@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
@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 --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
@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
@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
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