to list the contents of one
-volume, use @samp{tar --list}, without @samp{--multi-volume} specified.
-To extract an archive member from one volume (assuming it is described
-that volume), use @samp{tar --extract}, again without
-@samp{--multi-volume}.
+This second example could be corrected in many ways, among which the
+following are equivalent:
-If an archive member is split across volumes (ie. its entry begins on
-one volume of the media and ends on another), you need to specify
-@samp{--multi-volume} to extract it successfully. In this case, you
-should load the volume where the archive member starts, and use
-@samp{tar --extract --multi-volume}---@code{tar} will prompt for later
-volumes as it needs them. @xref{Extracting From Archives} for more
-information about extracting archives.
+@example
+@kbd{tar -czf archive.tar.gz file}
+@kbd{tar -cf archive.tar.gz -z file}
+@kbd{tar cf archive.tar.gz -z file}
+@end example
-@samp{--info-script=@var{program-file}} is like @samp{--multi-volume},
-except that @code{tar} does not prompt you directly to change media
-volumes when a volume is full---instead, @code{tar} runs commands you
-have stored in @var{program-file}. This option can be used to
-broadcast messages such as @samp{someone please come change my tape}
-when performing unattended backups. When @var{program-file} is done,
-@code{tar} will assume that the media has been changed.
+@FIXME{still could explain this better; it's redundant:}
+@cindex option syntax, traditional
+As far as we know, all @code{tar} programs, GNU and non-GNU, support
+old options. GNU @code{tar} supports them not only for historical
+reasons, but also because many people are used to them. For
+compatibility with Unix @code{tar}, the first argument is always
+treated as containing command and option letters even if it doesn't
+start with @samp{-}. Thus, @samp{tar c} is equivalent to @w{@samp{tar
+-c}:} both of them specify the @value{op-create} command to create an
+archive.
-<<< There should be a sample program here, including an exit before
-<<< end.
+@node Mixing, , Old Options, Styles
+@subsection Mixing Option Styles
-@table @samp
-@item --multi-volume
-@itemx -M
-Creates a multi-volume archive, when used in conjunction with
-@samp{tar --create}. To perform any other operation on a multi-volume
-archive, specify @samp{--multi-volume} in conjunction with that
-operation.
+All three styles may be intermixed in a single @code{tar} command, so
+long as the rules for each style are fully respected@footnote{Before GNU
+@code{tar} version 1.11.6, a bug prevented intermixing old style options
+with mnemonic options in some cases.}. Old style options and either of the
+modern styles of options may be mixed within a single @code{tar} command.
+However, old style options must be introduced as the first arguments only,
+following the rule for old options (old options must appear directly
+after the @code{tar} command and some whitespace). Modern options may
+be given only after all arguments to the old options have been collected.
+If this rule is not respected, a modern option might be falsely interpreted
+as the value of the argument to one of the old style options.
-@item --info-script=@var{program-file}
-@itemx -F @var{program-file}
-Creates a multi-volume archive via a script. Used in conjunction with
-@samp{tar --create}.
-@end table
+For example, all the following commands are wholly equivalent, and
+illustrate the many combinations and orderings of option styles.
-@node Sparse Files, Blocking Factor, Multi-Volume Archives, Format Variations
-@subsection Archiving Sparse Files
-@cindex Sparse Files
+@example
+@kbd{tar --create --file=archive.tar}
+@kbd{tar --create -f archive.tar}
+@kbd{tar --create -farchive.tar}
+@kbd{tar --file=archive.tar --create}
+@kbd{tar --file=archive.tar -c}
+@kbd{tar -c --file=archive.tar}
+@kbd{tar -c -f archive.tar}
+@kbd{tar -c -farchive.tar}
+@kbd{tar -cf archive.tar}
+@kbd{tar -cfarchive.tar}
+@kbd{tar -f archive.tar --create}
+@kbd{tar -f archive.tar -c}
+@kbd{tar -farchive.tar --create}
+@kbd{tar -farchive.tar -c}
+@kbd{tar c --file=archive.tar}
+@kbd{tar c -f archive.tar}
+@kbd{tar c -farchive.tar}
+@kbd{tar cf archive.tar}
+@kbd{tar f archive.tar --create}
+@kbd{tar f archive.tar -c}
+@kbd{tar fc archive.tar}
+@end example
-A file is sparse if it contains blocks of zeros whose existance is
-recorded, but that have no space allocated on disk. When you specify
-the @samp{--sparse} option in conjunction with the @samp{--create}
-operation, @code{tar} tests all files for sparseness while archiving.
-If @code{tar} finds a file to be sparse, it uses a sparse
-representation of the file in the archive. @xref{Creating Archives},
-for more information about creating archives.
+On the other hand, the following commands are @emph{not} equivalent to
+the previous set:
-@samp{--sparse} is useful when archiving files, such as dbm files,
-likely to contain many nulls. This option dramatically
-decreases the amount of space needed to store such an archive.
+@example
+@kbd{tar -f -c archive.tar}
+@kbd{tar -fc archive.tar}
+@kbd{tar -fcarchive.tar}
+@kbd{tar -farchive.tarc}
+@kbd{tar cfarchive.tar}
+@end example
-@quotation
-@strong{Please Note:} Always use @samp{--sparse} when performing file
-system backups, to avoid archiving the expanded forms of files stored
-sparsely in the system.@refill
+@noindent
+These last examples mean something completely different from what the
+user intended (judging based on the example in the previous set which
+uses long options, whose intent is therefore very clear). The first
+four specify that the @code{tar} archive would be a file named
+@samp{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
+respectively. The first two examples also specify a single non-option,
+@var{name} argument having the value @samp{archive.tar}. The last
+example contains only old style option letters (repeating option
+@samp{c} twice), not all of which are meaningful (eg., @samp{.},
+@samp{h}, or @samp{i}), with no argument value. @FIXME{not sure i liked
+the first sentence of this paragraph..}
+
+@node All Options, help, Styles, tar invocation
+@section All @code{tar} Options
+
+The coming manual sections contain an alphabetical listing of all
+@code{tar} operations and options, with brief descriptions and cross
+references to more in-depth explanations in the body of the manual.
+They also contain an alphabetically arranged table of the short option
+forms with their corresponding long option. You can use this table as
+a reference for deciphering @code{tar} commands in scripts.
-Even if your system has no no sparse files currently, some may be
-created in the future. If you use @samp{--sparse} while making file
-system backups as a matter of course, you can be assured the archive
-will always take no more space on the media than the files take on
-disk (otherwise, archiving a disk filled with sparse files might take
-hundreds of tapes).@refill
-<<< xref incremental when node name is set.
-@end quotation
+@menu
+* Operation Summary::
+* Option Summary::
+* Short Option Summary::
+@end menu
-@code{tar} ignores the @samp{--sparse} option when reading an archive.
+@node Operation Summary, Option Summary, All Options, All Options
+@subsection Operations
-@table @samp
-@item --sparse
-@itemx -S
-Files stored sparsely in the file system are represented sparsely in
-the archive. Use in conjunction with write operations.
-@end table
+@table @kbd
-@node Blocking Factor, Compressed Archives, Sparse Files, Format Variations
-@subsection The Blocking Factor of an Archive
-@cindex Blocking Factor
-@cindex Block Size
-@cindex Number of records per block
-@cindex Number of bytes per block
-@cindex Bytes per block
-@cindex Records per block
-
-The data in an archive is grouped into records, which are 512 bytes.
-Records are read and written in whole number multiples called
-@dfn{blocks}. The number of records in a block (ie. the size of a
-block in units of 512 bytes) is called the @dfn{blocking factor}. The
-@samp{--block-size=@var{number}} option specifies the blocking factor
-of an archive. The default blocking factor is typically 20 (ie.@:
-10240 bytes), but can be specified at installation. To find out the
-blocking factor of an existing archive, use @samp {tar --list
---file=@var{archive-name}}. This may not work on some devices.
-
-Blocks are seperated by gaps, which waste space on the archive media.
-If you are archiving on magnetic tape, using a larger blocking factor
-(and therefore larger blocks) provides faster throughput and allows
-you to fit more data on a tape (because there are fewer gaps). If you
-are archiving on cartridge, a very large blocking factor (say 126 or
-more) greatly increases performance. A
-smaller blocking factor, on the other hand, may be usefull when
-archiving small files, to avoid archiving lots of nulls as @code{tar}
-fills out the archive to the end of the block. In general, the ideal block size
-depends on the size of the inter-block gaps on the tape you are using,
-and the average size of the files you are archiving. @xref{Creating
-Archives}, for information on writing archives.
-
-Archives with blocking factors larger than 20 cannot be read by very
-old versions of @code{tar}, or by some newer versions of @code{tar}
-running on old machines with small address spaces. With GNU
-@code{tar}, the blocking factor of an archive is limited only by the
-maximum block size of the device containing the archive, or by the
-amount of available virtual memory.
-
-If you use a non-default blocking factor when you create an archive,
-you must specify the same blocking factor when you modify that
-archive. Some archive devices will also require you to specify the
-blocking factor when reading that archive, however this is not
-typically the case. Usually, you can use @samp{tar --list} without
-specifying a blocking factor---@code{tar} reports a non-default block
-size and then lists the archive members as it would normally. To
-extract files from an archive with a non-standard blocking factor
-(particularly if you're not sure what the blocking factor is), you can
-usually use the {--read-full-blocks} option while specifying a blocking
-factor larger then the blocking factor of the archive (ie. @samp{tar
---extract --read-full-blocks --block-size=300}. @xref{Listing Contents}
-for more information on the @samp{--list} operation.
-@xref{read-full-blocks} for a more detailed explanation of that
-option.
+@item --append
+@itemx -r
-@table @samp
-@item --block-size=@var{number}
-@itemx -b @var{number}
-Specifies the blocking factor of an archive. Can be used with any
-operation, but is usually not necessary with @samp{tar --list}.
-@end table
+Appends files to the end of the archive. @xref{append}.
-@node Compressed Archives, , Blocking Factor, Format Variations
-@subsection Creating and Reading Compressed Archives
-@cindex Compressed archives
-@cindex Storing archives in compressed format
+@item --catenate
+@itemx -A
-@samp{--compress} indicates an archive stored in compressed format.
-The @samp{--compress} option is useful in saving time over networks and
-space in pipes, and when storage space is at a premium.
-@samp{--compress} causes @code{tar} to compress when writing the
-archive, or to uncompress when reading the archive.
+Same as @samp{--concatenate}. @xref{concatenate}.
-To perform compression and uncompression on the archive, @code{tar}
-runs the @code{compress} utility. @code{tar} uses the default
-compression parameters; if you need to override them, avoid the
-@samp{--compress} option and run the @code{compress} utility
-explicitly. It is useful to be able to call the @code{compress}
-utility from within @code{tar} because the @code{compress} utility by
-itself cannot access remote tape drives.
+@item --compare
+@itemx -d
-The @samp{--compress} option will not work in conjunction with the
-@samp{--multi-volume} option or the @samp{--add-file}, @samp{--update},
-@samp{--add-file} and @samp{--delete} operations. @xref{Modifying}, for
-more information on these operations.
+Compares archive members with their counterparts in the file
+system, and reports differences in file size, mode, owner,
+modification date and contents. @xref{compare}.
-If there is no compress utility available, @code{tar} will report an
-error.
+@item --concatenate
+@itemx -A
-@samp{--compress-block} is like @samp{--compress}, but when used in
-conjunction with @samp{--create} also causes @code{tar} to pad the last
-block of the archive out to the next block boundary as it is written.
-This is useful with certain devices which require all write operations
-be a multiple of a specific size.
+Appends other @code{tar} archives to the end of the archive.
+@xref{concatenate}.
-@quotation
-@strong{Please Note:} The @code{compress} program may be covered by a patent,
-and therefore we recommend you stop using it. We hope to have a
-different compress program in the future. We may change the name of
-this option at that time.
-@end quotation
-
-@table @samp
-@item --compress
-@itemx --uncompress
-@itemx -z
-@itemx -Z
-When this option is specified, @code{tar} will compress (when writing
-an archive), or uncompress (when reading an archive). Used in
-conjunction with the @samp{--create}, @samp{--extract}, @samp{--list} and
-@samp{--compare} operations.
-
-@item --compress-block
-@itemx -z -z
-Acts like @samp{--compress}, but pads the archive out to the next block
-boundary as it is written when used in conjunction with the
-@samp{--create} operation.
-@end table
-
-@c >>> MIB -- why not use -Z instead of -z -z ? -ringo
+@item --create
+@itemx -c
-@node Reading and Writing, Insuring Accuracy, Archive Structure, Top
-@chapter Reading and Writing Archives
+Creates a new @code{tar} archive. @xref{create}.
-The @samp{--create} operation writes a new archive, and the
-@samp{--extract} operation reads files from an archive and writes them
-into the file system. You can use other @code{tar} operations to
-write new information into an existing archive (adding files to it,
-adding another archive to it, or deleting files from it), and you can
-read a list of the files in an archive without extracting it using the
-@samp{--list} operation.
+@item --delete
-@menu
-* Archive Name:: The name of an archive
-* Creating in Detail:: Creating in detail
-* Modifying:: Modifying archives
-* Listing Contents:: Listing the contents of an archive
-* Extracting From Archives:: Extracting files from an archive
-@end menu
+Deletes members from the archive. Don't try this on a archive on a
+tape! @xref{delete}.
-@node Archive Name, Creating in Detail, Reading and Writing, Reading and Writing
-@section The Name of an Archive
-@cindex Naming an archive
-@cindex Archive Name
-@cindex Directing output
-@cindex Where is the archive?
+@item --diff
+@itemx -d
-An archive can be saved as a file in the file system, sent through a
-pipe or over a network, or written to an I/O device such as a tape or
-disk drive. To specify the name of the archive, use the
-@samp{--file=@var{archive-name}} option.
+Same @samp{--compare}. @xref{compare}.
-An archive name can be the name of an ordinary file or the name of an
-I/O device. @code{tar} always needs an archive name---if you do not
-specify an archive name, the archive name comes from the environment
-variable @code{TAPE} or, if that variable is not specified, a default
-archive name, which is usually the name of tape unit zero (ie.
-/dev/tu00).
+@item --extract
+@itemx -x
-If you use @file{-} as an @var{archive-name}, @code{tar} reads the
-archive from standard input (when listing or extracting files), or
-writes it to standard output (when creating an archive). If you use
-@file{-} as an @var{archive-name} when modifying an archive,
-@code{tar} reads the original archive from its standard input and
-writes the entire new archive to its standard output.
+Extracts members from the archive into the file system. @xref{extract}.
-@c >>> MIB--does standard input and output redirection work with all
-@c >>> operations?
-@c >>> need example for standard input and output (screen and keyboard?)
+@item --get
+@itemx -x
-@cindex Standard input and output
-@cindex tar to standard input and output
+Same as @samp{--extract}. @xref{extract}.
-To specify an archive file on a device attached to a remote machine,
-use the following:
+@item --list
+@itemx -t
-@example
---file=@var{hostname}:/@var{dev}/@var{file name}
-@end example
+Lists the members in an archive. @xref{list}.
-@noindent
-@code{tar} will complete the remote connection, if possible, and
-prompt you for a username and password. If you use
-@samp{--file=@@@var{hostname}:/@var{dev}/@var{file-name}}, @code{tar}
-will complete the remote connection, if possible, using your username
-as the username on the remote machine.
+@item --update
+@itemx -u
-@c >>>MIB --- is this clear?
+@FIXME{It was: A combination of the @samp{--compare} and @samp{--append} operations.
+This is not true and rather misleading, as @value{op-compare}
+does a lot more than @value{op-update} for ensuring files are identical.}
+Adds files to the end of the archive, but only if they are newer than
+their counterparts already in the archive, or if they do not already
+exist in the archive.
+@xref{update}.
-@table @samp
-@item --file=@var{archive-name}
-@itemx -f @var{archive-name}
-Names the archive to create or operate on. Use in conjunction with
-any operation.
@end table
-@node Creating in Detail, Modifying, Archive Name, Reading and Writing
-@section Creating in Detail
-@c operations should probably have examples, not tables.
-@cindex Writing new archives
-@cindex Archive creation
+@node Option Summary, Short Option Summary, Operation Summary, All Options
+@subsection @code{tar} Options
-To create an archive, use @samp{tar --create}. To name the archive,
-use @samp{--file=@var{archive-name}} in conjunction with the
-@samp{--create} operation (@pxref{Archive Name}). If you do not name
-the archive, @code{tar} uses the value of the environment variable
-@code{TAPE} as the file name for the archive, or, if that is not
-available, @code{tar} uses a default archive name, usually that for tape
-unit zero. @xref{Archive Name}, for more information about specifying
-an archive name.
+@table @kbd
-The following example creates an archive named @file{stooges},
-containing the files @file{larry}, @file{moe} and @file{curley}:
+@item --absolute-names
+@itemx -P
-@example
-tar --create --file=stooges larry moe curley
-@end example
+Normally when creating an archive, @code{tar} strips an initial @samp{/} from
+member names. This option disables that behavior. @FIXME-xref{}.
-If you specify a directory name as a file-name argument, @code{tar}
-will archive all the files in that directory. The following example
-creates an archive named @file{hail/hail/fredonia}, containing the
-contents of the directory @file{marx}:
+@item --after-date
-@example
-tar --create --file=hail/hail/fredonia marx
-@end example
+(See @samp{--newer}; @FIXME-pxref{}.)
-If you don't specify files to put in the archive, @code{tar} archives
-all the files in the working directory. The following example creates
-an archive named @file{home} containing all the files in the working
-directory:
+@item --atime-preserve
-@example
-tar --create --file=home
-@end example
+Tells @code{tar} to preserve the access time field in a file's inode when
+dumping it. @FIXME-xref{}.
-@xref{File Name Lists}, for other ways to specify files to archive.
+@item --backup=@var{backup-type}
-Note: In the example above, an archive containing all the files in the
-working directory is being written to the working directory. GNU
-@code{tar} stores files in the working directory in an archive which
-is itself in the working directory without falling into an infinite
-loop. Other versions of @code{tar} may fall into this trap.
+Rather than deleting files from the file system, @code{tar} will back them up
+using simple or numbered backups, depending upon @var{backup-type}.
+@FIXME-xref{}.
-@node Modifying, Listing Contents, Creating in Detail, Reading and Writing
-@section Modifying Archives
-@cindex Modifying archives
+@item --block-number
+@itemx -R
-Once an archive is created, you can add new archive members to it, add
-the contents of another archive, add newer versions of members already
-stored, or delete archive members already stored.
+With this option present, @code{tar} prints error messages for read errors
+with the block number in the archive file. @FIXME-xref{}.
-To find out what files are already stored in an archive, use @samp{tar
---list --file=@var{archive-name}}. @xref{Listing Contents}.
+@item --blocking-factor=@var{blocking}
+@itemx -b @var{blocking}
-@menu
-* Adding Files::
-* Appending Archives::
-* Deleting Archive Files:: Deleting Files From an Archive
-* Matching Format Parameters::
-@end menu
+Sets the blocking factor @code{tar} uses to @var{blocking} x 512 bytes per
+record. @FIXME-xref{}.
-@node Adding Files, Appending Archives, Modifying, Modifying
-@subsection Adding Files to an Archive
-@cindex Adding files to an archive
-@cindex Updating an archive
+@item --checkpoint
-To add files to an archive, use @samp{tar --add-file}. The archive to
-be added to must already exist and be in proper archive format (which
-normally means it was created previously using @code{tar}). If the
-archive was created with a different block size than now specified,
-@code{tar} will report an error (@pxref{Blocking Factor}). If the
-archive is not a valid @code{tar} archive, the results will be
-unpredictable. You cannot add files to a compressed archive, however
-you can add files to the last volume of a multi-volume archive.
-@xref{Matching Format Parameters}.
+This option directs @code{tar} to print periodic checkpoint messages as it
+reads through the archive. Its intended for when you want a visual
+indication that @code{tar} is still running, but don't want to see
+@samp{--verbose} output. @FIXME-xref{}.
-The following example adds the file @file{shemp} to the archive
-@file{stooges} created above:
+@item --compress
+@itemx --uncompress
+@itemx -Z
-@example
-tar --add-file --file=stooges shemp
-@end example
+@code{tar} will use the @code{compress} program when reading or writing the
+archive. This allows you to directly act on archives while saving
+space. @FIXME-xref{}.
-You must specify the files to be added; there is no default.
+@item --confirmation
-@samp{tar --update} acts like @samp{tar --add-file}, but does not add
-files to the archive if there is already a file entry with that name
-in the archive that has the same modification time.
+(See @samp{--interactive}; @FIXME-pxref{}.)
-Both @samp{--update} and @samp{--add-file} 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. Because
-@samp{tar --extract} extracts files from an archive in sequence, and
-overwrites files with the same name in the file system, if a file name
-appears more than once in an archive the last version of the file will
-overwrite the previous versions which have just been extracted. You
-should avoid storing older versions of a file later in the archive.
+@item --dereference
+@itemx -h
-Note: @samp{--update} is not suitable for performing backups, because
-it doesn't change directory content entries, and because it lengthens
-the archive every time it is used.
-@c <<< xref to scripted backup, listed incremental, for info on backups.
+When creating a @code{tar} archive, @code{tar} will archive the file that a symbolic
+link points to, rather than archiving the symlink. @FIXME-xref{}.
-@node Appending Archives, Deleting Archive Files, Adding Files, Modifying
-@subsection Appending One Archive's Contents to Another Archive
-@cindex Adding archives to an archive
-@cindex Concatenating Archives
+@item --directory=@var{dir}
+@itemx -C @var{dir}
-To append copies of an archive or archives to the end of another
-archive, use @samp{tar --add-archive}. The source and target archives
-must already exist and have been created using compatable format
-parameters (@pxref{Matching Format Parameters}).
-
-@code{tar} will stop reading an archive if it encounters an
-end-of-archive marker. The @code{cat} utility does not remove
-end-of-archive markers, and is therefore unsuitable for concatenating
-archives. @samp{tar --add-archive} removes the end-of-archive marker
-from the target archive before each new archive is appended.
-@c <<< xref ignore-zeros
-
-You must specify the source archives using
-@samp{--file=@var{archive-name}} (@pxref{Archive Name}). If you do not
-specify the target archive , @code{tar} uses the value of the
-environment variable @code{TAPE}, or, if this has not been set, the
-default archive name.
+When this option is specified, @code{tar} will change its current directory
+to @var{dir} before performing any operations. When this option is used
+during archive creation, it is order sensitive. @FIXME-xref{}.
-The following example adds the contents of the archive
-@file{hail/hail/fredonia} to the archive @file{stooges} (both archives
-were created in examples above):
+@item --exclude=@var{pattern}
-@example
-tar --add-archive --file=stooges hail/hail/fredonia
-@end example
+When performing operations, @code{tar} will skip files that match
+@var{pattern}. @FIXME-xref{}.
-If you need to retrieve files from an archive that was added to using
-the @code{cat} utility, use the @samp{--ignore-zeros} option
-(@pxref{Archive Reading Options}).
+@item --exclude-from=@var{file}
+@itemx -X @var{file}
-@node Deleting Archive Files, Matching Format Parameters, Appending Archives, Modifying
-@subsection Deleting Files From an Archive
-@cindex Deleting files from an archive
-@cindex Removing files from an archive
+Similar to @samp{--exclude}, except @code{tar} will use the list of patterns
+in the file @var{file}. @FIXME-xref{}.
-To delete archive members from an archive, use @samp{tar --delete}.
-You must specify the file names of the members to be deleted. All
-archive members with the specified file names will be removed from the
-archive.
+@item --file=@var{archive}
+@itemx -f @var{archive}
-The following example removes the file @file{curley} from the archive
-@file{stooges}:
+@code{tar} will use the file @var{archive} as the @code{tar} archive it
+performs operations on, rather than @code{tar}'s compilation dependent
+default. @FIXME-xref{}.
-@example
-tar --delete --file=stooges curley
-@end example
+@item --files-from=@var{file}
+@itemx -T @var{file}
-You can only use @samp{tar --delete} on an archive if the archive
-device allows you to write to any point on the media.
+@code{tar} will use the contents of @var{file} as a list of archive members
+or files to operate on, in addition to those specified on the
+command-line. @FIXME-xref{}.
-@quotation
-@strong{Warning:} Don't try to delete an archive member from a
-magnetic tape, lest you scramble the archive. There is no safe way
-(except by completely re-writing the archive) to delete files from
-most kinds of magnetic tape.
-@end quotation
+@item --force-local
-@c <<< MIB -- how about automatic detection of archive media? give error
-@c <<< unless the archive device is either an ordinary file or different
-@c <<< input and output (--file=-).
+Forces @code{tar} to interpret the filename given to @samp{--file} as a local
+file, even if it looks like a remote tape drive name. @FIXME-xref{}.
-@node Matching Format Parameters, , Deleting Archive Files, Modifying
-@subsection Matching the Format Parameters
+@item --group=@var{group}
-Some format parameters must be taken into consideration when modifying
-an archive:
+Files added to the @code{tar} archive will have a group id of @var{group},
+rather than the group from the source file. @var{group} is first decoded
+as a group symbolic name, but if this interpretation fails, it has to be
+a decimal numeric group ID. @FIXME-xref{}.
-Compressed archives cannot be modified.
+Also see the comments for the @value{op-owner} option.
-You have to specify the block size of the archive when modifying an
-archive with a non-default block size.
+@item --gunzip
-Multi-volume archives can be modified like any other archive. To add
-files to a multi-volume archive, you need to only mount the last
-volume of the archive media (and new volumes, if needed). For all
-other operations, you need to use the entire archive.
-
-If a multi-volume archive was labeled using @samp{--label}
-(@pxref{Archive Label}) when it was created, @code{tar} will not
-automatically label volumes which are added later. To label
-subsequent volumes, specify @samp{--label=@var{archive-label}} again in
-conjunction with the @samp{--add-file}, @samp{--update} or
-@samp{--add-archive} operation.
-@cindex Labelling multi-volume archives
-@c <<< example
+(See @samp{--gzip}; @FIXME-pxref{}.)
-@c <<< xref somewhere, for more information about format parameters.
+@item --gzip
+@itemx --gunzip
+@itemx --ungzip
+@itemx -z
-@node Listing Contents, Extracting From Archives, Modifying, Reading and Writing
-@section Listing the Contents of an Archive
-@cindex Names of the files in an archive
-@cindex Archive contents, list of
-@cindex Archive members, list of
+This option tells @code{tar} to read or write archives through @code{gzip},
+allowing @code{tar} to directly operate on several kinds of compressed
+archives transparently. @FIXME-xref{}.
-@samp{tar --list} prints a list of the file names of the archive
-members on the standard output. If you specify @var{file-name}
-arguments on the command line (or using the @samp{--files-from} option,
-@pxref{File Name Lists}), only the files you specify will be listed,
-and only if they exist in the archive. Files not specified will be
-ignored, unless they are under a specific directory.
+@item --help
-If you include the @samp{--verbose} option, @code{tar} prints an
-@samp{ls -l} type listing for the archive. @pxref{Additional
-Information}, for a description of the @samp{--verbose} option.
+@code{tar} will print out a short message summarizing the operations and
+options to @code{tar} and exit. @FIXME-xref{}.
-If the blocking factor of the archive differs from the default,
-@code{tar} reports this. @xref{Blocking Factor}.
+@item --ignore-failed-read
-@xref{Archive Reading Options} for a list of options which can be used
-to modify @samp{--list}'s operation.
+Instructs @code{tar} to exit successfully if it encounters an
+unreadable file. @xref{Reading}.
-This example prints a list of the archive members of the archive
-@file{stooges}:
+@item --ignore-umask
+@FIXME{does this exist?}
-@example
-tar --list --file=stooges
-@end example
+(See @samp{--preserve-permissions}; @pxref{Writing}.)
-@noindent
-@code{tar} responds:
+@item --ignore-zeros
+@itemx -i
-@example
-larry
-moe
-shemp
-marx/julius
-marx/alexander
-marx/karl
-@end example
+With this option, @code{tar} will ignore zeroed blocks in the archive, which
+normally signals EOF. @xref{Reading}.
-This example generates a verbose list of the archive members of the
-archive file @file{dwarves}, which has a blocking factor of two:
+@item --incremental
+@itemx -G
-@example
-tar --list -v --file=blocks
-@end example
+Used to inform @code{tar} that it is working with an old GNU-format
+incremental backup archive. It is intended primarily for backwards
+compatibility only. @FIXME-xref{}.
-@noindent
-@code{tar} responds:
+@item --info-script=@var{script-file}
+@itemx --new-volume-script=@var{script-file}
+@itemx -F @var{script-file}
-@example
-tar: Blocksize = 2 records
--rw------- ringo/user 42 May 1 13:29 1990 .bashful
--rw-rw-rw- ringo/user 42 Oct 4 13:29 1990 doc
--rw-rw-rw- ringo/user 42 Jul 20 18:01 1969 dopey
--rw-rw---- ringo/user 42 Nov 26 13:42 1963 grumpy
--rw-rw-rw- ringo/user 42 May 5 13:29 1990 happy
--rw-rw-rw- ringo/user 42 May 1 12:00 1868 sleepy
--rw-rw-rw- ringo/user 42 Jul 4 17:29 1776 sneezy
-@end example
+When @code{tar} is performing multi-tape backups, @var{script-file} is run
+at the end of each tape. @FIXME-xref{}.
-@node Extracting From Archives, , Listing Contents, Reading and Writing
-@section Extracting Files from an Archive
-@cindex Extraction
-@cindex Retrieving files from an archive
-@cindex Resurrecting files from an archive
+@item --interactive
+@itemx --confirmation
+@itemx -w
-To read archive members from the archive and write them into the file
-system, use @samp{tar --extract}. The archive itself is left
-unchanged.
+Specifies that @code{tar} should ask the user for confirmation before
+performing potentially destructive options, such as overwriting files.
+@FIXME-xref{}.
-If you do not specify the files to extract, @code{tar} extracts all
-the files in the archive. If you specify the name of a directory as a
-file-name argument, @code{tar} will extract all files which have been
-stored as part of that directory. If a file was stored with a
-directory name as part of its file name, and that directory does not
-exist under the working directory when the file is extracted,
-@code{tar} will create the directory. @xref{Selecting Archive
-Members}, for information on specifying files to extract.
+@item --keep-old-files
+@itemx -k
-The following example shows the extraction of the archive
-@file{stooges} into an empty directory:
+When extracting files from an archive, @code{tar} will not overwrite existing
+files if this option is present. @xref{Writing}.
-@example
-tar --extract --file=stooges
-@end example
+@item --label=@var{name}
+@itemx -V @var{name}
-@noindent
-Generating a listing of the directory (@samp{ls}) produces:
+When creating an archive, instructs @code{tar} to write @var{name} as a name
+record in the archive. When extracting or listing archives, @code{tar} will
+only operate on archives that have a label matching the pattern
+specified in @var{name}. @FIXME-xref{}.
-@example
-larry
-moe
-shemp
-marx
-@end example
+@item --listed-incremental=@var{snapshot-file}
+@itemx -g @var{snapshot-file}
-@noindent
-The subdirectory @file{marx} contains the files @file{julius},
-@file{alexander} and @file{karl}.
+During a @samp{--create} operation, specifies that the archive that
+@code{tar} creates is a new GNU-format incremental backup, using
+@var{snapshot-file} to determine which files to backup.
+With other operations, informs @code{tar} that the archive is in incremental
+format. @FIXME-xref{}.
-If you wanted to just extract the files in the subdirectory
-@file{marx}, you could specify that directory as a file-name argument
-in conjunction with the @samp{--extract} operation:
+@item --mode=@var{permissions}
-@example
-tar --extract --file=stooges marx
-@end example
+When adding files to an archive, @code{tar} will use @var{permissions}
+for the archive members, rather than the permissions from the files.
+The program @code{chmod} and this @code{tar} option share the same syntax
+for what @var{permissions} might be. @xref{File permissions, Permissions,
+File permissions, filetutils, GNU file utilities}. This reference also
+has useful information for those not being overly familiar with the Unix
+permission system.
-@quotation
-@strong{Warning:} Extraction can overwrite files in the file system.
-To avoid losing files in the file system when extracting files from
-the archive with the same name, use the @samp{--keep-old-files} option
-(@pxref{File Writing Options}).
-@end quotation
+Of course, @var{permissions} might be plainly specified as an octal number.
+However, by using generic symbolic modifications to mode bits, this allows
+more flexibility. For example, the value @samp{a+rw} adds read and write
+permissions for everybody, while retaining executable bits on directories
+or on any other file already marked as executable.
-If the archive was created using @samp{--block-size}, @samp{--compress}
-or @samp{--multi-volume}, you must specify those format options again
-when extracting files from the archive (@pxref{Format Variations}).
+@item --multi-volume
+@itemx -M
-@menu
-* Archive Reading Options::
-* File Writing Options::
-* Scarce Disk Space:: Recovering From Scarce Disk Space
-@end menu
+Informs @code{tar} that it should create or otherwise operate on a
+multi-volume @code{tar} archive. @FIXME-xref{}.
-@node Archive Reading Options, File Writing Options, Extracting From Archives, Extracting From Archives
-@subsection Options to Help Read Archives
-@cindex Options when reading archives
-@cindex Reading incomplete blocks
-@cindex Blocks, incomplete
-@cindex End of archive markers, ignoring
-@cindex Ignoring end of archive markers
-@cindex Large lists of file names on small machines
-@cindex Small memory
-@cindex Running out of space
+@item --new-volume-script
-@c <<< each option wants its own node. summary after menu
+(see --info-script)
-Normally, @code{tar} will request data in full block increments from
-an archive storage device. If the device cannot return a full block,
-@code{tar} will report an error. However, some devices do not always
-return full blocks, or do not require the last block of an archive to
-be padded out to the next block boundary. To keep reading until you
-obtain a full block, or to accept an incomplete block if it contains
-an end-of-archive marker, specify the @samp{--read-full-blocks} option
-in conjunction with the @samp{--extract} or @samp{--list} operations.
-@xref{Listing Contents}.
-
-The @samp{--read-full-blocks} option is turned on by default when
-@code{tar} reads an archive from standard input, or from a remote
-machine. This is because on BSD Unix systems, attempting to read a
-pipe returns however much happens to be in the pipe, even if it is
-less than was requested. If this option were not enabled, @code{tar}
-would fail as soon as it read an incomplete block from the pipe.
+@item --newer=@var{date}
+@itemx --after-date=@var{date}
+@itemx -N
-If you're not sure of the blocking factor of an archive, you can read
-the archive by specifying @samp{--read-full-blocks} and
-@samp{--block-size=@var{n}}, where @var{n} is a blocking factor larger
-than the blocking factor of the archive. This lets you avoid having
-to determine the blocking factor of an archive. @xref{Blocking
-Factor}.
+When creating an archive, @code{tar} will only add files that have changed
+since @var{date}. @FIXME-xref{}.
-@table @samp
-@item --read-full-blocks
-@item -B
-Use in conjunction with @samp{tar --extract} to read an archive which
-contains incomplete blocks, or one which has a blocking factor less
-than the one specified.
-@end table
+@item --newer-mtime
-Normally @code{tar} stops reading when it encounters a block of zeros
-between file entries (which usually indicates the end of the archive).
-@samp{--ignore-zeros} allows @code{tar} to completely read an archive
-which contains a block of zeros before the end (i.e.@: a damaged
-archive, or one which was created by @code{cat}-ing several archives
-together).
+In conjunction with @samp{--newer}, @code{tar} will only add files whose
+contents have changed (as opposed to just @samp{--newer}, which will
+also back up files for which any status information has changed).
-The @samp{--ignore-zeros} option is turned off by default because many
-versions of @code{tar} write garbage after the end of archive entry,
-since that part of the media is never supposed to be read. GNU
-@code{tar} does not write after the end of an archive, but seeks to
-maintain compatablity among archiving utilities.
+@item --no-recursion
-@table @samp
-@item --ignore-zeros
-@itemx -i
-To ignore blocks of zeros (ie.@: end-of-archive entries) which may be
-encountered while reading an archive. Use in conjunction with
-@samp{tar --extract} or @samp{tar --list}.
-@end table
+With this option, @code{tar} will not recurse into directories unless a
+directory is explicitly named as an argument to @code{tar}. @FIXME-xref{}.
-If you are using a machine with a small amount of memory, and you need
-to process large list of file-names, you can reduce the amount of
-space @code{tar} needs to process the list. To do so, specify the
-@samp{--same-order} option and provide an ordered list of file names.
-This option tells @code{tar} that the @file{file-name} arguments
-(provided on the command line, or read from a file using the
-@samp{--files-from} option) are listed in the same order as the files
-in the archive.
+@item --null
-You can create a file containing an ordered list of files in the
-archive by storing the output produced by @samp{tar --list
---file=@var{archive-name}}. @xref{Listing Contents}, for information
-on the @samp{--list} operation.
+When @code{tar} is using the @samp{--files-from} option, this option
+instructs @code{tar} to expect filenames terminated with @kbd{NUL}, so
+@code{tar} can correctly work with file names that contain newlines.
+@FIXME-xref{}.
-This option is probably never needed on modern computer systems.
+@item --numeric-owner
-@table @samp
-@item --same-order
-@itemx --preserve-order
-@itemx -s
-To process large lists of file-names on machines with small amounts of
-memory. Use in conjunction with @samp{tar --compare}, @samp{tar --list}
-or @samp{tar --extract}.
-@end table
+This option will notify @code{tar} that it should use numeric user and group
+IDs when creating a @code{tar} file, rather than names. @FIXME-xref{}.
-@c we don't need/want --preserve to exist any more
+@item --old-archive
-@node File Writing Options, Scarce Disk Space, Archive Reading Options, Extracting From Archives
-@subsection Changing How @code{tar} Writes Files
-@c <<< find a better title
-@cindex Overwriting old files, prevention
-@cindex Protecting old files
-@cindex Modification times of extracted files
-@cindex Permissions of extracted files
-@cindex Modes of extracted files
-@cindex Writing extracted files to standard output
-@cindex Standard output, writing extracted files to
+(See @samp{--portability}; @FIXME-pxref{}.)
-Normally, @code{tar} writes extracted files into the file system
-without regard to the files already on the system---files with the
-same name as archive members are overwritten. To prevent @code{tar}
-from extracting an archive member from an archive, if doing so will
-overwrite a file in the file system, use @samp{--keep-old-files} in
-conjunction with the @samp{--extract} operation. When this option is
-specified, @code{tar} reports an error stating the name of the files
-in conflict, instead of writing the file from the archive.
+@item --one-file-system
+@itemx -l
-@table @samp
-@item --keep-old files
-@itemx -k
-Prevents @code{tar} from overwriting files in the file system during
-extraction.
-@end table
+Used when creating an archive. Prevents @code{tar} from recursing into
+directories that are on different file systems from the current
+directory. @FIXME-xref{}.
-Normally, @code{tar} sets the modification times of extracted files to
-the modification times recorded for the files in the archive, but
-limits the permissions of extracted files by the current @code{umask}
-setting.
+@item --owner=@var{user}
-To set the modification times of extracted files to the time when
-the files were extracted, use the @samp{--modification-time} option in
-conjunction with @samp{tar --extract}.
+Specifies that @code{tar} should use @var{user} as the owner of members
+when creating archives, instead of the user associated with the source
+file. @var{user} is first decoded as a user symbolic name, but if
+this interpretation fails, it has to be a decimal numeric user ID.
+@FIXME-xref{}.
-@table @samp
-@item --modification-time
-@itemx -m
-Sets the modification time of extracted archive members to the time
-they were extracted, not the time recorded for them in the archive.
-Use in conjunction with @samp{--extract}.
-@end table
+There is no value indicating a missing number, and @samp{0} usually means
+@code{root}. Some people like to force @samp{0} as the value to offer in
+their distributions for the owner of files, because the @code{root} user is
+anonymous anyway, so that might as well be the owner of anonymous archives.
-To set the modes (access permissions) of extracted files to those
-recorded for those files in the archive, use the
-@samp{--preserve-permissions} option in conjunction with the
-@samp{--extract} operation.
-@c <<<mib --- should be aliased to ignore-umask.
+@item --portability
+@itemx --old-archive
+@itemx -o
-@table @samp
-@item --preserve-permission
-@itemx --same-permission
-@itemx --ignore-umask
-@itemx -p
-Set modes of extracted archive members to those recorded in the
-archive, instead of current umask settings. Use in conjunction with
-@samp{--extract}.
-@end table
+Tells @code{tar} to create an archive that is compatible with Unix V7
+@code{tar}. @FIXME-xref{}.
-@c <<< following paragraph needs to be rewritten:
-@c <<< why doesnt' this cat files together, why is this useful. is it
-@c <<< really useful with more than one file?
-To write the files extracted to the standard output, instead of
-creating the files on the file system, use @samp{--to-stdout} in
-conjunction with @samp{tar --extract}. This option is useful if you
-are extracting files to send them through a pipe, and do not need to
-preserve them in the file system.
+@item --posix
-@table @samp
-@item --to-stdout
-@itemx -O
-Writes files to the standard output. Used in conjunction with
-@samp{--extract}.
-@end table
+Instructs @code{tar} to create a POSIX compliant @code{tar} archive. @FIXME-xref{}.
-@c <<< why would you want to do such a thing, how are files separated on
-@c <<< the standard output? is this useful with more that one file? are
-@c <<< pipes the real reason?
+@item --preserve
-@node Scarce Disk Space, , File Writing Options, Extracting From Archives
-@subsection Recovering From Scarce Disk Space
-@cindex Middle of the archive, starting in the
-@cindex Running out of space during extraction
-@cindex Disk space, running out of
-@cindex Space on the disk, recovering from lack of
+Synonymous with specifying both @samp{--preserve-permissions} and
+@samp{--same-order}. @FIXME-xref{}.
-If a previous attempt to extract files failed due to lack of disk
-space, you can use @samp{--starting-file=@var{file-name}} to start
-extracting only after file @var{file-name} when extracting files from
-the archive. This assumes, of course, that there is now free space,
-or that you are now extracting into a different file system.
+@item --preserve-order
-@table @samp
-@item --starting-file=@var{file-name}
-@itemx -K @var{file-name}
-Starts an operation in the middle of an archive. Use in conjunction
-with @samp{--extract} or @samp{--list}.
-@end table
+(See @samp{--same-order}; @pxref{Reading}.)
-If you notice you are running out of disk space during an extraction
-operation, you can also suspend @code{tar}, remove unnecessary files
-from the file system, and then restart the same @code{tar} operation.
-In this case, @samp{--starting-file} is not necessary.
+@item --preserve-permissions
+@itemx --same-permissions
+@itemx -p
-@c <<< xref incremental, xref --interactive, xref --exclude
+When @code{tar} is extracting an archive, it normally subtracts the users'
+umask from the permissions specified in the archive and uses that
+number as the permissions to create the destination file. Specifying
+this option instructs @code{tar} that it should use the permissions directly
+from the archive. @xref{Writing}.
-@node Insuring Accuracy, Selecting Archive Members, Reading and Writing, Top
-@chapter Insuring the Accuracy of an Archive
+@item --read-full-records
+@itemx -B
-You can insure the accuracy of an archive by comparing files in the
-system with archive members. @code{tar} can compare an archive to the
-file system as the archive is being written, to verify a write
-operation, or can compare a previously written archive, to insure that
-it is up to date.
+Specifies that @code{tar} should reblock its input, for reading from pipes on
+systems with buggy implementations. @xref{Reading}.
-@menu
-* Write Verification::
-* Comparing::
-@end menu
+@item --record-size=@var{size}
-@node Write Verification, Comparing, Insuring Accuracy, Insuring Accuracy
-@section Verifying Data as It is Stored
-@cindex Verifying a write operation
-@cindex Double-checking a write operation
+Instructs @code{tar} to use @var{size} bytes per record when accessing the
+archive. @FIXME-xref{}.
-To check for discrepancies in an archive immediately after it is
-written, use the @samp{--verify} option in conjunction with the
-@samp{tar --create} operation. When this option is specified,
-@code{tar} checks archive members against their counterparts in the file
-system, and reports discrepancies on the standard error. In
-multi-volume archives, each volume is verified after it is written,
-before the next volume is written.
+@item --recursive-unlink
-To verify an archive, you must be able to read it from before the end
-of the last written entry. This option is useful for detecting data
-errors on some tapes. Archives written to pipes, some cartridge tape
-drives, and some other devices cannot be verified.
+Similar to the @samp{--unlink-first} option, removing existing
+directory hierarchies before extracting directories of the same name
+from the archive. @xref{Writing}.
-@table @samp
-@item --verify
-@itemx -W
-Checks for discrepancies in the archive immediately after it is
-written. Use in conjunction with @samp{tar --create}.
-@end table
+@item --remove-files
-@node Comparing, , Write Verification, Insuring Accuracy
-@section Comparing an Archive with the File System
-@cindex Verifying the currency of an archive
+Directs @code{tar} to remove the source file from the file system after
+appending it to an archive. @FIXME-xref{}.
-@samp{tar --compare} compares archive members in an existing archive
-with their counterparts in the file system, and reports differences in
-file size, mode, owner, modification date and contents. If a file is
-represented in the archive but does not exist in the file system,
-@code{tar} reports a difference.
-
-If you use @var{file-name} arguments in conjunction with @samp{tar
---compare}, @code{tar} compares the archived versions of the files
-specified with their counterparts in the file system. If you specify
-a file that is not in the archive, @code{tar} will report an error. If
-you don't specify any files, @code{tar} compares all the files in the
-archive.
+@item --rsh-command=@var{cmd}
-Because @code{tar} only checks files in the archive against files in
-the file system, and not vice versa, it ignores files in the file
-system that do not exist in the archive.
+Notifies @code{tar} that is should use @var{cmd} to communicate with remote
+devices. @FIXME-xref{}.
-The following example compares the archive members @file{larry},
-@file{moe} and @file{curly} in the archive @file{stooges} with files
-of the same name in the file system.
+@item --same-order
+@itemx --preserve-order
+@itemx -s
-@example
-tar --compare --file=stooges larry moe curly
-@end example
+This option is an optimization for @code{tar} when running on machines with
+small amounts of memory. It informs @code{tar} that the list of file
+arguments has already been sorted to match the order of files in the
+archive. @xref{Reading}.
-@noindent
-If a file, for example @file{curly}, did not exist in the archive,
-@code{tar} would report an error, as follows:
+@item --same-owner
-@example
-curly: does not exist
-@end example
+When extracting an archive, @code{tar} will attempt to preserve the owner
+specified in the @code{tar} archive with this option present. @FIXME-xref{}.
-@node Selecting Archive Members, User Interaction, Insuring Accuracy, Top
-@chapter Selecting Archive Members
-@cindex Specifying files to act on
-@cindex Specifying archive members
+@item --same-permissions
-@dfn{File-name arguments} specify which files in the file system
-@code{tar} operates on, when creating or adding to an archive, or
-which archive members @code{tar} operates on, when reading or
-deleting from an archive. (@pxref{Reading and Writing}.)
+(See @samp{--preserve-permissions}; @pxref{Writing}.)
-To specify file names, you can include them as the last arguments on
-the command line, as follows:
-@example
-tar @var{operation} [@var{option1} @var{option2} ..] [@var{file-name-1} @var{file-name-2} ...]
-@end example
+@item --show-omitted-dirs
-If you specify a directory name as a file name argument, all the files
-in that directory are operated on by @code{tar}.
+Instructs @code{tar} to mention directories its skipping over when operating
+on a @code{tar} archive. @FIXME-xref{}.
-If you do not specify files when @code{tar} is invoked, @code{tar}
-operates on all the non-directory files in the working directory (if
-the operation is @samp{--create}), all the archive members in the
-archive (if a read operation is specified), or does nothing (if any
-other operation is specified).
+@item --sparse
+@itemx -S
-@menu
-* File Name Lists:: Reading File Names from a File
-* File Name Interpretation:: this needs a better title
-* File Exclusion:: so does this
-@end menu
+Invokes a GNU extension when adding files to an archive that handles
+sparse files efficiently. @FIXME-xref{}.
-@node File Name Lists, File Name Interpretation, Selecting Archive Members, Selecting Archive Members
-@section Reading a List of File Names from a File
-@cindex Lists of file names
-@cindex File-name arguments, alternatives
+@item --starting-file=@var{name}
+@itemx -K @var{name}
-To read file names from a file on the file system, instead of from the
-command line, use the @samp{--files-from=@var{file}} option. If you
-specify @samp{-} as @var{file}, the file names are read from standard
-input. Note that using both @samp{--files-from=-} and @samp{--file=-}
-in the same command will not work unless the operation is
-@samp{--create}. @xref{Archive Name}, for an explanation of the
-@samp{--file} option.
+This option affects extraction only; @code{tar} will skip extracting
+files in the archive until it finds one that matches @var{name}.
+@xref{Scarce}.
-@table @samp
-@item --files-from=@var{file}
-@itemx -T @var{file}
-Reads file-name arguments from a file on the file system, instead of
-from the command line. Use in conjunction with any operation.
-@end table
+@item --suffix=@var{suffix}
-@node File Name Interpretation, File Exclusion, File Name Lists, Selecting Archive Members
-@section File Name Interpretation
-@cindex File Names, interpreting
+Alters the suffix @code{tar} uses when backing up files from the default
+@samp{~}. @FIXME-xref{}.
-@c <<<<add some text -ringo
+@item --tape-length=@var{num}
+@itemx -L @var{num}
-@menu
-* Absolute File Names::
-* Changing Working Directory::
-* Archiving with Symbolic Links:: Archiving Using Symbolic Links
-@end menu
+Specifies the length of tapes that @code{tar} is writing as being
+@w{@var{num} x 1024} bytes long. @FIXME-xref{}.
-@node Absolute File Names, Changing Working Directory, File Name Interpretation, File Name Interpretation
-@subsection Storing and Extracting Files Relative to Root
+@item --to-stdout
+@itemx -O
-@c <<< is this what this does, or does it just preserve the slash?
-@c <<< is it still called --absolute-paths?
+During extraction, @code{tar} will extract files to stdout rather than to the
+file system. @xref{Writing}.
-@c To archive or extract files relative to the root directory, specify
-@c the @samp{--absolute-paths} option.
+@item --totals
-@c Normally, @code{tar} acts on files relative to the working
-@c directory---ignoring superior directory names when archiving, and
-@c ignoring leading slashes when extracting.
+Displays the total number of bytes written after creating an archive.
+@FIXME-xref{}.
-@c When you specify @samp{--absolute-paths}, @code{tar} stores file names
-@c including all superior directory names, and preserves leading slashes.
-@c If you only invoked @code{tar} from the root directory you would never
-@c need the @samp{--absolute-paths} option, but using this option may be
-@c more convenient than switching to root.
+@item --touch
+@itemx -m
-@c >>> should be an example in the tutorial/wizardry section using this
-@c >>> to transfer files between systems.
+Sets the modification time of extracted files to the extraction time,
+rather than the modification time stored in the archive.
+@xref{Writing}.
-@c >>> is write access an issue?
+@item --uncompress
-@table @samp
-@item --absolute-paths
-Preserves full file names (inclusing superior dirctory names) when
-archiving files. Preserves leading slash when extracting files.
-@end table
+(See @samp{--compress}; @FIXME-pxref{}.)
-@node Changing Working Directory, Archiving with Symbolic Links, Absolute File Names, File Name Interpretation
-@subsection Changing the Working Directory Within a List of File-names
-@cindex Directory, changing in mid-stream
-@cindex Working directory, specifying
+@item --ungzip
-To change working directory in the middle of a list of file names,
-(either on the command line or in a file specified using
-@samp{--files-from}), use @samp{--directory=@var{directory}}. This will
-change the working directory to the directory @var{directory} after
-that point in the list. For example,
+(See @samp{--gzip}; @FIXME-pxref{}.)
-@example
-tar --create iggy ziggy --directory=baz melvin
-@end example
+@item --unlink-first
+@itemx -U
-@noindent
-will place the files @file{iggy} and @file{ziggy} from the current
-directory into the archive, followed by the file @file{melvin} from
-the directory @file{baz}. This option is especially useful when you
-have several widely separated files that you want to store in the same
-directory in the archive.
-
-Note that the file @file{melvin} is recorded in the archive under the
-precise name @file{melvin}, @emph{not} @file{baz/melvin}. Thus, the
-archive will contain three files that all appear to have come from the
-same directory; if the archive is extracted with plain @samp{tar
---extract}, all three files will be written in the current directory.
+Directs @code{tar} to remove the corresponding file from the file system
+before extracting it from the archive. @xref{Writing}.
-Contrast this with the command
+@item --use-compress-program=@var{prog}
-@example
-tar -c iggy ziggy bar/melvin
-@end example
+Instructs @code{tar} to access the archive through @var{prog}, which is
+presumed to be a compression program of some sort. @FIXME-xref{}.
-@noindent
-which records the third file in the archive under the name
-@file{bar/melvin} so that, if the archive is extracted using @samp{tar
---extract}, the third file will be written in a subdirectory named
-@file{bar}.
+@item --verbose
+@itemx -v
-@table @samp
-@item --directory=@file{directory}
-@itemx -C @file{directory}
-Changes the working directory.
-@end table
+Specifies that @code{tar} should be more verbose about the operations its
+performing. This option can be specified multiple times for some
+operations to increase the amount of information displayed. @FIXME-xref{}.
-@c <<<need to test how extract deals with this, and add an example -ringo
+@item --verify
+@itemx -W
-@node Archiving with Symbolic Links, , Changing Working Directory, File Name Interpretation
-@subsection Archiving Using Symbolic Links
-@cindex File names, using symbolic links
-@cindex Symbolic link as file name
+Verifies that the archive was correctly written when creating an
+archive. @FIXME-xref{}.
-@samp{--dereference} is used with @samp{tar --create}, and causes
-@code{tar} to archive files which are referenced by a symbolic link,
-using the name of the link as the file name.
+@item --version
-<<<this needs to be checked by MIB and then re-written, with an example
-The name under which the file is stored in the file system is not
-recorded in the archive. To record both the symbolic link name and
-the file name in the system, archive the file under both names. If
-all links were recorded automatically by @code{tar}, an extracted file
-might be linked to a file name that no longer exists in the file
-system.
+@code{tar} will print an informational message about what version it is and a
+copyright message, some credits, and then exit. @FIXME-xref{}.
-@c <<< is the following still true? - ringo
-If a linked-to file is encountered again by @code{tar} while creating
-the same archive, an entire second copy of it will be stored. This
-could be considered a bug.
+@item --volno-file=@var{file}
-@table @samp
-@item --dereference
-@itemx -h
-Stores files referenced by a symbolic link, using the name of the link
-as the file name. Use in conjunction with any write operation.
+Used in conjunction with @samp{--multi-volume}. @code{tar} will keep track
+of which volume of a multi-volume archive its working in @var{file}.
+@FIXME-xref{}.
@end table
-@node File Exclusion, , File Name Interpretation, Selecting Archive Members
-@section Selecting Files by Characteristic
-@cindex File names, excluding files by
-@cindex Excluding files by name and pattern
-@cindex Excluding files by file system
-@cindex File system boundaries, not crossing
-@cindex Excluding file by age
-@cindex Modification time, excluding files by
-@cindex Age, excluding files by
+@node Short Option Summary, , Option Summary, All Options
+@subsection Short Options Cross Reference
-To avoid crossing file system boundaries when archiving parts of a
-directory tree, use @samp{--one-file-system}. This option only affects
-files that are archived because they are in a directory that is being
-archived; files explicitly named on the command line are archived
-regardless of where they reside.
+Here is an alphabetized list of all of the short option forms, matching
+them with the equivalent long option.
-This option is useful for making full or incremental archival backups
-of a file system.
+@table @kbd
-If this option is used in conjunction with @samp{--verbose}, files that
-are excluded are mentioned by name on the standard error.
+@item -A
-@table @samp
-@item --one-file-system
-@itemx -l
-Prevents @code{tar} from crossing file system boundaries when
-archiving. Use in conjunction with any write operation.
-@end table
+@samp{--concatenate}
-To avoid operating on files whose names match a particular pattern,
-use the @samp{--exclude=@var{pattern}} or
-@samp{--exclude-from=@var{file}} options.
+@item -B
-When you specify the @samp{--exclude=@var{pattern}} option, @code{tar}
-ignores files which match the @var{pattern}, which can be a single
-file name or a more complex expression. Thus, if you invoke
-@code{tar} with @samp{tar --create --exclude=*.o}, no files whose names
-end in @file{.o} are included in the archive.
-@c <<< what other things can you use besides "*"?
+@samp{--read-full-records}
-@samp{--exclude-from=@var{file}} acts like @samp{--exclude}, but
-specifies a file @var{file} containing a list of patterns. @code{tar}
-ignores files with names that fit any of these patterns.
+@item -C
-You can use either option more than once in a single command.
+@samp{--directory}
-@table @samp
-@item --exclude=@var{pattern}
-Causes @code{tar} to ignore files that match the @var{pattern}.
+@item -F
-@item --exclude-from=@var{file}
-Causes @code{tar} to ignore files that match the patterns listed in
-@var{file}.
-@end table
-@c --exclude-from used to be "--exclude", --exclude didn't used to exist.
+@samp{--info-script}
-To operate only on files with modification or status-change times
-after a particular date, use @samp{--after-date=@var{date}}. You can
-use this option with @samp{tar --create} or @samp{tar --add-file} to
-insure only new files are archived, or with @samp{tar --extract} to
-insure only recent files are resurrected. @refill
-@c --after-date @var{date} or --newer @var{date}
+@item -G
-@samp{--newer-mtime=@var{date}} acts like @samp{--after-date=@var{date}},
-but tests just the modification times of the files, ignoring
-status-change times.
+@samp{--incremental}
-@c <<<need example of --newer-mtime with quoted argument
-Remember that the entire date argument should be quoted if it contains
-any spaces.
+@item -K
+@samp{--starting-file}
-@strong{Please Note:} @samp{--after-date} and @samp{--newer-mtime}
-should not be used for incremental backups. Some files (such as those
-in renamed directories) are not selected up properly by these options.
-@c xref to incremental backup chapter when node name is decided.
+@item -L
-@table @samp
-@item --after-date=@var{date}
-@itemx --newer=@var{date}
-@itemx -N @var{date}
-Acts on files only if their modification or inode-changed times are
-later than @var{date}. Use in conjunction with any operation.
-@item --newer-mtime=@var{date}
-Acts like @samp{--after-date}, but only looks at modification times.
-@end table
+@samp{--tape-length}
-@c <<< following is the getdate date format --- needs to be re-written,
-@c <<< made a sub-node:
+@item -M
-Time/Date Formats Accepted by getdate
-(omitting obscure constructions)
+@samp{--multi-volume}
-The input consists of one or more of: time zone day date year
-in any order.
+@item -N
-Those in turn consist of (`|' and `/' mean `or', `[]' means `optional'):
+@samp{--newer}
-time: H am/pm | H:M [am/pm] | H:M:S [am/pm]
-zone: timezone-name | timezone-name dst
-day: day-name | day-name, | N day-name
-date: M/D | M/D/Y | month-name D | month-name D, Y | D month-name | D month-name Y
-year: Y
+@item -O
-am can also be a.m., pm can also be p.m.
-case and spaces around punctuation are not significant.
-month and day names can be abbreviated. >>>
+@samp{--to-stdout}
-@node User Interaction, Backups and Restoration, Selecting Archive Members, Top
-@chapter User Interaction
-@cindex Getting more information during the operation
-@cindex Information during operation
-@cindex Feedback from @code{tar}
+@item -P
-Once you have typed a @code{tar}command, it is usually performed
-without any further information required of the user, or provided by
-@code{tar}. The following options allow you to generate progress and
-status information during an operation, or to confirm operations on
-files as they are performed.
+@samp{--absolute-names}
-@menu
-* Additional Information::
-* Interactive Operation::
-@end menu
+@item -R
-@node Additional Information, Interactive Operation, User Interaction, User Interaction
-@section Progress and Status Information
-@cindex Progress information
-@cindex Status information
-@cindex Information on progress and status of operations
-@cindex Verbose operation
-@cindex Record number where error occured
-@cindex Error message, record number of
-@cindex Version of the @code{tar} program
+@samp{--block-number}
-Typically, @code{tar} performs most operations without reporting any
-information to the user except error messages. If you have
-encountered a problem when operating on an archive, however, you may
-need more information than just an error message in order to solve the
-problem. The following options can be helpful diagnostic tools.
-
-When used with most operations, @samp{--verbose} causes @code{tar} to
-print the file names of the files or archive members it is operating
-on. When used with @samp{tar --list}, the verbose option causes
-@code{tar} to print out an @samp{ls -l} type listing of the files in
-the archive.
-
-Verbose output appears on the standard output except when an archive
-is being written to the standard output (as with @samp{tar --create
---file=- --verbose}). In that case @code{tar} writes verbose output to
-the standard error stream.
+@item -S
-@table @samp
-@item --verbose
-@itemx -v
-Prints the names of files or archive members as they are being
-operated on. Can be used in conjunction with any operation. When
-used with @samp{--list}, generates an @samp{ls -l} type listing.
-@end table
+@samp{--sparse}
-To find out where in an archive a message was triggered, use
-@samp{--record-number}. @samp{--record-number} causes @code{tar} to
-print, along with every message it produces, the record number within
-the archive where the message was triggered.
+@item -T
-This option is especially useful when reading damaged archives, since
-it helps pinpoint the damaged sections. It can also be used with
-@samp{tar --list} when listing a file-system backup tape, allowing you
-to choose among several backup tapes when retrieving a file later, in
-favor of the tape where the file appears earliest (closest to the
-front of the tape).
-@c <<< xref when the node name is set and the backup section written
+@samp{--files-from}
-@table @samp
-@item --record-number
-@itemx -R
-Prints the record number whenever a message is generated by
-@code{tar}. Use in conjunction with any operation.
-@end table
+@item -U
-@c rewrite below
-To print the version number of the @code{tar} program, use @samp{tar
---version}. @code{tar} prints the version number to the standard
-error. For example:
+@samp{--unlink-first}
-@example
-tar --version
-@end example
+@item -V
-@noindent
-might return:
+@samp{--label}
-@example
-GNU tar version 1.09
-@end example
-@c used to be an option. has been fixed.
+@item -W
-@node Interactive Operation, , Additional Information, User Interaction
-@section Asking for Confirmation During Operations
-@cindex Interactive operation
+@samp{--verify}
-Typically, @code{tar} carries out a command without stopping for
-further instructions. In some situations however, you
-may want to exclude some files and archive members from the operation
-(for instance if disk or storage space is tight). You can do this by
-excluding certain files automatically (@pxref{File Exclusion}), or by
-performing an operation interactively, using the @samp{--interactive}
-operation.
-
-When the @samp{--interactive} option is specified, @code{tar} asks for
-confirmation before reading, writing, or deleting each file it
-encounters while carrying out an operation. To confirm the action you
-must type a line of input beginning with @samp{y}. If your input line
-begins with anything other than @samp{y}, @code{tar} skips that file.
-
-Commands which might be useful to perform interactively include
-appending files to an archive, extracting files from an archive,
-deleting a file from an archive, and deleting a file from disk during
-an incremental restore.
+@item -X
-If @code{tar} is reading the archive from the standard input,
-@code{tar} opens the file @file{/dev/tty} to support the interactive
-communications.
-<<< this aborts if you won't OK the working directory. this is a bug. -ringo
+@samp{--exclude-from}
-@table @samp
-@item --interactive
-@itemx --confirmation
-@itemx -w
-Asks for confirmation before reading, writing or deleting an archive
-member (when listing, comparing or writing an archive or deleting
-archive members), or before writing or deleting a file (when
-extracting an archive).
-@end table
+@item -Z
-@node Backups and Restoration, Media, User Interaction, Top
-@chapter Performing Backups and Restoring Files
+@samp{--compress}
-To @dfn{back up} a file system means to create archives that contain
-all the files in that file system. Those archives can then be used to
-restore any or all of those files (for instance if a disk crashes or a
-file is accidently deleted). File system @dfn{backups} are also
-called @dfn{dumps}.
+@item -b
-@menu
-* Backup Levels:: Levels of backups
-* Backup Scripts:: Using scripts to perform backups
- and restoration
-* incremental and listed-incremental:: The --incremental
- and --listed-incremental Options
-* Problems:: Some common problems and their solutions
-@end menu
+@samp{--blocking-factor}
-@node Backup Levels, Backup Scripts, Backups and Restoration, Backups and Restoration
-@section Levels of Backups
+@item -c
-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
-creating a full dump every day. This strategy, however, would waste a
-substantial amount of archive media and user time, as unchanged files
-are daily re-archived.
+@samp{--create}
-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
-one} dump archives all the files that have changed since the last full
-dump.
+@item -d
-A typical dump strategy would be to perform a full dump once a week,
-and a level one dump once a day. This means some versions of files
-will in fact be archived more than once, but this dump strategy makes
-it possible to restore a file system to within one day of accuracy by
-only extracting two archives---the last weekly (full) dump and the
-last daily (level one) dump. The only information lost would be in
-files changed or created since the last daily backup. (Doing dumps
-more than once a day is usually not worth the trouble).
+@samp{--compare}
-@node Backup Scripts, incremental and listed-incremental, Backup Levels, Backups and Restoration
-@section Using Scripts to Perform Backups and Restoration
+@item -f
-GNU @code{tar} comes with scripts you can use to do full and level-one
-dumps. Using scripts (shell programs) to perform backups and
-restoration is a convenient and reliable alternative to typing out
-file name lists and @code{tar} commands by hand.
+@samp{--file}
-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. @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}. 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. @xref{Scripted Restoration}, for more information
-on running the restoration script. @xref{Scripted Backups}, for more
-information on running the backup scripts.
+@item -g
-@emph{Please Note:} The backup scripts and the 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. @xref{incremental
-and listed-incremental}, before making such an attempt.
+@samp{--listed-incremental}
-@c shorten node names
-@menu
-* Backup Parameters:: Setting parameters for backups and restoration
-* Scripted Backups:: Using the backup scripts
-* Scripted Restoration:: Using the restore script
-@end menu
+@item -h
-@node Backup Parameters, Scripted Backups, Backup Scripts, Backup Scripts
-@subsection Setting Parameters for Backups and Restoration
+@samp{--dereference}
-The file @file{backup-specs} specifies backup parameters for the
-backup and restoration scripts provided with @code{tar}. You must
-edit @file{backup-specs} to fit your system configuration and schedule
-before using these scripts.
+@item -i
-@c <<< This about backup scripts needs to be written:
-@c <<<BS is a shell script .... thus ... @file{backup-specs} is in shell
-@c script syntax. @xref{Script Syntax}, for an explanation of this
-@c syntax.
+@samp{--ignore-zeros}
-@c whats a parameter .... looked at by the backup scripts ... which will
-@c be expecting to find ... now syntax ... value is linked to lame ...
-@c @file{backup-specs} specifies the following parameters:
+@item -k
+@samp{--keep-old-files}
-@table @code
-@item ADMINISTRATOR
-The user name of the backup administrator.
+@item -l
-@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}.
+@samp{--one-file-system}
-@item TAPE_FILE
-The device @code{tar} writes the archive to. This device should be
-attached to the host on which the dump scripts are run.
-@c <<< examples for all ...
+@item -m
-@item TAPE_STATUS
-The command to use to obtain the status of the archive device,
-including error count. On some tape drives there may not be such a
-command; in that case, simply use `TAPE_STATUS=false'.
+@samp{--touch}
-@item BLOCKING
-The blocking factor @code{tar} will use when writing the dump archive.
-@xref{Blocking Factor}.
+@item -o
-@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
-included, regardless of how they may look to other networked machines.
-Subdirectories on other file systems will be ignored.
+@samp{--portability}
-The host name specifies which host to run @code{tar} on, and should
-normally be the host that actually contains the file system. However,
-the host machine must have GNU @code{tar} installed, and must be able
-to access the directory containing the backup scripts and their
-support files using the same file name that is used on the machine
-where the scripts are run (ie. what @code{pwd} will print when in that
-directory on that machine). If the host that contains the file system
-does not have this capability, you can specify another host as long as
-it can access the file system through NFS.
+@item -p
-@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.
-@c <<<same file name, be specific. through nfs ...
-@end table
+@samp{--preserve-permissions}
-@menu
-* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-@end menu
+@item -r
-@node backup-specs example, Script Syntax, Backup Parameters, Backup Parameters
-@subsubsection An Example Text of @file{Backup-specs}
+@samp{--append}
-The following is the text of @file{backup-specs} as it appears at FSF:
+@item -s
-@example
-# site-specific parameters for file system backup.
+@samp{--same-order}
-ADMINISTRATOR=friedman
-BACKUP_HOUR=1
-TAPE_FILE=/dev/nrsmt0
-TAPE_STATUS="mts -t $TAPE_FILE"
-BLOCKING=124
-BACKUP_DIRS="
- albert:/fs/fsf
- apple-gunkies:/gd
- albert:/fs/gd2
- albert:/fs/gp
- geech:/usr/jla
- churchy:/usr/roland
- albert:/
- albert:/usr
- apple-gunkies:/
- apple-gunkies:/usr
- gnu:/hack
- gnu:/u
- apple-gunkies:/com/mailer/gnu
- apple-gunkies:/com/archive/gnu"
+@item -t
-BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
+@samp{--list}
-@end example
+@item -u
-@node Script Syntax, , backup-specs example, Backup Parameters
-@subsubsection Syntax for @file{Backup-specs}
+@samp{--update}
-@file{backup-specs} is in shell script syntax. The following
-conventions should be considered when editing the script:
-@c <<< "conventions?"
+@item -v
-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.
+@samp{--verbose}
-A quoted string typically cannot contain wildcards. In
-@file{backup-specs}, however, the parameters BACKUP_DIRS and
-BACKUP_FILES can contain wildcards.
+@item -w
-@node Scripted Backups, Scripted Restoration, Backup Parameters, Backup Scripts
-@subsection Using the Backup Scripts
+@samp{--interactive}
-The syntax for running a backup script is:
+@item -x
-@example
-@file{script-name} [@var{time-to-be-run}]
-@end example
+@samp{--extract}
-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} (@pxref{Script Syntax}).
-
-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 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. @xref{Scripted Restoration}.
-
-@c <<<have file names changed? -ringo
-The backup scripts write two files on the file system. The first is a
-record file in @file{/etc/tar-backup/}, which is used by the scripts
-to store and retrieve information about which files were dumped. This
-file is not meant to be read by humans, and should not be deleted by
-them. @xref{incremental and listed-incremental}, for a more
-detailed explanation of this file.
+@item -z
-The second file is a log file containing the names of the file systems
-and files dumped, what time the backup was made, and any error
-messages that were generated, as well as how much space was left in
-the media volume after the last volume of the archive was written.
-You should check this log file after every backup. The file name is
-@file{log-@var{mmm-ddd-yyyy}-level-1} or
-@file{log-@var{mmm-ddd-yyyy}-full}.
+@samp{--gzip}
-The script also prints the name of each system being dumped to the
-standard output.
-@c <<<the section on restore scripts is commented out.
-@c <<< a section on non-scripted testore mya be a good idea
-@ignore
-@node Scripted Restoration, , Scripted Backups, Backup Scripts
-@subsection Using the Restore Script
-@c subject to change as things develop
+@end table
-To restore files that were archived using a scripted backup, use the
-@code{restore} script. The syntax for the script is:
+@node help, verbose, All Options, tar invocation
+@section GNU @code{tar} documentation
+Being careful, the first thing is really checking that you are using GNU
+@code{tar}, indeed. The @value{op-version} option will generate a message
+giving confirmation that you are using GNU @code{tar}, with the precise
+version of GNU @code{tar} you are using. @code{tar} identifies itself
+and prints the version number to the standard output, then immediately
+exits successfully, without doing anything else, ignoring all other
+options. For example, @w{@samp{tar --version}} might return:
-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.
+@example
+tar (GNU tar) @value{VERSION}
+@end example
-You should start the restore script with the media containing the
-first volume of the archive mounted. The script will prompt for other
-volumes as they are needed. If the archive is on tape, you don't need
-to rewind the tape to to its beginning---if the tape head is
-positioned past the beginning of the archive, the script will rewind
-the tape as needed. @xref{Media}, for a discussion of tape
-positioning.
+@noindent
+The first occurrence of @samp{tar} in the result above is the program
+name in the package (for example, @code{rmt} is another program), while
+the second occurrence of @samp{tar} is the name of the package itself,
+containing possibly many programs. The package is currently named
+@samp{tar}, after the name of the main program it contains@footnote{There
+are plans to merge the @code{cpio} and @code{tar} packages into a single one
+which would be called @code{paxutils}. So, who knows if, one of this days,
+the @value{op-version} would not yield @w{@samp{tar (GNU paxutils) 3.2}}}.
+
+Another thing you might want to do is checking the spelling or meaning
+of some particular @code{tar} option, without resorting to this manual,
+for once you have carefully read it. GNU @code{tar} has a short help
+feature, triggerable through the @value{op-help} option. By using this
+option, @code{tar} will print a usage message listing all available
+options on standard output, then exit successfully, without doing
+anything else and ignoring all other options. Even if this is only a
+brief summary, it may be several screens long. So, if you are not
+using some kind of scrollable window, you might prefer to use something
+like:
-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.
+@example
+$ @kbd{tar --help | less}
+@end example
-@quotation
-@strong{Warning:}The script will delete files from the active file
-system if they were not in the file system when the archive was made.
-@end quotation
+@noindent
+presuming, here, that you like using @code{less} for a pager. Other
+popular pagers are @code{more} and @code{pg}. If you know about some
+@var{keyword} which interests you and do not want to read all the
+@value{op-help} output, another common idiom is doing:
-@xref{incremental and listed-incremental}, for an explanation of how
-the script makes that determination.
-@c this may be an option, not a given
-@end ignore
+@example
+tar --help | grep @var{keyword}
+@end example
-@node incremental and listed-incremental, Problems, Backup Scripts, Backups and Restoration
-@section The @code{--incremental} and @code{--listed-incremental} Options
+@noindent
+for getting only the pertinent lines.
+
+The perceptive reader would have noticed some contradiction in the
+previous paragraphs. It is written that both @value{op-version} and
+@value{op-help} print something, and have all other options ignored. In
+fact, they cannot ignore each other, and one of them has to win. We do
+not specify which is stronger, here; experiment if you really wonder!
+
+The short help output is quite succint, and you might have to get back
+to the full documentation for precise points. If you are reading this
+paragraph, you already have the @code{tar} manual in some form. This
+manual is available in printed form, as a kind of small book. It may
+printed out of the GNU @code{tar} distribution, provided you have @TeX{}
+already installed somewhere, and a laser printer around. Just configure
+the distribution, execute the command @w{@samp{make dvi}}, then print
+@file{doc/tar.dvi} the usual way (contact your local guru to know how).
+If GNU @code{tar} has been conveniently installed at your place, this
+manual is also available in interactive, hypertextual form as an Info
+file. Just call @w{@samp{info tar}} or, if you do not have the
+@code{info} program handy, use the Info reader provided within GNU
+Emacs, calling @samp{tar} from the main Info menu.
+
+There is currently no @code{man} page for GNU @code{tar}. If you observe
+such a @code{man} page on the system you are running, either it does not
+long to GNU @code{tar}, or it has not been produced by GNU. Currently,
+GNU @code{tar} documentation is provided in Texinfo format only, if we
+except, of course, the short result of @kbd{tar --help}.
+
+@node verbose, interactive, help, tar invocation
+@section Checking @code{tar} progress
-@samp{--incremental} is used in conjunction with @samp{--create},
-@samp{--extract} or @samp{--list} when backing up and restoring file
-systems. An archive cannot be extracted or listed with the
-@samp{--incremental} option specified unless it was created with the
-option specified. This option should only be used by a script, not by
-the user, and is usually disregarded in favor of
-@samp{--listed-incremental}, which is described below.
+@cindex Progress information
+@cindex Status information
+@cindex Information on progress and status of operations
+@cindex Verbose operation
+@cindex Block number where error occured
+@cindex Error message, block number of
+@cindex Version of the @code{tar} program
-@samp{--incremental} in conjunction with @samp{--create} causes
-@code{tar} to write, at the beginning of the archive, an entry for
-each of the directories that will be archived. The entry for a
-directory includes a list of all the files in the directory at the
-time the archive was created and a flag for each file indicating
-whether or not the file is going to be put in the archive.
-
-Note that this option causes @code{tar} to create a non-standard
-archive that may not be readable by non-GNU versions of the @code{tar}
-program.
+@cindex Getting more information during the operation
+@cindex Information during operation
+@cindex Feedback from @code{tar}
-@samp{--incremental} in conjunction with @samp{--extract} causes
-@code{tar} to read the lists of directory contents previously stored
-in the archive, @emph{delete} files in the file system that did not
-exist in their directories when the archive was created, and then
-extract the files in the archive.
+Typically, @code{tar} performs most operations without reporting any
+information to the user except error messages. When using @code{tar}
+with many options, particularly ones with complicated or
+difficult-to-predict behavior, it is possible to make serious mistakes.
+@code{tar} provides several options that make observing @code{tar}
+easier. These options cause @code{tar} to print information as it
+progresses in its job, and you might want to use them just for being
+more careful about what is going on, or merely for entertaining
+yourself. If you have encountered a problem when operating on an
+archive, however, you may need more information than just an error
+message in order to solve the problem. The following options can be
+helpful diagnostic tools.
+
+Normally, the @value{op-list} command to list an archive prints just
+the file names (one per line) and the other commands are silent.
+When used with most operations, the @value{op-verbose} option causes
+@code{tar} to print the name of each file or archive member as it
+is processed. This and the other options which make @code{tar} print
+status information can be useful in monitoring @code{tar}.
+
+With @value{op-create} or @value{op-extract}, @value{op-verbose} used once
+just prints the names of the files or members as they are processed.
+Using it twice causes @code{tar} to print a longer listing (reminiscent
+of @samp{ls -l}) for each member. Since @value{op-list} already prints
+the names of the members, @value{op-verbose} used once with @value{op-list}
+causes @code{tar} to print an @samp{ls -l} type listing of the files
+in the archive. The following examples both extract members with
+long list output:
-This behavior is convenient when restoring a damaged file system from
-a succession of incremental backups: it restores the entire state of
-the file system to that which obtained when the backup was made. If
-@samp{--incremental} isn't specified, the file system will probably
-fill up with files that shouldn't exist any more.
+@example
+$ @kbd{tar --extract --file=archive.tar --verbose --verbose}
+$ @kbd{tar xvv archive.tar}
+@end example
-@samp{--incremental} in conjunction with @samp{--list}, causes
-@code{tar} to print, for each directory in the archive, the list of
-files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is followed
-by an additional null and a newline to indicate the end of the data.
+Verbose output appears on the standard output except when an archive is
+being written to the standard output, as with @samp{tar --create
+--file=- --verbose} (@samp{tar cfv -}, or even @samp{tar cv}---if the
+installer let standard output be the default archive). In that case
+@code{tar} writes verbose output to the standard error stream.
+
+The @value{op-totals} option---which is only meaningful when used with
+@value{op-create}---causes @code{tar} to print the total
+amount written to the archive, after it has been fully created.
+
+The @value{op-checkpoint} option prints an occasional message
+as @code{tar} reads or writes the archive. In fact, it print
+directory names while reading the archive. It is designed for
+those who don't need the more detailed (and voluminous) output of
+@value{op-block-number}, but do want visual confirmation that @code{tar}
+is actually making forward progress.
-@samp{--listed-incremental}=@var{file} acts like @samp{--incremental},
-but when used in conjunction with @samp{--create} will also cause
-@code{tar} to use the file @var{file}, which contains information
-about the state of the file system at the time of the last backup, to
-decide which files to include in the archive being created. That file
-will then be updated by @code{tar}. If the file @var{file} does not
-exist when this option is specified, @code{tar} will create it, and
-include all appropriate files in the archive.
+@FIXME{There is some confusion here. It seems that -R once wrote a
+message at @samp{every} record read or written.}
+
+The @value{op-show-omitted-dirs} option, when reading an archive---with
+@value{op-list} or @value{op-extract}, for example---causes a message
+to be printed for each directory in the archive which is skipped.
+This happens regardless of the reason for skipping: the directory might
+not have been named on the command line (implicitly or explicitly),
+it might be excluded by the use of the @value{op-exclude} option, or
+some other reason.
+
+If @value{op-block-number} is used, @code{tar} prints, along with every
+message it would normally produce, the block number within the archive
+where the message was triggered. Also, supplementary messages are
+triggered when reading blocks full of NULs, or when hitting end of file on
+the archive. As of now, if the archive if properly terminated with a NUL
+block, the reading of the file may stop before end of file is met, so the
+position of end of file will not usually show when @value{op-block-number}
+is used. Note that GNU @code{tar} drains the archive before exiting when
+reading the archive from a pipe.
-The file @var{file}, which is archive independent, contains the date
-it was last modified and a list of devices, inode numbers and
-directory names. @code{tar} will archive files with newer mod dates
-or inode change times, and directories with an unchanged inode number
-and device but a changed directory name. The file is updated after
-the files to be archived are determined, but before the new archive is
-actually created.
+This option is especially useful when reading damaged archives, since
+it helps pinpoint the damaged sections. It can also be used with
+@value{op-list} when listing a file-system backup tape, allowing you to
+choose among several backup tapes when retrieving a file later, in
+favor of the tape where the file appears earliest (closest to the
+front of the tape). @FIXME-xref{when the node name is set and the
+backup section written}.
-@c <<< this section needs to be written
-@node Problems, , incremental and listed-incremental, Backups and Restoration
-@section Some Common Problems and their Solutions
+@node interactive, , verbose, tar invocation
+@section Asking for Confirmation During Operations
+@cindex Interactive operation
-errors from system:
-permission denied
-no such file or directory
-not owner
+Typically, @code{tar} carries out a command without stopping for
+further instructions. In some situations however, you may want to
+exclude some files and archive members from the operation (for instance
+if disk or storage space is tight). You can do this by excluding
+certain files automatically (@pxref{Choosing}), or by performing
+an operation interactively, using the @value{op-interactive} option.
+@code{tar} also accepts @samp{--confirmation} for this option.
+
+When the @value{op-interactive} option is specified, before
+reading, writing, or deleting files, @code{tar} first prints a message
+for each such file, telling what operation it intends to take, then asks
+for confirmation on the terminal. The actions which require
+confirmation include adding a file to the archive, extracting a file
+from the archive, deleting a file from the archive, and deleting a file
+from disk. To confirm the action, you must type a line of input
+beginning with @samp{y}. If your input line begins with anything other
+than @samp{y}, @code{tar} skips that file.
-errors from tar:
-directory checksum error
-header format error
+If @code{tar} is reading the archive from the standard input,
+@code{tar} opens the file @file{/dev/tty} to support the interactive
+communications.
-errors from media/system:
-i/o error
-device busy
+Verbose output is normally sent to standard output, separate from
+other error messages. However, if the archive is produced directly
+on standard output, then verbose output is mixed with errors on
+@code{stderr}. Producing the archive on standard output may be used
+as a way to avoid using disk space, when the archive is soon to be
+consumed by another process reading it, say. Some people felt the need
+of producing an archive on stdout, still willing to segregate between
+verbose output and error output. A possible approach would be using a
+named pipe to receive the archive, and having the consumer process to
+read from that named pipe. This has the advantage of letting standard
+output free to receive verbose output, all separate from errors.
+
+@node operations, Backups, tar invocation, Top
+@chapter GNU @code{tar} Operations
-@node Media, Quick Reference, Backups and Restoration, Top
-@chapter Tapes and Other Archive Media
+@menu
+* Basic tar::
+* Advanced tar::
+* extract options::
+* backup::
+* Applications::
+* looking ahead::
+@end menu
-Archives are usually written on dismountable media---tape cartridges,
-mag tapes, or floppy disks.
+@node Basic tar, Advanced tar, operations, operations
+@section Basic GNU @code{tar} Operations
+
+The basic @code{tar} operations, @value{op-create}, @value{op-list} and
+@value{op-extract}, are currently presented and described in the tutorial
+chapter of this manual. This section provides some complementary notes
+for these operations.
+
+@table @asis
+@item @value{op-create}
+
+Creating an empty archive would have some kind of elegance. One can
+initialize an empty archive and later use @value{op-append} for adding
+all members. Some applications would not welcome making an exception
+in the way of adding the first archive member. On the other hand,
+many people reported that it is dangerously too easy for @code{tar}
+to destroy a magnetic tape with an empty archive@footnote{This is well
+described in @cite{Unix-haters Handbook}, by Simson Garfinkel, Daniel
+Weise & Steven Strassmann, IDG Books, ISBN 1-56884-203-1.}. The two most
+common errors are:
+
+@enumerate
+@item
+Mistakingly using @code{create} instead of @code{extract}, when the
+intent was to extract the full contents of an archive. This error
+is likely: keys @kbd{c} and @kbd{x} are right next ot each other on
+the QWERTY keyboard. Instead of being unpacked, the archive then
+gets wholly destroyed. When users speak about @dfn{exploding} an
+archive, they usually mean something else :-).
+
+@item
+Forgetting the argument to @code{file}, when the intent was to create
+an archive with a single file in it. This error is likely because a
+tired user can easily add the @kbd{f} key to the cluster of option
+letters, by the mere force of habit, without realizing the full
+consequence of doing so. The usual consequence is that the single
+file, which was meant to be saved, is rather destroyed.
+@end enumerate
+
+So, recognizing the likelihood and the catastrophical nature of these
+errors, GNU @code{tar} now takes some distance from elegance, and
+cowardly refuses to create an archive when @value{op-create} option is
+given, there are no arguments besides options, and @value{op-files-from}
+option is @emph{not} used. To get around the cautiousness of GNU
+@code{tar} and nevertheless create an archive with nothing in it,
+one may still use, as the value for the @value{op-files-from} option,
+a file with no names in it, as shown in the following commands:
-The amount of data a tape or disk holds depends not only on its size,
-but also on how it is formatted. A 2400 foot long reel of mag tape
-holds 40 megabytes of data when formated at 1600 bits per inch. The
-physically smaller EXABYTE tape cartridge holds 2.3 gigabytes.
+@example
+@kbd{tar --create --file=empty-archive.tar --files-from=/dev/null}
+@kbd{tar cfT empty-archive.tar /dev/null}
+@end example
-Magnetic media are re-usable---once the archive on a tape is no longer
-needed, the archive can be erased and the tape or disk used over.
-Media quality does deteriorate with use, however. Most tapes or disks
-should be disgarded when they begin to produce data errors. EXABYTE
-tape cartridges should be disgarded when they generate an @dfn{error
-count} (number of non-usable bits) of more than 10k.
+@item @value{op-extract}
-Magnetic media are written and erased using magnetic fields, and
-should be protected from such fields to avoid damage to stored data.
-Sticking a floppy disk to a filing cabinet using a magnet is probably
-not a good idea.
+A socket is stored, within a GNU @code{tar} archive, as a pipe.
+
+@item @value{op-list}
+
+GNU @code{tar} now shows dates as @samp{1996-11-09}, while it used to
+show them as @samp{Nov 11 1996}. (One can revert to the old behavior by
+defining @code{USE_OLD_CTIME} in @file{src/list.c} before reinstalling.)
+But preferrably, people you should get used to ISO 8601 dates. Local
+American dates should be made available again with full date localisation
+support, once ready. In the meantime, programs not being localisable
+for dates should prefer international dates, that's really the way to go.
+Look up @url{http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html} if you
+are curious, it contains a detailed explanation of the ISO 8601 standard.
+
+@end table
+
+@node Advanced tar, extract options, Basic tar, operations
+@section Advanced GNU @code{tar} Operations
+
+Now that you have learned the basics of using GNU @code{tar}, you may
+want to learn about further ways in which @code{tar} can help you.
+
+This chapter presents five, more advanced operations which you probably
+won't use on a daily basis, but which serve more specialized functions.
+We also explain the different styles of options and why you might want
+to use one or another, or a combination of them in your @code{tar}
+commands. Additionally, this chapter includes options which allow you to
+define the output from @code{tar} more carefully, and provide help and
+error correction in special circumstances.
+
+@FIXME{check this after the chapter is actually revised to make sure
+it still introduces the info in the chapter correctly : ).}
@menu
-* Write Protection:: Write Protection
-* Tape Positioning:: Tape Positions and Tape Marks
+* Operations::
+* current state::
+* append::
+* update::
+* concatenate::
+* delete::
+* compare::
@end menu
-@node Write Protection, Tape Positioning, Media, Media
-@section Write Protection
+@node Operations, current state, Advanced tar, Advanced tar
+@subsection The Five Advanced @code{tar} Operations
+@UNREVISED
+
+In the last chapter, you learned about the first three operations to
+@code{tar}. This chapter presents the remaining five operations to
+@code{tar}: @samp{--append}, @samp{--update}, @samp{--concatenate},
+@samp{--delete}, and @samp{--compare}.
+
+You are not likely to use these operations as frequently as those
+covered in the last chapter; however, since they perform specialized
+functions, they are quite useful when you do need to use them. We
+will give examples using the same directory and files that you created
+in the last chapter. As you may recall, the directory is called
+@file{practice}, the files are @samp{jazz}, @samp{blues}, @samp{folk},
+@samp{rock}, and the two archive files you created are
+@samp{collection.tar} and @samp{music.tar}.
+
+We will also use the archive files @samp{afiles.tar} and
+@samp{bfiles.tar}. @samp{afiles.tar} contains the members @samp{apple},
+@samp{angst}, and @samp{aspic}. @samp{bfiles.tar} contains the members
+@samp{./birds}, @samp{baboon}, and @samp{./box}.
+
+Unless we state otherwise, all practicing you do and examples you follow
+in this chapter will take place in the @file{practice} directory that
+you created in the previous chapter; see @ref{prepare for examples}.
+(Below in this section, we will remind you of the state of the examples
+where the last chapter left them.)
+
+The five operations that we will cover in this chapter are:
+
+@table @kbd
+@item --append
+@itemx -r
+Add new entries to an archive that already exists.
+@item --update
+@itemx -r
+Add more recent copies of archive members to the end of an archive, if
+they exist.
+@item --concatenate
+@itemx --catenate
+@itemx -A
+Add one or more pre-existing archives to the end of another archive.
+@item --delete
+Delete items from an archive (does not work on tapes).
+@item --compare
+@itemx --diff
+@itemx -d
+Compare archive members to their counterparts in the file system.
+@end table
-All tapes and disks can be @dfn{write protected}, to protect data on
-them from being changed. Once an archive is written, you should write
-protect the media to prevent the archive from being accidently
-overwritten or deleted. (This will protect the archive from being
-changed with a tape or floppy drive---it will not protect it from
-magnet fields or other physical hazards).
+@node current state, append, Operations, Advanced tar
+@ifinfo
+@subsection The Current State of the Practice Files
+@end ifinfo
-The write protection device itself is usually an integral part of the
-physical media, and can be a two position (write enabled/write
-disabled) switch, a notch which can be popped out or covered, a ring
-which can be removed from the center of a tape reel, or some other
-changeable feature.
+Currently, the listing of the directory using @code{ls} is as follows:
-@node Tape Positioning, , Write Protection, Media
-@section Tape Positions and Tape Marks
+@example
-Just as archives can store more than one file from the file system,
-tapes can store more than one archive file. To keep track of where
-archive files (or any other type of file stored on tape) begin and
-end, tape archive devices write magnetic @dfn{tape marks} on the
-archive media. Tape drives write one tape mark between files,
-two at the end of all the file entries.
+@end example
-If you think of data as a series of "0000"'s, and tape marks as "x"'s,
-a tape might look like the following:
+@noindent
+The archive file @samp{collection.tar} looks like this:
@example
-0000x000000x00000x00x00000xx-------------------------
-@end example
+$ @kbd{tar -tvf collection.tar}
-Tape devices read and write tapes using a read/write @dfn{tape
-head}---a physical part of the device which can only access one point
-on the tape at a time. When you use @code{tar} to read or write
-archive data from a tape device, the device will begin reading or
-writing from wherever on the tape the tape head happens to be,
-regardless of which archive or what part of the archive the tape head
-is on. Before writing an archive, you should make sure that no data
-on the tape will be overwritten (unless it is no longer needed).
-Before reading an archive, you should make sure the tape head is at
-the beginning of the archive you want to read. (The @code{restore}
-script will find the archive automatically. @xref{Scripted
-Restoration}). @xref{mt}, for an explanation of the tape moving
-utility.
+@end example
-If you want to add new archive file entries to a tape, you should
-advance the tape to the end of the existing file entries, backspace
-over the last tape mark, and write the new archive file. If you were
-to add two archives to the example above, the tape might look like the
-following:
+@noindent
+The archive file @samp{music.tar} looks like this:
@example
-0000x000000x00000x00x00000x000x0000xx----------------
+$ @kbd{tar -tvf music.tar}
+
@end example
+@FIXME{need to fill in the above!!!}
+
+@node append, update, current state, Advanced tar
+@subsection How to Add Files to Existing Archives: @code{--append}
+@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
+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.}
+
+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. @code{tar} @emph{allows} you to have infinite numbers of files
+with the same name. Some operations treat these same-named members no
+differently than any other set of archive members: for example, if you
+view an archive with @value{op-list}, you will see all of those members
+listed, with their modification times, owners, etc.
+
+Other operations don't deal with these members as perfectly as you might
+prefer; if you were to use @value{op-extract} to extract the archive,
+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
+in the archive; the most recently archived members will be extracted
+last. Additionally, an extracted member will @emph{overwrite} a file of
+the same name which existed in the directory already, and @code{tar}
+will not prompt you about this. Thus, only the most recently archived
+member will end up being extracted, as it will overwrite the one
+extracted before it, and so on.
+
+@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...}
+
+There are a few ways to get around this. @FIXME-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
+that you can not change the order of the archive; the most recently
+added member will still appear last. In this sense, you cannot truely
+``replace'' one member with another. (Replacing one member with another
+will not work on certain types of media, such as tapes; see @ref{delete}
+and @ref{Media}, for more information.)
+
@menu
-* mt:: The @code{mt} Utility
+* appending files:: Appending Files to an Archive
+* multiple::
@end menu
-@node mt, , Tape Positioning, Tape Positioning
-@subsection The @code{mt} Utility
+@node appending files, multiple, append, append
+@subsubsection Appending Files to an Archive
+@UNREVISED
+@cindex Adding files to an Archive
+@cindex Appending files to an Archive
+@cindex Archives, Appending files to
+
+The simplest way to add a file to an already existing archive is the
+@value{op-append} operation, which writes specified files into the
+archive whether or not they are already among the archived files.
+When you use @samp{--append}, you @emph{must} specify file name
+arguments, as there is no default. If you specify a file that already
+exists in the archive, another copy of the file will be added to the
+end of the archive. As with other operations, the member names of the
+newly added files will be exactly the same as their names given on the
+command line. The @value{op-verbose} option will print out the names
+of the files as they are written into the archive.
+
+@samp{--append} cannot be performed on some tape drives, unfortunately,
+due to deficiencies in the formats those tape drives use. The archive
+must be a valid @code{tar} archive, or else the results of using this
+operation will be unpredictable. @xref{Media}.
+
+To demonstrate using @samp{--append} to add a file to an archive,
+create a file called @file{rock} in the @file{practice} directory.
+Make sure you are in the @file{practice} directory. Then, run the
+following @code{tar} command to add @file{rock} to
+@file{collection.tar}:
-<<< is it true that this only works on non-block devices? should
-<<< explain the difference, xref to block-size (fixed or variable).
+@example
+$ @kbd{tar --append --file=collection.tar rock}
+@end example
-You can use the @code{mt} utility to advance or rewind a tape past a
-specified number of archive files on the tape. This will allow you to
-move to the beginning of an archive before extracting or reading it,
-or to the end of all the archives before writing a new one.
-@c why isn't there an "advance 'til you find two tape marks together"?
+@noindent
+If you now use the @value{op-list} operation, you will see that
+@file{rock} has been added to the archive:
-The syntax of the @code{mt} command is:
+@example
+$ @kbd{tar --list --file=collection.tar}
+-rw-rw-rw- me user 28 1996-10-18 16:31 jazz
+-rw-rw-rw- me user 21 1996-09-23 16:44 blues
+-rw-rw-rw- me user 20 1996-09-23 16:44 folk
+-rw-rw-rw- me user 20 1996-09-23 16:44 rock
+@end example
+
+@FIXME{in theory, dan will (soon) try to turn this node into what it's
+title claims it will become...}
+
+@node multiple, , appending files, append
+@subsubsection Multiple Files with the Same Name
+
+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 @code{tar} option called
+@samp{--update}; @pxref{update} for more information. We describe this
+use of @samp{--append} here for the sake of completeness.) @FIXME{is
+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
+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
+archive in the order in which they were archived. Thus, when the
+archive is extracted, a file archived later in time will overwrite a
+file of the same name which was archived earlier, even though the older
+version of the file will remain in the archive unless you delete all
+versions of the file.
+
+Supposing you change the file @file{blues} and then append the changed
+version to @file{collection.tar}. As you saw above, the original
+@file{blues} is in the archive @file{collection.tar}. If you change the
+file and append the new version of the file to the archive, there will
+be two copies in the archive. When you extract the archive, the older
+version of the file will be extracted first, and then overwritten by the
+newer version when it is extracted.
+
+You can append the new, changed copy of the file @file{blues} to the
+archive in this way:
@example
-mt [-f @var{tapename}] @var{operation} [@var{number}]
+$ @kbd{tar --append --verbose --file=collection.tar blues}
+blues
@end example
-where @var{tapename} is the name of the tape device, @var{number} is
-the number of times an operation is performed (with a default of one),
-and @var{operation} is one of the following:
+@noindent
+Because you specified the @samp{--verbose} option, @code{tar} has
+printed the name of the file being appended as it was acted on. Now
+list the contents of the archive:
-@table @code
-@item eof
-@itemx weof
-Writes @var{number} tape marks at the current position on the tape.
+@example
+$ @kbd{tar --list --verbose --file=collection.tar}
+-rw-rw-rw- me user 28 1996-10-18 16:31 jazz
+-rw-rw-rw- me user 21 1996-09-23 16:44 blues
+-rw-rw-rw- me user 20 1996-09-23 16:44 folk
+-rw-rw-rw- me user 20 1996-09-23 16:44 rock
+-rw-rw-rw- me user 58 1996-10-24 18:30 blues
+@end example
+@noindent
+The newest version of @file{blues} is now at the end of the archive
+(note the different creation dates and file sizes). If you extract
+the archive, the older version of the file @file{blues} will be
+overwritten by the newer version. You can confirm this by extracting
+the archive and running @samp{ls} on the directory. @xref{Writing}
+for more information. (@emph{Please note:} This is the case unless
+you employ the @value{op-backup} option; @FIXME-ref{Multiple Members
+with the Same Name}.)
+
+@node update, concatenate, append, Advanced tar
+@subsection Updating an Archive
+@UNREVISED
+@cindex Updating an archive
-@item fsf
-Moves tape position forward @var{number} files.
+In the previous section, you learned how to use @value{op-append} to add
+a file to an existing archive. A related operation is
+@value{op-update}. The @samp{--update} operation updates a @code{tar}
+archive by comparing the date of the specified archive members against
+the date of the file with the same name. If the file has been modified
+more recently than the archive member, then the newer version of the
+file is added to the archive (as with @value{op-append}).
+Unfortunately, you cannot use @samp{--update} with magnetic tape drives.
+The operation will fail.
-@item bsf
-Moves tape position back @var{number} files.
+@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
+of the archive. When you extract a file from the archive, only the
+version stored last will wind up in the file system, unless you use
+the @value{op-backup} option (@FIXME-ref{Multiple Members with the
+Same Name}).
-@item rewind
-Rewinds the tape. (Ignores @var{number}).
+@menu
+* how to update::
+@end menu
+@node how to update, , update, update
+@subsubsection How to Update an Archive Using @code{--update}
-@item offline
-@itemx rewoff1
-Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
+You must use file name arguments with the @value{op-update} operation.
+If you don't specify any files, @code{tar} won't act on any files and
+won't tell you that it didn't do anything (which may end up confusing
+you).
+@FIXME{note: the above parenthetical added because in fact, this
+behavior just confused the author. :-) }
-@item status
-Prints status information about the tape unit.
-@end table
-<<< is there a better way to frob the spacing on the list? -ringo
+To see the @samp{--update} option at work, create a new file,
+@file{classical}, in your practice directory, and some extra text to the
+file @file{blues}, using any text editor. Then invoke @code{tar} with
+the @samp{update} operation and the @value{op-verbose} option specified,
+using the names of all the files in the practice directory as file name
+arguments:
-If you don't specify a @var{tapename}, @code{mt} uses the environment
-variable TAPE; if TAPE does not exist, @code{mt} uses the device
-@file{/dev/rmt12}.
+@example
+$ @kbd{tar --update -v -f collection.tar blues folk rock classical}
+blues
+classical
+$
+@end example
-@code{mt} returns a 0 exit status when the operation(s) were
-successful, 1 if the command was unrecognized, and 2 if an operation
-failed.
+@noindent
+Because we have specified verbose mode, @code{tar} prints out the names
+of the files it is working on, which in this case are the names of the
+files that needed to be updated. If you run @samp{tar --list} and look
+at the archive, you will see @file{blues} and @file{classical} at its
+end. There will be a total of two versions of the member @samp{blues};
+the one at the end will be newer and larger, since you added text before
+updating it.
+
+(The reason @code{tar} does not overwrite the older file when updating
+it is because writing to the middle of a section of tape is a difficult
+process. Tapes are not designed to go backward. @xref{Media} for more
+information about tapes.
+
+@value{op-update} is not suitable for performing backups for two
+reasons: it does not change directory content entries, and it lengthens
+the archive every time it is used. The GNU @code{tar} options intended
+specifically for backups are more efficient. If you need to run
+backups, please consult @ref{Backups}.
+
+@node concatenate, delete, update, Advanced tar
+@subsection Combining Archives with @code{--concatenate}
-@c <<< new node on how to find an archive? -ringo
-If you use @code{tar --extract} with the
-@samp{--label=@var{archive-name}} option specified, @code{tar} will
-read an archive label (the tape head has to be positioned on it) and
-print an error if the archive label doesn't match the
-@var{archive-name} specified. @var{archive-name} can be any regular
-expression. If the labels match, @code{tar} extracts the archive.
-@xref{Archive Label}. @xref{Matching Format Parameters}.
-<<< fix cross references
+@cindex Adding archives to an archive
+@cindex Concatenating Archives
+Sometimes it may be convenient to add a second archive onto the end of
+an archive rather than adding individual files to the archive. To add
+one or more archives to the end of another archive, you should use the
+@value{op-concatenate} operation.
+
+To use @samp{--concatenate}, name the archives to be concatenated on the
+command line. (Nothing happens if you don't list any.) The members,
+and their member names, will be copied verbatim from those archives. If
+this causes multiple members to have the same name, it does not delete
+any members; all the members with the same name coexist. For
+information on how this affects reading the archive, @FIXME-ref{Multiple
+Members with the Same Name}.
+
+To demonstrate how @samp{--concatenate} works, create two small archives
+called @file{bluesrock.tar} and @file{folkjazz.tar}, using the relevant
+files from @file{practice}:
-@code{tar --list --label} will cause @code{tar} to print the label.
+@example
+$ @kbd{tar -cvf bluesrock.tar blues rock}
+blues
+classical
+$ @kbd{tar -cvf folkjazz.tar folk jazz}
+folk
+jazz
+@end example
-@c <<< MIB -- program to list all the labels on a tape?
+@noindent
+If you like, You can run @samp{tar --list} to make sure the archives
+contain what they are supposed to:
-@node Quick Reference, Data Format Details, Media, Top
-@appendix A Quick Reference Guide to @code{tar} Operations and Options
-@c put in proper form for appendix. (unnumbered?)
+@example
+$ @kbd{tar -tvf bluesrock.tar}
+-rw-rw-rw- melissa user 105 1997-01-21 19:42 blues
+-rw-rw-rw- melissa user 33 1997-01-20 15:34 rock
+$ @kbd{tar -tvf folkjazz.tar}
+-rw-rw-rw- melissa user 20 1996-09-23 16:44 folk
+-rw-rw-rw- melissa user 65 1997-01-30 14:15 jazz
+@end example
-@menu
-* Operations:: A Table of Operations
-* Options:: Table of Options
-@end menu
+We can concatenate these two archives with @code{tar}:
-@node Operations, Options, Quick Reference, Quick Reference
-@appendixsec A Table of Operations
-@c add xrefs, note synonyms
+@example
+$ @kbd{cd ..}
+$ @kbd{tar --concatenate --file=bluesrock.tar jazzfolk.tar}
+@end example
-The operation argument to @code{tar} specifies which action you want to
-take.
+If you now list the contents of the @file{bluesclass.tar}, you will see
+that now it also contains the archive members of @file{jazzfolk.tar}:
-@table @samp
-@item -A
-Adds copies of an archive or archives to the end of another archive.
+@example
+$ @kbd{tar --list --file=bluesrock.tar}
+blues
+rock
+jazz
+folk
+@end example
-@item -c
-Creates a new archive.
+When you use @samp{--concatenate}, the source and target archives must
+already exist and must have been created using compatable format
+parameters (@FIXME-pxref{Matching Format Parameters}). The new,
+concatenated archive will be called by the same name as the first
+archive listed on the command line. @FIXME{is there a way to specify a
+new name?}
+
+Like @value{op-append}, this operation cannot be performed on some
+tape drives, due to deficiencies in the formats those tape drives use.
+
+@cindex @code{concatenate} vs @code{cat}
+@cindex @code{cat} vs @code{concatenate}
+It may seem more intuitive to you to want or try to use @code{cat} to
+concatenate two archives instead of using the @samp{--concatenate}
+operation; after all, @code{cat} is the utility for combining files.
+
+However, @code{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
+from the target archive before each new archive is appended. If you use
+@code{cat} to combine the archives, the result will not be a valid
+@code{tar} format archive. If you need to retrieve files from an
+archive that was added to using the @code{cat} utility, use the
+@value{op-ignore-zeros} option. @xref{Ignore Zeros} for further
+information on dealing with archives improperly combined using the
+@code{cat} shell utility.
+
+@FIXME{this shouldn't go here. where should it go?} You must specify
+the source archives using @value{op-file} (@value{pxref-file}). If you
+do not specify the target archive, @code{tar} uses the value of the
+environment variable @code{TAPE}, or, if this has not been set, the
+default archive name.
-@item -d
-Compares files in the archive with their counterparts in the file
-system, and reports differences in file size, mode, owner,
-modification date and contents.
+@node delete, compare, concatenate, Advanced tar
+@subsection Removing Archive Members Using @samp{--delete}
+@UNREVISED
+@cindex Deleting files from an archive
+@cindex Removing files from an archive
-@item -r
-Adds files to the end of the archive.
+You can remove members from an archive by using the @value{op-delete}
+option. Specify the name of the archive with @value{op-file} and then
+specify the names of the members to be deleted; if you list no member
+names, nothing will be deleted. The @value{op-verbose} option will
+cause @code{tar} to print the names of the members as they are deleted.
+As with @value{op-extract}, you must give the exact member names when
+using @samp{tar --delete}. @samp{--delete} will remove all versions of
+the named file from the archive. The @samp{--delete} operation can run
+very slowly.
+
+Unlike other operations, @samp{--delete} has no short form.
+
+@cindex Tapes, using @code{--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
+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
+likely to scramble the archive and damage your tape. There is no safe
+way (except by completely re-writing the archive) to delete files from
+most kinds of magnetic tape. @xref{Media}.
+
+To delete all versions of the file @file{blues} from the archive
+@file{collection.tar} in the @file{practice} directory, make sure you
+are in that directory, and then,
-@item -t
-Prints a list of the contents of the archive.
+@example
+$ @kbd{tar --list --file=collection.tar}
+blues
+folk
+jazz
+rock
+practice/blues
+practice/folk
+practice/jazz
+practice/rock
+practice/blues
+$ @kbd{tar --delete --file=collection.tar blues}
+$ @kbd{tar --list --file=collection.tar}
+folk
+jazz
+rock
+$
+@end example
-@item -x
-Reads files from the archive and writes them into the active file
-system.
+@FIXME{I changed the order of these nodes around and haven't had a chance
+to fix the above example's results, yet. I have to play with this and
+follow it and see what it actually does!}
-@item -u
-Adds files to the end of the archive, but only if they are newer than
-their counterparts already in the archive, or if they do not already
-exist in the archive.
+The @value{op-delete} option has been reported to work properly when
+@code{tar} acts as a filter from @code{stdin} to @code{stdout}.
-@item --add-archive
-Adds copies of an archive or archives to the end of another archive.
+@node compare, , delete, Advanced tar
+@subsection Comparing Archive Members with the File System
+@cindex Verifying the currency of an archive
+@UNREVISED
-@item --add-file
-Adds files to the end of the archive.
+The @samp{--compare} (@samp{-d}), or @samp{--diff} operation compares
+specified archive members against files with the same names, and then
+reports differences in file size, mode, owner, modification date and
+contents. You should @emph{only} specify archive member names, not file
+names. If you do not name any members, then @code{tar} will compare the
+entire archive. If a file is represented in the archive but does not
+exist in the file system, @code{tar} reports a difference.
-@item --append
-Adds files to the end of the archive.
+You have to specify the record size of the archive when modifying an
+archive with a non-default record size.
-@item --catenate
-Adds copies of an archive or archives to the end of another archive.
+@code{tar} ignores files in the file system that do not have
+corresponding members in the archive.
-@item --compare
-Compares files in the archive with their counterparts in the file
-system, and reports differences in file size, mode, owner,
-modification date and contents.
+The following example compares the archive members @file{rock},
+@file{blues} and @file{funk} in the archive @file{bluesrock.tar} with
+files of the same name in the file system. (Note that there is no file,
+@file{funk}; @code{tar} will report an error message.)
-@item --concatenate
-Adds copies of an archive or archives to the end of another archive.
+@example
+$ @kbd{tar --compare --file=bluesrock.tar rock blues funk}
+rock
+blues
+tar: funk not found in archive
+@end example
-@item --create
-Creates a new archive.
+@noindent
+@FIXME{what does this actually depend on? i'm making a guess,
+here.}Depending on the system where you are running @code{tar} and the
+version you are running, @code{tar} may have a different error message,
+such as:
-@item --delete
-Deletes files from the archive. All versions of the files are deleted.
+@example
+funk: does not exist
+@end example
-@item --diff
-Compares files in the archive with their counterparts in the file
-system, and reports differences in file size, mode, owner,
-modification date and contents.
+@FIXME-xref{somewhere, for more information about format parameters.
+Melissa says: such as "format variations"? But why? Clearly I don't
+get it yet; I'll deal when I get to that section.}
-@item --extract
-Reads files from the archive and writes them into the active file
-system.
+The spirit behind the @value{op-compare} option is to check whether the
+archive represents the current state of files on disk, more than validating
+the integrity of the archive media. For this later goal, @xref{verify}.
-@item --get
-Reads files from the archive and writes them into the active file
+@node extract options, backup, Advanced tar, operations
+@section Options Used by @code{--extract}
+@UNREVISED
+
+@FIXME{i need to get dan to go over these options with me and see if
+there's a better way of organizing them.}
+
+The previous chapter showed how to use @value{op-extract} to extract
+an archive into the filesystem. Various options cause @code{tar} to
+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
+considerations arise. You may review the information presented in
+@ref{extract} for more basic information about the
+@samp{--extract} operation.
+
+@menu
+* Reading:: Options to Help Read Archives
+* Writing:: Changing How @code{tar} Writes Files
+* Scarce:: Coping with Scarce Resources
+@end menu
+
+@node Reading, Writing, extract options, extract options
+@subsection Options to Help Read Archives
+@cindex Options when reading archives
+@cindex Reading incomplete records
+@cindex Records, incomplete
+@cindex End-of-archive entries, ignoring
+@cindex Ignoring end-of-archive entries
+@cindex Large lists of file names on small machines
+@cindex Small memory
+@cindex Running out of space
+@UNREVISED
+
+Normally, @code{tar} will request data in full record increments from
+an archive storage device. If the device cannot return a full record,
+@code{tar} will report an error. However, some devices do not always
+return full records, or do not require the last record of an archive to
+be padded out to the next record boundary. To keep reading until you
+obtain a full record, or to accept an incomplete record if it contains
+an end-of-archive marker, specify the @value{op-read-full-records} option
+in conjunction with the @value{op-extract} or @value{op-list} operations.
+@value{xref-read-full-records}.
+
+The @value{op-read-full-records} option is turned on by default when
+@code{tar} reads an archive from standard input, or from a remote
+machine. This is because on BSD Unix systems, attempting to read a
+pipe returns however much happens to be in the pipe, even if it is
+less than was requested. If this option were not enabled, @code{tar}
+would fail as soon as it read an incomplete record from the pipe.
+
+If you're not sure of the blocking factor of an archive, you can
+read the archive by specifying @value{op-read-full-records} and
+@value{op-blocking-factor}, using a blocking factor larger than what the
+archive uses. This lets you avoid having to determine the blocking factor
+of an archive. @value{xref-blocking-factor}.
+
+@menu
+* read full records::
+* Ignore Zeros::
+* Ignore Failed Read::
+@end menu
+
+@node read full records, Ignore Zeros, Reading, Reading
+@unnumberedsubsubsec Reading Full Records
+
+@FIXME{need sentence or so of intro here}
+
+@table @kbd
+@item --read-full-records
+@item -B
+Use in conjunction with @value{op-extract} to read an archive which
+contains incomplete records, or one which has a blocking factor less
+than the one specified.
+@end table
+
+@node Ignore Zeros, Ignore Failed Read, read full records, Reading
+@unnumberedsubsubsec Ignoring Blocks of Zeros
+
+Normally, @code{tar} stops reading when it encounters a block of zeros
+between file entries (which usually indicates the end of the archive).
+@value{op-ignore-zeros} allows @code{tar} to completely read an archive
+which contains a block of zeros before the end (i.e.@: a damaged
+archive, or one which was created by @code{cat}-ing several archives
+together).
+
+The @value{op-ignore-zeros} option is turned off by default because many
+versions of @code{tar} write garbage after the end-of-archive entry,
+since that part of the media is never supposed to be read. GNU
+@code{tar} does not write after the end of an archive, but seeks to
+maintain compatablity among archiving utilities.
+
+@table @kbd
+@item --ignore-zeros
+@itemx -i
+To ignore blocks of zeros (ie.@: end-of-archive entries) which may be
+encountered while reading an archive. Use in conjunction with
+@value{op-extract} or @value{op-list}.
+@end table
+
+@node Ignore Failed Read, , Ignore Zeros, Reading
+@unnumberedsubsubsec Ignore Fail Read
+
+@FIXME{Is this in the right place? It doesn't exist anywhere else in
+the book (except the appendix), and has no further explanation. For that
+matter, what does it mean?!}
+
+@table @kbd
+@item --ignore-failed-read
+Do not exit with nonzero on unreadable files or directories.
+@end table
+
+@node Writing, Scarce, Reading, extract options
+@subsection Changing How @code{tar} Writes Files
+@cindex Overwriting old files, prevention
+@cindex Protecting old files
+@cindex Modification times of extracted files
+@cindex Permissions of extracted files
+@cindex Modes of extracted files
+@cindex Writing extracted files to standard output
+@cindex Standard output, writing extracted files to
+@UNREVISED
+
+@FIXME{need to mention the brand new option, --backup}
+
+@menu
+* Prevention Overwriting::
+* Keep Old Files::
+* Unlink First::
+* Recursive Unlink::
+* Modification Times::
+* Setting Access Permissions::
+* Writing to Standard Output::
+* remove files::
+@end menu
+
+@node Prevention Overwriting, Keep Old Files, Writing, Writing
+@unnumberedsubsubsec Options to Prevent Overwriting Files
+
+Normally, @code{tar} writes extracted files into the file system without
+regard to the files already on the system; i.e., files with the same
+names as archive members are overwritten when the archive is extracted.
+If the name of a corresponding file name is a symbolic link, the file
+pointed to by the symbolic link will be overwritten instead of the
+symbolic link itself (if this is possible). Moreover, special devices,
+empty directories and even symbolic links are automatically removed if
+they are found to be on the way of the proper extraction.
+
+To prevent @code{tar} from extracting an archive member from an archive
+if doing so will overwrite a file in the file system, use
+@value{op-keep-old-files} in conjunction with @samp{--extract}. When
+this option is specified, @code{tar} will report an error stating the
+name of the files in conflict instead of overwriting the file with the
+corresponding extracted archive member.
+
+@FIXME{these two P's have problems. i don't understand what they're
+trying to talk about well enough to fix them; i may have just made them
+worse (in particular the first of the two). waiting to talk with hag.}
+
+The @value{op-unlink-first} option removes existing files, symbolic links,
+empty directories, devices, etc., @emph{prior} to extracting over them.
+In particular, using this option will prevent replacing an already existing
+symbolic link by the name of an extracted file, since the link itself
+is removed prior to the extraction, rather than the file it points to.
+On some systems, the backing store for the executable @emph{is} the
+original program text. You could use the @value{op-unlink-first} option
+to prevent segmentation violations or other woes when extracting arbitrary
+executables over currently running copies. Note that if something goes
+wrong with the extraction and you @emph{did} use this option, you might
+end up with no file at all. Without this option, if something goes wrong
+with the extraction, the existing file is not overwritten and preserved.
+
+@FIXME{huh?} If you specify the @value{op-recursive-unlink} option,
+@code{tar} removes @emph{anything} that keeps you from extracting a file
+as far as current permissions will allow it. This could include removal
+of the contents of a full directory hierarchy. For example, someone
+using this feature may be very surprised at the results when extracting
+a directory entry from the archive. This option can be dangerous; be
+very aware of what you are doing if you choose to use it.
+
+@menu
+* Keep Old Files::
+* Unlink First::
+* Recursive Unlink::
+@end menu
+
+@node Keep Old Files, Unlink First, Prevention Overwriting, Writing
+@unnumberedsubsubsec Keep Old Files
+
+@table @kbd
+@item --keep-old-files
+@itemx -k
+Do not overwrite existing files from archive. The
+@value{op-keep-old-files} option prevents @code{tar} from over-writing
+existing files with files with the same name from the archive.
+The @value{op-keep-old-files} option is meaningless with @value{op-list}.
+Prevents @code{tar} from overwriting files in the file system during
+extraction.
+@end table
+
+@node Unlink First, Recursive Unlink, Keep Old Files, Writing
+@unnumberedsubsubsec Unlink First
+
+@table @kbd
+@item --unlink-first
+@itemx -U
+Try removing files before extracting over them, instead of trying to
+overwrite them.
+@end table
+
+@node Recursive Unlink, Modification Times, Unlink First, Writing
+@unnumberedsubsubsec Recursive Unlink
+
+@table @kbd
+@item --recursive-unlink
+When this option is specified, try removing files and directory hierarchies
+before extracting over them. @emph{This is a dangerous option!}
+@end table
+
+Some people argue that GNU @code{tar} should not hesitate to overwrite
+files with other files when extracting. When extracting a @code{tar}
+archive, they expect to see a faithful copy of the state of the filesystem
+when the archive was created. It is debatable that this would always
+be a proper behaviour. For example, suppose one has an archive in
+which @file{usr/local} is a link to @file{usr/local2}. Since then,
+maybe the site removed the link and renamed the whole hierarchy from
+@file{/usr/local2} to @file{/usr/local}. Such things happen all the time.
+I guess it would not be welcome at all that GNU @code{tar} removes the
+whole hierarchy just to make room for the link to be reinstated (unless it
+@emph{also} simultaneously restores the full @file{/usr/local2}, of course!
+GNU @code{tar} is indeed able to remove a whole hierarchy to reestablish a
+symbolic link, for example, but @emph{only if} @value{op-recursive-unlink}
+is specified to allow this behaviour. In any case, single files are
+silently removed.
+
+@node Modification Times, Setting Access Permissions, Recursive Unlink, Writing
+@unnumberedsubsubsec Setting Modification Times
+
+Normally, @code{tar} sets the modification times of extracted files to
+the modification times recorded for the files in the archive, but
+limits the permissions of extracted files by the current @code{umask}
+setting.
+
+To set the modification times of extracted files to the time when
+the files were extracted, use the @value{op-touch} option in
+conjunction with @value{op-extract}.
+
+@table @kbd
+@item --touch
+@itemx -m
+Sets the modification time of extracted archive members to the time
+they were extracted, not the time recorded for them in the archive.
+Use in conjunction with @value{op-extract}.
+@end table
+
+@node Setting Access Permissions, Writing to Standard Output, Modification Times, Writing
+@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-persmissions}
+in conjunction with the @value{op-extract} operation. @FIXME{Should be
+aliased to ignore-umask.}
+
+@table @kbd
+@item --preserve-permission
+@itemx --same-permission
+@itemx --ignore-umask
+@itemx -p
+Set modes of extracted archive members to those recorded in the
+archive, instead of current umask settings. Use in conjunction with
+@value{op-extract}.
+@end table
+
+@FIXME{Following paragraph needs to be rewritten: why doesnt' this cat
+files together, why is this useful. is it really useful with
+more than one file?}
+
+@node Writing to Standard Output, remove files, Setting Access Permissions, Writing
+@unnumberedsubsubsec Writing to Standard Output
+
+To write the extracted files to the standard output, instead of
+creating the files on the file system, use @value{op-to-stdout} in
+conjunction with @value{op-extract}. This option is useful if you are
+extracting files to send them through a pipe, and do not need to
+preserve them in the file system. If you extract multiple members,
+they appear on standard output concatenated, in the order they are
+found in the archive.
+
+@table @kbd
+@item --to-stdout
+@itemx -O
+Writes files to the standard output. Used in conjunction with
+@value{op-extract}. Extract files to standard output. When this option
+is used, instead of creating the files specified, @code{tar} writes
+the contents of the files extracted to its standard output. This may
+be useful if you are only extracting the files in order to send them
+through a pipe. This option is meaningless with @value{op-list}.
+@end table
+
+@FIXME{Why would you want to do such a thing, how are files separated on
+the standard output? is this useful with more that one file? Are
+pipes the real reason?}
+
+@node remove files, , Writing to Standard Output, Writing
+@unnumberedsubsubsec Removing Files
+
+@FIXME{the various macros in the front of the manual think that this
+option goes in this section. i have no idea; i only know it's nowhere
+else in the book...}
+
+@table @kbd
+@item --remove-files
+Remove files after adding them to the archive.
+@end table
+
+@node Scarce, , Writing, extract options
+@subsection Coping with Scarce Resources
+@cindex Middle of the archive, starting in the
+@cindex Running out of space during extraction
+@cindex Disk space, running out of
+@cindex Space on the disk, recovering from lack of
+@UNREVISED
+
+@menu
+* Starting File::
+* Same Order::
+@end menu
+
+@node Starting File, Same Order, Scarce, Scarce
+@unnumberedsubsubsec Starting File
+
+@table @kbd
+@item --starting-file=@var{name}
+@itemx -K @var{name}
+Starts an operation in the middle of an archive. Use in conjunction
+with @value{op-extract} or @value{op-list}.
+@end table
+
+If a previous attempt to extract files failed due to lack of disk
+space, you can use @value{op-starting-file} to start extracting only
+after member @var{name} of the archive. This assumes, of course, that
+there is now free space, or that you are now extracting into a
+different file system. (You could also choose to suspend @code{tar},
+remove unnecessary files from the file system, and then restart the
+same @code{tar} operation. In this case, @value{op-starting-file} is
+not necessary. @value{xref-incremental}, @value{xref-interactive},
+and @value{ref-exclude}.)
+
+@node Same Order, , Starting File, Scarce
+@unnumberedsubsubsec Same Order
+
+@table @kbd
+@item --same-order
+@itemx --preserve-order
+@itemx -s
+To process large lists of file names on machines with small amounts of
+memory. Use in conjunction with @value{op-compare},
+@value{op-list}
+or @value{op-extract}.
+@end table
+
+@FIXME{we don't need/want --preserve to exist any more (from melissa:
+ie, don't want that *version* of the option to exist, or don't want
+the option to exist in either version?}
+
+@FIXME{i think this explanation is lacking.}
+
+The @value{op-same-order} option tells @code{tar} that the list of file
+names to be listed or extracted is sorted in the same order as the
+files in the archive. This allows a large list of names to be used,
+even on a small machine that would not otherwise be able to hold all
+the names in memory at the same time. Such a sorted list can easily be
+created by running @samp{tar -t} on the archive and editing its output.
+
+This option is probably never needed on modern computer systems.
+
+@node backup, Applications, extract options, operations
+@section Backup options
+
+@cindex backup options
+
+GNU @code{tar} offers options for making backups of files before writing
+new versions. These options control the details of these backups.
+They may apply to the archive itself before it is created or rewritten,
+as well as individual extracted members. Other GNU programs (@code{cp},
+@code{install}, @code{ln}, and @code{mv}, for example) offer similar
+options.
+
+Backup options may prove unexpectedly useful when extracting archives
+containing many members having identical name, or when extracting archives
+on systems having file name limitations, making different members appear
+has having similar names through the side-effect of name truncation.
+(This is true only if we have a good scheme for truncated backup names,
+which I'm not sure at all: I suspect work is needed in this area.)
+When any existing file is backed up before being overwritten by extraction,
+then clashing files are automatically be renamed to be unique, and the
+true name is kept for only the last file of a series of clashing files.
+By using verbose mode, users may track exactly what happens.
+
+At the detail level, some decisions are still experimental, and may
+change in the future, we are waiting comments from our users. So, please
+do not learn to depend blindly on the details of the backup features.
+For example, currently, directories themselves are never renamed through
+using these options, so, extracting a file over a directory still has
+good chances to fail. Also, backup options apply to created archives,
+not only to extracted members. For created archives, backups will not
+be attempted when the archive is a block or character device, or when it
+refers to a remote file.
+
+For the sake of simplicity and efficiency, backups are made by renaming old
+files prior to creation or extraction, and not by copying. The original
+name is restored if the file creation fails. If a failure occurs after a
+partial extraction of a file, both the backup and the partially extracted
+file are kept.
+
+@table @samp
+
+@item --backup
+@opindex --backup
+@cindex backups, making
+Make backups of files that are about to be overwritten or removed.
+Without this option, the original versions are destroyed.
+
+@item --suffix=@var{suffix}
+@opindex --suffix
+@cindex backup suffix
+@vindex SIMPLE_BACKUP_SUFFIX
+Append @var{suffix} to each backup file made with @samp{-b}. If this
+option is not specified, the value of the @code{SIMPLE_BACKUP_SUFFIX}
+environment variable is used. And if @code{SIMPLE_BACKUP_SUFFIX} is not
+set, the default is @samp{~}, just as in Emacs.
+
+@item --version-control=@var{method}
+@opindex --version-control
+@vindex VERSION_CONTROL
+@cindex backup files, type made
+Use @var{method} to determine the type of backups made with @value{op-backup}.
+If this option is not specified, the value of the @code{VERSION_CONTROL}
+environment variable is used. And if @code{VERSION_CONTROL} is not set,
+the default backup type is @samp{existing}.
+
+@vindex version-control @r{Emacs variable}
+This option corresponds to the Emacs variable @samp{version-control};
+the same values for @var{method} are accepted as in Emacs. This options
+also more descriptive name. The valid @var{method}s (unique
+abbreviations are accepted):
+
+@table @samp
+@item t
+@itemx numbered
+@opindex numbered @r{backup method}
+Always make numbered backups.
+
+@item nil
+@itemx existing
+@opindex existing @r{backup method}
+Make numbered backups of files that already have them, simple backups
+of the others.
+
+@item never
+@itemx simple
+@opindex simple @r{backup method}
+Always make simple backups.
+
+@end table
+
+@end table
+
+Some people express the desire to @emph{always} use the @var{op-backup}
+option, by defining some kind of alias or script. This is not as easy
+as one may thing, due to the fact old style options should appear first
+and consume arguments a bit inpredictably for an alias or script. But,
+if you are ready to give up using old style options, you may resort to
+using something like (a Bourne shell function here):
+
+@example
+tar () @{ /usr/local/bin/tar --backup $*; @}
+@end example
+
+@node Applications, looking ahead, backup, operations
+@section Notable @code{tar} Usages
+@UNREVISED
+
+@FIXME{Using Unix file linking capability to recreate directory
+structures---linking files into one subdirectory and then
+@code{tar}ring that directory.}
+
+@FIXME{Nice hairy example using absolute-names, newer, etc.}
+
+@findex uuencode
+You can easily use archive files to transport a group of files from
+one system to another: put all relevant files into an archive on one
+computer system, transfer the archive to another system, and extract
+the contents there. The basic transfer medium might be magnetic tape,
+Internet FTP, or even electronic mail (though you must encode the
+archive with @code{uuencode} in order to transport it properly by
+mail). Both machines do not have to use the same operating system, as
+long as they both support the @code{tar} program.
+
+For example, here is how you might copy a directory's contents from
+one disk to another, while preserving the dates, modes, owners and
+link-structure of all the files therein. In this case, the transfer
+medium is a @dfn{pipe}, which is one a Unix redirection mechanism:
+
+@smallexample
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+@end smallexample
+
+@noindent
+The command also works using short option forms:
+
+@FIXME{The following using standard input/output correct??}
+@smallexample
+$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
+@end smallexample
+
+@noindent
+This is one of the easiest methods to transfer a @code{tar} archive.
+
+@node looking ahead, , Applications, operations
+@section Looking Ahead: The Rest of this Manual
+
+You have now seen how to use all eight of the operations available to
+@code{tar}, and a number of the possible options. The next chapter
+explains how to choose and change file and archive names, how to use
+files to store names of other files which you can then call as
+arguments to @code{tar} (this can help you save time if you expect to
+archive the same list of files a number of times), and how to
+@FIXME{in case it's not obvious, i'm making this up in some sense
+based on my imited memory of what the next chapter *really* does. i
+just wanted to flesh out this final section a little bit so i'd
+remember to sitck it in here. :-)}
+
+If there are too many files to conveniently list on the command line,
+you can list the names in a file, and @code{tar} will read that file.
+@value{xref-files-from}.
+
+There are various ways of causing @code{tar} to skip over some files,
+and not archive them. @xref{Choosing}.
+
+@node Backups, Choosing, operations, Top
+@chapter Performing Backups and Restoring Files
+@UNREVISED
+
+GNU @code{tar} is distributed along with the scripts which the Free
+Software Foundation uses for performing backups. There is no corresponding
+scripts available yet for doing restoration of files. Even if there is
+a good chance those scripts may be satisfying to you, they are not the
+only scripts or methods available for doing backups and restore. You may
+well create your own, or use more sophisticated packages dedicated to
+that purpose.
+
+Some users are enthusiastic about @code{Amanda} (The Advanced Maryland
+Automatic Network Disk Archiver), a backup system developed by James
+da Silva @file{jds@@cs.umd.edu} and available on many Unix systems.
+This is free software, and it is available at these places:
+
+@example
+http://www.cs.umd.edu/projects/amanda/amanda.html
+ftp://ftp.cs.umd.edu/pub/amanda
+@end example
+
+@ifclear PUBLISH
+
+Here is a possible plan for a future documentation about the backuping
+scripts which are provided within the GNU @code{tar} distribution.
+
+@example
+.* dumps
+. + what are dumps
+
+. + different levels of dumps
+. - full dump = dump everything
+. - level 1, level 2 dumps etc, -
+ A level n dump dumps everything changed since the last level
+ n-1 dump (?)
+
+. + how to use scripts for dumps (ie, the concept)
+. - scripts to run after editing backup specs (details)
+
+. + Backup Specs, what is it.
+. - how to customize
+. - actual text of script [/sp/dump/backup-specs]
+
+. + Problems
+. - rsh doesn't work
+. - rtape isn't installed
+. - (others?)
+
+. + the --incremental option of tar
+
+. + tapes
+. - write protection
+. - types of media
+. : different sizes and types, useful for different things
+. - files and tape marks
+ one tape mark between files, two at end.
+. - positioning the tape
+ MT writes two at end of write,
+ backspaces over one when writing again.
+@end example
+
+@end ifclear
+
+This chapter documents both the provided FSF scripts and @code{tar}
+options which are more specific to usage as a backup tool.
+
+To @dfn{back up} a file system means to create archives that contain
+all the files in that file system. Those archives can then be used to
+restore any or all of those files (for instance if a disk crashes or a
+file is accidently deleted). File system @dfn{backups} are also
+called @dfn{dumps}.
+
+@menu
+* Full Dumps:: Using @code{tar} to Perform Full Dumps
+* Inc Dumps:: Using @code{tar} to Perform Incremental Dumps
+* incremental and listed-incremental:: The Incremental Options
+* Backup Levels:: Levels of Backups
+* Backup Parameters:: Setting Parameters for Backups and Restoration
+* Scripted Backups:: Using the Backup Scripts
+* Scripted Restoration:: Using the Restore Script
+@end menu
+
+@node Full Dumps, Inc Dumps, Backups, Backups
+@section Using @code{tar} to Perform Full Dumps
+@UNREVISED
+
+@cindex full dumps
+@cindex dumps, full
+
+@cindex corrupted archives
+Full dumps should only be made when no other people or programs
+are modifying files in the filesystem. If files are modified while
+@code{tar} is making the backup, they may not be stored properly in
+the archive, in which case you won't be able to restore them if you
+have to. (Files not being modified are written with no trouble, and do
+not corrupt the entire archive.)
+
+You will want to use the @value{op-label} option to give the archive a
+volume label, so you can tell what this archive is even if the label
+falls off the tape, or anything like that.
+
+Unless the filesystem you are dumping is guaranteed to fit on
+one volume, you will need to use the @value{op-multi-volume} option.
+Make sure you have enough tapes on hand to complete the backup.
+
+If you want to dump each filesystem separately you will need to use
+the @value{op-one-file-system} option to prevent @code{tar} from crossing
+filesystem boundaries when storing (sub)directories.
+
+The @value{op-incremental} option is not needed, since this is a complete
+copy of everything in the filesystem, and a full restore from this
+backup would only be done onto a completely empty disk.
+
+Unless you are in a hurry, and trust the @code{tar} program (and your
+tapes), it is a good idea to use the @value{op-verify} option, to make
+sure your files really made it onto the dump properly. This will
+also detect cases where the file was modified while (or just after)
+it was being archived. Not all media (notably cartridge tapes) are
+capable of being verified, unfortunately.
+
+@value{op-listed-incremental} take a file name argument always. If the
+file doesn't exist, run a level zero dump, creating the file. If the
+file exists, uses that file to see what has changed.
+
+@value{op-incremental} @FIXME{look it up}
+
+@value{op-incremental} handle old GNU-format incremental backup.
+
+This option should only be used when creating an incremental backup of
+a filesystem. When the @value{op-incremental} option is used, @code{tar}
+writes, at the beginning of the archive, an entry for each of the
+directories that will be operated on. The entry for a directory
+includes a list of all the files in the directory at the time the
+dump was done, and a flag for each file indicating whether the file
+is going to be put in the archive. This information is used when
+doing a complete incremental restore.
+
+Note that this option causes @code{tar} to create a non-standard
+archive that may not be readable by non-GNU versions of the @code{tar}
+program.
+
+The @value{op-incremental} option means the archive is an incremental
+backup. Its meaning depends on the command that it modifies.
+
+If the @value{op-incremental} option is used with @value{op-list}, @code{tar}
+will list, for each directory in the archive, the list of files in
+that directory at the time the archive was created. This information
+is put out in a format that is not easy for humans to read, but which
+is unambiguous for a program: each file name is preceded by either a
+@samp{Y} if the file is present in the archive, an @samp{N} if the
+file is not included in the archive, or a @samp{D} if the file is
+a directory (and is included in the archive). Each file name is
+terminated by a null character. The last file is followed by an
+additional null and a newline to indicate the end of the data.
+
+If the @value{op-incremental} option is used with @value{op-extract}, then
+when the entry for a directory is found, all files that currently
+exist in that directory but are not listed in the archive @emph{are
+deleted from the directory}.
+
+This behavior is convenient when you are restoring a damaged file
+system from a succession of incremental backups: it restores the
+entire state of the file system to that which obtained when the backup
+was made. If you don't use @value{op-incremental}, the file system will
+probably fill up with files that shouldn't exist any more.
+
+@value{op-listed-incremental} handle new GNU-format incremental backup.
+This option handles new GNU-format incremental backup. It has much the
+same effect as @value{op-incremental}, but also the time when the dump
+is done and the list of directories dumped is written to the given
+@var{file}. When restoring, only files newer than the saved time are
+restored, and the direcotyr list is used to speed up operations.
+
+@value{op-listed-incremental} acts like @value{op-incremental}, but when
+used in conjunction with @value{op-create} will also cause @code{tar} to
+use the file @var{file}, which contains information about the state
+of the filesystem at the time of the last backup, to decide which
+files to include in the archive being created. That file will then
+be updated by @code{tar}. If the file @var{file} does not exist when
+this option is specified, @code{tar} will create it, and include all
+appropriate files in the archive.
+
+The file, which is archive independent, contains the date it was last
+modified and a list of devices, inode numbers and directory names.
+@code{tar} will archive files with newer mod dates or inode change
+times, and directories with an unchanged inode number and device but
+a changed directory name. The file is updated after the files to
+be archived are determined, but before the new archive is actually
+created.
+
+GNU @code{tar} actually writes the file twice: once before the data
+and written, and once after.
+
+@node Inc Dumps, incremental and listed-incremental, Full Dumps, Backups
+@section Using @code{tar} to Perform Incremental Dumps
+@UNREVISED
+
+@cindex incremental dumps
+@cindex dumps, incremental
+
+Performing incremental dumps is similar to performing full dumps,
+although a few more options will usually be needed.
+
+You will need to use the @samp{-N @var{date}} option to tell @code{tar}
+to only store files that have been modified since @var{date}.
+@var{date} should be the date and time of the last full/incremental
+dump.
+
+A standard scheme is to do a @emph{monthly} (full) dump once a month,
+a @emph{weekly} dump once a week of everything since the last monthly
+and a @emph{daily} every day of everything since the last (weekly or
+monthly) dump.
+
+Here is a copy of the script used to dump the filesystems of the
+machines here at the Free Software Foundation. This script is run via
+@code{cron} late at night when people are least likely to be using the
+machines. This script dumps several filesystems from several machines
+at once (via NFS). The operator is responsible for ensuring that all
+the machines will be up at the time the dump happens. If a machine is
+not running, its files will not be dumped, and the next day's
+incremental dump will @emph{not} store files that would have gone onto
+that dump.
+
+@example
+#!/bin/csh
+# Dump thingie
+set now = `date`
+set then = `cat date.nfs.dump`
+/u/hack/bin/tar -c -G -v\
+ -f /dev/rtu20\
+ -b 126\
+ -N "$then"\
+ -V "Dump from $then to $now"\
+ /alpha-bits/gp\
+ /gnu/hack\
+ /hobbes/u\
+ /spiff/u\
+ /sugar-bombs/u
+echo $now > date.nfs.dump
+mt -f /dev/rtu20 rew
+@end example
+
+Output from this script is stored in a file, for the operator to
+read later.
+
+This script uses the file @file{date.nfs.dump} to store the date/time
+of the last dump.
+
+Since this is a streaming tape drive, no attempt to verify the archive
+is done. This is also why the high blocking factor (126) is used.
+The tape drive must also be rewound by the @code{mt} command after
+the dump is made.
+
+@node incremental and listed-incremental, Backup Levels, Inc Dumps, Backups
+@section The Incremental Options
+@UNREVISED
+
+@value{op-incremental} is used in conjunction with @value{op-create},
+@value{op-extract} or @value{op-list} when backing up and restoring file
+systems. An archive cannot be extracted or listed with the
+@value{op-incremental} option specified unless it was created with the
+option specified. This option should only be used by a script, not by
+the user, and is usually disregarded in favor of
+@value{op-listed-incremental}, which is described below.
+
+@value{op-incremental} in conjunction with @value{op-create} causes
+@code{tar} to write, at the beginning of the archive, an entry for
+each of the directories that will be archived. The entry for a
+directory includes a list of all the files in the directory at the
+time the archive was created and a flag for each file indicating
+whether or not the file is going to be put in the archive.
+
+Note that this option causes @code{tar} to create a non-standard
+archive that may not be readable by non-GNU versions of the @code{tar}
+program.
+
+@value{op-incremental} in conjunction with @value{op-extract} causes
+@code{tar} to read the lists of directory contents previously stored
+in the archive, @emph{delete} files in the file system that did not
+exist in their directories when the archive was created, and then
+extract the files in the archive.
+
+This behavior is convenient when restoring a damaged file system from
+a succession of incremental backups: it restores the entire state of
+the file system to that which obtained when the backup was made. If
+@value{op-incremental} isn't specified, the file system will probably
+fill up with files that shouldn't exist any more.
+
+@value{op-incremental} in conjunction with @value{op-list}, causes
+@code{tar} to print, for each directory in the archive, the list of
+files in that directory at the time the archive was created. This
+information is put out in a format that is not easy for humans to
+read, but which is unambiguous for a program: each file name is
+preceded by either a @samp{Y} if the file is present in the archive,
+an @samp{N} if the file is not included in the archive, or a @samp{D}
+if the file is a directory (and is included in the archive). Each
+file name is terminated by a null character. The last file is followed
+by an additional null and a newline to indicate the end of the data.
+
+@value{op-listed-incremental} acts like @value{op-incremental}, but when
+used in conjunction with @value{op-create} will also cause @code{tar}
+to use the file @var{snapshot-file}, which contains information about
+the state of the file system at the time of the last backup, to decide
+which files to include in the archive being created. That file will
+then be updated by @code{tar}. If the file @var{file} does not exist
+when this option is specified, @code{tar} will create it, and include
+all appropriate files in the archive.
+
+The file @var{file}, which is archive independent, contains the date
+it was last modified and a list of devices, inode numbers and
+directory names. @code{tar} will archive files with newer mod dates
+or inode change times, and directories with an unchanged inode number
+and device but a changed directory name. The file is updated after
+the files to be archived are determined, but before the new archive is
+actually created.
+
+Despite it should be obvious that a device has a non-volatile value, NFS
+devices have non-dependable values when an automounter gets in the picture.
+This led to a great deal of spurious redumping in incremental dumps,
+so it is somewhat useless to compare two NFS devices numbers over time.
+So @code{tar} now considers all NFS devices as being equal when it comes
+to comparing directories; this is fairly gross, but there does not seem
+to be a better way to go.
+
+@FIXME{this section needs to be written}
+
+@node Backup Levels, Backup Parameters, incremental and listed-incremental, Backups
+@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
+creating a full dump every day. This strategy, however, would waste a
+substantial amount of archive media and user time, as unchanged files
+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
+one} dump archives all the files that have changed since the last full
+dump.
+
+A typical dump strategy would be to perform a full dump once a week,
+and a level one dump once a day. This means some versions of files
+will in fact be archived more than once, but this dump strategy makes
+it possible to restore a file system to within one day of accuracy by
+only extracting two archives---the last weekly (full) dump and the
+last daily (level one) dump. The only information lost would be in
+files changed or created since the last daily backup. (Doing dumps
+more than once a day is usually not worth the trouble).
+
+GNU @code{tar} comes with scripts you can use to do full and level-one
+dumps. Using scripts (shell programs) to perform backups and
+restoration is a convenient and reliable alternative to typing out
+file name lists and @code{tar} commands by hand.
+
+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
+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}
+
+@node Backup Parameters, Scripted Backups, Backup Levels, Backups
+@section Setting Parameters for Backups and Restoration
+@UNREVISED
+
+The file @file{backup-specs} specifies backup parameters for the
+backup and restoration scripts provided with @code{tar}. You must
+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.}
+
+@FIXME-xref{Script Syntax}, for an explanation of this syntax.
+
+@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:}
+
+@table @samp
+@item ADMINISTRATOR
+The user name of the backup administrator.
+
+@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}.
+
+@item TAPE_FILE
+The device @code{tar} writes the archive to. This device should be
+attached to the host on which the dump scripts are run.
+
+@FIXME{examples for all ...}
+
+@item TAPE_STATUS
+The command to use to obtain the status of the archive device,
+including error count. On some tape drives there may not be such a
+command; in that case, simply use `TAPE_STATUS=false'.
+
+@item BLOCKING
+The blocking factor @code{tar} will use when writing the dump archive.
+@value{xref-blocking-factor}.
+
+@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
+included, regardless of how they may look to other networked machines.
+Subdirectories on other file systems will be ignored.
+
+The host name specifies which host to run @code{tar} on, and should
+normally be the host that actually contains the file system. However,
+the host machine must have GNU @code{tar} installed, and must be able
+to access the directory containing the backup scripts and their
+support files using the same file name that is used on the machine
+where the scripts are run (ie. what @code{pwd} will print when in that
+directory on that machine). If the host that contains the file system
+does not have this capability, you can specify another host as long as
+it can access the file system through NFS.
+
+@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.
+
+@FIXME{Same file name, be specific. Through NFS ...}
+
+@end table
+
+@menu
+* backup-specs example:: An Example Text of @file{Backup-specs}
+* Script Syntax:: Syntax for @file{Backup-specs}
+@end menu
+
+@node backup-specs example, Script Syntax, Backup Parameters, Backup Parameters
+@subsection An Example Text of @file{Backup-specs}
+@UNREVISED
+
+The following is the text of @file{backup-specs} as it appears at FSF:
+
+@example
+# site-specific parameters for file system backup.
+
+ADMINISTRATOR=friedman
+BACKUP_HOUR=1
+TAPE_FILE=/dev/nrsmt0
+TAPE_STATUS="mts -t $TAPE_FILE"
+BLOCKING=124
+BACKUP_DIRS="
+ albert:/fs/fsf
+ apple-gunkies:/gd
+ albert:/fs/gd2
+ albert:/fs/gp
+ geech:/usr/jla
+ churchy:/usr/roland
+ albert:/
+ albert:/usr
+ apple-gunkies:/
+ apple-gunkies:/usr
+ gnu:/hack
+ gnu:/u
+ apple-gunkies:/com/mailer/gnu
+ apple-gunkies:/com/archive/gnu"
+
+BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
+
+@end example
+
+@node Script Syntax, , backup-specs example, Backup Parameters
+@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, Scripted Restoration, Backup Parameters, Backups
+@section Using the Backup Scripts
+@UNREVISED
+
+The syntax for running a backup script is:
+
+@example
+@file{script-name} [@var{time-to-be-run}]
+@end example
+
+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}).
+
+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
+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?}
+
+The backup scripts write two files on the file system. The first is a
+record file in @file{/etc/tar-backup/}, which is used by the scripts
+to store and retrieve information about which files were dumped. This
+file is not meant to be read by humans, and should not be deleted by
+them. @FIXME-xref{incremental and listed-incremental}, for a more
+detailed explanation of this file.
+
+The second file is a log file containing the names of the file systems
+and files dumped, what time the backup was made, and any error
+messages that were generated, as well as how much space was left in
+the media volume after the last volume of the archive was written.
+You should check this log file after every backup. The file name is
+@file{log-@var{mmm-ddd-yyyy}-level-1} or
+@file{log-@var{mmm-ddd-yyyy}-full}.
+
+The script also prints the name of each system being dumped to the
+standard output.
+
+@node Scripted Restoration, , Scripted Backups, Backups
+@section Using the Restore Script
+@UNREVISED
+
+@ifset PUBLISH
+
+The @code{tar} distribution does not provide restoring scripts.
+
+@end ifset
+
+@ifclear PUBLISH
+
+@quotation
+@strong{Warning:} The GNU @code{tar} distribution does @emph{not}
+provide any such @code{restore} script yet. This section is only
+listed here for documentation maintenance purposes. In any case,
+all contents is subject to change as things develop.
+@end quotation
+
+@FIXME{A section on non-scripted restore may be a good idea.}
+
+To restore files that were archived using a scripted backup, use the
+@code{restore} script. The syntax for the script is:
+
+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.
+
+You should start the restore script with the media containing the
+first volume of the archive mounted. The script will prompt for other
+volumes as they are needed. If the archive is on tape, you don't need
+to rewind the tape to to its beginning---if the tape head is
+positioned past the beginning of the archive, the script will rewind
+the tape as needed. @FIXME-xref{Media}, for a discussion of tape
+positioning.
+
+If you specify @samp{--all} as the @var{files} argument, the
+@code{restore} script extracts all the files in the archived file
+system into the active file system.
+
+@quotation
+@strong{Warning:} The script will delete files from the active file
+system if they were not in the file system when the archive was made.
+@end quotation
+
+@value{xref-incremental}, and @value{ref-listed-incremental},
+for an explanation of how the script makes that determination.
+
+@FIXME{this may be an option, not a given}
+
+@end ifclear
+
+@node Choosing, Date input formats, Backups, Top
+@chapter Choosing Files and Names for @code{tar}
+@UNREVISED
+
+@FIXME{Melissa (still) Doesn't Really Like This ``Intro'' Paragraph!!!}
+
+Certain options to @code{tar} enable you to specify a name for your
+archive. Other options let you decide which files to include or exclude
+from the archive, based on when or whether files were modified, whether
+the file names do or don't match specified patterns, or whether files
+are in specified directories.
+
+@menu
+* file:: Choosing the Archive's Name
+* Selecting Archive Members::
+* files:: Reading Names from a File
+* exclude:: Excluding Some Files
+* Wildcards::
+* after:: Operating Only on New Files
+* recurse:: Descending into Directories
+* one:: Crossing Filesystem Boundaries
+@end menu
+
+@node file, Selecting Archive Members, Choosing, Choosing
+@section Choosing and Naming Archive Files
+@cindex Naming an archive
+@cindex Archive Name
+@cindex Directing output
+@cindex Choosing an archive file
+@cindex Where is the archive?
+@UNREVISED
+
+@FIXME{should the title of this section actually be, "naming an
+archive"?}
+
+By default, @code{tar} uses an archive file name that was compiled when
+it was built on the system; usually this name refers to some physical
+tape drive on the machine. However, the person who installed @code{tar}
+on the system may not set the default to a meaningful value as far as
+most users are concerned. As a result, you will usually want to tell
+@code{tar} where to find (or create) the archive. The @value{op-file}
+option allows you to either specify or name a file to use as the archive
+instead of the default archive file location.
+
+@table @kbd
+@item --file=@var{archive-name}
+@itemx -f @var{archive-name}
+Name the archive to create or operate on. Use in conjunction with
+any operation.
+@end table
+
+For example, in this @code{tar} command,
+
+@example
+$ @kbd{tar -cvf collection.tar blues folk jazz}
+@end example
+
+@noindent
+@file{collection.tar} is the name of the archive. It must directly
+follow the @samp{-f} option, since whatever directly follows @samp{-f}
+@emph{will} end up naming the archive. If you neglect to specify an
+archive name, you may end up overwriting a file in the working directory
+with the archive you create since @code{tar} will use this file's name
+for the archive name.
+
+An archive can be saved as a file in the file system, sent through a
+pipe or over a network, or written to an I/O device such as a tape,
+floppy disk, or CD write drive.
+
+@cindex Writing new archives
+@cindex Archive creation
+If you do not name the archive, @code{tar} uses the value of the
+environment variable @code{TAPE} as the file name for the archive. If
+that is not available, @code{tar} uses a default, compiled-in archive
+name, usually that for tape unit zero (ie. @file{/dev/tu00}).
+@code{tar} always needs an archive name.
+
+If you use @file{-} as an @var{archive-name}, @code{tar} reads the
+archive from standard input (when listing or extracting files), or
+writes it to standard output (when creating an archive). If you use
+@file{-} as an @var{archive-name} when modifying an archive,
+@code{tar} reads the original archive from its standard input and
+writes the entire new archive to its standard output.
+
+@FIXME{might want a different example here; this is already used in
+"notable tar usages".}
+
+@example
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+@end example
+
+@FIXME{help!}
+
+@cindex Standard input and output
+@cindex tar to standard input and output
+To specify an archive file on a device attached to a remote machine,
+use the following:
+
+@example
+@kbd{--file=@var{hostname}:/@var{dev}/@var{file name}}
+@end example
+
+@noindent
+@code{tar} will complete the remote connection, if possible, and
+prompt you for a username and password. If you use
+@samp{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @code{tar}
+will complete the remote connection, if possible, using your username
+as the username on the remote machine.
+
+If the archive file name includes a colon (@samp{:}), then it is assumed
+to be a file on another machine. If the archive file is
+@samp{@var{user}@@@var{host}:@var{file}}, then @var{file} is used on the
+host @var{host}. The remote host is accessed using the @code{rsh}
+program, with a username of @var{user}. If the username is omitted
+(along with the @samp{@@} sign), then your user name will be used.
+(This is the normal @code{rsh} behavior.) It is necessary for the
+remote machine, in addition to permitting your @code{rsh} access, to
+have the @file{/usr/ucb/rmt} program installed. If you need to use a
+file whose name includes a colon, then the remote tape drive behavior
+can be inhibited by using the @value{op-force-local} option.
+
+@FIXME{i know we went over this yesterday, but bob (and now i do again,
+too) thinks it's out of the middle of nowhere. it doesn't seem to tie
+into what came before it well enough <<i moved it now, is it better
+here?>>. bob also comments that if Amanda isn't free software, we
+shouldn't mention it..}
+
+When the archive is being created to @file{/dev/null}, GNU @code{tar}
+tries to minimize input and output operations. The Amanda backup
+system, when used with GNU @code{tar}, has an initial sizing pass which
+uses this feature.
+
+@node Selecting Archive Members, files, file, Choosing
+@section Selecting Archive Members
+@cindex Specifying files to act on
+@cindex Specifying archive members
+
+@dfn{File Name arguments} specify which files in the file system
+@code{tar} operates on, when creating or adding to an archive, or which
+archive members @code{tar} operates on, when reading or deleting from
+an archive. @xref{Operations}.
+
+To specify file names, you can include them as the last arguments on
+the command line, as follows:
+@smallexample
+@kbd{tar} @var{operation} [@var{option1} @var{option2} @dots{}] [@var{file name-1} @var{file name-2} @dots{}]
+@end smallexample
+
+If you specify a directory name as a file name argument, all the files
+in that directory are operated on by @code{tar}.
+
+If you do not specify files when @code{tar} is invoked with
+@value{op-create}, @code{tar} operates on all the non-directory files in
+the working directory. If you specify either @value{op-list} or
+@value{op-extract}, @code{tar} operates on all the archive members in the
+archive. If you specify any operation other than one of these three,
+@code{tar} does nothing.
+
+By default, @code{tar} takes file names from the command line. However,
+there are other ways to specify file or member names, or to modify the
+manner in which @code{tar} selects the files or members upon which to
+operate; @FIXME{add xref here}. In general, these methods work both for
+specifying the names of files and archive members.
+
+@node files, exclude, Selecting Archive Members, Choosing
+@section Reading Names from a File
+@UNREVISED
+
+@cindex Reading file names from a file
+@cindex Lists of file names
+@cindex File Name arguments, alternatives
+Instead of giving the names of files or archive members on the command
+line, you can put the names into a file, and then use the
+@value{op-files-from} option to @code{tar}. Give the name of the file
+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
+the list of files to archive with the @code{find} utility.
+
+@table @kbd
+@item --files-from=@var{file name}
+@itemx -T @var{file name}
+Get names to extract or create from file @var{file name}.
+@end table
+
+If you give a single dash as a file name for @samp{--files-from}, (i.e.,
+you specify either @samp{--files-from=-} or @samp{-T -}), then the file
+names are read from standard input.
+
+Unless you are running @code{tar} with @samp{--create}, you can not use
+both @samp{--files-from=-} and @samp{--file=-} (@samp{-f -}) in the same
+command.
+
+@FIXME{add bob's example, from his message on 2-10-97}
+
+The following example shows how to use @code{find} to generate a list of
+files smaller than 400K in length and put that list into a file
+called @file{small-files}. You can then use the @samp{-T} option to
+@code{tar} to specify the files from that file, @file{small-files}, to
+create the archive @file{little.tgz}. (The @samp{-z} option to
+@code{tar} compresses the archive with @code{gzip}; @pxref{gzip} for
+more information.)
+
+@example
+$ @kbd{find . -size -400 -print > small-files}
+$ @kbd{tar -c -v -z -T small-files -f little.tgz}
+@end example
+
+@noindent
+@FIXME{say more here to conclude the example/section?}
+
+@menu
+* nul::
+@end menu
+
+@node nul, , files, files
+@ifinfo
+@unnumberedsubsec @kbd{NUL} Terminated File Names
+@end ifinfo
+
+@cindex File names, terminated by @kbd{NUL}
+@cindex @kbd{NUL} terminated file names
+The @value{op-null} option causes @value{op-files-from} to read file
+names terminated by a @code{NUL} instead of a newline, so files whose
+names contain newlines can be archived using @samp{--files-from}.
+
+@table @kbd
+@item --null
+Only consider @kbd{NUL} terminated file names, instead of files that
+terminate in a newline.
+@end table
+
+The @samp{--null} option is just like the one in GNU @code{xargs} and
+@code{cpio}, and is useful with the @samp{-print0} predicate of GNU
+@code{find}. In @code{tar}, @samp{--null} also causes
+@value{op-directory} options to be treated as file names to archive, in
+case there are any files out there called @file{-C}.
+
+This example shows how to use @code{find} to generate a list of files
+larger than 800K in length and put that list into a file called
+@file{long-files}. The @samp{-print0} option to @code{find} just just
+like @samp{-print}, except that it separates files with a @kbd{NUL}
+rather than with a newline. You can then run @code{tar} with both the
+@samp{--null} and @samp{-T} options to specify that @code{tar} get the
+files from that file, @file{long-files}, to create the archive
+@file{big.tgz}. The @samp{--null} option to @code{tar} will cause
+@code{tar} to recognize the @kbd{NUL} separator between files.
+
+@example
+$ @kbd{find . -size +800 -print0 > long-files}
+$ @kbd{tar -c -v --null --files-from=long-files --file=big.tar}
+@end example
+
+@FIXME{say anything else here to conclude the section?}
+
+@node exclude, Wildcards, files, Choosing
+@section Excluding Some Files
+@cindex File names, excluding files by
+@cindex Excluding files by name and pattern
+@cindex Excluding files by file system
+@UNREVISED
+
+To avoid operating on files whose names match a particular pattern,
+use the @value{op-exclude} or @value{op-exclude-from} options.
+
+@table @kbd
+@item --exclude=@var{pattern}
+Causes @code{tar} to ignore files that match the @var{pattern}.
+@end table
+
+@findex exclude
+The @value{op-exclude} option will prevent any file or member which
+matches the shell wildcards (@var{pattern}) from being operated on
+(@var{pattern} can be a single file name or a more complex expression).
+For example, if you want to create an archive with all the contents of
+@file{/tmp} except the file @file{/tmp/foo}, you can use the command
+@samp{tar --create --file=arch.tar --exclude=foo}. You may give
+multiple @samp{--exclude} options.
+
+@table @kbd
+@item --exclude-from=@var{file}
+@itemx -X @var{file}
+Causes @code{tar} to ignore files that match the patterns listed in
+@var{file}.
+@end table
+
+@findex exclude-from
+Use the @samp{--exclude-from=@var{file-of-patterns}} option to read a
+list of shell wildcards, one per line, from @var{file}; @code{tar} will
+ignore files matching those regular expressions. Thus if @code{tar} is
+called as @w{@samp{tar -c -X foo .}} and the file @file{foo} contains a
+single line @file{*.o}, no files whose names end in @file{.o} will be
+added to the archive.
+
+@FIXME{do the exclude options files need to have stuff separated by
+newlines the same as the files-from option does?}
+
+@menu
+* problems with exclude::
+@end menu
+
+@node problems with exclude, , exclude, exclude
+@unnumberedsubsec Problems with Using the @code{exclude} Options
+
+@FIXME{put in for the editor's/editors' amusement, but should be taken
+out in the final draft, just in case! : }
+
+@ignore
+subtitled: getting screwed using exclewed
+@end ignore
+
+Some users find @samp{exclude} options confusing. Here are some common
+pitfalls:
+
+@itemize @bullet
+@item
+The main operating mode of @code{tar} will always act on file names
+listed on the command line, no matter whether or not there is an
+exclusion which would otherwise affect them. In the example above, if
+you create an archive and exclude files that end with @samp{*.o}, but
+explicitly name the file @samp{catc.o} after all the options have been
+listed, @samp{catc.o} @emph{will} be included in the archive.
+
+@item
+You can sometimes confuse the meanings of @value{op-exclude} and
+@value{op-exclude-from}. Be careful: use @value{op-exclude} when files
+to be excluded are given as a pattern on the command line. Use
+@samp{--exclude-from=@var{file-of-patterns}} to introduce the name of a
+file which contains a list of patterns, one per line; each of these
+patterns can exclude zero, one, or many files.
+
+@item
+When you use @value{op-exclude}, be sure to quote the @var{pattern}
+parameter, so GNU @code{tar} sees wildcard characters like @samp{*}.
+If you do not do this, the shell might expand the @samp{*} itself
+using files at hand, so @code{tar} might receive a list of files
+instead of one pattern, or none at all, making the command somewhat
+illegal. This might not correspond to what you want.
+
+For example, write:
+
+@example
+$ @kbd{tar -c -f @var{archive.tar} -X '*/tmp/*' @var{directory}}
+@end example
+
+@noindent
+rather than:
+
+@example
+$ @kbd{tar -c -f @var{archive.tar} -X */tmp/* @var{directory}}
+@end example
+
+@item
+You must use use shell syntax, or globbing, rather than @code{regexp}
+syntax, when using exclude options in @code{tar}. If you try to use
+@code{regexp} syntax to describe files to be excluded, your command
+might fail.
+
+@item
+In earlier versions of @code{tar}, what is now the
+@samp{--exclude-from=@var{file-of-patterns}} option was called
+@samp{--exclude-@var{pattern}} instead. Now,
+@samp{--exclude=@var{pattern}} applies to patterns listed on the command
+line and @samp{--exclude-from=@var{file-of-patterns}} applies to
+patterns listed in a file.
+
+@end itemize
+
+@node Wildcards, after, exclude, Choosing
+@section Wildcards Patterns and Matching
+
+@dfn{Globbing} is the operation by which @dfn{wildcard} characters,
+@samp{*} or @samp{?} for example, are replaced and expanded into all
+existing files matching the given pattern. However, @code{tar} often
+uses wildcard patterns for matching (or globbing) archive members instead
+of actual files in the filesystem. Wildcard patterns are also used for
+verifying volume labels of @code{tar} archives. This section has the
+purpose of explaining wildcard syntax for @code{tar}.
+
+@FIXME{the next few paragraphs need work.}
+
+A @var{pattern} should be written according to shell syntax, using wildcard
+characters to effect globbing. Most characters in the pattern stand
+for themselves in the matched string, and case is significant: @samp{a}
+will match only @samp{a}, and not @samp{A}. The character @samp{?} in the
+pattern matches any single character in the matched string. The character
+@samp{*} in the pattern matches zero, one, or more single characters in
+the matched string. The character @samp{\} says to take the following
+character of the pattern @emph{literally}; it is useful when one needs to
+match the @samp{?}, @samp{*}, @samp{[} or @samp{\} characters, themselves.
+
+The character @samp{[}, up to the matching @samp{]}, introduces a character
+class. A @dfn{character class} is a list of acceptable characters
+for the next single character of the matched string. For example,
+@samp{[abcde]} would match any of the first five letters of the alphabet.
+Note that within a character class, all of the ``special characters''
+listed above other than @samp{\} lose their special meaning; for example,
+@samp{[-\\[*?]]} would match any of the characters, @samp{-}, @samp{\},
+@samp{[}, @samp{*}, @samp{?}, or @samp{]}. (Due to parsing constraints,
+the characters @samp{-} and @samp{]} must either come @emph{first} or
+@emph{last} in a character class.)
+
+@cindex Excluding characters from a character class
+@cindex Character class, excluding characters from
+If the first character of the class after the opening @samp{[}
+is @samp{!} or @samp{^}, then the meaning of the class is reversed.
+Rather than listing character to match, it lists those characters which
+are @emph{forbidden} as the next single character of the matched string.
+
+Other characters of the class stand for themselves. The special
+construction @samp{[@var{a}-@var{e}]}, using an hyphen between two
+letters, is meant to represent all characters between @var{a} and
+@var{e}, inclusive.
+
+@FIXME{need to add a sentence or so here to make this clear for those
+who don't have dan around.}
+
+Periods (@samp{.}) or forward slashes (@samp{/}) are not considered
+special for wildcard matches. However, if a pattern completely matches
+a directory prefix of a matched string, then it matches the full matched
+string: excluding a directory also excludes all the files beneath it.
+
+There are some discussions floating in the air and asking for modifications
+in the way GNU @code{tar} accomplishes wildcard matches. We perceive
+any change of semantics in this area as a delicate thing to impose on
+GNU @code{tar} users. On the other hand, the GNU project should be
+progressive enough to correct any ill design: compatibility at all price
+is not always a good attitude. In conclusion, it is @emph{possible}
+that slight amendments be later brought to the previous description.
+Your opinions on the matter are welcome.
+
+@node after, recurse, Wildcards, Choosing
+@section Operating Only on New Files
+@cindex Excluding file by age
+@cindex Modification time, excluding files by
+@cindex Age, excluding files by
+@UNREVISED
+
+The @value{op-after-date} option causes @code{tar} to only work on files
+whose modification or inode-changed times are newer than the @var{date}
+given. If you use this option when creating or appending to an archive,
+the archive will only include new files. If you use @samp{--after-date}
+when extracting an archive, @code{tar} will only extract files newer
+than the @var{date} you specify.
+
+If you only want @code{tar} to make the date comparison based on
+modification of the actual contents of the file (rather than inode
+changes), then use the @value{op-newer-mtime} option.
+
+You may use these options with any operation. Note that these options
+differ from the @value{op-update} operation in that they allow you to
+specify a particular date against which @code{tar} can compare when
+deciding whether or not to archive the files.
+
+@table @kbd
+@item --after-date=@var{date}
+@itemx --newer=@var{date}
+@itemx -N @var{date}
+Only store files newer than @var{date}.
+
+Acts on files only if their modification or inode-changed times are
+later than @var{date}. Use in conjunction with any operation.
+
+@item --newer-mtime=@var{date}
+Acts like @value{op-after-date}, but only looks at modification times.
+@end table
+
+These options limit @code{tar} to only operating on files which have
+been modified after the date specified. A file is considered to have
+changed if the contents have been modified, or if the owner,
+permissions, and so forth, have been changed. (For more information on
+how to specify a date, see @ref{Date input formats}; remember that the
+entire date argument must be quoted if it contains any spaces.)
+
+Gurus would say that @value{op-after-date} tests both the @code{mtime}
+(time the contents of the file were last modified) and @code{ctime}
+(time the file's status was last changed: owner, permissions, etc)
+fields, while @value{op-newer-mtime} tests only @code{mtime} field.
+
+To be precise, @value{op-after-date} checks @emph{both} @code{mtime} and
+@code{ctime} and processes the file if either one is more recent than
+@var{date}, while @value{op-newer-mtime} only checks @code{mtime} and
+disregards @code{ctime}. Neither uses @code{atime} (the last time the
+contents of the file were looked at).
+
+Date specifiers can have embedded spaces. Because of this, you may need
+to quote date arguments to keep the shell from parsing them as separate
+arguments.
+
+@FIXME{Need example of --newer-mtime with quoted argument.}
+
+@quotation
+@strong{Please Note:} @value{op-after-date} and @value{op-newer-mtime}
+should not be used for incremental backups. Some files (such as those
+in renamed directories) are not selected properly by these options.
+@xref{incremental and listed-incremental}.
+@end quotation
+
+To select files newer than the modification time of a file that already
+exists, you can use the @samp{--reference} (@samp{-r}) option of GNU
+@code{date}, available in GNU shell utilities 1.13 or later. It returns
+the timestamp of that already existing file; this timestamp expands to
+become the referent date which @samp{--newer} uses to determine which
+files to archive. For example, you could say,
+
+@example
+$ @kbd{tar -cf @var{archive.tar} --newer="`date -r @var{file}`" /home}
+@end example
+
+@noindent
+which tells @FIXME{need to fill this in!}.
+
+@node recurse, one, after, Choosing
+@section Descending into Directories
+@cindex Avoiding recursion in directories
+@cindex Descending directories, avoiding
+@cindex Directories, avoiding recursion
+@cindex Recursion in directories, avoiding
+@UNREVISED
+
+@FIXME{arrggh! this is still somewhat confusing to me. :-< }
+
+@FIXME{show dan bob's comments, from 2-10-97}
+
+Usually, @code{tar} will recursively explore all directories (either
+those given on the command line or through the @value{op-files-from}
+option) for the various files they contain. However, you may not always
+want @code{tar} to act this way.
+
+The @value{op-no-recursion} option inhibits @code{tar}'s recursive descent
+into specified directories. If you specify @samp{--no-recursion}, you can
+use the @code{find} utility for hunting through levels of directories to
+construct a list of file names which you could then pass to @code{tar}.
+@code{find} allows you to be more selective when choosing which files to
+archive; see @ref{files} for more information on using @code{find} with
+@code{tar}, or look.
+
+@table @kbd
+@item --no-recursion
+Prevents @code{tar} from recursively descending directories.
+@end table
+
+When you use @samp{--no-recursion}, GNU @code{tar} grabs directory entries
+themselves, but does not descend on them recursively. Many people use
+@code{find} for locating files they want to back up, and since
+@code{tar} @emph{usually} recursively descends on directories, they have
+to use the @samp{@w{! -d}} option to @code{find} @FIXME{needs more
+explanation or a cite to another info file} as they usually do not want
+all the files in a directory. They then use the @value{op-file-from}
+option to archive the files located via @code{find}.
+
+The problem when restoring files archived in this manner is that the
+directories themselves are not in the archive; so the
+@value{op-same-permissions} option does not affect them---while users
+might really like it to. Specifying @value{op-no-recursion} is a way to
+tell @code{tar} to grab only the directory entries given to it, adding
+no new files on its own.
+
+@FIXME{example here}
+
+@node one, , recurse, Choosing
+@section Crossing Filesystem Boundaries
+@cindex File system boundaries, not crossing
+@UNREVISED
+
+@code{tar} will normally automatically cross file system boundaries in
+order to archive files which are part of a directory tree. You can
+change this behavior by running @code{tar} and specifying
+@value{op-one-file-system}. This option only affects files that are
+archived because they are in a directory that is being archived;
+@code{tar} will still archive files explicitly named on the command line
+or through @value{op-files-from}, regardless of where they reside.
+
+@table @kbd
+@item --one-file-system
+@itemx -l
+Prevents @code{tar} from crossing file system boundaries when
+archiving. Use in conjunction with any write operation.
+@end table
+
+The @samp{--one-file-system} option causes @code{tar} to modify its
+normal behavior in archiving the contents of directories. If a file in
+a directory is not on the same filesystem as the directory itself, then
+@code{tar} will not archive that file. If the file is a directory
+itself, @code{tar} will not archive anything beneath it; in other words,
+@code{tar} will not cross mount points.
+
+It is reported that using this option, the mount point is is archived,
+but nothing under it.
+
+This option is useful for making full or incremental archival backups of
+a file system. If this option is used in conjunction with
+@value{op-verbose}, files that are excluded are mentioned by name on the
+standard error.
+
+@menu
+* directory:: Changing Directory
+* absolute:: Absolute File Names
+@end menu
+
+@node directory, absolute, one, one
+@subsection Changing the Working Directory
+
+@FIXME{need to read over this node now for continuity; i've switched
+things around some.}
+
+@cindex Changing directory mid-stream
+@cindex Directory, changing mid-stream
+@cindex Working directory, specifying
+@UNREVISED
+
+To change the working directory in the middle of a list of file names,
+either on the command line or in a file specified using
+@value{op-files-from}, use @value{op-directory}. This will change the
+working directory to the directory @var{directory} after that point in
+the list.
+
+@table @kbd
+@item --directory=@var{directory}
+@itemx -C @var{directory}
+Changes the working directory in the middle of a command line.
+@end table
+
+For example,
+
+@example
+$ @kbd{tar -c -f jams.tar grape prune -C food cherry}
+@end example
+
+@noindent
+will place the files @file{grape} and @file{prune} from the current
+directory into the archive @file{jams.tar}, followed by the file
+@file{cherry} from the directory @file{food}. This option is especially
+useful when you have several widely separated files that you want to
+store in the same archive.
+
+Note that the file @file{cherry} is recorded in the archive under the
+precise name @file{cherry}, @emph{not} @file{food/cherry}. Thus, the
+archive will contain three files that all appear to have come from the
+same directory; if the archive is extracted with plain @samp{tar
+--extract}, all three files will be written in the current directory.
+
+Contrast this with the command,
+
+@example
+$ @kbd{tar -c -f jams.tar grape prune -C food red/cherry}
+@end example
+
+@noindent
+which records the third file in the archive under the name
+@file{red/cherry} so that, if the archive is extracted using
+@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
+independent of the original name of the directory holding the files.
+The following command places the files @file{/etc/passwd},
+@file{/etc/hosts}, and @file{/lib/libc.a} into the archive
+@file{foo.tar}:
+
+@example
+$ @kbd{tar -c -f foo.tar -C /etc passwd hosts -C /lib libc.a}
+@end example
+
+@noindent
+However, the names of the archive members will be exactly what they were
+on the command line: @file{passwd}, @file{hosts}, and @file{libc.a}.
+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
+relative to the then current directory, which might not be the same as
+the original current working directory of @code{tar}, due to a previous
+@samp{--directory} option.
+
+@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?}
+
+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.)
+
+@node absolute, , directory, one
+@subsection Absolute File Names
+@UNREVISED
+
+@table @kbd
+@item -P
+@itemx --absolute-names
+Do not strip leading slashes from file names.
+@end table
+
+By default, GNU @code{tar} drops a leading @samp{/} on input or output.
+This option turns off this behavior; it is equivalent to changing to the
+root directory before running @code{tar} (except it also turns off the
+usual warning message).
+
+When @code{tar} extracts archive members from an archive, it strips any
+leading slashes (@samp{/}) from the member name. This causes absolute
+member names in the archive to be treated as relative file names. This
+allows you to have such members extracted wherever you want, instead of
+being restricted to extracting the member in the exact directory named
+in the archive. For example, if the archive member has the name
+@file{/etc/passwd}, @code{tar} will extract it as if the name were
+really @file{etc/passwd}.
+
+Other @code{tar} programs do not do this. As a result, if you create an
+archive whose member names start with a slash, they will be difficult
+for other people with a non-GNU @code{tar} program to use. Therefore,
+GNU @code{tar} also strips leading slashes from member names when
+putting members into the archive. For example, if you ask @code{tar} to
+add the file @file{/bin/ls} to an archive, it will do so, but the member
+name will be @file{bin/ls}.
+
+If you use the @value{op-absolute-names} option, @code{tar} will do
+neither of these transformations.
+
+To archive or extract files relative to the root directory, specify
+the @value{op-absolute-names} option.
+
+Normally, @code{tar} acts on files relative to the working
+directory---ignoring superior directory names when archiving, and
+ignoring leading slashes when extracting.
+
+When you specify @value{op-absolute-names}, @code{tar} stores file names
+including all superior directory names, and preserves leading slashes.
+If you only invoked @code{tar} from the root directory you would never
+need the @value{op-absolute-names} option, but using this option may be
+more convenient than switching to root.
+
+@FIXME{Should be an example in the tutorial/wizardry section using this
+to transfer files between systems.}
+
+@FIXME{Is write access an issue?}
+
+@table @kbd
+@item --absolute-names
+Preserves full file names (inclusing superior dirctory names) when
+archiving files. Preserves leading slash when extracting files.
+
+@end table
+
+@FIXME{this is still horrible; need to talk with dan on monday.}
+
+@code{tar} prints out a message about removing the @samp{/} from file
+names. This message appears once per GNU @code{tar} invocation. It
+represents something which ought to be told; ignoring what it means can
+cause very serious surprises, later.
+
+Some people, nevertheless, do not want to see this message. Wanting to
+play really dangerously, one may of course redirect @code{tar} standard
+error to the sink. For example, under @code{sh}:
+
+@example
+$ @kbd{tar -c -f archive.tar /home 2> /dev/null}
+@end example
+
+@noindent
+Another solution, both nicer and simpler, would be to change to
+the @file{/} directory first, and then avoid absolute notation.
+For example:
+
+@example
+$ @kbd{(cd / && tar -c -f archive.tar home)}
+$ @kbd{tar -c -f archive.tar -C / home}
+@end example
+
+@node Date input formats, Formats, Choosing, Top
+@chapter Date input formats
+
+@cindex date input formats
+@findex getdate
+
+@quotation
+Our units of temporal measurement, from seconds on up to months, are so
+complicated, asymmetrical and disjunctive so as to make coherent mental
+reckoning in time all but impossible. Indeed, had some tyrannical god
+contrived to enslave our minds to time, to make it all but impossible
+for us to escape subjection to sodden routines and unpleasant surprises,
+he could hardly have done better than handing down our present system.
+It is like a set of trapezoidal building blocks, with no vertical or
+horizontal surfaces, like a language in which the simplest thought
+demands ornate constructions, useless particles and lengthy
+circumlocutions. Unlike the more successful patterns of language and
+science, which enable us to face experience boldly or at least
+level-headedly, our system of temporal calculation silently and
+persistently encourages our terror of time.
+
+@dots{} It is as though architects had to measure length in feet, width
+in meters and height in ells; as though basic instruction manuals
+demanded a knowledge of five different languages. It is no wonder then
+that we often look into our own immediate past or future, last Tuesday
+or a week from Sunday, with feelings of helpless confusion. @dots{}
+
+--- Robert Grudin, @cite{Time and the Art of Living}.
+@end quotation
+
+This section describes the textual date representations that GNU
+programs accept. These are the strings you, as a user, can supply as
+arguments to the various programs. The C interface (via the
+@code{getdate} function) is not described here.
+
+@cindex beginning of time, for Unix
+@cindex epoch, for Unix
+Although the date syntax here can represent any possible time since zero
+A.D., computer integers are not big enough for such a (comparatively)
+long time. The earliest date semantically allowed on Unix systems is
+midnight, 1 January 1970 UCT.
+
+@menu
+* General date syntax:: Common rules.
+* Calendar date item:: 19 Dec 1994.
+* Time of day item:: 9:20pm.
+* Timezone item:: EST, DST, BST, UCT, AHST, ...
+* Day of week item:: Monday and others.
+* Relative item in date strings:: next tuesday, 2 years ago.
+* Pure numbers in date strings:: 19931219, 1440.
+* Authors of getdate:: Bellovin, Salz, Berets, et al.
+@end menu
+
+
+@node General date syntax, Calendar date item, Date input formats, Date input formats
+@section General date syntax
+
+@cindex general date syntax
+
+@cindex items in date strings
+A @dfn{date} is a string, possibly empty, containing many items
+separated by whitespace. The whitespace may be omitted when no
+ambiguity arises. The empty string means the beginning of today (i.e.,
+midnight). Order of the items is immaterial. A date string may contain
+many flavors of items:
+
+@itemize @bullet
+@item calendar date items
+@item time of the day items
+@item time zone items
+@item day of the week items
+@item relative items
+@item pure numbers.
+@end itemize
+
+@noindent We describe each of these item types in turn, below.
+
+@cindex numbers, written-out
+@cindex ordinal numbers
+@findex first @r{in date strings}
+@findex next @r{in date strings}
+@findex last @r{in date strings}
+A few numbers may be written out in words in most contexts. This is
+most useful for specifying day of the week items or relative items (see
+below). Here is the list: @samp{first} for 1, @samp{next} for 2,
+@samp{third} for 3, @samp{fourth} for 4, @samp{fifth} for 5,
+@samp{sixth} for 6, @samp{seventh} for 7, @samp{eighth} for 8,
+@samp{ninth} for 9, @samp{tenth} for 10, @samp{eleventh} for 11 and
+@samp{twelfth} for 12. Also, @samp{last} means exactly @math{-1}.
+
+@cindex months, written-out
+When a month is written this way, it is still considered to be written
+numerically, instead of being ``spelled in full''; this changes the
+allowed strings.
+
+@cindex case, ignored in dates
+@cindex comments, in dates
+Alphabetic case is completely ignored in dates. Comments may be introduced
+between round parentheses, as long as included parentheses are properly
+nested. Hyphens not followed by a digit are currently ignored. Leading
+zeros on numbers are ignored.
+
+
+@node Calendar date item, Time of day item, General date syntax, Date input formats
+@section Calendar date item
+
+@cindex calendar date item
+
+A @dfn{calendar date item} specifies a day of the year. It is
+specified differently, depending on whether the month is specified
+numerically or literally. All these strings specify the same calendar date:
+
+@example
+1970-09-17 # ISO 8601.
+70-9-17 # This century assumed by default.
+70-09-17 # Leading zeros are ignored.
+9/17/72 # Common U.S. writing.
+24 September 1972
+24 Sept 72 # September has a special abbreviation.
+24 Sep 72 # Three-letter abbreviations always allowed.
+Sep 24, 1972
+24-sep-72
+24sep72
+@end example
+
+The year can also be omitted. In this case, the last specified year is
+used, or the current year if none. For example:
+
+@example
+9/17
+sep 17
+@end example
+
+Here are the rules.
+
+@cindex ISO 8601 date format
+@cindex date format, ISO 8601
+For numeric months, the ISO 8601 format
+@samp{@var{year}-@var{month}-@var{day}} is allowed, where @var{year} is
+any positive number, @var{month} is a number between 01 and 12, and
+@var{day} is a number between 01 and 31. A leading zero must be present
+if a number is less than ten. If @var{year} is less than 100, then 1900
+is added to it to force a date in this century. The construct
+@samp{@var{month}/@var{day}/@var{year}}, popular in the United States,
+is accepted. Also @samp{@var{month}/@var{day}}, omitting the year.
+
+@cindex month names in date strings
+@cindex abbreviations for months
+Literal months may be spelled out in full: @samp{January},
+@samp{February}, @samp{March}, @samp{April}, @samp{May}, @samp{June},
+@samp{July}, @samp{August}, @samp{September}, @samp{October},
+@samp{November} or @samp{December}. Literal months may be abbreviated
+to their first three letters, possibly followed by an abbreviating dot.
+It is also permitted to write @samp{Sept} instead of @samp{September}.
+
+When months are written literally, the calendar date may be given as any
+of the following:
+
+@example
+@var{day} @var{month} @var{year}
+@var{day} @var{month}
+@var{month} @var{day} @var{year}
+@var{day}-@var{month}-@var{year}
+@end example
+
+Or, omitting the year:
+
+@example
+@var{month} @var{day}
+@end example
+
+
+@node Time of day item, Timezone item, Calendar date item, Date input formats
+@section Time of day item
+
+@cindex time of day item
+
+A @dfn{time of day item} in date strings specifies the time on a given
+day. Here are some examples, all of which represent the same time:
+
+@example
+20:02:0
+20:02
+8:02pm
+20:02-0500 # In EST (Eastern U.S. Standard Time).
+@end example
+
+More generally, the time of the day may be given as
+@samp{@var{hour}:@var{minute}:@var{second}}, where @var{hour} is
+a number between 0 and 23, @var{minute} is a number between 0 and
+59, and @var{second} is a number between 0 and 59. Alternatively,
+@samp{:@var{second}} can be omitted, in which case it is taken to
+be zero.
+
+@findex am @r{in date strings}
+@findex pm @r{in date strings}
+@findex midnight @r{in date strings}
+@findex noon @r{in date strings}
+If the time is followed by @samp{am} or @samp{pm} (or @samp{a.m.}
+or @samp{p.m.}), @var{hour} is restricted to run from 1 to 12, and
+@samp{:@var{minute}} may be omitted (taken to be zero). @samp{am}
+indicates the first half of the day, @samp{pm} indicates the second
+half of the day. In this notation, 12 is the predecessor of 1:
+midnight is @samp{12am} while noon is @samp{12pm}.
+
+@cindex timezone correction
+@cindex minutes, timezone correction by
+The time may alternatively be followed by a timezone correction,
+expressed as @samp{@var{s}@var{hh}@var{mm}}, where @var{s} is @samp{+}
+or @samp{-}, @var{hh} is a number of zone hours and @var{mm} is a number
+of zone minutes. When a timezone correction is given this way, it
+forces interpretation of the time in UTC, overriding any previous
+specification for the timezone or the local timezone. The @var{minute}
+part of the time of the day may not be elided when a timezone correction
+is used. This is the only way to specify a timezone correction by
+fractional parts of an hour.
+
+Either @samp{am}/@samp{pm} or a timezone correction may be specified,
+but not both.
+
+
+@node Timezone item, Day of week item, Time of day item, Date input formats
+@section Timezone item
+
+@cindex timezone item
+
+A @dfn{timezone item} specifies an international timezone, indicated by
+a small set of letters. Any included period is ignored. Military
+timezone designations use a single letter. Currently, only integral
+zone hours may be represented in a timezone item. See the previous
+section for a finer control over the timezone correction.
+
+Here are many non-daylight-savings-time timezones, indexed by the zone
+hour value.
+
+@table @asis
+@item +000
+@cindex Greenwich Mean Time
+@cindex Universal Coordinated Time
+@cindex Western European Time
+@samp{GMT} for Greenwich Mean, @samp{UT} or @samp{UTC} for Universal
+(Coordinated), @samp{WET} for Western European and @samp{Z} for
+militaries.
+@item +100
+@cindex West African Time
+@samp{WAT} for West Africa and
+@samp{A} for militaries.
+@item +200
+@cindex Azores Time
+@samp{AT} for Azores and @samp{B} for militaries.
+@item +300
+@samp{C} for militaries.
+@item +400
+@cindex Atlantic Standard Time
+@samp{AST} for Atlantic Standard and @samp{D} for militaries.
+@item +500
+@cindex Eastern Standard Time
+@samp{E} for militaries and @samp{EST} for Eastern Standard.
+@item +600
+@cindex Central Standard Time
+@samp{CST} for Central Standard and @samp{F} for militaries.
+@item +700
+@cindex Mountain Standard Time
+@samp{G} for militaries and @samp{MST} for Mountain Standard.
+@item +800
+@cindex Pacific Standard Time
+@samp{H} for militaries and @samp{PST} for Pacific Standard.
+@item +900
+@cindex Yukon Standard Time
+@samp{I} for militaries and @samp{YST} for Yukon Standard.
+@item +1000
+@cindex Alaska-Hawaii Time
+@cindex Central Alaska Time
+@cindex Hawaii Standard Time
+@samp{AHST} for Alaska-Hawaii Standard, @samp{CAT} for Central Alaska,
+@samp{HST} for Hawaii Standard and @samp{K} for militaries.
+@item +1100
+@cindex Nome Standard Time
+@samp{L} for militaries and @samp{NT} for Nome.
+@item +1200
+@cindex International Date Line West
+@samp{IDLW} for International Date Line West and @samp{M} for
+militaries.
+@item -100
+@cindex Central European Time
+@cindex Middle European Time
+@cindex Middle European Winter Time
+@cindex French Winter Time
+@cindex Swedish Winter Time
+@samp{CET} for Central European, @samp{FWT} for French Winter,
+@samp{MET} for Middle European, @samp{MEWT} for Middle European
+Winter, @samp{N} for militaries and @samp{SWT} for Swedish Winter.
+@item -200
+@cindex Eastern European Time
+@cindex USSR Zone
+@samp{EET} for Eastern European, USSR Zone 1 and @samp{O} for militaries.
+@item -300
+@cindex Baghdad Time
+@samp{BT} for Baghdad, USSR Zone 2 and @samp{P} for militaries.
+@item -400
+@samp{Q} for militaries and @samp{ZP4} for USSR Zone 3.
+@item -500
+@samp{R} for militaries and @samp{ZP5} for USSR Zone 4.
+@item -600
+@samp{S} for militaries and @samp{ZP6} for USSR Zone 5.
+@item -700
+@cindex West Australian Standard Time
+@samp{T} for militaries and @samp{WAST} for West Australian Standard.
+@item -800
+@cindex China Coast Time
+@samp{CCT} for China Coast, USSR Zone 7 and @samp{U} for militaries.
+@item -900
+@cindex Japan Standard Time
+@samp{JST} for Japan Standard, USSR Zone 8 and @samp{V} for militaries.
+@item -1000
+@cindex East Australian Standard Time
+@cindex Guam Standard Time
+@samp{EAST} for East Australian Standard, @samp{GST} for Guam
+Standard, USSR Zone 9 and @samp{W} for militaries.
+@item -1100
+@samp{X} for militaries.
+@item -1200
+@cindex International Date Line East
+@cindex New Zealand Standard Time
+@samp{IDLE} for International Date Line East, @samp{NZST} for
+New Zealand Standard, @samp{NZT} for New Zealand and @samp{Y} for
+militaries.
+@end table
+
+@cindex daylight savings time
+Here are many DST timezones, indexed by the zone hour value. Also, by
+following a non-DST timezone by the string @samp{DST} in a separate word
+(that is, separated by some whitespace), the corresponding DST timezone
+may be specified.
+
+@table @asis
+@item 0
+@samp{BST} for British Summer.
+@item +400
+@samp{ADT} for Atlantic Daylight.
+@item +500
+@samp{EDT} for Eastern Daylight.
+@item +600
+@samp{CDT} for Central Daylight.
+@item +700
+@samp{MDT} for Mountain Daylight.
+@item +800
+@samp{PDT} for Pacific Daylight.
+@item +900
+@samp{YDT} for Yukon Daylight.
+@item +1000
+@samp{HDT} for Hawaii Daylight.
+@item -100
+@samp{MEST} for Middle European Summer, @samp{MESZ} for Middle European
+Summer, @samp{SST} for Swedish Summer and @samp{FST} for French Summer.
+@item -700
+@samp{WADT} for West Australian Daylight.
+@item -1000
+@samp{EADT} for Eastern Australian Daylight.
+@item -1200
+@samp{NZDT} for New Zealand Daylight.
+@end table
+
+
+@node Day of week item, Relative item in date strings, Timezone item, Date input formats
+@section Day of week item
+
+@cindex day of week item
+
+The explicit mention of a day of the week will forward the date
+(only if necessary) to reach that day of the week in the future.
+
+Days of the week may be spelled out in full: @samp{Sunday},
+@samp{Monday}, @samp{Tuesday}, @samp{Wednesday}, @samp{Thursday},
+@samp{Friday} or @samp{Saturday}. Days may be abbreviated to their
+first three letters, optionally followed by a period. The special
+abbreviations @samp{Tues} for @samp{Tuesday}, @samp{Wednes} for
+@samp{Wednesday} and @samp{Thur} or @samp{Thurs} for @samp{Thursday} are
+also allowed.
+
+@findex next @var{day}
+@findex last @var{day}
+A number may precede a day of the week item to move forward
+supplementary weeks. It is best used in expression like @samp{third
+monday}. In this context, @samp{last @var{day}} or @samp{next
+@var{day}} is also acceptable; they move one week before or after
+the day that @var{day} by itself would represent.
+
+A comma following a day of the week item is ignored.
+
+
+@node Relative item in date strings, Pure numbers in date strings, Day of week item, Date input formats
+@section Relative item in date strings
+
+@cindex relative items in date strings
+@cindex displacement of dates
+
+@dfn{Relative items} adjust a date (or the current date if none) forward
+or backward. The effects of relative items accumulate. Here are some
+examples:
+
+@example
+1 year
+1 year ago
+3 years
+2 days
+@end example
+
+@findex year @r{in date strings}
+@findex month @r{in date strings}
+@findex fortnight @r{in date strings}
+@findex week @r{in date strings}
+@findex day @r{in date strings}
+@findex hour @r{in date strings}
+@findex minute @r{in date strings}
+The unit of time displacement may be selected by the string @samp{year}
+or @samp{month} for moving by whole years or months. These are fuzzy
+units, as years and months are not all of equal duration. More precise
+units are @samp{fortnight} which is worth 14 days, @samp{week} worth 7
+days, @samp{day} worth 24 hours, @samp{hour} worth 60 minutes,
+@samp{minute} or @samp{min} worth 60 seconds, and @samp{second} or
+@samp{sec} worth one second. An @samp{s} suffix on these units is
+accepted and ignored.
+
+@findex ago @r{in date strings}
+The unit of time may be preceded by a multiplier, given as an optionally
+signed number. Unsigned numbers are taken as positively signed. No
+number at all implies 1 for a multiplier. Following a relative item by
+the string @samp{ago} is equivalent to preceding the unit by a
+multiplicator with value @math{-1}.
+
+@findex day @r{in date strings}
+@findex tomorrow @r{in date strings}
+@findex yesterday @r{in date strings}
+The string @samp{tomorrow} is worth one day in the future (equivalent
+to @samp{day}), the string @samp{yesterday} is worth
+one day in the past (equivalent to @samp{day ago}).
+
+@findex now @r{in date strings}
+@findex today @r{in date strings}
+@findex this @r{in date strings}
+The strings @samp{now} or @samp{today} are relative items corresponding
+to zero-valued time displacement, these strings come from the fact
+a zero-valued time displacement represents the current time when not
+otherwise change by previous items. They may be used to stress other
+items, like in @samp{12:00 today}. The string @samp{this} also has
+the meaning of a zero-valued time displacement, but is preferred in
+date strings like @samp{this thursday}.
+
+When a relative item makes the resulting date to cross the boundary
+between DST and non-DST (or vice-versa), the hour is adjusted according
+to the local time.
+
+
+@node Pure numbers in date strings, Authors of getdate, Relative item in date strings, Date input formats
+@section Pure numbers in date strings
+
+@cindex pure numbers in date strings
+
+The precise intepretation of a pure decimal number is dependent of
+the context in the date string.
+
+If the decimal number is of the form @var{yyyy}@var{mm}@var{dd} and no
+other calendar date item (@pxref{Calendar date item}) appears before it
+in the date string, then @var{yyyy} is read as the year, @var{mm} as the
+month number and @var{dd} as the day of the month, for the specified
+calendar date.
+
+If the decimal number is of the form @var{hh}@var{mm} and no other time
+of day item appears before it in the date string, then @var{hh} is read
+as the hour of the day and @var{mm} as the minute of the hour, for the
+specified time of the day. @var{mm} can also be omitted.
+
+If both a calendar date and a time of day appear to the left of a number
+in the date string, but no relative item, then the number overrides the
+year.
+
+
+@node Authors of getdate, , Pure numbers in date strings, Date input formats
+@section Authors of @code{getdate}
+
+@cindex authors of @code{getdate}
+
+@cindex Bellovin, Steven M.
+@cindex Salz, Rich
+@cindex Berets, Jim
+@cindex MacKenzie, David
+@cindex Meyering, Jim
+@code{getdate} was originally implemented by Steven M. Bellovin
+(@samp{smb@@research.att.com}) while at the University of North Carolina
+at Chapel Hill. The code was later tweaked by a couple of people on
+Usenet, then completely overhauled by Rich $alz (@samp{rsalz@@bbn.com})
+and Jim Berets (@samp{jberets@@bbn.com}) in August, 1990. Various
+revisions for the GNU system were made by David MacKenzie, Jim Meyering,
+and others.
+
+@cindex Pinard, F.
+@cindex Berry, K.
+This chapter was originally produced by Fran@,{c}ois Pinard
+(@samp{pinard@@iro.umontreal.ca}) from the @file{getdate.y} source code,
+and then edited by K.@: Berry (@samp{kb@@cs.umb.edu}).
+
+@node Formats, Media, Date input formats, Top
+@chapter Controlling the Archive Format
+
+@FIXME{need an intro here}
+
+@menu
+* Portability:: Making @code{tar} Archives More Portable
+* Compression:: Using Less Space through Compression
+* Attributes:: Handling File Attributes
+* Standard:: The Standard Format
+* Extensions:: GNU Extensions to the Archive Format
+* cpio:: Comparison of @code{tar} and @code{cpio}
+@end menu
+
+@node Portability, Compression, Formats, Formats
+@section Making @code{tar} Archives More Portable
+
+Creating a @code{tar} archive on a particular system that is meant to be
+useful later on many other machines and with other versions of @code{tar}
+is more challenging than you might think. @code{tar} archive formats
+have been evolving since the first versions of Unix. Many such formats
+are around, and are not always comptible with each other. This section
+discusses a few problems, and gives some advice about making @code{tar}
+archives more portable.
+
+One golden rule is simplicity. For example, limit your @code{tar}
+archives to contain only regular files and directories, avoiding
+other kind of special files. Do not attempt to save sparse files or
+contiguous files as such. Let's discuss a few more problems, in turn.
+
+@menu
+* Portable Names:: Portable Names
+* dereference:: Symbolic Links
+* old:: Old V7 Archives
+* posix:: POSIX archives
+* Checksumming:: Checksumming Problems
+@end menu
+
+@node Portable Names, dereference, Portability, Portability
+@subsection Portable Names
+
+Use @emph{straight} file and directory names, made up of printable
+ASCII characters, avoiding colons, slashes, backslashes, spaces, and
+other @emph{dangerous} characters. Avoid deep directory nesting.
+Accounting for oldish System V machines, limit your file and directory
+names to 14 characters or less.
+
+If you intend to have your @code{tar} archives to be read under MSDOS,
+you should not rely on case distinction for file names, and you might
+use the GNU @code{doschk} program for helping you further diagnosing
+illegal MSDOS names, which are even more limited than System V's.
+
+@node dereference, old, Portable Names, Portability
+@subsection Symbolic Links
+@cindex File names, using symbolic links
+@cindex Symbolic link as file name
+
+Normally, when @code{tar} archives a symbolic link, it writes a
+block to the archive naming the target of the link. In that way, the
+@code{tar} archive is a faithful record of the filesystem contents.
+@value{op-dereference} is used with @value{op-create}, and causes @code{tar}
+to archive the files symbolic links point to, instead of the links
+themselves. When this option is used, when @code{tar} encounters a
+symbolic link, it will archive the linked-to file, instead of simply
+recording the presence of a symbolic link.
+
+The name under which the file is stored in the file system is not
+recorded in the archive. To record both the symbolic link name and
+the file name in the system, archive the file under both names. If
+all links were recorded automatically by @code{tar}, an extracted file
+might be linked to a file name that no longer exists in the file
system.
-@item --help
-Prints a list of @code{tar} operations and options.
+If a linked-to file is encountered again by @code{tar} while creating
+the same archive, an entire second copy of it will be stored. (This
+@emph{might} be considered a bug.)
+
+So, for portable archives, do not archive symbolic links as such,
+and use @value{op-dereference}: many systems do not support
+symbolic links, and moreover, your distribution might be unusable if
+it contains unresolved symbolic links.
+
+@node old, posix, dereference, Portability
+@subsection Old V7 Archives
+@cindex Format, old style
+@cindex Old style format
+@cindex Old style archives
+
+Certain old versions of @code{tar} cannot handle additional
+information recorded by newer @code{tar} programs. To create an
+archive in V7 format (not ANSI), which can be read by these old
+versions, specify the @value{op-old-archive} option in
+conjunction with the @value{op-create}. @code{tar} also
+accepts @samp{--portability} for this option. When you specify it,
+@code{tar} leaves out information about directories, pipes, fifos,
+contiguous files, and device files, and specifies file ownership by
+group and user IDs instead of group and user names.
+
+When updating an archive, do not use @value{op-old-archive}
+unless the archive was created with using this option.
+
+In most cases, a @emph{new} format archive can be read by an @emph{old}
+@code{tar} program without serious trouble, so this option should
+seldom be needed. On the other hand, most modern @code{tar}s are
+able to read old format archives, so it might be safer for you to
+always use @value{op-old-archive} for your distributions.
+
+@node posix, Checksumming, old, Portability
+@subsection GNU @code{tar} and POSIX @code{tar}
+
+GNU @code{tar} was based on an early draft of the POSIX 1003.1
+@code{ustar} standard. GNU extensions to @code{tar}, such as the
+support for file names longer than 100 characters, use portions of the
+@code{tar} header record which were specified in that POSIX draft as
+unused. Subsequent changes in POSIX have allocated the same parts of
+the header record for other purposes. As a result, GNU @code{tar} is
+incompatible with the current POSIX spec, and with @code{tar} programs
+that follow it.
+
+We plan to reimplement these GNU extensions in a new way which is
+upward compatible with the latest POSIX @code{tar} format, but we
+don't know when this will be done.
+
+In the mean time, there is simply no telling what might happen if you
+read a GNU @code{tar} archive, which uses the GNU extensions, using
+some other @code{tar} program. So if you want to read the archive
+with another @code{tar} program, be sure to write it using the
+@samp{--old-archive} option (@samp{-o}).
+
+@FIXME{is there a way to tell which flavor of tar was used to write a
+particular archive before you try to read it?}
+
+Traditionally, old @code{tar}s have a limit of 100 characters. GNU
+@code{tar} attempted two different approaches to overcome this limit,
+using and extending a format specified by a draft of some P1003.1.
+The first way was not that successful, and involved @file{@@MaNgLeD@@}
+file names, or such; while a second approach used @file{././@@LongLink}
+and other tricks, yielding better success. In theory, GNU @code{tar}
+should be able to handle file names of practically unlimited length.
+So, if GNU @code{tar} fails to dump and retrieve files having more
+than 100 characters, then there is a bug in GNU @code{tar}, indeed.
+
+But, being strictly POSIX, the limit was still 100 characters.
+For various other purposes, GNU @code{tar} used areas left unassigned
+in the POSIX draft. POSIX later revised P1003.1 @code{ustar} format by
+assigning previously unused header fields, in such a way that the upper
+limit for file name length was raised to 256 characters. However, the
+actual POSIX limit oscillates between 100 and 256, depending on the
+precise location of slashes in full file name (this is rather ugly).
+Since GNU @code{tar} use the same fields for quite other purposes,
+it became incompatible with the latest POSIX standards.
+
+For longer or non-fitting file names, we plan to use yet another set
+of GNU extensions, but this time, complying with the provisions POSIX
+offers for extending the format, rather than conflicting with it.
+Whenever an archive uses old GNU @code{tar} extension format or POSIX
+extensions, would it be for very long file names or other specialities,
+this archive becomes non-portable to other @code{tar} implementations.
+In fact, anything can happen. The most forgiving @code{tar}s will
+merely unpack the file using a wrong name, and maybe create another
+file named something like @file{@@LongName}, with the true file name
+in it. @code{tar}s not protecting themselves may segment violate!
+
+Compatibility concerns make all this thing more difficult, as we
+will have to support @emph{all} these things together, for a while.
+GNU @code{tar} should be able to produce and read true POSIX format
+files, while being able to detect old GNU @code{tar} formats, besides
+old V7 format, and process them conveniently. It would take years
+before this whole area stabilizes@dots{}
+
+There are plans to raise this 100 limit to 256, and yet produce POSIX
+conformant archives. Past 256, I do not know yet if GNU @code{tar}
+will go non-POSIX again, or merely refuse to archive the file.
+
+There are plans so GNU @code{tar} support more fully the latest POSIX
+format, while being able to read old V7 format, GNU (semi-POSIX plus
+extension), as well as full POSIX. One may ask if there is part of
+the POSIX format that we still cannot support. This simple question
+has a complex answer. Maybe that, on intimate look, some strong
+limitations will pop up, but until now, nothing sounds too difficult
+(but see below). I only have these few pages of POSIX telling about
+`Extended tar Format' (P1003.1-1990 -- section 10.1.1), and there are
+references to other parts of the standard I do not have, which should
+normally enforce limitations on stored file names (I suspect things
+like fixing what @kbd{/} and @kbd{@key{NUL}} means). There are also
+some points which the standard does not make clear, Existing practice
+will then drive what I should do.
+
+POSIX mandates that, when a file name cannot fit within 100 to
+256 characters (the variance comes from the fact a @kbd{/} is
+ideally needed as the 156'th character), or a link name cannot
+fit within 100 characters, a warning should be issued and the file
+@emph{not} be stored. Unless some @value{op-posix} option is given
+(or @code{POSIXLY_CORRECT} is set), I suspect that GNU @code{tar}
+should disobey this specification, and automatically switch to using
+GNU extensions to overcome file name or link name length limitations.
+
+There is a problem, however, which I did not intimately studied yet.
+Given a truly POSIX archive with names having more than 100 characters,
+I guess that GNU @code{tar} up to 1.11.8 will process it as if it were an
+old V7 archive, and be fooled by some fields which are coded differently.
+So, the question is to decide if the next generation of GNU @code{tar}
+should produce POSIX format by default, whenever possible, producing
+archives older versions of GNU @code{tar} might not be able to read
+correctly. I fear that we will have to suffer such a choice one of these
+days, if we want GNU @code{tar} to go closer to POSIX. We can rush it.
+Another possibility is to produce the current GNU @code{tar} format
+by default for a few years, but have GNU @code{tar} versions from some
+1.@var{POSIX} and up able to recognize all three formats, and let older
+GNU @code{tar} fade out slowly. Then, we could switch to producing POSIX
+format by default, with not much harm to those still having (very old at
+that time) GNU @code{tar} versions prior to 1.@var{POSIX}.
+
+POSIX format cannot represent very long names, volume headers,
+splitting of files in multi-volumes, sparse files, and incremental
+dumps; these would be all disallowed if @value{op-posix} or
+@code{POSIXLY_CORRECT}. Otherwise, if @code{tar} is given long
+names, or @samp{-[VMSgG]}, then it should automatically go non-POSIX.
+I think this is easily granted without much discussion.
+
+Another point is that only @code{mtime} is stored in POSIX
+archives, while GNU @code{tar} currently also store @code{atime}
+and @code{ctime}. If we want GNU @code{tar} to go closer to POSIX,
+my choice would be to drop @code{atime} and @code{ctime} support on
+average. On the other hand, I perceive that full dumps or incremental
+dumps need @code{atime} and @code{ctime} support, so for those special
+applications, POSIX has to be avoided altogether.
+
+A few users requested that @value{op-sparse} be always active by
+default, I think that before replying to them, we have to decide
+if we want GNU @code{tar} to go closer to POSIX on average, while
+producing files. My choice would be to go closer to POSIX in the
+long run. Besides possible double reading, I do not see any point
+of not trying to save files as sparse when creating archives which
+are neither POSIX nor old-V7, so the actual @value{op-sparse} would
+become selected by default when producing such archives, whatever
+the reason is. So, @value{op-sparse} alone might be redefined to force
+GNU-format archives, and recover its previous meaning from this fact.
+
+GNU-format as it exists now can easily fool other POSIX @code{tar},
+as it uses fields which POSIX considers to be part of the file name
+prefix. I wonder if it would not be a good idea, in the long run,
+to try changing GNU-format so any added field (like @code{ctime},
+@code{atime}, file offset in subsequent volumes, or sparse file
+descriptions) be wholly and always pushed into an extension block,
+instead of using space in the POSIX header block. I could manage
+to do that portably between future GNU @code{tar}s. So other POSIX
+@code{tar}s might be at least able to provide kind of correct listings
+for the archives produced by GNU @code{tar}, if not able to process
+them otherwise.
+
+Using these projected extensions might induce older @code{tar}s to fail.
+We would use the same approach as for POSIX. I'll put out a @code{tar}
+capable of reading POSIXier, yet extended archives, but will not produce
+this format by default, in GNU mode. In a few years, when newer GNU
+@code{tar}s will have flooded out @code{tar} 1.11.X and previous, we
+could switch to producing POSIXier extended archives, with no real harm
+to users, as almost all existing GNU @code{tar}s will be ready to read
+POSIXier format. In fact, I'll do both changes at the same time, in a
+few years, and just prepare @code{tar} for both changes, without effecting
+them, from 1.@var{POSIX}. (Both changes: 1---using POSIX convention for
+getting over 100 characters; 2---avoiding mangling POSIX headers for GNU
+extensions, using only POSIX mandated extension techniques).
+
+So, a future @code{tar} will have a @value{op-posix}
+flag forcing the usage of truly POSIX headers, and so, producing
+archives previous GNU @code{tar} will not be able to read.
+So, @emph{once} pretest will announce that feature, it would be
+particularly useful that users test how exchangeable will be archives
+between GNU @code{tar} with @value{op-posix} and other POSIX @code{tar}.
+
+In a few years, when GNU @code{tar} will produce POSIX headers by
+default, @value{op-posix} will have a strong meaning and will disallow
+GNU extensions. But in the meantime, for a long while, @value{op-posix}
+in GNU tar will not disallow GNU extensions like @value{op-label},
+@value{op-multi-volume}, @value{op-sparse}, or very long file or link names.
+However, @value{op-posix} with GNU extensions will use POSIX
+headers with reserved-for-users extensions to headers, and I will be
+curious to know how well or bad POSIX @code{tar}s will react to these.
+
+GNU @code{tar} prior to 1.@var{POSIX}, and after 1.@var{POSIX} without
+@value{op-posix}, generates and checks @samp{ustar@w{ }@w{ }}, with two
+suffixed spaces. This is sufficient for older GNU @code{tar} not to
+recognize POSIX archives, and consequently, wrongly decide those archives
+are in old V7 format. It is a useful bug for me, because GNU @code{tar}
+has other POSIX incompatibilities, and I need to segregate GNU @code{tar}
+semi-POSIX archives from truly POSIX archives, for GNU @code{tar} should
+be somewhat compatible with itself, while migrating closer to latest
+POSIX standards. So, I'll be very careful about how and when I will do
+the correction.
+
+@node Checksumming, , posix, Portability
+@subsection Checksumming Problems
+
+SunOS and HP-UX @code{tar} fail to accept archives created using GNU
+@code{tar} and containing non-ASCII file names, that is, file names
+having characters with the eight bit set, because they use signed
+checksums, while GNU @code{tar} uses unsigned checksums while creating
+archives, as per POSIX standards. On reading, GNU @code{tar} computes
+both checksums and accept any. It is somewhat worrying that a lot of
+people may go around doing backup of their files using faulty (or at
+least non-standard) software, not learning about it until it's time
+to restore their missing files with an incompatible file extractor,
+or vice versa.
+
+GNU @code{tar} compute checksums both ways, and accept any on read,
+so GNU tar can read Sun tapes even with their wrong checksums.
+GNU @code{tar} produces the standard checksum, however, raising
+incompatibilities with Sun. That is to say, GNU @code{tar} has not
+been modified to @emph{produce} incorrect archives to be read by buggy
+@code{tar}'s. I've been told that more recent Sun @code{tar} now
+read standard archives, so maybe Sun did a similar patch, after all?
+
+The story seems to be that when Sun first imported @code{tar}
+sources on their system, they recompiled it without realizing that
+the checksums were computed differently, because of a change in
+the default signing of @code{char}'s in their compiler. So they
+started computing checksums wrongly. When they later realized their
+mistake, they merely decided to stay compatible with it, and with
+themselves afterwards. Presumably, but I do not really know, HP-UX
+has chosen that their @code{tar} archives to be compatible with Sun's.
+The current standards do not favor Sun @code{tar} format. In any
+case, it now falls on the shoulders of SunOS and HP-UX users to get
+a @code{tar} able to read the good archives they receive.
+
+@node Compression, Attributes, Portability, Formats
+@section Using Less Space through Compression
+
+@menu
+* gzip:: Creating and Reading Compressed Archives
+* sparse:: Archiving Sparse Files
+@end menu
+
+@node gzip, sparse, Compression, Compression
+@subsection Creating and Reading Compressed Archives
+@cindex Compressed archives
+@cindex Storing archives in compressed format
+@UNREVISED
+
+@table @kbd
+@item -z
+@itemx --gzip
+@itemx --ungzip
+Filter the archive through @code{gzip}.
+@end table
+
+@FIXME{ach; these two bits orig from "compare" (?). where to put?} Some
+format parameters must be taken into consideration when modifying an
+archive: @FIXME{???}. Compressed archives cannot be modified.
+
+You can use @samp{--gzip} and @samp{--gunzip} on physical devices
+(tape drives, etc.) and remote files as well as on normal files; data
+to or from such devices or remote files is reblocked by another copy
+of the @code{tar} program to enforce the specified (or default) record
+size. The default compression parameters are used; if you need to
+override them, avoid the @value{op-gzip} option and run @code{gzip}
+explicitly. (Or set the @samp{GZIP} environment variable.)
+
+The @value{op-gzip} option does not work with the @value{op-multi-volume}
+option, or with the @value{op-update}, @value{op-append},
+@value{op-concatenate}, or @value{op-delete} operations.
+
+It is not exact to say that GNU @code{tar} is to work in concert
+with @code{gzip} in a way similar to @code{zip}, say. Surely, it is
+possible that @code{tar} and @code{gzip} be done with a single call,
+like in:
+
+@example
+$ @kbd{tar cfz archive.tar.gz subdir}
+@end example
+
+@noindent
+to save all of @samp{subdir} into a @code{gzip}'ed archive. Later you
+can do:
+
+@example
+$ @kbd{tar xfz archive.tar.gz}
+@end example
+
+@noindent
+to explode and unpack.
+
+The difference is that the whole archive is compressed. With
+@code{zip}, archive members are archived individually. @code{tar}'s
+method yields better compression. On the other hand, one can view the
+contents of a @code{zip} archive without having to decompress it. As
+for the @code{tar} and @code{gzip} tandem, you need to decompress the
+archive to see its contents. However, this may be done without needing
+disk space, by using pipes internally:
+
+@example
+$ @kbd{tar tfz archive.tar.gz}
+@end example
+
+@cindex corrupted archives
+About corrupted compressed archives: @code{gzip}'ed files have no
+redundancy, for maximum compression. The adaptive nature of the
+compression scheme means that the compression tables are implicitly
+spread all over the archive. If you lose a few blocks, the dynamic
+construction of the compression tables becomes unsychronized, and there
+is little chance that you could recover later in the archive.
+
+There are pending suggestions for having a per-volume or per-file
+compression in GNU @code{tar}. This would allow for viewing the
+contents without decompression, and for resynchronizing decompression at
+every volume or file, in case of corrupted archives. Doing so, we might
+loose some compressibility. But this would have make recovering easier.
+So, there are pros and cons. We'll see!
+
+@table @kbd
+@item -Z
+@itemx --compress
+@itemx --uncompress
+Filter the archive through @code{compress}. Otherwise like @value{op-gzip}.
+
+@item --use-compress-program=@var{prog}
+Filter through @var{prog} (must accept @samp{-d}).
+@end table
+
+@value{op-compress} stores an archive in compressed format. This
+option is useful in saving time over networks and space in pipes, and
+when storage space is at a premium. @value{op-compress} causes
+@code{tar} to compress when writing the archive, or to uncompress when
+reading the archive.
+
+To perform compression and uncompression on the archive, @code{tar}
+runs the @code{compress} utility. @code{tar} uses the default
+compression parameters; if you need to override them, avoid the
+@value{op-compress} option and run the @code{compress} utility
+explicitly. It is useful to be able to call the @code{compress}
+utility from within @code{tar} because the @code{compress} utility by
+itself cannot access remote tape drives.
+
+The @value{op-compress} option will not work in conjunction with the
+@value{op-multi-volume} option or the @value{op-append}, @value{op-update},
+@value{op-append} and @value{op-delete} operations. @xref{Operations}, for
+more information on these operations.
+
+If there is no compress utility available, @code{tar} will report an error.
+@strong{Please note} that the @code{compress} program may be covered by
+a patent, and therefore we recommend you stop using it.
+
+@table @kbd
+@item --compress
+@itemx --uncompress
+@itemx -z
+@itemx -Z
+When this option is specified, @code{tar} will compress (when writing
+an archive), or uncompress (when reading an archive). Used in
+conjunction with the @value{op-create}, @value{op-extract}, @value{op-list} and
+@value{op-compare} operations.
+@end table
+
+You can have archives be compressed by using the @value{op-gzip} option.
+This will arrange for @code{tar} to use the @code{gzip} program to be
+used to compress or uncompress the archive wren writing or reading it.
+
+To use the older, obsolete, @code{compress} program, use the
+@value{op-compress} option. The GNU Project recommends you not use
+@code{compress}, because there is a patent covering the algorithm it
+uses. You could be sued for patent infringment merely by running
+@code{compress}.
+
+I have one question, or maybe it's a suggestion if there isn't a way
+to do it now. I would like to use @value{op-gzip}, but I'd also like the
+output to be fed through a program like GNU @code{ecc} (actually, right
+now that's @samp{exactly} what I'd like to use :-)), basically adding
+ECC protection on top of compression. It seems as if this should be
+quite easy to do, but I can't work out exactly how to go about it.
+Of course, I can pipe the standard output of @code{tar} through
+@code{ecc}, but then I lose (though I haven't started using it yet,
+I confess) the ability to have @code{tar} use @code{rmt} for it's I/O
+(I think).
+
+I think the most straightforward thing would be to let me specify a
+general set of filters outboard of compression (preferably ordered,
+so the order can be automatically reversed on input operations, and
+with the options they require specifiable), but beggars shouldn't be
+choosers and anything you decide on would be fine with me.
+
+By the way, I like @code{ecc} but if (as the comments say) it can't
+deal with loss of block sync, I'm tempted to throw some time at adding
+that capability. Supposing I were to actually do such a thing and
+get it (apparantly) working, do you accept contributed changes to
+utilities like that? (Leigh Clayton @file{loc@@soliton.com}, May 1995).
+
+Isn't that exactly the role of the @value{op-use-compress-prog} option?
+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
+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.
+
+@node sparse, , gzip, Compression
+@subsection Archiving Sparse Files
+@cindex Sparse Files
+@UNREVISED
+
+@table @kbd
+@item -S
+@itemx --sparse
+Handle sparse files efficiently.
+@end table
+
+This option causes all files to be put in the archive to be tested for
+sparseness, and handled specially if they are. The @value{op-sparse}
+option is useful when many @code{dbm} files, for example, are being
+backed up. Using this option dramatically decreases the amount of
+space needed to store such a file.
+
+In later versions, this option may be removed, and the testing and
+treatment of sparse files may be done automatically with any special
+GNU options. For now, it is an option needing to be specified on
+the command line with the creation or updating of an archive.
+
+Files in the filesystem occasionally have ``holes.'' A hole in a file
+is a section of the file's contents which was never written. The
+contents of a hole read as all zeros. On many operating systems,
+actual disk storage is not allocated for holes, but they are counted
+in the length of the file. If you archive such a file, @code{tar}
+could create an archive longer than the original. To have @code{tar}
+attempt to recognize the holes in a file, use @value{op-sparse}. When
+you use the @value{op-sparse} option, then, for any file using less
+disk space than would be expected from its length, @code{tar} searches
+the file for consecutive stretches of zeros. It then records in the
+archive for the file where the consecutive stretches of zeros are, and
+only archives the ``real contents'' of the file. On extraction (using
+@value{op-sparse} is not needed on extraction) any such files have
+hols created wherever the continuous stretches of zeros were found.
+Thus, if you use @value{op-sparse}, @code{tar} archives won't take
+more space than the original.
+
+A file is sparse if it contains blocks of zeros whose existence is
+recorded, but that have no space allocated on disk. When you specify
+the @value{op-sparse} option in conjunction with the @value{op-create}
+operation, @code{tar} tests all files for sparseness while archiving.
+If @code{tar} finds a file to be sparse, it uses a sparse representation of
+the file in the archive. @value{xref-create}, for more information
+about creating archives.
+
+@value{op-sparse} is useful when archiving files, such as dbm files,
+likely to contain many nulls. This option dramatically
+decreases the amount of space needed to store such an archive.
+
+@quotation
+@strong{Please Note:} Always use @value{op-sparse} when performing file
+system backups, to avoid archiving the expanded forms of files stored
+sparsely in the system.
+
+Even if your system has no sparse files currently, some may be
+created in the future. If you use @value{op-sparse} while making file
+system backups as a matter of course, you can be assured the archive
+will never take more space on the media than the files take on disk
+(otherwise, archiving a disk filled with sparse files might take
+hundreds of tapes). @FIXME-xref{incremental when node name is set.}
+@end quotation
+
+@code{tar} ignores the @value{op-sparse} option when reading an archive.
+
+@table @kbd
+@item --sparse
+@itemx -S
+Files stored sparsely in the file system are represented sparsely in
+the archive. Use in conjunction with write operations.
+@end table
+
+However, users should be well aware that at archive creation time, GNU
+@code{tar} still has to read whole disk file to locate the @dfn{holes}, and
+so, even if sparse files use little space on disk and in the archive, they
+may sometimes require inordinate amount of time for reading and examining
+all-zero blocks of a file. Although it works, it's painfully slow for a
+large (sparse) file, even though the resulting tar archive may be small.
+(One user reports that dumping a @file{core} file of over 400 megabytes,
+but with only about 3 megabytes of actual data, took about 9 minutes on
+a Sun Sparstation ELC, with full CPU utilisation.)
+
+This reading is required in all cases and is not related to the fact
+the @value{op-sparse} option is used or not, so by merely @emph{not}
+using the option, you are not saving time@footnote{Well! We should say
+the whole truth, here. When @value{op-sparse} is selected while creating
+an archive, the current @code{tar} algorithm requires sparse files to be
+read twice, not once. We hope to develop a new archive format for saving
+sparse files in which one pass will be sufficient.}.
+
+Programs like @code{dump} do not have to read the entire file; by examining
+the file system directly, they can determine in advance exactly where the
+holes are and thus avoid reading through them. The only data it need read
+are the actual allocated data blocks. GNU @code{tar} uses a more portable
+and straightforward archiving approach, it would be fairly difficult that
+it does otherwise. Elizabeth Zwicky writes to @file{comp.unix.internals},
+on 1990-12-10:
+
+@quotation
+What I did say is that you cannot tell the difference between a hole and an
+equivalent number of nulls without reading raw blocks. @code{st_blocks} at
+best tells you how many holes there are; it doesn't tell you @emph{where}.
+Just as programs may, conceivably, care what @code{st_blocks} is (care
+to name one that does?), they may also care where the holes are (I have
+no examples of this one either, but it's equally imaginable).
+
+I conclude from this that good archivers are not portable. One can
+arguably conclude that if you want a portable program, you can in good
+conscience restore files with as many holes as possible, since you can't
+get it right.
+@end quotation
+
+@node Attributes, Standard, Compression, Formats
+@section Handling File Attributes
+@UNREVISED
+
+When @code{tar} reads files, this causes them to have the access times
+updated. To have @code{tar} attempt to set the access times back to
+what they were before they were read, use the @value{op-atime-preserve}
+option. This doesn't work for files that you don't own, unless
+you're root, and it doesn't interact with incremental dumps nicely
+(@pxref{Backups}), but it is good enough for some purposes.
+
+Handling of file attributes
+
+@table @kbd
+@item --atime-preserve
+Do not change access times on dumped files.
+
+@item -m
+@itemx --touch
+Do not extract file modified time.
+
+When this option is used, @code{tar} leaves the modification times
+of the files it extracts as the time when the files were extracted,
+instead of setting it to the time recorded in the archive.
+
+This option is meaningless with @value{op-list}.
+
+@item --same-owner
+Create extracted files with the same ownership they have in the
+archive.
+
+When using super-user at extraction time, ownership is always restored.
+So, this option is meaningful only for non-root users, when @code{tar}
+is executed on those systems able to give files away. This is
+considered as a security flaw by many people, at least because it
+makes quite difficult to correctly account users for the disk space
+they occupy. Also, the @code{suid} or @code{sgid} attributes of
+files are easily and silently lost when files are given away.
+
+When writing an archive, @code{tar} writes the user id and user name
+separately. If it can't find a user name (because the user id is not
+in @file{/etc/passwd}), then it does not write one. When restoring,
+and doing a @code{chmod} like when you use @value{op-same-permissions}
+(@FIXME{same-owner?}), it tries to look the name (if one was written)
+up in @file{/etc/passwd}. If it fails, then it uses the user id
+stored in the archive instead.
+
+@item --numeric-owner
+The @value{op-numeric-owner} option allows (ANSI) archives to be written
+without user/group name information or such information to be ignored
+when extracting. It effectively disables the generation and/or use
+of user/group name information. This option forces extraction using
+the numeric ids from the archive, ignoring the names.
+
+This is useful in certain circumstances, when restoring a backup from
+an emergency floppy with different passwd/group files for example.
+It is otherwise impossible to extract files with the right ownerships
+if the password file in use during the extraction does not match the
+one belonging to the filesystem(s) being extracted. This occurs,
+for example, if you are restoring your files after a major crash and
+had booted from an emergency floppy with no password file or put your
+disk into another machine to do the restore.
+
+The numeric ids are @emph{always} saved into @code{tar} archives.
+The identifying names are added at create time when provided by the
+system, unless @value{op-old-archive} is used. Numeric ids could be
+used when moving archives between a collection of machines using
+a centralized management for attribution of numeric ids to users
+and groups. This is often made through using the NIS capabilities.
+
+When making a @code{tar} file for distribution to other sites, it
+is sometimes cleaner to use a single owner for all files in the
+distribution, and nicer to specify the write permission bits of the
+files as stored in the archive independently of their actual value on
+the file system. The way to prepare a clean distribution is usually
+to have some Makefile rule creating a directory, copying all needed
+files in that directory, then setting ownership and permissions as
+wanted (there are a lot of possible schemes), and only then making a
+@code{tar} archive out of this directory, before cleaning everything
+out. Of course, we could add a lot of options to GNU @code{tar} for
+fine tuning permissions and ownership. This is not the good way,
+I think. GNU @code{tar} is already crowded with options and moreover,
+the approach just explained gives you a great deal of control already.
+
+@item -p
+@itemx --same-permissions
+@itemx --preserve-permissions
+Extract all protection information.
+
+This option causes @code{tar} to set the modes (access permissions) of
+extracted files exactly as recorded in the archive. If this option
+is not used, the current @code{umask} setting limits the permissions
+on extracted files.
+
+This option is meaningless with @value{op-list}.
+
+@item --preserve
+Same as both @value{op-same-permissions} and @value{op-same-order}.
+
+The @value{op-preserve} option has no equivalent short option name.
+It is equivalent to @value{op-same-permissions} plus @value{op-same-order}.
+
+@FIXME{I do not see the purpose of such an option. (Neither I. FP.)}
+
+@end table
+
+@node Standard, Extensions, Attributes, Formats
+@section The Standard Format
+@UNREVISED
+
+While an archive may contain many files, the archive itself is a
+single ordinary file. Like any other file, an archive file can be
+written to a storage device such as a tape or disk, sent through a
+pipe or over a network, saved on the active file system, or even
+stored in another archive. An archive file is not easy to read or
+manipulate without using the @code{tar} utility or Tar mode in GNU
+Emacs.
+
+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
+entry usually describes one of the files in the archive (an
+@dfn{archive member}), and consists of a file header and the contents
+of the file. File headers contain file names and statistics, checksum
+information which @code{tar} uses to detect file corruption, and
+information about file types.
+
+Archives are permitted to have more than one member with the same
+member name. One way this situation can occur is if more than one
+version of a file has been stored in the archive. For information
+about adding new versions of a file to an archive, see @ref{update},
+and to learn more about having more than one archive member with the
+same name, see @FIXME-xref{-backup node, when it's written}.
+
+In addition to entries describing archive members, an archive may
+contain entries which @code{tar} itself uses to store information.
+@value{xref-label}, for an example of such an archive entry.
+
+A @code{tar} archive file contains a series of blocks. Each block
+contains @code{BLOCKSIZE} bytes. Although this format may be thought
+of as being on magnetic tape, other media are often used.
+
+Each file archived is represented by a header block which describes
+the file, followed by zero or more blocks which give the contents
+of the file. At the end of the archive file there may be a block
+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.
+
+The blocks may be @dfn{blocked} for physical I/O operations.
+Each record of @var{n} blocks (where @var{n} is set by the
+@value{op-blocking-factor} option to @code{tar}) is written with a single
+@w{@samp{write ()}} operation. On magnetic tapes, the result of
+such a write is a single record. When writing an archive,
+the last record of blocks should be written at the full size, with
+blocks after the zero block containing all zeros. When reading
+an archive, a reasonable system should properly handle an archive
+whose last record is shorter than the rest, or which contains garbage
+records after a zero block.
+
+The header block is defined in C as follows. In the GNU @code{tar}
+distribution, this is part of file @file{src/tar.h}:
+
+@example
+@include header.texi
+@end example
+
+All characters in header blocks are represented by using 8-bit
+characters in the local variant of ASCII. Each field within the
+structure is contiguous; that is, there is no padding used within
+the structure. Each character on the archive medium is stored
+contiguously.
+
+Bytes representing the contents of files (after the header block
+of each file) are not translated in any way and are not constrained
+to represent characters in any character set. The @code{tar} format
+does not distinguish text files from binary files, and no translation
+of file contents is performed.
+
+The @code{name}, @code{linkname}, @code{magic}, @code{uname}, and
+@code{gname} are null-terminated character strings. All other fileds
+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.
+
+The @code{name} field is the file name of the file, with directory names
+(if any) preceding the file name, separated by slashes.
+
+@FIXME{how big a name before field overflows?}
+
+The @code{mode} field provides nine bits specifying file permissions
+and three bits to specify the Set UID, Set GID, and Save Text
+(@dfn{sticky}) modes. Values for these bits are defined above.
+When special permissions are required to create a file with a given
+mode, and the user restoring files from the archive does not hold such
+permissions, the mode bit(s) specifying those special permissions
+are ignored. Modes which are not supported by the operating system
+restoring files from the archive will be ignored. Unsupported modes
+should be faked up when creating or updating an archive; e.g. the
+group permission could be copied from the @emph{other} permission.
+
+The @code{uid} and @code{gid} fields are the numeric user and group
+ID of the file owners, respectively. If the operating system does
+not support numeric user or group IDs, these fields should be ignored.
+
+The @code{size} field is the size of the file in bytes; linked files
+are archived with this field specified as zero. @FIXME-xref{Modifiers}, in
+particular the @value{op-incremental} option.
+
+The @code{mtime} field is the modification time of the file at the time
+it was archived. It is the ASCII representation of the octal value of
+the last time the file was modified, represented as an integer number of
+seconds since January 1, 1970, 00:00 Coordinated Universal Time.
+
+The @code{chksum} field is the ASCII representation of the octal value
+of the simple sum of all bytes in the header block. Each 8-bit
+byte in the header is added to an unsigned integer, initialized to
+zero, the precision of which shall be no less than seventeen bits.
+When calculating the checksum, the @code{chksum} field is treated as
+if it were all blanks.
+
+The @code{typeflag} field specifies the type of file archived. If a
+particular implementation does not recognize or permit the specified
+type, the file will be extracted as if it were a regular file. As this
+action occurs, @code{tar} issues a warning to the standard error.
+
+The @code{atime} and @code{ctime} fields are used in making incremental
+backups; they store, respectively, the particular file's access time
+and last inode-change time.
+
+The @code{offset} is used by the @value{op-multi-volume} option, when
+making a multi-volume archive. The offset is number of bytes into
+the file that we need to restart at to continue the file on the next
+tape, i.e., where we store the location that a continued file is
+continued at.
+
+The following fields were added to deal with sparse files. A file
+is @dfn{sparse} if it takes in unallocated blocks which end up being
+represented as zeros, i.e., no useful data. A test to see if a file
+is sparse is to look at the number blocks allocated for it versus the
+number of characters in the file; if there are fewer blocks allocated
+for the file than would normally be allocated for a file of that
+size, then the file is sparse. This is the method @code{tar} uses to
+detect a sparse file, and once such a file is detected, it is treated
+differently from non-sparse files.
+
+Sparse files are often @code{dbm} files, or other database-type files
+which have data at some points and emptiness in the greater part of
+the file. Such files can appear to be very large when an @samp{ls
+-l} is done on them, when in truth, there may be a very small amount
+of important data contained in the file. It is thus undesirable
+to have @code{tar} think that it must back up this entire file, as
+great quantities of room are wasted on empty blocks, which can lead
+to running out of room on a tape far earlier than is necessary.
+Thus, sparse files are dealt with so that these empty blocks are
+not written to the tape. Instead, what is written to the tape is a
+description, of sorts, of the sparse file: where the holes are, how
+big the holes are, and how much data is found at the end of the hole.
+This way, the file takes up potentially far less room on the tape,
+and when the file is extracted later on, it will look exactly the way
+it looked beforehand. The following is a description of the fields
+used to handle a sparse file:
+
+The @code{sp} is an array of @code{struct sparse}. Each @code{struct
+sparse} contains two 12-character strings which represent an offset
+into the file and a number of bytes to be written at that offset.
+The offset is absolute, and not relative to the offset in preceding
+array element.
+
+The header can hold four of these @code{struct sparse} at the moment;
+if more are needed, they are not stored in the header.
+
+The @code{isextended} flag is set when an @code{extended_header}
+is needed to deal with a file. Note that this means that this flag
+can only be set when dealing with a sparse file, and it is only set
+in the event that the description of the file will not fit in the
+alloted room for sparse structures in the header. In other words,
+an extended_header is needed.
+
+The @code{extended_header} structure is used for sparse files which
+need more sparse structures than can fit in the header. The header can
+fit 4 such structures; if more are needed, the flag @code{isextended}
+gets set and the next block is an @code{extended_header}.
+
+Each @code{extended_header} structure contains an array of 21
+sparse structures, along with a similar @code{isextended} flag
+that the header had. There can be an indeterminate number of such
+@code{extended_header}s to describe a sparse file.
+
+@table @asis
+
+@item @code{REGTYPE}
+@itemx @code{AREGTYPE}
+These flags represent a regular file. In order to be compatible
+with older versions of @code{tar}, a @code{typeflag} value of
+@code{AREGTYPE} should be silently recognized as a regular file.
+New archives should be created using @code{REGTYPE}. Also, for
+backward compatibility, @code{tar} treats a regular file whose name
+ends with a slash as a directory.
+
+@item @code{LNKTYPE}
+This flag represents a file linked to another file, of any type,
+previously archived. Such files are identified in Unix by each
+file having the same device and inode number. The linked-to name is
+specified in the @code{linkname} field with a trailing null.
+
+@item @code{SYMTYPE}
+This represents a symbolic link to another file. The linked-to name
+is specified in the @code{linkname} field with a trailing null.
+
+@item @code{CHRTYPE}
+@itemx @code{BLKTYPE}
+These represent character special files and block special files
+respectively. In this case the @code{devmajor} and @code{devminor}
+fields will contain the major and minor device numbers respectively.
+Operating systems may map the device specifications to their own
+local specification, or may ignore the entry.
+
+@item @code{DIRTYPE}
+This flag specifies a directory or sub-directory. The directory
+name in the @code{name} field should end with a slash. On systems where
+disk allocation is performed on a directory basis, the @code{size} field
+will contain the maximum number of bytes (which may be rounded to
+the nearest disk block allocation unit) which the directory may
+hold. A @code{size} field of zero indicates no such limiting. Systems
+which do not support limiting in this manner should ignore the
+@code{size} field.
+
+@item @code{FIFOTYPE}
+This specifies a FIFO special file. Note that the archiving of a
+FIFO file archives the existence of this file and not its contents.
+
+@item @code{CONTTYPE}
+This specifies a contiguous file, which is the same as a normal
+file except that, in operating systems which support it, all its
+space is allocated contiguously on the disk. Operating systems
+which do not allow contiguous allocation should silently treat this
+type as a normal file.
+
+@item @code{A} @dots{} @code{Z}
+These are reserved for custom implementations. Some of these are
+used in the GNU modified format, as described below.
+
+@end table
+
+Other values are reserved for specification in future revisions of
+the P1003 standard, and should not be used by any @code{tar} program.
+
+The @code{magic} field indicates that this archive was output in
+the P1003 archive format. If this field contains @code{TMAGIC},
+the @code{uname} and @code{gname} fields will contain the ASCII
+representation of the owner and group of the file respectively.
+If found, the user and group IDs are used rather than the values in
+the @code{uid} and @code{gid} fields.
+
+For references, see ISO/IEC 9945-1:1990 or IEEE Std 1003.1-1990, pages
+169-173 (section 10.1) for @cite{Archive/Interchange File Format}; and
+IEEE Std 1003.2-1992, pages 380-388 (section 4.48) and pages 936-940
+(section E.4.48) for @cite{pax - Portable archive interchange}.
+
+@node Extensions, cpio, Standard, Formats
+@section GNU Extensions to the Archive Format
+@UNREVISED
+
+The GNU format uses additional file types to describe new types of
+files in an archive. These are listed below.
+
+@table @code
+@item GNUTYPE_DUMPDIR
+@itemx 'D'
+This represents a directory and a list of files created by the
+@value{op-incremental} option. The @code{size} field gives the total
+size of the associated list of files. Each file name is preceded by
+either a @samp{Y} (the file should be in this archive) or an @samp{N}.
+(The file is a directory, or is not stored in the archive.) Each file
+name is terminated by a null. There is an additional null after the
+last file name.
+
+@item GNUTYPE_MULTIVOL
+@itemx 'M'
+This represents a file continued from another volume of a multi-volume
+archive created with the @value{op-multi-volume} option. The original
+type of the file is not given here. The @code{size} field gives the
+maximum size of this piece of the file (assuming the volume does
+not end before the file is written out). The @code{offset} field
+gives the offset from the beginning of the file where this part of
+the file begins. Thus @code{size} plus @code{offset} should equal
+the original size of the file.
+
+@item GNUTYPE_SPARSE
+@itemx 'S'
+This flag indicates that we are dealing with a sparse file. Note
+that archiving a sparse file requires special operations to find
+holes in the file, which mark the positions of these holes, along
+with the number of bytes of data to be found after the hole.
+
+@item GNUTYPE_VOLHDR
+@itemx 'V'
+This file type is used to mark the volume header that was given with
+the @value{op-label} option when the archive was created. The @code{name}
+field contains the @code{name} given after the @value{op-label} option.
+The @code{size} field is zero. Only the first file in each volume
+of an archive should have this type.
+
+@end table
+
+You may have trouble reading a GNU format archive on a non-GNU
+system if the options @value{op-incremental}, @value{op-multi-volume},
+@value{op-sparse}, or @value{op-label} were used when writing the archive.
+In general, if @code{tar} does not use the GNU-added fields of the
+header, other versions of @code{tar} should be able to read the
+archive. Otherwise, the @code{tar} program will give an error, the
+most likely one being a checksum error.
+
+@node cpio, , Extensions, Formats
+@section Comparison of @code{tar} and @code{cpio}
+@UNREVISED
+
+@FIXME{Reorganize the following material}
+
+The @code{cpio} archive formats, like @code{tar}, do have maximum
+pathname lengths. The binary and old ASCII formats have a max path
+length of 256, and the new ASCII and CRC ASCII formats have a max
+path length of 1024. GNU @code{cpio} can read and write archives
+with arbitrary pathname lengths, but other @code{cpio} implementations
+may crash unexplainedly trying to read them.
+
+@code{tar} handles symbolic links in the form in which it comes in BSD;
+@code{cpio} doesn't handle symbolic links in the form in which it comes
+in System V prior to SVR4, and some vendors may have added symlinks
+to their system without enhancing @code{cpio} to know about them.
+Others may have enhanced it in a way other than the way I did it
+at Sun, and which was adopted by AT&T (and which is, I think, also
+present in the @code{cpio} that Berkeley picked up from AT&T and put
+into a later BSD release---I think I gave them my changes).
+
+(SVR4 does some funny stuff with @code{tar}; basically, its @code{cpio}
+can handle @code{tar} format input, and write it on output, and it
+probably handles symbolic links. They may not have bothered doing
+anything to enhance @code{tar} as a result.)
+
+@code{cpio} handles special files; traditional @code{tar} doesn't.
+
+@code{tar} comes with V7, System III, System V, and BSD source;
+@code{cpio} comes only with System III, System V, and later BSD
+(4.3-tahoe and later).
+
+@code{tar}'s way of handling multiple hard links to a file can handle
+file systems that support 32-bit inumbers (e.g., the BSD file system);
+@code{cpio}s way requires you to play some games (in its "binary"
+format, i-numbers are only 16 bits, and in its "portable ASCII" format,
+they're 18 bits---it would have to play games with the "file system ID"
+field of the header to make sure that the file system ID/i-number pairs
+of different files were always different), and I don't know which
+@code{cpio}s, if any, play those games. Those that don't might get
+confused and think two files are the same file when they're not, and
+make hard links between them.
+
+@code{tar}s way of handling multiple hard links to a file places only
+one copy of the link on the tape, but the name attached to that copy
+is the @emph{only} one you can use to retrieve the file; @code{cpio}s
+way puts one copy for every link, but you can retrieve it using any
+of the names.
+
+@quotation
+What type of check sum (if any) is used, and how is this calculated.
+@end quotation
+
+See the attached manual pages for @code{tar} and @code{cpio} format.
+@code{tar} uses a checksum which is the sum of all the bytes in the
+@code{tar} header for a file; @code{cpio} uses no checksum.
+
+@quotation
+If anyone knows why @code{cpio} was made when @code{tar} was present
+at the unix scene,
+@end quotation
+
+It wasn't. @code{cpio} first showed up in PWB/UNIX 1.0; no
+generally-available version of UNIX had @code{tar} at the time. I don't
+know whether any version that was generally available @emph{within AT&T}
+had @code{tar}, or, if so, whether the people within AT&T who did
+@code{cpio} knew about it.
+
+On restore, if there is a corruption on a tape @code{tar} will stop at
+that point, while @code{cpio} will skip over it and try to restore the
+rest of the files.
+
+The main difference is just in the command syntax and header format.
+
+@code{tar} is a little more tape-oriented in that everything is blocked
+to start on a record boundary.
+
+@quotation
+Is there any differences between the ability to recover crashed
+archives between the two of them. (Is there any chance of recovering
+crashed archives at all.)
+@end quotation
+
+Theoretically it should be easier under @code{tar} since the blocking
+lets you find a header with some variation of @samp{dd skip=@var{nn}}.
+However, modern @code{cpio}'s and variations have an option to just
+search for the next file header after an error with a reasonable chance
+of re-syncing. However, lots of tape driver software won't allow you to
+continue past a media error which should be the only reason for getting
+out of sync unless a file changed sizes while you were writing the
+archive.
+
+@quotation
+If anyone knows why @code{cpio} was made when @code{tar} was present
+at the unix scene, please tell me about this too.
+@end quotation
+
+Probably because it is more media efficient (by not blocking everything
+and using only the space needed for the headers where @code{tar}
+always uses 512 bytes per file header) and it knows how to archive
+special files.
+
+You might want to look at the freely available alternatives. The major
+ones are @code{afio}, GNU @code{tar}, and @code{pax}, each of which
+have their own extensions with some backwards compatibility.
+
+Sparse files were @code{tar}red as sparse files (which you can easily
+test, because the resulting archive gets smaller, and GNU @code{cpio}
+can no longer read it).
+
+@node Media, Index, Formats, Top
+@chapter Tapes and Other Archive Media
+@UNREVISED
+
+A few special cases about tape handling warrant more detailed
+description. These special cases are discussed below.
+
+Many complexities surround the use of @code{tar} on tape drives. Since
+the creation and manipulation of archives located on magnetic tape was
+the original purpose of @code{tar}, it contains many features making
+such manipulation easier.
+
+Archives are usually written on dismountable media---tape cartridges,
+mag tapes, or floppy disks.
+
+The amount of data a tape or disk holds depends not only on its size,
+but also on how it is formatted. A 2400 foot long reel of mag tape
+holds 40 megabytes of data when formated at 1600 bits per inch. The
+physically smaller EXABYTE tape cartridge holds 2.3 gigabytes.
+
+Magnetic media are re-usable---once the archive on a tape is no longer
+needed, the archive can be erased and the tape or disk used over.
+Media quality does deteriorate with use, however. Most tapes or disks
+should be disgarded when they begin to produce data errors. EXABYTE
+tape cartridges should be disgarded when they generate an @dfn{error
+count} (number of non-usable bits) of more than 10k.
+
+Magnetic media are written and erased using magnetic fields, and
+should be protected from such fields to avoid damage to stored data.
+Sticking a floppy disk to a filing cabinet using a magnet is probably
+not a good idea.
+
+@menu
+* Device:: Device selection and switching
+* Remote Tape Server::
+* Common Problems and Solutions::
+* Blocking:: Blocking
+* Many:: Many archives on one tape
+* Using Multiple Tapes:: Using Multiple Tapes
+* label:: Including a Label in the Archive
+* verify::
+* Write Protection::
+@end menu
+
+@node Device, Remote Tape Server, Media, Media
+@section Device Selection and Switching
+@UNREVISED
+
+@table @kbd
+@item -f [@var{hostname}:]@var{file}
+@itemx --file=[@var{hostname}:]@var{file}
+Use archive file or device @var{file} on @var{hostname}.
+@end table
+
+This option is used to specify the file name of the archive @code{tar}
+works on.
+
+If the file name is @samp{-}, @code{tar} reads the archive from standard
+input (when listing or extracting), or writes it to standard output
+(when creating). If the @samp{-} file name is given when updating an
+archive, @code{tar} will read the original archive from its standard
+input, and will write the entire new archive to its standard output.
+
+If the file name contains a @samp{:}, it is interpreted as
+@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
+sign (@kbd{@@}), it is treated as @samp{user@@hostname:file name}. In
+either case, @code{tar} will invoke the command @code{rsh} (or
+@code{remsh}) to start up an @file{/etc/rmt} on the remote machine. If
+you give an alternate login name, it will be given to the @code{rsh}.
+Naturally, the remote machine must have an executable @file{/etc/rmt}.
+This program is free software from the University of California, and a
+copy of the source code can be found with the sources for @code{tar};
+it's compiled and installed by default.
+
+If this option is not given, but the environment variable @code{TAPE} is
+set, its value is used; otherwise, old versions of @code{tar} used a default
+archive name (which was picked when @code{tar} was compiled). The
+default is normally set up to be the @dfn{first} tape drive or other
+transportable I/O medium on the system.
+
+Starting with version 1.11.5, GNU @code{tar} uses standard input and
+standard output as the default device, and I will not try anymore
+supporting automatic device detection at installation time. This was
+failing really in too many cases, it was hopeless. This is now
+completely left to the installer to override standard input and standard
+output for default device, if this seems preferrable to him/her.
+Further, I think @emph{most} actual usages of @code{tar} are done with
+pipes or disks, not really tapes, cartridges or diskettes.
+
+Some users think that using standard input and output is running
+after trouble. This could lead to a nasty surprise on your screen if
+you forget to specify an output file name---especially if you are going
+through a network or terminal server capable of buffering large amounts
+of output. We had so many bug reports in that area of configuring
+default tapes automatically, and so many contradicting requests, that
+we finally consider the problem to be portably intractable. We could
+of course use something like @samp{/dev/tape} as a default, but this
+is @emph{also} running after various kind of trouble, going from hung
+processes to accidental destruction of real tapes. After having seen
+all this mess, using standard input and output as a default really
+sounds like the only clean choice left, and a very useful one too.
+
+GNU @code{tar} reads and writes archive in records, I suspect this is the
+main reason why block devices are preferred over character devices.
+Most probably, block devices are more efficient too. The installer
+could also check for @samp{DEFTAPE} in @file{<sys/mtio.h>}.
+
+@table @kbd
+@item --force-local
+Archive file is local even if it contains a colon.
+
+@item --rsh-command=@var{command}
+Use remote @var{command} instead of @code{rsh}. This option exists
+so that people who use something other than the standard @code{rsh}
+(e.g., a Kerberized @code{rsh}) can access a remote device.
+
+When this command is not used, the shell command found when
+the @code{tar} program was installed is used instead. This is
+the first found of @file{/usr/ucb/rsh}, @file{/usr/bin/remsh},
+@file{/usr/bin/rsh}, @file{/usr/bsd/rsh} or @file{/usr/bin/nsh}.
+The installer may have overriden this by defining the environment
+variable @code{RSH} @emph{at installation time}.
+
+@item -[0-7][lmh]
+Specify drive and density.
+
+@item -M
+@itemx --multi-volume
+Create/list/extract multi-volume archive.
+
+This option causes @code{tar} to write a @dfn{multi-volume} archive---one
+that may be larger than will fit on the medium used to hold it.
+@xref{Multi-Volume Archives}.
+
+@item -L @var{num}
+@itemx --tape-length=@var{num}
+Change tape after writing @var{num} x 1024 bytes.
+
+This option might be useful when your tape drivers do not properly
+detect end of physical tapes. By being slightly conservative on the
+maximum tape length, you might avoid the problem entirely.
+
+@item -F @var{file}
+@itemx --info-script=@var{file}
+@itemx --new-volume-script=@var{file}
+Execute @file{file} at end of each tape. This implies
+@value{op-multi-volume}.
+@end table
+
+@node Remote Tape Server, Common Problems and Solutions, Device, Media
+@section The Remote Tape Server
+
+@cindex remote tape drive
+@pindex rmt
+In order to access the tape drive on a remote machine, @code{tar}
+uses the remote tape server written at the University of California at
+Berkeley. The remote tape server must be installed as @file{/etc/rmt}
+on any machine whose tape drive you want to use. @code{tar} calls
+@file{/etc/rmt} by running an @code{rsh} or @code{remsh} to the remote
+machine, optionally using a different login name if one is supplied.
+
+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}.
+
+@cindex absolute file names
+Unless you use the @value{op-absolute-names} option, GNU @code{tar} will
+not allow you to create an archive that contains absolute file names
+(a file name beginning with @samp{/}.) If you try, @code{tar} will
+automatically remove the leading @samp{/} from the file names it
+stores in the archive. It will also type a warning message telling
+you what it is doing.
+
+When reading an archive that was created with a different @code{tar}
+program, GNU @code{tar} automatically extracts entries in the archive
+which have absolute file names as if the file names were not absolute.
+This is an important feature. A visitor here once gave a
+@code{tar} tape to an operator to restore; the operator used Sun @code{tar}
+instead of GNU @code{tar}, and the result was that it replaced large
+portions of our @file{/bin} and friends with versions from the tape;
+needless to say, we were unhappy about having to recover the file system
+from backup tapes.
+
+For example, if the archive contained a file @file{/usr/bin/computoy},
+GNU @code{tar} would extract the file to @file{usr/bin/computoy},
+relative to the current directory. If you want to extract the files in
+an archive to the same absolute names that they had when the archive
+was created, you should do a @samp{cd /} before extracting the files
+from the archive, or you should either use the @value{op-absolute-names}
+option, or use the command @samp{tar -C / @dots{}}.
+
+@cindex Ultrix 3.1 and write failure
+Some versions of Unix (Ultrix 3.1 is know to have this problem),
+can claim that a short write near the end of a tape succeeded,
+when it actually failed. This will result in the -M option not
+working correctly. The best workaround at the moment is to use a
+significantly larger blocking factor than the default 20.
+
+In order to update an archive, @code{tar} must be able to backspace the
+archive in order to reread or rewrite a record that was just read (or
+written). This is currently possible only on two kinds of files: normal
+disk files (or any other file that can be backspaced with @samp{lseek}),
+and industry-standard 9-track magnetic tape (or any other kind of tape
+that can be backspaced with the @code{MTIOCTOP} @code{ioctl}.
+
+This means that the @value{op-append}, @value{op-update},
+@value{op-concatenate}, and @value{op-delete} commands will not work on any
+other kind of file. Some media simply cannot be backspaced, which
+means these commands and options will never be able to work on them.
+These non-backspacing media include pipes and cartridge tape drives.
+
+Some other media can be backspaced, and @code{tar} will work on them
+once @code{tar} is modified to do so.
+
+Archives created with the @value{op-multi-volume}, @value{op-label}, and
+@value{op-incremental} options may not be readable by other version
+of @code{tar}. In particular, restoring a file that was split over
+a volume boundary will require some careful work with @code{dd}, if
+it can be done at all. Other versions of @code{tar} may also create
+an empty file whose name is that of the volume header. Some versions
+of @code{tar} may create normal files instead of directories archived
+with the @value{op-incremental} option.
+
+@node Common Problems and Solutions, Blocking, Remote Tape Server, Media
+@section Some Common Problems and their Solutions
+
+@ifclear PUBLISH
+
+@format
+errors from system:
+permission denied
+no such file or directory
+not owner
+
+errors from @code{tar}:
+directory checksum error
+header format error
+
+errors from media/system:
+i/o error
+device busy
+@end format
+
+@end ifclear
+
+@node Blocking, Many, Common Problems and Solutions, Media
+@section Blocking
+@UNREVISED
+
+@dfn{Block} and @dfn{record} terminology is rather confused, and it
+is also confusing to the expert reader. On the other hand, readers
+who are new to the field have a fresh mind, and they may safely skip
+the next two paragraphs, as the remainder of this manual uses those
+two terms in a quite consistent way.
+
+John Gilmore, the writer of the public domain @code{tar} from which
+GNU @code{tar} was originally derived, wrote (June 1995):
+
+@quotation
+The nomenclature of tape drives comes from IBM, where I believe
+they were invented for the IBM 650 or so. On IBM mainframes, what
+is recorded on tape are tape blocks. The logical organization of
+data is into records. There are various ways of putting records into
+blocks, including @code{F} (fixed sized records), @code{V} (variable
+sized records), @code{FB} (fixed blocked: fixed size records, @var{n}
+to a block), @code{VB} (variable size records, @var{n} to a block),
+@code{VSB} (variable spanned blocked: variable sized records that can
+occupy more than one block), etc. The @code{JCL} @samp{DD RECFORM=}
+parameter specified this to the operating system.
+
+The Unix man page on @code{tar} was totally confused about this.
+When I wrote @code{PD TAR}, I used the historically correct terminology
+(@code{tar} writes data records, which are grouped into blocks).
+It appears that the bogus terminology made it into POSIX (no surprise
+here), and now Fran@,{c}ois has migrated that terminology back
+into the source code too.
+@end quotation
+
+The term @dfn{physical block} means the basic transfer chunk from or
+to a device, after which reading or writing may stop without anything
+being lost. In this manual, the term @dfn{block} usually refers to
+a disk physical block, @emph{assuming} that each disk block is 512
+bytes in length. It is true that some disk devices have different
+physical blocks, but @code{tar} ignore these differences in its own
+format, which is meant to be portable, so a @code{tar} block is always
+512 bytes in length, and @dfn{block} always mean a @code{tar} block.
+The term @dfn{logical block} often represents the basic chunk of
+allocation of many disk blocks as a single entity, which the operating
+system treats somewhat atomically; this concept is only barely used
+in GNU @code{tar}.
+
+The term @dfn{physical record} is another way to speak of a physical
+block, those two terms are somewhat interchangeable. In this manual,
+the term @dfn{record} usually refers to a tape physical block,
+@emph{assuming} that the @code{tar} archive is kept on magnetic tape.
+It is true that archives may be put on disk or used with pipes,
+but nevertheless, @code{tar} tries to read and write the archive one
+@dfn{record} at a time, whatever the medium in use. One record is made
+up of an integral number of blocks, and this operation of putting many
+disk blocks into a single tape block is called @dfn{reblocking}, or
+more simply, @dfn{blocking}. The term @dfn{logical record} refers to
+the logical organization of many characters into something meaningful
+to the application. The term @dfn{unit record} describes a small set
+of characters which are transmitted whole to or by the application,
+and often refers to a line of text. Those two last terms are unrelated
+to what we call a @dfn{record} in GNU @code{tar}.
+
+When writing to tapes, @code{tar} writes the contents of the archive
+in chunks known as @dfn{records}. To change the default blocking
+factor, use the @value{op-blocking-factor} option. Each record will
+then be composed of @var{512-size} blocks. (Each @code{tar} block is
+512 bytes. @xref{Standard}.) Each file written to the archive uses
+at least one full record. As a result, using a larger record size
+can result in more wasted space for small files. On the other hand, a
+larger record size can often be read and written much more efficiently.
+
+Further complicating the problem is that some tape drives ignore the
+blocking entirely. For these, a larger record size can still improve
+performance (because the software layers above the tape drive still
+honor the blocking), but not as dramatically as on tape drives that
+honor blocking.
+
+When reading an archive, @code{tar} can usually figure out the record
+size on itself. When this is the case, and a non-standard record size
+was used when the archive was created, @code{tar} will print a message
+about a non-standard blocking factor, and then operate normally. On
+some tape devices, however, @code{tar} cannot figure out the record size
+itself. On most of those, you can specify a blocking factor (with
+@value{op-blocking-factor}) larger than the actual blocking factor, and then use
+the @value{op-read-full-records} option. (If you specify a blocking factor
+with @value{op-blocking-factor} and don't use the @value{op-read-full-records}
+option, then @code{tar} will not attempt to figure out the recording size
+itself.) On some devices, you must always specify the record size
+exactly with @value{op-blocking-factor} when reading, because @code{tar} cannot
+figure it out. In any case, use @value{op-list} before doing any
+extractions to see whether @code{tar} is reading the archive correctly.
+
+@code{tar} blocks are all fixed size (512 bytes), and its scheme for
+putting them into records is to put a whole number of them (one or
+more) into each record. @code{tar} records are all the same size;
+at the end of the file there's a block containing all zeros, which
+is how you tell that the remainder of the last record(s) are garbage.
+
+In a standard @code{tar} file (no options), the block size is 512
+and the record size is 10240, for a blocking factor of 20. What the
+@value{op-blocking-factor} option does is sets the blocking factor,
+changing the record size while leaving the block size at 512 bytes.
+20 was fine for ancient 800 or 1600 bpi reel-to-reel tape drives;
+most tape drives these days prefer much bigger records in order to
+stream and not waste tape. When writing tapes for myself, some tend
+to use a factor of the order of 2048, say, giving a record size of
+around one megabyte.
+
+If you use a blocking factor larger than 20, older @code{tar} programs
+might not be able to read the archive, so we recommend this as a limit
+to use in practice. GNU @code{tar}, however, will support arbitrarily
+large record sizes, limited only by the amount of virtual memory or the
+physical characteristics of the tape device.
+
+@menu
+* Format Variations:: Format Variations
+* Blocking Factor:: The Blocking Factor of an Archive
+@end menu
+
+@node Format Variations, Blocking Factor, Blocking, Blocking
+@subsection Format Variations
+@cindex Format Parameters
+@cindex Format Options
+@cindex Options, archive format specifying
+@cindex Options, format specifying
+@UNREVISED
+
+Format parameters specify how an archive is written on the archive
+media. The best choice of format parameters will vary depending on
+the type and number of files being archived, and on the media used to
+store the archive.
-@item --list
-Prints a list of the contents of the archive.
+To specify format parameters when accessing or creating an archive,
+you can use the options described in the following sections.
+If you do not specify any format parameters, @code{tar} uses
+default parameters. You cannot modify a compressed archive.
+If you create an archive with the @value{op-blocking-factor} option
+specified (@value{pxref-blocking-factor}), you must specify that
+blocking-factor when operating on the archive. @xref{Formats}, for other
+examples of format parameter considerations.
+
+@node Blocking Factor, , Format Variations, Blocking
+@subsection The Blocking Factor of an Archive
+@cindex Blocking Factor
+@cindex Record Size
+@cindex Number of blocks per record
+@cindex Number of bytes per record
+@cindex Bytes per record
+@cindex Blocks per record
+@UNREVISED
+
+The data in an archive is grouped into blocks, which are 512 bytes.
+Blocks are read and written in whole number multiples called
+@dfn{records}. The number of blocks in a record (ie. the size of a
+record in units of 512 bytes) is called the @dfn{blocking factor}.
+The @value{op-blocking-factor} option specifies the blocking factor of
+an archive. The default blocking factor is typically 20 (ie.@:
+10240 bytes), but can be specified at installation. To find out
+the blocking factor of an existing archive, use @samp{tar --list
+--file=@var{archive-name}}. This may not work on some devices.
+
+Records are separated by gaps, which waste space on the archive media.
+If you are archiving on magnetic tape, using a larger blocking factor
+(and therefore larger records) provides faster throughput and allows you
+to fit more data on a tape (because there are fewer gaps). If you are
+archiving on cartridge, a very large blocking factor (say 126 or more)
+greatly increases performance. A smaller blocking factor, on the other
+hand, may be usefull when archiving small files, to avoid archiving lots
+of nulls as @code{tar} fills out the archive to the end of the record.
+In general, the ideal record size depends on the size of the
+inter-record gaps on the tape you are using, and the average size of the
+files you are archiving. @xref{create}, for information on
+writing archives.
+
+@FIXME{Need example of using a cartridge with blocking factor=126 or more.}
+
+Archives with blocking factors larger than 20 cannot be read
+by very old versions of @code{tar}, or by some newer versions
+of @code{tar} running on old machines with small address spaces.
+With GNU @code{tar}, the blocking factor of an archive is limited
+only by the maximum record size of the device containing the archive,
+or by the amount of available virtual memory.
+
+Also, on some systems, not using adequate blocking factors, as sometimes
+imposed by the device drivers, may yield unexpected diagnostics. For
+example, this has been reported:
-@item --update
-Adds files to the end of the archive, but only if they are newer than
-their counterparts already in the archive, or if they do not already
-exist in the archive.
+@example
+Cannot write to /dev/dlt: Invalid argument
+@end example
-@item --version
-Prints the version number of the @code{tar} program to the standard
-error.
+@noindent
+In such cases, it sometimes happen that the @code{tar} bundled by the
+system is aware of block size idiosyncrasies, while GNU @code{tar} requires
+an explicit specification for the block size, which it cannot guess.
+This yields some people to consider GNU @code{tar} is misbehaving, because
+by comparison, @cite{the bundle @code{tar} works OK}. Adding @w{@kbd{-b
+256}}, for example, might resolve the problem.
+
+If you use a non-default blocking factor when you create an archive, you
+must specify the same blocking factor when you modify that archive. Some
+archive devices will also require you to specify the blocking factor when
+reading that archive, however this is not typically the case. Usually, you
+can use @value{op-list} without specifying a blocking factor---@code{tar}
+reports a non-default record size and then lists the archive members as
+it would normally. To extract files from an archive with a non-standard
+blocking factor (particularly if you're not sure what the blocking factor
+is), you can usually use the @value{op-read-full-records} option while
+specifying a blocking factor larger then the blocking factor of the archive
+(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
+@xref{list}, for more information on the @value{op-list}
+operation. @xref{Reading}, for a more detailed explanation of that option.
+
+@table @kbd
+@item --blocking-factor=@var{number}
+@itemx -b @var{number}
+Specifies the blocking factor of an archive. Can be used with any
+operation, but is usually not necessary with @value{op-list}.
@end table
-@node Options, , Operations, Quick Reference
-@appendixsec Table of Options
+Device blocking
-Options change the way @code{tar} performs an operation.
+@table @kbd
+@item -b @var{blocks}
+@itemx --blocking-factor=@var{blocks}
+Set record size to @math{@var{blocks} * 512} bytes.
-@table @samp
-@item --absolute-paths
-WILL BE INPUT WHEN QUESTION IS RESOLVED
+This option is used to specify a @dfn{blocking factor} for the archive.
+When reading or writing the archive, @code{tar}, will do reads and writes
+of the archive in records of @math{@var{block}*512} bytes. This is true
+even when the archive is compressed. Some devices requires that all
+write operations be a multiple of a certain size, and so, @code{tar}
+pads the archive out to the next record boundary.
-@item --after-date=@var{date}
-Limit the operation to files changed after the given date.
-@xref{File Exclusion}.
+The default blocking factor is set when @code{tar} is compiled, and is
+typically 20. Blocking factors larger than 20 cannot be read by very
+old versions of @code{tar}, or by some newer versions of @code{tar}
+running on old machines with small address spaces.
+
+With a magnetic tape, larger records give faster throughput and fit
+more data on a tape (because there are fewer inter-record gaps).
+If the archive is in a disk file or a pipe, you may want to specify
+a smaller blocking factor, since a large one will result in a large
+number of null bytes at the end of the archive.
+
+When writing cartridge or other streaming tapes, a much larger
+blocking factor (say 126 or more) will greatly increase performance.
+However, you must specify the same blocking factor when reading or
+updating the archive.
+
+Apparently, Exabyte drives have a physical block size of 8K bytes.
+If we choose our blocksize as a multiple of 8k bytes, then the problem
+seems to dissapper. Id est, we are using block size of 112 right
+now, and we haven't had the problem since we switched@dots{}
+
+With GNU @code{tar} the blocking factor is limited only by the maximum
+record size of the device containing the archive, or by the amount of
+available virtual memory.
+
+However, deblocking or reblocking is virtually avoided in a special
+case which often occurs in practice, but which requires all the
+following conditions to be simultaneously true:
+@itemize @bullet
+@item
+the archive is subject to a compression option,
+@item
+the archive is not handled through standard input or output, nor
+redirected nor piped,
+@item
+the archive is directly handled to a local disk, instead of any special
+device,
+@item
+@value{op-blocking-factor} is not explicitely specified on the @code{tar}
+invocation.
+@end itemize
-@item --block-size=@var{number}
-Specify the blocking factor of an archive. @xref{Blocking Factor}.
+In previous versions of GNU @code{tar}, the @samp{--compress-block}
+option (or even older: @samp{--block-compress}) was necessary to
+reblock compressed archives. It is now a dummy option just asking
+not to be used, and otherwise ignored. If the output goes directly
+to a local disk, and not through stdout, then the last write is
+not extended to a full record size. Otherwise, reblocking occurs.
+Here are a few other remarks on this topic:
+
+@itemize @bullet
+
+@item
+@code{gzip} will complain about trailing garbage if asked to
+uncompress a compressed archive on tape, there is an option to turn
+the message off, but it breaks the regularity of simply having to use
+@samp{@var{prog} -d} for decompression. It would be nice if gzip was
+silently ignoring any number of trailing zeros. I'll ask Jean-loup
+Gailly, by sending a copy of this message to him.
+
+@item
+@code{compress} does not show this problem, but as Jean-loup pointed
+out to Michael, @samp{compress -d} silently adds garbage after
+the result of decompression, which tar ignores because it already
+recognized its end-of-file indicator. So this bug may be safely
+ignored.
+
+@item
+@samp{gzip -d -q} will be silent about the trailing zeros indeed,
+but will still return an exit status of 2 which tar reports in turn.
+@code{tar} might ignore the exit status returned, but I hate doing
+that, as it weakens the protection @code{tar} offers users against
+other possible problems at decompression time. If @code{gzip} was
+silently skipping trailing zeros @emph{and} also avoiding setting the
+exit status in this innocuous case, that would solve this situation.
+
+@item
+@code{tar} should become more solid at not stopping to read a pipe at
+the first null block encountered. This inelegantly breaks the pipe.
+@code{tar} should rather drain the pipe out before exiting itself.
+@end itemize
-@item --compress
-Specify a compressed archive. @xref{Compressed Archives}.
+@item -i
+@itemx --ignore-zeros
+Ignore blocks of zeros in archive (means EOF).
+
+The @value{op-ignore-zeros} option causes @code{tar} to ignore blocks
+of zeros in the archive. Normally a block of zeros indicates the
+end of the archive, but when reading a damaged archive, or one which
+was created by @code{cat}-ing several archives together, this option
+allows @code{tar} to read the entire archive. This option is not on
+by default because many versions of @code{tar} write garbage after
+the zeroed blocks.
+
+Note that this option causes @code{tar} to read to the end of the
+archive file, which may sometimes avoid problems when multiple files
+are stored on a single physical tape.
+
+@item -B
+@itemx --read-full-records
+Reblock as we read (for reading 4.2BSD pipes).
+
+If @value{op-read-full-records} is used, @code{tar} will not panic if an
+attempt to read a record from the archive does not return a full record.
+Instead, @code{tar} will keep reading until it has obtained a full
+record.
+
+This option is turned on by default when @code{tar} is reading
+an archive from standard input, or from a remote machine. This is
+because on BSD Unix systems, a read of a pipe will return however
+much happens to be in the pipe, even if it is less than @code{tar}
+requested. If this option was not used, @code{tar} would fail as
+soon as it read an incomplete record from the pipe.
+
+This option is also useful with the commands for updating an archive.
-@item --compress-block.
-Create a whole block sized compressed archive. @xref{Compressed Archives}.
+@end table
-@item --confirmation
-Solicit confirmation for each file. @xref{Interactive Operation}
-<<< --selective should be a synonym.
+Tape blocking
+
+@FIXME{Appropriate options should be moved here from elsewhere.}
+
+@cindex blocking factor
+@cindex tape blocking
+
+When handling various tapes or cartridges, you have to take care of
+selecting a proper blocking, that is, the number of disk blocks you
+put together as a single tape block on the tape, without intervening
+tape gaps. A @dfn{tape gap} is a small landing area on the tape
+with no information on it, used for decelerating the tape to a
+full stop, and for later regaining the reading or writing speed.
+When the tape driver starts reading a record, the record has to
+be read whole without stopping, as a tape gap is needed to stop the
+tape motion without loosing information.
+
+@cindex Exabyte blocking
+@cindex DAT blocking
+Using higher blocking (putting more disk blocks per tape block) will use
+the tape more efficiently as there will be less tape gaps. But reading
+such tapes may be more difficult for the system, as more memory will be
+required to receive at once the whole record. Further, if there is a
+reading error on a huge record, this is less likely that the system will
+succeed in recovering the information. So, blocking should not be too
+low, nor it should be too high. @code{tar} uses by default a blocking of
+20 for historical reasons, and it does not really matter when reading or
+writing to disk. Current tape technology would easily accomodate higher
+blockings. Sun recommends a blocking of 126 for Exabytes and 96 for DATs.
+We were told that for some DLT drives, the blocking should be a multiple
+of 4Kb, preferably 64Kb (@w{@kbd{-b 128}}) or 256 for decent performance.
+Other manufacturers may use different recommendations for the same tapes.
+This might also depends of the buffering techniques used inside modern
+tape controllers. Some imposes a minimum blocking, or a maximum blocking.
+Others request blocking to be some exponent of two.
+
+So, there is no fixed rule for blocking. But blocking at read time
+should ideally be the same as blocking used at write time. At one place
+I know, with a wide variety of equipment, they found it best to use a
+blocking of 32 to guarantee that their tapes are fully interchangeable.
+
+I was also told that, for recycled tapes, prior erasure (by the same
+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.
+
+@node Many, Using Multiple Tapes, Blocking, Media
+@section Many Archives on One Tape
+
+@FIXME{Appropriate options should be moved here from elsewhere.}
+
+@findex ntape @r{device}
+Most tape devices have two entries in the @file{/dev} directory, or
+entries that come in pairs, which differ only in the minor number for
+this device. Let's take for example @file{/dev/tape}, which often
+points to the only or usual tape device of a given system. There might
+be a corresponding @file{/dev/nrtape} or @file{/dev/ntape}. The simpler
+name is the @emph{rewinding} version of the device, while the name
+having @samp{nr} in it is the @emph{no rewinding} version of the same
+device.
+
+A rewinding tape device will bring back the tape to its beginning point
+automatically when this device is opened or closed. Since @code{tar}
+opens the archive file before using it and closes it afterwards, this
+means that a simple:
-@item --dereference
-Treat a symbolic link as an alternate name for the file the link
-points to. @xref{Symbolic Links}.
+@example
+$ @kbd{tar cf /dev/tape @var{directory}}
+@end example
-@item --directory=@file{directory}
-Change the working directory. @xref{Changing Working Directory}.
+@noindent
+will reposition the tape to its beginning both prior and after saving
+@var{directory} contents to it, thus erasing prior tape contents and
+making it so that any subsequent write operation will destroy what has
+just been saved.
+
+@cindex tape positioning
+So, a rewinding device is normally meant to hold one and only one file.
+If you want to put more than one @code{tar} archive on a given tape, you
+will need to avoid using the rewinding version of the tape device. You
+will also have to pay special attention to tape positioning. Errors in
+positionning may overwrite the valuable data already on your tape. Many
+people, burnt by past experiences, will only use rewinding devices and
+limit themselves to one file per tape, precisely to avoid the risk of
+such errors. Be fully aware that writing at the wrong position on a
+tape loses all information past this point and most probably until the
+end of the tape, and this destroyed information @emph{cannot} be
+recovered.
+
+To save @var{directory-1} as a first archive at the beginning of a
+tape, and leave that tape ready for a second archive, you should use:
-@item --exclude=@var{pattern}
-Exclude files which match the regular expression @var{pattern}.
-@xref{File Exclusion}.
+@example
+$ @kbd{mt -f /dev/nrtape rewind}
+$ @kbd{tar cf /dev/nrtape @var{directory-1}}
+@end example
-@item --exclude-from=@file{file}
-Exclude files which match any of the regular expressions listed in
-the file @file{file}. @xref{File Exclusion}.
+@cindex tape marks
+@dfn{Tape marks} are special magnetic patterns written on the tape
+media, which are later recognizable by the reading hardware. These
+marks are used after each file, when there are many on a single tape.
+An empty file (that is to say, two tape marks in a row) signal the
+logical end of the tape, after which no file exist. Usually,
+non-rewinding tape device drivers will react to the close request issued
+by @code{tar} by first writing two tape marks after your archive, and by
+backspacing over one of these. So, if you remove the tape at that time
+from the tape drive, it is properly terminated. But if you write
+another file at the current position, the second tape mark will be
+erased by the new information, leaving only one tape mark between files.
+
+So, you may now save @var{directory-2} as a second archive after the
+first on the same tape by issuing the command:
-@item --file=@var{archive-name}
-Name the archive. @xref{Archive Name}).
+@example
+$ @kbd{tar cf /dev/nrtape @var{directory-2}}
+@end example
-@item --files-from=@file{file}
-Read file-name arguments from a file on the file system.
-@xref{File Name Lists}.
+@noindent
+and so on for all the archives you want to put on the same tape.
-@item --ignore-umask
-Set modes of extracted files to those recorded in the archive.
-@xref{File Writing Options}.
+Another usual case is that you do not write all the archives the same
+day, and you need to remove and store the tape between two archive
+sessions. In general, you must remember how many files are already
+saved on your tape. Suppose your tape already has 16 files on it, and
+that you are ready to write the 17th. You have to take care of skipping
+the first 16 tape marks before saving @var{directory-17}, say, by using
+these commands:
-@item --ignore-zeros
-Ignore end-of-archive entries. @xref{Archive Reading Options}.
-<<< this should be changed to --ignore-end
+@example
+$ @kbd{mt -f /dev/nrtape rewind}
+$ @kbd{mt -f /dev/nrtape fsf 16}
+$ @kbd{tar cf /dev/nrtape @var{directory-17}}
+@end example
-@item --listed-incremental=@var{file-name} (-g)
-Take a file name argument always. If the file doesn't exist, run a level
-zero dump, creating the file. If the file exists, uses that file to see
-what has changed.
+In all the previous examples, we put aside blocking considerations, but
+you should do the proper things for that as well. @xref{Blocking}.
-@item --incremental (-G)
-@c <<<look it up>>>
+@menu
+* Tape Positioning:: Tape Positions and Tape Marks
+* mt:: The @code{mt} Utility
+@end menu
-@item --tape-length=@var{n} (-L)
-@c <<<alternate way of doing multi archive, will go to that length and
-@c prompts for new tape, automatically turns on multi-volume. >>>
-@c <<< this needs to be written into main body as well -ringo
+@node Tape Positioning, mt, Many, Many
+@subsection Tape Positions and Tape Marks
+@UNREVISED
-@item --info-script=@var{program-file}
-Create a multi-volume archive via a script. @xref{Multi-Volume Archives}.
+Just as archives can store more than one file from the file system,
+tapes can store more than one archive file. To keep track of where
+archive files (or any other type of file stored on tape) begin and
+end, tape archive devices write magnetic @dfn{tape marks} on the
+archive media. Tape drives write one tape mark between files,
+two at the end of all the file entries.
-@item --interactive
-Ask for confirmation before performing any operation on a file or
-archive member.
+If you think of data as a series of records "rrrr"'s, and tape marks as
+"*"'s, a tape might look like the following:
-@item --keep-old-files
-Prevent overwriting during extraction. @xref{File Writing Options}.
+@example
+rrrr*rrrrrr*rrrrr*rr*rrrrr**-------------------------
+@end example
-@item --label=@var{archive-label}
-Include an archive-label in the archive being created. @xref{Archive
-Label}.
+Tape devices read and write tapes using a read/write @dfn{tape
+head}---a physical part of the device which can only access one
+point on the tape at a time. When you use @code{tar} to read or
+write archive data from a tape device, the device will begin reading
+or writing from wherever on the tape the tape head happens to be,
+regardless of which archive or what part of the archive the tape
+head is on. Before writing an archive, you should make sure that no
+data on the tape will be overwritten (unless it is no longer needed).
+Before reading an archive, you should make sure the tape head is at
+the beginning of the archive you want to read. (The @code{restore}
+script will find the archive automatically. @FIXME{There is no such
+restore script!}. @FIXME-xref{Scripted Restoration}). @xref{mt}, for
+an explanation of the tape moving utility.
-@item --modification-time
-Set the modification time of extracted files to the time they were
-extracted. @xref{File Writing Options}.
+If you want to add new archive file entries to a tape, you should
+advance the tape to the end of the existing file entries, backspace
+over the last tape mark, and write the new archive file. If you were
+to add two archives to the example above, the tape might look like the
+following:
-@item --multi-volume
-Specify a multi-volume archive. @xref{Multi-Volume Archives}.
+@example
+rrrr*rrrrrr*rrrrr*rr*rrrrr*rrr*rrrr**----------------
+@end example
-@item --newer=@var{date}
-Limit the operation to files changed after the given date.
-@xref{File Exclusion}.
+@node mt, , Tape Positioning, Many
+@subsection The @code{mt} Utility
+@UNREVISED
-@item --newer-mtime=@var{date}
-Limit the operation to files modified after the given date. @xref{File
-Exclusion}.
+@FIXME{Is it true that this only works on non-block devices?
+should explain the difference, (fixed or variable).}
+@value{xref-blocking-factor}.
-@item --old
-Create an old format archive. @xref{Old Style File Information}.
-@c <<< did we agree this should go away as a synonym?
+You can use the @code{mt} utility to advance or rewind a tape past a
+specified number of archive files on the tape. This will allow you
+to move to the beginning of an archive before extracting or reading
+it, or to the end of all the archives before writing a new one.
+@FIXME{Why isn't there an "advance 'til you find two tape marks
+together"?}
-@item --old-archive
-Create an old format archive. @xref{Old Style File Information}.
+The syntax of the @code{mt} command is:
-@item --one-file-system
-Prevent @code{tar} from crossing file system boundaries when
-archiving. @xref{File Exclusion}.
+@example
+@kbd{mt [-f @var{tapename}] @var{operation} [@var{number}]}
+@end example
-@item --portable
-Create an old format archive. @xref{Old Style File Information}.
-@c <<< was portability, may still need to be changed
+where @var{tapename} is the name of the tape device, @var{number} is
+the number of times an operation is performed (with a default of one),
+and @var{operation} is one of the following:
-@item --preserve-order
-Help process large lists of file-names on machines with small amounts of
-memory. @xref{Archive Reading Options}.
+@FIXME{is there any use for record operations?}
-@item --preserve-permission
-Set modes of extracted files to those recorded in the archive.
-@xref{File Writing Options}.
-
-@item --read-full-blocks
-Read an archive with a smaller than specified block size or which
-contains incomplete blocks. @xref{Archive Reading Options}).
-@c should be --partial-blocks (!!!)
-
-@item --record-number
-Print the record number where a message is generated.
-@xref{Additional Information}.
+@table @kbd
+@item eof
+@itemx weof
+Writes @var{number} tape marks at the current position on the tape.
-@item --same-order
-Help process large lists of file-names on machines with small amounts of
-memory. @xref{Archive Reading Options}.
+@item fsf
+Moves tape position forward @var{number} files.
-@item --same-permission
-Set the modes of extracted files to those recorded in the archive.
-@xref{File Writing Options}.
+@item bsf
+Moves tape position back @var{number} files.
-@item --sparse
-Archive sparse files sparsely. @xref{Sparse Files}.
+@item rewind
+Rewinds the tape. (Ignores @var{number}).
-@item --starting-file=@var{file-name}
-Begin reading in the middle of an archive. @xref{Scarce Disk Space}.
+@item offline
+@itemx rewoff1
+Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
-@item --to-stdout
-Write files to the standard output. @xref{File Writing Options}.
+@item status
+Prints status information about the tape unit.
-@item --uncompress
-Specifdo a compressed archive. @xref{Compressed Archives}.
+@end table
-@item -V @var{archive-label}
-Include an archive-label in the archive being created. @xref{Archive
-Label}.
-@c was --volume
+@FIXME{Is there a better way to frob the spacing on the list?}
-@item --verbose
-Print the names of files or archive members as they are being
-operated on. @xref{Additional Information}.
+If you don't specify a @var{tapename}, @code{mt} uses the environment
+variable TAPE; if TAPE does not exist, @code{mt} uses the device
+@file{/dev/rmt12}.
-@item --verify
-Check for discrepancies in the archive immediately after it is
-written. @xref{Write Verification}.
+@code{mt} returns a 0 exit status when the operation(s) were
+successful, 1 if the command was unrecognized, and 2 if an operation
+failed.
-@item -B
-Read an archive with a smaller than specified block size or which
-contains incomplete blocks. @xref{Archive Reading Options}).
+@FIXME{New node on how to find an archive?}
-@item -K @var{file-name}
-Begin reading in the middle of an archive. @xref{Scarce Disk Space}.
+If you use @value{op-extract} with the @value{op-label} option specified,
+@code{tar} will read an archive label (the tape head has to be positioned
+on it) and print an error if the archive label doesn't match the
+@var{archive-name} specified. @var{archive-name} can be any regular
+expression. If the labels match, @code{tar} extracts the archive.
+@value{xref-label}. @FIXME-xref{Matching Format Parameters}.
+@FIXME{fix cross references} @samp{tar --list --label} will cause
+@code{tar} to print the label.
-@item -M
-Specify a multi-volume archive. @xref{Multi-Volume Archives}.
+@FIXME{Program to list all the labels on a tape?}
-@item -N @var{date}
-Limit operation to files changed after the given date. @xref{File Exclusion}.
+@node Using Multiple Tapes, label, Many, Media
+@section Using Multiple Tapes
+@UNREVISED
-@item -O
-Write files to the standard output. @xref{File Writing Options}.
+Often you might want to write a large archive, one larger than will fit
+on the actual tape you are using. In such a case, you can run multiple
+@code{tar} commands, but this can be inconvenient, particularly if you
+are using options like @value{op-exclude} or dumping entire filesystems.
+Therefore, @code{tar} supports multiple tapes automatically.
-@c <<<<- P is absolute paths, add when resolved. -ringo>>>
+Use @value{op-multi-volume} on the command line, and then @code{tar} will,
+when it reaches the end of the tape, prompt for another tape, and
+continue the archive. Each tape will have an independent archive, and
+can be read without needing the other. (As an exception to this, the
+file that @code{tar} was archiving when it ran out of tape will usually
+be split between the two archives; in this case you need to extract from
+the first archive, using @value{op-multi-volume}, and then put in the
+second tape when prompted, so @code{tar} can restore both halves of the
+file.)
-@item -R
-Print the record number where a message is generated.
-@xref{Additional Information}.
+GNU @code{tar} multi-volume archives do not use a truly portable format.
+You need GNU @code{tar} at both end to process them properly.
-@item -S
-Archive sparse files sparsely. @xref{Sparse Files}.
+When prompting for a new tape, @code{tar} accepts any of the following
+responses:
-@item -T @var{file}
-Read file-name arguments from a file on the file system.
-@xref{File Name Lists}.
+@table @kbd
+@item ?
+Request @code{tar} to explain possible responses
+@item q
+Request @code{tar} to exit immediately.
+@item n @var{file name}
+Request @code{tar} to write the next volume on the file @var{file name}.
+@item !
+Request @code{tar} to run a subshell.
+@item y
+Request @code{tar} to begin writing the next volume.
+@end table
-@item -W
-Check for discrepancies in the archive immediately after it is
-written. @xref{Write Verification}.
+(You should only type @samp{y} after you have changed the tape;
+otherwise @code{tar} will write over the volume it just finished.)
-@item -Z
-Specify a compressed archive. @xref{Compressed Archives}.
+If you want more elaborate behavior than this, give @code{tar} the
+@value{op-info-script} option. The file @var{script-name} is expected
+to be a program (or shell script) to be run instead of the normal
+prompting procedure. When the program finishes, @code{tar} will
+immediately begin writing the next volume. The behavior of the
+@samp{n} response to the normal tape-change prompt is not available
+if you use @value{op-info-script}.
-@item -b @var{number}
-Specify the blocking factor of an archive. @xref{Blocking Factor}.
+The method @code{tar} uses to detect end of tape is not perfect, and
+fails on some operating systems or on some devices. You can use the
+@value{op-tape-length} option if @code{tar} can't detect the end of the
+tape itself. This option selects @value{op-multi-volume} automatically.
+The @var{size} argument should then be the usable size of the tape.
+But for many devices, and floppy disks in particular, this option is
+never required for real, as far as we know.
+
+The volume number used by @code{tar} in its tape-change prompt
+can be changed; if you give the @value{op-volno-file} option, then
+@var{file-of-number} should be an unexisting file to be created, or else,
+a file already containing a decimal number. That number will be used
+as the volume number of the first volume written. When @code{tar} is
+finished, it will rewrite the file with the now-current volume number.
+(This does not change the volume number written on a tape label, as
+per @value{ref-label}, it @emph{only} affects the number used in
+the prompt.)
-@item -f @var{archive-name}
-Name the archive. @xref{Archive Name}).
+If you want @code{tar} to cycle through a series of tape drives, then
+you can use the @samp{n} response to the tape-change prompt. This is
+error prone, however, and doesn't work at all with @value{op-info-script}.
+Therefore, if you give @code{tar} multiple @value{op-file} options, then
+the specified files will be used, in sequence, as the successive volumes
+of the archive. Only when the first one in the sequence needs to be
+used again will @code{tar} prompt for a tape change (or run the info
+script).
-@item -h
-Treat a symbolic link as an alternate name for the file the link
-points to. @xref{Symbolic Links}.
+Multi-volume archives
-@item -i
-Ignore end-of-archive entries. @xref{Archive Reading Options}.
+With @value{op-multi-volume}, @code{tar} will not abort when it cannot
+read or write any more data. Instead, it will ask you to prepare a new
+volume. If the archive is on a magnetic tape, you should change tapes
+now; if the archive is on a floppy disk, you should change disks, etc.
-@item -k
-Prevent overwriting during extraction. @xref{File Writing Options}.
+Each volume of a multi-volume archive is an independent @code{tar}
+archive, complete in itself. For example, you can list or extract any
+volume alone; just don't specify @value{op-multi-volume}. However, if one
+file in the archive is split across volumes, the only way to extract
+it successfully is with a multi-volume extract command @samp{--extract
+--multi-volume} (@samp{-xM}) starting on or before the volume where
+the file begins.
-@item -l
-Prevent @code{tar} from crossing file system boundaries when
-archiving. @xref{File Exclusion}.
+For example, let's presume someone has two tape drives on a system
+named @file{/dev/tape0} and @file{/dev/tape1}. For having GNU
+@code{tar} to switch to the second drive when it needs to write the
+second tape, and then back to the first tape, etc., just do either of:
-@item -m
-Set the modification time of extracted files to the time they were
-extracted. @xref{File Writing Options}.
+@smallexample
+$ @kbd{tar --create --multi-volume --file=/dev/tape0 --file=/dev/tape1 @var{files}}
+$ @kbd{tar cMff /dev/tape0 /dev/tape1 @var{files}}
+@end smallexample
-@item -o
-Create an old format archive. @xref{Old Style File Information}.
+@menu
+* Multi-Volume Archives:: Archives Longer than One Tape or Disk
+* Tape Files:: Tape Files
+@end menu
-@item -p
-Set the modes of extracted files to those recorded in the archive.
-@xref{File Writing Options}.
+@node Multi-Volume Archives, Tape Files, Using Multiple Tapes, Using Multiple Tapes
+@subsection Archives Longer than One Tape or Disk
+@cindex Multi-volume archives
+@UNREVISED
-@item -s
-Help process large lists of file-names on machines with small amounts of
-memory. @xref{Archive Reading Options}.
+To create an archive that is larger than will fit on a single unit of
+the media, use the @value{op-multi-volume} option in conjunction with
+the @value{op-create} option (@pxref{create}). A
+@dfn{multi-volume} archive can be manipulated like any other archive
+(provided the @value{op-multi-volume} option is specified), but is
+stored on more than one tape or disk.
-@item -v
-Print the names of files or archive members they are being operated
-on. @xref{Additional Information}.
+When you specify @value{op-multi-volume}, @code{tar} does not report an
+error when it comes to the end of an archive volume (when reading), or
+the end of the media (when writing). Instead, it prompts you to load
+a new storage volume. If the archive is on a magnetic tape, you
+should change tapes when you see the prompt; if the archive is on a
+floppy disk, you should change disks; etc.
-@item -w
-@c <<<see --interactive. WILL BE INPUT WHEN QUESTIONS ARE RESOLVED.>>>
+You can read each individual volume of a multi-volume archive as if it
+were an archive by itself. For example, to list the contents of one
+volume, use @value{op-list}, without @value{op-multi-volume} specified.
+To extract an archive member from one volume (assuming it is described
+that volume), use @value{op-extract}, again without
+@value{op-multi-volume}.
-@item -z
-Specify a compressed archive. @xref{Compressed Archives}.
+If an archive member is split across volumes (ie. its entry begins on
+one volume of the media and ends on another), you need to specify
+@value{op-multi-volume} to extract it successfully. In this case, you
+should load the volume where the archive member starts, and use
+@samp{tar --extract --multi-volume}---@code{tar} will prompt for later
+volumes as it needs them. @xref{extracting archives}, for more
+information about extracting archives.
-@item -z -z
-Create a whole block sized compressed archive. @xref{Compressed Archives}.
-@c I would rather this were -Z. it is the only double letter short
-@c form.
+@value{op-info-script} is like @value{op-multi-volume}, except that
+@code{tar} does not prompt you directly to change media volumes when
+a volume is full---instead, @code{tar} runs commands you have stored
+in @var{script-name}. For example, this option can be used to eject
+cassettes, or to broadcast messages such as @samp{Someone please come
+change my tape} when performing unattended backups. When @var{script-name}
+is done, @code{tar} will assume that the media has been changed.
-@item -C @file{directory}
-Change the working directory. @xref{Changing Working Directory}.
+Multi-volume archives can be modified like any other archive. To add
+files to a multi-volume archive, you need to only mount the last
+volume of the archive media (and new volumes, if needed). For all
+other operations, you need to use the entire archive.
-@item -F @var{program-file}
-Create a multi-volume archive via a script. @xref{Multi-Volume Archives}.
+If a multi-volume archive was labeled using @value{op-label}
+(@value{pxref-label}) when it was created, @code{tar} will not
+automatically label volumes which are added later. To label subsequent
+volumes, specify @value{op-label} again in conjunction with the
+@value{op-append}, @value{op-update} or @value{op-concatenate} operation.
-@item -X @file{file}
-Exclude files which match any of the regular expressions listed in
-the file @file{file}. @xref{File Exclusion}.
-@end table
+@cindex Labelling multi-volume archives
+@FIXME{example}
-@node Data Format Details, Concept Index, Quick Reference, Top
-@appendix Details of the Archive Data Format
+@FIXME{There should be a sample program here, including an exit
+before end. Is the exit status even checked in tar? :-(}
-This chapter is based heavily on John Gilmore's @i{tar}(5) manual page
-for the public domain @code{tar} that GNU @code{tar} is based on.
-@c it's been majorly edited since, we may be able to lose this.
+@table @kbd
+@item --multi-volume
+@itemx -M
+Creates a multi-volume archive, when used in conjunction with
+@value{op-create}. To perform any other operation on a multi-volume
+archive, specify @value{op-multi-volume} in conjunction with that
+operation.
-The archive media contains a series of records, each of which contains
-512 bytes. Each archive member is represented by a header record,
-which describes the file, followed by zero or more records which
-represent the contents of the file. At the end of the archive file
-there may be a record consisting of a series of binary zeros, as an
-end-of-archive marker. GNU @code{tar} writes a record of zeros at the
-end of an archive, but does not assume that such a record exists when
-reading an archive.
+@item --info-script=@var{program-file}
+@itemx -F @var{program-file}
+Creates a multi-volume archive via a script. Used in conjunction with
+@value{op-create}.
+@end table
-Records may be grouped into @dfn{blocks} for I/O operations. A block
-of records is written with a single @code{write()} operation. The
-number of records in a block is specified using the @samp{--block-size}
-option. @xref{Blocking Factor}, for more information about specifying
-block size.
+Beware that there is @emph{no} real standard about the proper way, for a
+@code{tar} archive, to span volume boundaries. If you have a multi-volume
+created by some vendor's @code{tar}, there is almost no chance you could
+read all the volumes with GNU @code{tar}. The converse is also true:
+you may not expect multi-volume archives created by GNU @code{tar} to
+be fully recovered by vendor's @code{tar}. Since there is little chance
+that, in mixed system configurations, some vendor's @code{tar} will work on
+another vendor's machine, and there is a great chance that GNU @code{tar}
+will work on most of them, your best bet is to install GNU @code{tar}
+on all machines between which you know exchange of files is possible.
+
+@node Tape Files, , Multi-Volume Archives, Using Multiple Tapes
+@subsection Tape Files
+@UNREVISED
-@menu
-* Header Data:: The Distribution of Data in the Header
-* Header Fields:: The Meaning of Header Fields
-* Sparse File Handling:: Fields to Handle Sparse Files
-@end menu
+To give the archive a name which will be recorded in it, use the
+@value{op-label} option. This will write a special block identifying
+@var{volume-label} as the name of the archive to the front of the archive
+which will be displayed when the archive is listed with @value{op-list}.
+If you are creating a multi-volume archive with @value{op-multi-volume}
+(@FIXME-pxref{Using Multiple Tapes}), then the volume label will have
+@samp{Volume @var{nnn}} appended to the name you give, where @var{nnn} is
+the number of the volume of the archive. (If you use the @value{op-label}
+option when reading an archive, it checks to make sure the label on the
+tape matches the one you give. @value{xref-label}.
+
+When @code{tar} writes an archive to tape, it creates a single
+tape file. If multiple archives are written to the same tape, one
+after the other, they each get written as separate tape files. When
+extracting, it is necessary to position the tape at the right place
+before running @code{tar}. To do this, use the @code{mt} command.
+For more information on the @code{mt} command and on the organization
+of tapes into a sequence of tape files, see @ref{mt}.
+
+People seem to often do:
-@node Header Data, Header Fields, Data Format Details, Data Format Details
-@appendixsec The Distribution of Data in the Header
-
-The header record is defined in C as follows:
-@c I am taking the following code on faith.
-
-@example
-@r{Standard Archive Format - Standard TAR - USTAR}
-
-#define RECORDSIZE 512
-#define NAMSIZ 100
-#define TUNMLEN 32
-#define TGNMLEN 32
-#define SPARSE_EXT_HDR 21
-#define SPARSE_IN_HDR 4
-
-struct sparse @{
- char offset[12];
- char numbytes[12];
-@};
-
-union record @{
- char charptr[RECORDSIZE];
- struct header @{
- char name[NAMSIZ];
- char mode[8];
- char uid[8];
- char gid[8];
- char size[12];
- char mtime[12];
- char chksum[8];
- char linkflag;
- char linkname[NAMSIZ];
- char magic[8];
- char uname[TUNMLEN];
- char gname[TGNMLEN];
- char devmajor[8];
- char devminor[8];
-
-@r{The following fields were added by gnu and are not used by other}
-@r{versions of @code{tar}}.
- char atime[12];
- char ctime[12];
- char offset[12];
- char longnames[4];
-@r{The next three fields were added by gnu to deal with shrinking down}
-@r{sparse files.}
- struct sparse sp[SPARSE_IN_HDR];
- char isextended;
-@r{This is the number of nulls at the end of the file, if any.}
- char ending_blanks[12];
-
- @} header;
-
- struct extended_header @{
- struct sparse sp[21];
- char isextended;
- @} ext_hdr;
-
-@};
-@c <<< this whole thing needs to be put into better english
-
-@r{The checksum field is filled with this while the checksum is computed.}
-#define CHKBLANKS " " @r{8 blanks, no null}
-
-@r{Inclusion of this field marks an archive as being in standard}
-@r{Posix format (though GNU tar itself is not Posix conforming). GNU}
-@r{tar puts "ustar" in this field if uname and gname are valid.}
-#define TMAGIC "ustar " @r{7 chars and a null}
-
-@r{The magic field is filled with this if this is a GNU format dump entry.}
-#define GNUMAGIC "GNUtar " @r{7 chars and a null}
-
-@r{The linkflag defines the type of file.}
-#define LF_OLDNORMAL '\0' @r{Normal disk file, Unix compatible}
-#define LF_NORMAL '0' @r{Normal disk file}
-#define LF_LINK '1' @r{Link to previously dumped file}
-#define LF_SYMLINK '2' @r{Symbolic link}
-#define LF_CHR '3' @r{Character special file}
-#define LF_BLK '4' @r{Block special file}
-#define LF_DIR '5' @r{Directory}
-#define LF_FIFO '6' @r{FIFO special file}
-#define LF_CONTIG '7' @r{Contiguous file}
-
-@r{hhe following are further link types which were defined later.}
-
-@r{This is a dir entry that contains the names of files that were in}
-@r{the dir at the time the dump was made.}
-#define LF_DUMPDIR 'D'
-
-@r{This is the continuation of a file that began on another volume}
-#define LF_MULTIVOL 'M'
-
-@r{This is for sparse files}
-#define LF_SPARSE 'S'
-
-@r{This file is a tape/volume header. Ignore it on extraction.}
-#define LF_VOLHDR 'V'
-
-@r{These are bits used in the mode field - the values are in octal}
-#define TSUID 04000 @r{Set UID on execution}
-#define TSGID 02000 @r{Set GID on execution}
-#define TSVTX 01000 @r{Save text (sticky bit)}
-
-@r{These are file permissions}
-#define TUREAD 00400 @r{read by owner}
-#define TUWRITE 00200 @r{write by owner}
-#define TUEXEC 00100 @r{execute/search by owner}
-#define TGREAD 00040 @r{read by group}
-#define TGWRITE 00020 @r{write by group}
-#define TGEXEC 00010 @r{execute/search by group}
-#define TOREAD 00004 @r{read by other}
-#define TOWRITE 00002 @r{write by other}
-#define TOEXEC 00001 @r{execute/search by other}
-@end example
-
-
-All characters in headers are 8-bit characters in the local variant of
-ASCII. Each field in the header is contiguous; that is, there is no
-padding in the header format.
-
-Data representing the contents of files is not translated in any way
-and is not constrained to represent characters in any character set.
-@code{tar} does not distinguish between text files and binary files.
+@example
+@kbd{--label="@var{some-prefix} `date +@var{some-format}`"}
+@end example
-The @code{name}, @code{linkname}, @code{magic}, @code{uname}, and
-@code{gname} fields contain null-terminated character strings. All
-other fields contain 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.
-
-@node Header Fields, Sparse File Handling, Header Data, Data Format Details
-@appendixsec The Meaning of Header Fields
-
-The @code{name} field contains the name of the file.
-<<< how big a name before field overflows?
-
-The @code{mode} field contains nine bits which specify file
-permissions, and three bits which specify the Set UID, Set GID, and
-Save Text (``stick'') modes. Values for these bits are defined above.
-@xref{File Writing Options}, for information on how file permissions
-and modes are used by @code{tar}.
-
-The @code{uid} and @code{gid} fields contain the numeric user and
-group IDs of the file owners. If the operating system does not
-support numeric user or group IDs, these fields should be ignored.
-@c but are they?
-
-The @code{size} field contains the size of the file in bytes; this
-field contains a zero if the header describes a link to a file.
-
-The @code{mtime} field contains the modification time of the file.
-This is the ASCII representation of the octal value of the last time
-the file was modified, represented as an integer number of seconds
-since January 1, 1970, 00:00 Coordinated Universal Time.
-@xref{File Writing Options}, for a description of how @code{tar} uses
-this information.
-
-The @code{chksum} field contains the ASCII representation of the octal
-value of the simple sum of all bytes in the header record. To
-generate this sum, each 8-bit byte in the header is added to an
-unsigned integer, which has been initialized to zero. The precision
-of the integer is seventeen bits. When calculating the checksum, the
-@code{chksum} field itself is treated as blank.
-
-The @code{atime} and @code{ctime} fields are used when making
-incremental backups; they store, respectively, the file's access time
-and last inode-change time.
+or such, for pushing a common date in all volumes or an archive set.
-The value in the @code{offset} field is used when making a
-multi-volume archive. The offset is number of bytes into the file
-that we need to go to pick up where we left off in the previous
-volume, i.e the location that a continued file is continued from.
+@node label, verify, Using Multiple Tapes, Media
+@section Including a Label in the Archive
+@cindex Labeling an archive
+@cindex Labels on the archive media
+@UNREVISED
-The @code{longnames} field supports a feature that is not yet
-implemented. This field should be empty.
+@table @kbd
+@item -V @var{name}
+@itemx --label=@var{name}
+Create archive with volume name @var{name}.
+@end table
-The @code{magic} field indicates that this archive was output in the
-P1003 archive format. If this field contains @code{TMAGIC}, the
-@code{uname} and @code{gname} fields will contain the ASCII
-representation of the owner and group of the file respectively. If
-found, the user and group IDs are used rather than the values in the
-@code{uid} and @code{gid} fields.
+This option causes @code{tar} to write out a @dfn{volume header} at
+the beginning of the archive. If @value{op-multi-volume} is used, each
+volume of the archive will have a volume header of @samp{@var{name}
+Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
+next, and so on.
-The @code{sp} field is used to archive sparse files efficiently.
-@xref{Sparse File Handling}, for a description of this field, and
-other fields it may imply.
+@FIXME{Should the arg to --label be a quoted string?? No.}
-The @code{typeflag} field specifies the file's type. If a particular
-implementation does not recognize or permit the specified type,
-@code{tar} extracts the file as if it were a regular file, and reports
-the discrepancy on the standard error. @xref{File Types}. @xref{GNU
-File Types}.
+To avoid problems caused by misplaced paper labels on the archive
+media, you can include a @dfn{label} entry---an archive member which
+contains the name of the archive---in the archive itself. Use the
+@value{op-label} option in conjunction with the @value{op-create} operation
+to include a label entry in the archive as it is being created.
-@menu
-* File Types:: File Types
-* GNU File Types:: Additional File Types Supported by GNU
-@end menu
+If you create an archive using both @value{op-label} and
+@value{op-multi-volume}, each volume of the archive will have an
+archive label of the form @samp{@var{archive-label} Volume @var{n}},
+where @var{n} is 1 for the first volume, 2 for the next, and so on.
+@FIXME-xref{Multi-Volume Archives}, for information on creating multiple
+volume archives.
-@node File Types, GNU File Types, Header Fields, Header Fields
-@appendixsubsec File Types
+If you list or extract an archive using @value{op-label}, @code{tar} will
+print an error if the archive label doesn't match the @var{archive-label}
+specified, and will then not list nor extract the archive. In those cases,
+@var{archive-label} argument is interpreted as a globbing-style pattern
+which must match the actual magnetic volume label. @xref{exclude}, for
+a precise description of how match is attempted@footnote{Previous versions
+of @code{tar} used full regular expression matching, or before that, only
+exact string matching, instead of wildcard matchers. We decided for the
+sake of simplicity to use a uniform matching device through @code{tar}.}.
+If the switch @value{op-multi-volume} is being used, the volume label
+matcher will also suffix @var{archive-label} by @w{@samp{ Volume [1-9]*}}
+if the initial match fails, before giving up. Since the volume numbering
+is automatically added in labels at creation time, it sounded logical to
+equally help the user taking care of it when the archive is being read.
+
+The @value{op-label} was once called @samp{--volume}, but is not available
+under that name anymore.
-The following flags are used to describe file types:
+To find out an archive's label entry (or to find out if an archive has
+a label at all), use @samp{tar --list --verbose}. @code{tar} will print the
+label first, and then print archive member information, as in the
+example below:
-@table @code
-@item LF_NORMAL
-@itemx LF_OLDNORMAL
-Indicates a regular file. In order to be compatible with older
-versions of @code{tar}, a @code{typeflag} value of @code{LF_OLDNORMAL}
-should be silently recognized as a regular file. New archives should
-be created using @code{LF_NORMAL} for regular files. For backward
-compatibility, @code{tar} treats a regular file whose name ends with a
-slash as a directory.
-
-@item LF_LINK
-Indicates a link to another file, of any type, which has been
-previously archived. @code{tar} identifies linked files in Unix by
-matching device and inode numbers. The linked-to name is specified in
-the @code{linkname} field with a trailing null.
-
-@item LF_SYMLINK
-Indicates a symbolic link to another file. The linked-to
-name is specified in the @code{linkname} field with a trailing null.
-@xref{File Writing Options}, for information on archiving files
-referenced by a symbolic link.
-
-@item LF_CHR
-@itemx LF_BLK
-Indicate character special files and block special files,
-respectively. In this case the @code{devmajor} and @code{devminor}
-fields will contain the major and minor device numbers. Operating
-systems may map the device specifications to their own local
-specification, or may ignore the entry.
-
-@item LF_DIR
-Indicates a directory or sub-directory. The directory name in the
-@code{name} field should end with a slash. On systems where disk
-allocation is performed on a directory basis, the @code{size} field
-will contain the maximum number of bytes (which may be rounded to the
-nearest disk block allocation unit) that the directory can hold. A
-@code{size} field of zero indicates no size limitations. Systems that
-do not support size limiting in this manner should ignore the
-@code{size} field.
+@example
+$ @kbd{tar --verbose --list --file=iamanarchive}
+V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
+-rw-rw-rw- ringo user 40 1990-05-21 13:30 iamafilename
+@end example
-@item LF_FIFO
-Indicates a FIFO special file. Note that archiving a FIFO file
-archives the existence of the file and not its contents.
-
-@item LF_CONTIG
-Indicates a contiguous file. Contiguous files are the same as normal
-files except that, in operating systems that support it, all the
-files' disk space is allocated contiguously. Operating systems which
-do not allow contiguous allocation should silently treat this type as
-a normal file.
-
-@item 'A' @dots{}
-@itemx 'Z'
-These are reserved for custom implementations. Some of these are used
-in the GNU modified format, which is described below. @xref{GNU File
-Types}.
+@table @kbd
+@item --label=@var{archive-label}
+@itemx -V @var{archive-label}
+Includes an @dfn{archive-label} at the beginning of the archive when
+the archive is being created, when used in conjunction with the
+@value{op-create} option. Checks to make sure the archive label
+matches the one specified (when used in conjunction with the
+@value{op-extract} option.
@end table
-Certain other flag values are reserved for specification in future
-revisions of the P1003 standard, and should not be used by any
-@code{tar} program.
+To get a common information on all tapes of a series, use the
+@value{op-label} option. For having this information different in each
+series created through a single script used on a regular basis, just
+manage to get some date string as part of the label. For example:
+
+@example
+$ @kbd{tar cfMV /dev/tape "Daily backup for `date +%Y-%m-%d`"}
+$ @kbd{tar --create --file=/dev/tape --multi-volume \
+ --volume="Daily backup for `date +%Y-%m-%d`"}
+@end example
-@node GNU File Types, , File Types, Header Fields
-@appendixsubsec Additional File Types Supported by GNU
+Also note that each label has its own date and time, which corresponds
+to when GNU @code{tar} initially attempted to write it, often soon
+after the operator launches @code{tar} or types the carriage return
+telling that the next tape is ready. Comparing date labels does give
+an idea of tape throughput only if the delays for rewinding tapes
+and the operator switching them were negligible, which is ususally
+not the case.
-GNU @code{tar} uses additional file types to describe new types of
-files in an archive. These are listed below.
+@FIXME{was --volume}
-@table @code
-@item LF_DUMPDIR
-@itemx 'D'
-Indicates a directory and a list of files created by the
-@samp{--incremental} option. The @code{size} field gives the total
-size of the associated list of files. Each file name is preceded by
-either a @code{'Y'} (the file should be in this archive) or an
-@code{'N'} (the file is a directory, or is not stored in the archive).
-Each file name is terminated by a null. There is an additional null
-after the last file name.
+@node verify, Write Protection, label, Media
+@section Verifying Data as It is Stored
+@cindex Verifying a write operation
+@cindex Double-checking a write operation
-@item LF_MULTIVOL
-@itemx 'M'
-Indicates a file continued from another volume of a multi-volume
-archive (@pxref{Multi-Volume Archives}). The original type of the file is not
-given here. The @code{size} field gives the maximum size of this
-piece of the file (assuming the volume does not end before the file is
-written out). The @code{offset} field gives the offset from the
-beginning of the file where this part of the file begins. Thus
-@code{size} plus @code{offset} should equal the original size of the
-file.
-
-@item LF_SPARSE
-@itemx 'S'
-Indicates a sparse file. @xref{Sparse Files}. @xref{Sparse File
-Handling}.
-
-@item LF_VOLHDR
-@itemx 'V'
-Marks an archive label that was created using the @samp{--label} option
-when the archive was created (@pxref{Archive Label}. The @code{name}
-field contains the argument to the option. The @code{size} field is
-zero. Only the first file in each volume of an archive should have
-this type.
+@table @kbd
+@item -W
+@itemx --verify
+Attempt to verify the archive after writing.
@end table
-@node Sparse File Handling, , Header Fields, Data Format Details
-@appendixsec Fields to Handle Sparse Files
+This option causes @code{tar} to verify the archive after writing it.
+Each volume is checked after it is written, and any discrepancies
+are recorded on the standard error output.
-The following header information was added to deal with sparse files
-(@pxref{Sparse Files}):
+Verification requires that the archive be on a back-space-able medium.
+This means pipes, some cartridge tape drives, and some other devices
+cannot be verified.
+
+You can insure the accuracy of an archive by comparing files in the
+system with archive members. @code{tar} can compare an archive to the
+file system as the archive is being written, to verify a write
+operation, or can compare a previously written archive, to insure that
+it is up to date.
-@c TALK TO MIB
-The @code{sp} field (fields? something else?) is an array of
-@code{struct sparse}. Each @code{struct sparse} contains two
-12-character strings, which represent the offset into the file and the
-number of bytes to be written at that offset. The offset is absolute,
-and not relative to the offset in preceding array elements.
+To check for discrepancies in an archive immediately after it is
+written, use the @value{op-verify} option in conjunction with
+the @value{op-create} operation. When this option is
+specified, @code{tar} checks archive members against their counterparts
+in the file system, and reports discrepancies on the standard error. In
+multi-volume archives, each volume is verified after it is written,
+before the next volume is written.
-The header can contain four of these @code{struct sparse}; if more are
-needed, they are not stored in the header, instead, the flag
-@code{isextended} is set and the next record is an
-@code{extended_header}.
-@c @code{extended_header} or @dfn{extended_header} ??? the next
-@c record after the header, or in the middle of it.
+To verify an archive, you must be able to read it from before the end
+of the last written entry. This option is useful for detecting data
+errors on some tapes. Archives written to pipes, some cartridge tape
+drives, and some other devices cannot be verified.
-The @code{isextended} flag is only set for sparse files, and then only
-if extended header records are needed when archiving the file.
+One can explicitely compare an already made archive with the file system
+by using the @value{op-compare} option, instead of using the more automatic
+@value{op-verify} option. @value{xref-compare}.
+
+Note that these two options have a slightly different intent. The
+@value{op-compare} option how identical are the logical contents of some
+archive with what is on your disks, while the @value{op-verify} option is
+really for checking if the physical contents agree and if the recording
+media itself is of dependable quality. So, for the @value{op-verify}
+operation, @code{tar} tries to defeat all in-memory cache pertaining to
+the archive, while it lets the speed optimization undisturbed for the
+@value{op-compare} option. If you nevertheless use @value{op-compare} for
+media verification, you may have to defeat the in-memory cache yourself,
+maybe by opening and reclosing the door latch of your recording unit,
+forcing some doubt in your operating system about the fact this is really
+the same volume as the one just written or read.
+
+The @value{op-verify} option would not be necessary if drivers were indeed
+able to detect dependably all write failures. This sometimes require many
+magnetic heads, some able to read after the writes occurred. One would
+not say that drivers unable to detect all cases are necessarily flawed,
+as long as programming is concerned.
+
+@node Write Protection, , verify, Media
+@section Write Protection
-Each extended header record can contain an array of 21 sparse
-structures, as well as another @code{isextended} flag. There is no
-limit (except that implied by the archive media) on the number of
-extended header records that can be used to describe a sparse file.
+Almost all tapes and diskettes, and in a few rare cases, even disks can
+be @dfn{write protected}, to protect data on them from being changed.
+Once an archive is written, you should write protect the media to prevent
+the archive from being accidently overwritten or deleted. (This will
+protect the archive from being changed with a tape or floppy drive---it
+will not protect it from magnet fields or other physical hazards).
-@c so is @code{extended_header} the right way to write this?
+The write protection device itself is usually an integral part of the
+physical media, and can be a two position (write enabled/write
+disabled) switch, a notch which can be popped out or covered, a ring
+which can be removed from the center of a tape reel, or some other
+changeable feature.
-@node Concept Index, , Data Format Details, Top
-@unnumbered Concept Index
+@node Index, , Media, Top
+@unnumbered Index
@printindex cp
@contents
@bye
-
+@c Local variables:
+@c texinfo-column-for-description: 32
+@c End:
projects / chaz / tar / commitdiff
