available on some systems. However, mounting typically requires
superuser privileges and can be a pain to manage.
+@opsummary{auto-compress}
+@item --auto-compress
+@itemx -a
+
+During a @option{--create} operation, enables automatic compressed
+format recognition based on the archive suffix. @xref{gzip}.
+
@opsummary{backup}
@item --backup=@var{backup-type}
Exclude from dump any directory containing file named @var{file}.
@xref{exclude}.
+@opsummary{exclude-vcs}
+@item --exclude-vcs
+
+Exclude from dump directories and files, that are internal for some
+widely used version control systems.
+
+@xref{exclude}.
+
@opsummary{file}
@item --file=@var{archive}
@itemx -f @var{archive}
With other operations, informs @command{tar} that the archive is in
incremental format. @xref{Incremental Dumps}.
+@opsummary{lzma}
+@item --lzma
+
+This option tells @command{tar} to read or write archives through
+@command{lzma}. @xref{gzip}.
+
@opsummary{mode}
@item --mode=@var{permissions}
single line @file{*.o}, no files whose names end in @file{.o} will be
added to the archive.
+Notice, that lines from @var{file} are read verbatim. One of the
+frequent errors is leaving some extra whitespace after a file name,
+which is difficult to catch using text editors.
+
+However, empty lines are OK.
+
+@cindex version control system, excluding files
+@cindex VCS, excluding files
+@cindex SCCS, excluding files
+@cindex RCS, excluding files
+@cindex CVS, excluding files
+@cindex SVN, excluding files
+@cindex git, excluding files
+@table @option
+@opindex exclude-vcs
+@item --exclude-vcs
+Exclude files and directories used by some version control systems.
+@end table
+
+As of version @value{VERSION}, the following files are excluded:
+
+@itemize @bullet
+@item @file{CVS/}, and everything under it
+@item @file{RCS/}, and everything under it
+@item @file{SCCS/}, and everything under it
+@item @file{.git/}, and everything under it
+@item @file{.gitignore}
+@item @file{.cvsignore}
+@item @file{.svn/}, and everything under it
+@item @file{.arch-ids/}, and everything under it
+@item @file{@{arch@}/}, and everything under it
+@item @file{=RELEASE-ID}
+@item @file{=meta-update}
+@item @file{=update}
+@end itemize
+
@findex exclude-caches
When creating an archive, the @option{--exclude-caches} option family
causes @command{tar} to exclude all directories that contain a @dfn{cache
use to hold regenerable, non-precious data, so that such data can be
more easily excluded from backups.
-There are three @samp{exclude-caches} option, providing a different
+There are three @samp{exclude-caches} options, each providing a different
exclusion semantics:
@table @option
@cindex Storing archives in compressed format
@GNUTAR{} is able to create and read compressed archives. It supports
-@command{gzip} and @command{bzip2} compression programs. For backward
-compatibility, it also supports @command{compress} command, although
-we strongly recommend against using it, since there is a patent
-covering the algorithm it uses and you could be sued for patent
-infringement merely by running @command{compress}! Besides, it is less
-effective than @command{gzip} and @command{bzip2}.
+@command{gzip}, @command{bzip2} and @command{lzma} compression
+programs. For backward compatibility, it also supports
+@command{compress} command, although we strongly recommend against
+using it, because it is by far less effective than other compression
+programs@footnote{It also had patent problems in the past.}.
Creating a compressed archive is simple: you just specify a
@dfn{compression option} along with the usual archive creation
commands. The compression option is @option{-z} (@option{--gzip}) to
create a @command{gzip} compressed archive, @option{-j}
-(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
+(@option{--bzip2}) to create a @command{bzip2} compressed archive,
+@command{lzma} to create an @asis{LZMA} compressed archive and
@option{-Z} (@option{--compress}) to use @command{compress} program.
For example:
$ @kbd{tar cfz archive.tar.gz .}
@end smallexample
+You can also let @GNUTAR{} select the compression program basing on
+the suffix of the archive file name. This is done using
+@option{--auto-compress} (@option{-a}) command line option. For
+example, the following invocation will use @command{bzip2} for
+compression:
+
+@smallexample
+$ @kbd{tar cfa archive.tar.bz2 .}
+@end smallexample
+
+@noindent
+whereas the following one will use @command{lzma}:
+
+@smallexample
+$ @kbd{tar cfa archive.tar.lzma .}
+@end smallexample
+
+For a complete list of file name suffixes recognized by @GNUTAR{},
+@ref{auto-compress}.
+
Reading compressed archive is even simpler: you don't need to specify
any additional options as @GNUTAR{} recognizes its format
automatically. Thus, the following commands will list and extract the
The following table summarizes compression options used by @GNUTAR{}.
@table @option
+@anchor{auto-compress}
+@opindex auto-compress
+@item --auto-compress
+@itemx -a
+Select a compression program to use by the archive file name
+suffix. The following suffixes are recognized:
+
+@multitable @columnfractions 0.3 0.6
+@headitem Suffix @tab Compression program
+@item @samp{.gz} @tab @command{gzip}
+@item @samp{.tgz} @tab @command{gzip}
+@item @samp{.taz} @tab @command{gzip}
+@item @samp{.Z} @tab @command{compress}
+@item @samp{.taZ} @tab @command{compress}
+@item @samp{.bz2} @tab @command{bzip2}
+@item @samp{.tz2} @tab @command{bzip2}
+@item @samp{.tbz2} @tab @command{bzip2}
+@item @samp{.tbz} @tab @command{bzip2}
+@item @samp{.lzma} @tab @command{lzma}
+@item @samp{.tlz} @tab @command{lzma}
+@end multitable
+
@opindex gzip
@opindex ungzip
@item -z
@itemx --bzip2
Filter the archive through @code{bzip2}. Otherwise like @option{--gzip}.
+@opindex lzma
+@item --lzma
+Filter the archive through @command{lzma}. Otherwise like @option{--gzip}.
+
@opindex compress
@opindex uncompress
@item -Z
@itemx --uncompress
Filter the archive through @command{compress}. Otherwise like @option{--gzip}.
-The @acronym{GNU} Project recommends you not use
-@command{compress}, because there is a patent covering the algorithm it
-uses. You could be sued for patent infringement merely by running
-@command{compress}.
-
@opindex use-compress-program
@item --use-compress-program=@var{prog}
Use external compression program @var{prog}. Use this option if you
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