@c Maintenance notes:
@c 1. Pay attention to @FIXME{}s and @UNREVISED{}s
@c 2. Before creating final variant:
-@c 2.1. Run `make check-options' to make sure all options are properly
+@c 2.1. Run 'make check-options' to make sure all options are properly
@c documented;
-@c 2.2. Run `make master-menu' (see comment before the master menu).
+@c 2.2. Run 'make master-menu' (see comment before the master menu).
@include rendition.texi
@include value.texi
@value{VERSION}, @value{UPDATED}), which creates and extracts files
from archives.
-Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
-2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+Copyright @copyright{} 1992, 1994--1997, 1999--2001, 2003--2013 Free
+Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
-any later version published by the Free Software Foundation; with no
-Invariant Sections, with the Front-Cover Texts being ``A GNU Manual'',
-and with the Back-Cover Texts as in (a) below. A copy of the license
-is included in the section entitled ``GNU Free Documentation
-License''.
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'', with the
+Front-Cover Texts being ``A GNU Manual'', and with the Back-Cover Texts
+as in (a) below. A copy of the license is included in the section
+entitled ``GNU Free Documentation License''.
(a) The FSF's Back-Cover Text is: ``You have the freedom to
-copy and modify this GNU manual. Buying copies from the FSF
-supports it in developing GNU and promoting software freedom.''
+copy and modify this GNU manual.''
@end quotation
@end copying
@smallexample
@group
$ @kbd{tar --create --verbose --file archive /etc/mail}
-tar: Removing leading `/' from member names
+tar: Removing leading '/' from member names
/etc/mail/
/etc/mail/sendmail.cf
/etc/mail/aliases
@option{--extract}, @option{--compare}, and @option{--update})
will act on the entire contents of the archive.
+@anchor{exit status}
@cindex exit status
@cindex return status
Besides successful exits, @GNUTAR{} may fail for
@itemx -P
Normally when creating an archive, @command{tar} strips an initial
-@samp{/} from member names. This option disables that behavior.
-@xref{absolute}.
+@samp{/} from member names, and when extracting from an archive @command{tar}
+treats names specially if they have initial @samp{/} or internal
+@samp{..}. This option disables that behavior. @xref{absolute}.
@opsummary{after-date}
@item --after-date
@item --ignore-failed-read
Do not exit unsuccessfully merely because an unreadable file was encountered.
-@xref{Reading}.
+@xref{Ignore Failed Read}.
@opsummary{ignore-zeros}
@item --ignore-zeros
@item --keep-old-files
@itemx -k
-Do not overwrite existing files when extracting files from an archive.
+Do not overwrite existing files when extracting files from an
+archive. Return error if such files exist. See also
+@ref{--skip-old-files}.
+
@xref{Keep Old Files}.
@opsummary{label}
member names stored in the archive, as opposed to the actual file
names. @xref{listing member and file names}.
+@opsummary{skip-old-files}
+@item --skip-old-files
+
+Do not overwrite existing files when extracting files from an
+archive. @xref{Keep Old Files}.
+
+This option differs from @option{--keep-old-files} in that it does not
+treat such files as an error, instead it just silently avoids
+overwriting them.
+
+The @option{--warning=existing-file} option can be used together with
+this option to produce warning messages about existing old files
+(@pxref{warnings}).
+
@opsummary{sparse}
@item --sparse
@itemx -S
@smallexample
tar (GNU tar) @value{VERSION}
-Copyright (C) 2010 Free Software Foundation, Inc.
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
@item symlink-cast
@samp{Attempting extraction of symbolic links as hard links}
@kwindex unknown-cast
-@cindex @samp{Unknown file type `%c', extracted as normal file}, warning message
+@cindex @samp{Unknown file type '%c', extracted as normal file}, warning message
@item unknown-cast
-@samp{%s: Unknown file type `%c', extracted as normal file}
+@samp{%s: Unknown file type '%c', extracted as normal file}
@kwindex ignore-newer
@cindex @samp{Current %s is newer or same age}, warning message
@item ignore-newer
@samp{Current %s is newer or same age}
@kwindex unknown-keyword
-@cindex @samp{Ignoring unknown extended header keyword `%s'}, warning message
+@cindex @samp{Ignoring unknown extended header keyword '%s'}, warning message
@item unknown-keyword
-@samp{Ignoring unknown extended header keyword `%s'}
+@samp{Ignoring unknown extended header keyword '%s'}
@kwindex decompress-program
@item decompress-program
Controls verbose description of failures occurring when trying to run
last. Additionally, an extracted member will @emph{replace} a file of
the same name which existed in the directory already, and @command{tar}
will not prompt you about this@footnote{Unless you give it
-@option{--keep-old-files} option, or the disk copy is newer than
-the one in the archive and you invoke @command{tar} with
-@option{--keep-newer-files} option.}. Thus, only the most recently archived
-member will end up being extracted, as it will replace the one
-extracted before it, and so on.
+@option{--keep-old-files} (or @option{--skip-old-files}) option, or
+the disk copy is newer than the one in the archive and you invoke
+@command{tar} with @option{--keep-newer-files} option.}. Thus, only
+the most recently archived member will end up being extracted, as it
+will replace the one extracted before it, and so on.
@cindex extracting @var{n}th copy of the file
@xopindex{occurrence, described}
@smallexample
$ @kbd{tar -c -f archive.tar -v --mtime=yesterday .}
-tar: Option --mtime: Treating date `yesterday' as 2006-06-20
+tar: Option --mtime: Treating date 'yesterday' as 2006-06-20
13:06:29.152478
@dots{}
@end smallexample
@cindex Overwriting old files, prevention
@xopindex{keep-old-files, introduced}
To be even more cautious and prevent existing files from being replaced, use
-the @option{--keep-old-files} (@option{-k}) option. It causes @command{tar} to refuse
-to replace or update a file that already exists, i.e., a file with the
-same name as an archive member prevents extraction of that archive
-member. Instead, it reports an error.
+the @option{--keep-old-files} (@option{-k}) option. It causes
+@command{tar} to refuse to replace or update a file that already
+exists, i.e., a file with the same name as an archive member prevents
+extraction of that archive member. Instead, it reports an error. For
+example:
+
+@example
+$ @kbd{ls}
+blues
+$ @kbd{tar -x -k -f archive.tar}
+tar: blues: Cannot open: File exists
+tar: Exiting with failure status due to previous errors
+@end example
+
+@xopindex{skip-old-files, introduced}
+If you wish to preserve old files untouched, but don't want
+@command{tar} to treat them as errors, use the
+@option{--skip-old-files} option. This option causes @command{tar} to
+silently skip extracting over existing files.
@xopindex{overwrite, introduced}
To be more aggressive about altering existing files, use the
@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
+@GNUTAR{} provides two options to control its actions in a situation
+when it is about to extract a file which already exists on disk.
+
@table @option
@opindex keep-old-files
@item --keep-old-files
@itemx -k
-Do not replace existing files from archive. The
-@option{--keep-old-files} (@option{-k}) option prevents @command{tar}
-from replacing existing files with files with the same name from the
-archive. The @option{--keep-old-files} option is meaningless with
-@option{--list} (@option{-t}). Prevents @command{tar} from replacing
-files in the file system during extraction.
+Do not replace existing files from archive. When such a file is
+encountered, @command{tar} issues an error message. Upon end of
+extraction, @command{tar} exits with code 2 (@pxref{exit status}).
+
+@item --skip-old-files
+Do not replace existing files from archive, but do not treat that
+as error. Such files are silently skipped and do not affect
+@command{tar} exit status.
+
+Additional verbosity can be obtained using @option{--warning=existing-file}
+together with that option (@pxref{warnings}).
@end table
@node Keep Newer Files
@group
$ @kbd{tar cf a.tar}
tar: Cowardly refusing to create an empty archive
-Try `tar --help' or `tar --usage' for more information.
+Try 'tar --help' or 'tar --usage' for more information.
@end group
@end smallexample
Control characters, single quote and backslash are printed using
backslash notation. All names are quoted using left and right
quotation marks, appropriate to the current locale. If it does not
-define quotation marks, use @samp{`} as left and @samp{'} as right
+define quotation marks, use @samp{'} as left and as right
quotation marks. Any occurrences of the right quotation mark in a
name are escaped with @samp{\}, for example:
@smallexample
@group
$ @kbd{tar tf arch.tar --quoting-style=locale}
-`./'
-`./a space'
-`./a\'single\'quote'
-`./a"double"quote'
-`./a\\backslash'
-`./a\ttab'
-`./a\nnewline'
+'./'
+'./a space'
+'./a\'single\'quote'
+'./a"double"quote'
+'./a\\backslash'
+'./a\ttab'
+'./a\nnewline'
@end group
@end smallexample
@smallexample
@group
$ @kbd{tar -c -f archive.tar --after-date='10 days ago' .}
-tar: Option --after-date: Treating date `10 days ago' as 2006-06-11
+tar: Option --after-date: Treating date '10 days ago' as 2006-06-11
13:19:37.232434
@end group
@end smallexample
scripts for comparing both outputs. @xref{listing member and file names},
for the information on how to handle this case.}.
+Symbolic links containing @file{..} or leading @samp{/} can also cause
+problems when extracting, so @command{tar} normally extracts them last;
+it may create empty files as placeholders during extraction.
+
If you use the @option{--absolute-names} (@option{-P}) option,
@command{tar} will do none of these transformations.
@table @option
@item --absolute-names
Preserves full file names (including superior directory names) when
-archiving files. Preserves leading slash when extracting files.
+archiving and extracting files.
@end table
such devices or remote files is reblocked by another copy of the
@command{tar} program to enforce the specified (or default) record
size. The default compression parameters are used. Most compression
-programs allow to override these by setting a program-specific
-environment variable. For example, when using @command{gzip} you can
-use @env{GZIP} as in the example below:
+programs let you override these by setting a program-specific
+environment variable. For example, with @command{gzip} you can set
+@env{GZIP}:
@smallexample
-$ @kbd{GZIP=--best tar czf archive.tar.gz subdir}
+$ @kbd{GZIP='-9 -n' tar czf archive.tar.gz subdir}
@end smallexample
@noindent
-Another way would be to use the @option{-I} option instead (see
-below), e.g.:
+The traditional way to do this is to use a pipe:
@smallexample
-$ @kbd{tar -cf archive.tar.gz -I 'gzip --best' subdir}
-@end smallexample
-
-@noindent
-Finally, the third, traditional, way to achieve the same result is to
-use pipe:
-
-@smallexample
-$ @kbd{tar cf - subdir | gzip --best -c - > archive.tar.gz}
+$ @kbd{tar cf - subdir | gzip -9 -n > archive.tar.gz}
@end smallexample
@cindex corrupted archives
-About corrupted compressed archives: compressed files have no
-redundancy, for maximum compression. The adaptive nature of the
+Compressed archives are easily corrupted, because compressed files
+have little redundancy. 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 unsynchronized, and there
is little chance that you could recover later in the archive.
-Another compression options provide a better control over creating
+Other compression options provide better control over creating
compressed archives. These are:
@table @option
Use external compression program @var{prog}. Use this option if you
are not happy with the compression program associated with the suffix
at compile time or if you have a compression program that @GNUTAR{}
-does not support. There are two requirements to which @var{prog}
-should comply:
+does not support. The program should follow two conventions:
-First, when called without options, it should read data from standard
+First, when invoked without options, it should read data from standard
input, compress it and output it on standard output.
-Secondly, if called with @option{-d} argument, it should do exactly
+Secondly, if invoked with the @option{-d} option, it should do exactly
the opposite, i.e., read the compressed data from the standard input
and produce uncompressed data on the standard output.
@end table
@smallexample
$ tar -c -f ../archive.tar -l jeden
-tar: Missing links to `jeden'.
+tar: Missing links to 'jeden'.
@end smallexample
Although creating special records for hard links helps keep a faithful
@smallexample
$ tar xf archive.tar ./one
-tar: ./one: Cannot hard link to `./jeden': No such file or directory
+tar: ./one: Cannot hard link to './jeden': No such file or directory
tar: Error exit delayed from previous errors
@end smallexample
@group
$ @kbd{xsparse -n /home/gray/GNUSparseFile.6058/sparsefile}
Reading v.1.0 sparse map
-Expanding file `/home/gray/GNUSparseFile.6058/sparsefile' to
-`/home/gray/sparsefile'
+Expanding file '/home/gray/GNUSparseFile.6058/sparsefile' to
+'/home/gray/sparsefile'
Finished dry run
@end group
@end smallexample
@group
$ @kbd{xsparse -v /home/gray/GNUSparseFile.6058/sparsefile}
Reading v.1.0 sparse map
-Expanding file `/home/gray/GNUSparseFile.6058/sparsefile' to
-`/home/gray/sparsefile'
+Expanding file '/home/gray/GNUSparseFile.6058/sparsefile' to
+'/home/gray/sparsefile'
Done
@end group
@end smallexample
Found variable GNU.sparse.name = sparsefile
Found variable GNU.sparse.realsize = 217481216
Reading v.1.0 sparse map
-Expanding file `/home/gray/GNUSparseFile.6058/sparsefile' to
-`/home/gray/sparsefile'
+Expanding file '/home/gray/GNUSparseFile.6058/sparsefile' to
+'/home/gray/sparsefile'
Done
@end group
@end smallexample
Found variable GNU.sparse.numblocks = 208
Found variable GNU.sparse.name = sparsefile
Found variable GNU.sparse.map = 0,2048,1050624,2048,@dots{}
-Expanding file `GNUSparseFile.28124/sparsefile' to `sparsefile'
+Expanding file 'GNUSparseFile.28124/sparsefile' to 'sparsefile'
Done
@end group
@end smallexample
@command{rsh} or @command{remsh} to the remote machine, optionally
using a different login name if one is supplied.
-A copy of the source for the remote tape server is provided. It is
-Copyright @copyright{} 1983 by the Regents of the University of
-California, but can be freely distributed. It is compiled and
+A copy of the source for the remote tape server is provided. Its
+source code can be freely distributed. It is compiled and
installed by default.
@cindex absolute file names
translation to the locale's language will be used.}:
@smallexample
-Prepare volume #@var{n} for `@var{archive}' and hit return:
+Prepare volume #@var{n} for '@var{archive}' and hit return:
@end smallexample
@noindent
@smallexample
@group
-#! /bin/sh
+#! /bin/bash
+# For this script it's advisable to use a shell, such as Bash,
+# that supports a TAR_FD value greater than 9.
+
echo Preparing volume $TAR_VOLUME of $TAR_ARCHIVE.
name=`expr $TAR_ARCHIVE : '\(.*\)-.*'`
@smallexample
@group
$ @kbd{tar -rf archive --label 'My volume' .}
-tar: Archive not labeled to match `My volume'
+tar: Archive not labeled to match 'My volume'
@end group
@end smallexample
the @option{--absolute-names} (@option{-P}) option should be used only
for trusted archives.
-Conversely, with the @option{--keep-old-files} (@option{-k}) option,
-@command{tar} refuses to replace existing files when extracting; and
-with the @option{--no-overwrite-dir} option, @command{tar} refuses to
-replace the permissions or ownership of already-existing directories.
-These options may help when extracting from untrusted archives.
+Conversely, with the @option{--keep-old-files} (@option{-k}) and
+@option{--skip-old-files} options, @command{tar} refuses to replace
+existing files when extracting. The difference between the two
+options is that the former treats existing files as errors whereas the
+latter just silently ignores them.
+
+Finally, with the @option{--no-overwrite-dir} option, @command{tar}
+refuses to replace the permissions or ownership of already-existing
+directories. These options may help when extracting from untrusted
+archives.
@node Live untrusted data
@subsection Dealing with Live Untrusted Data
projects / chaz / tar / blobdiff