@itemx -a
During a @option{--create} operation, enables automatic compressed
-format recognition based on the archive suffix. @xref{gzip}.
+format recognition based on the archive suffix. The effect of this
+option is cancelled by @option{--no-auto-compress}. @xref{gzip}.
@opsummary{backup}
@item --backup=@var{backup-type}
@opsummary{lzma}
@item --lzma
+@itemx -J
This option tells @command{tar} to read or write archives through
@command{lzma}. @xref{gzip}.
+@item --lzop
+
+This option tells @command{tar} to read or write archives through
+@command{lzop}. @xref{gzip}.
+
@opsummary{mode}
@item --mode=@var{permissions}
An exclude pattern can match any subsequence of the name's components.
@xref{controlling pattern-matching}.
+@opsummary{no-auto-compress}
+@item --no-auto-compress
+
+Disables automatic compressed format recognition based on the archive
+suffix. @xref{--auto-compress}. @xref{gzip}.
+
@opsummary{no-check-device}
@item --no-check-device
Do not check device numbers when creating a list of modified files
Print warnings about subprocesses that terminated with a nonzero exit
code. @xref{Writing to an External Program}.
+@opsummary{no-null}
+@item --no-null
+
+If the @option{--null} option was given previously, this option
+cancels its effect, so that any following @option{--files-from}
+options will expect their file lists to be newline-terminated.
+
@opsummary{no-overwrite-dir}
@item --no-overwrite-dir
@xref{Data Modification Times}.
@opsummary{transform}
+@opsummary{xform}
@item --transform=@var{sed-expr}
-
+@itemx --xform=@var{sed-expr}
Transform file or member names using @command{sed} replacement expression
@var{sed-expr}. For example,
@item -G @tab @ref{--incremental}.
+@item -J @tab @ref{--lzma}.
+
@item -K @tab @ref{--starting-file}.
@item -L @tab @ref{--tape-length}.
@item -o @tab When creating, @ref{--no-same-owner}, when extracting ---
@ref{--portability}.
-The later usage is deprecated. It is retained for compatibility with
+The latter usage is deprecated. It is retained for compatibility with
the earlier versions of @GNUTAR{}. In future releases
@option{-o} will be equivalent to @option{--no-same-owner} only.
@vrindex TAR_BLOCKING_FACTOR, checkpoint script environment
@item TAR_BLOCKING_FACTOR
-Current blocking factor (@pxref{Blocking}.
+Current blocking factor (@pxref{Blocking}).
@vrindex TAR_CHECKPOINT, checkpoint script environment
@item TAR_CHECKPOINT
-The checkpoint number.
+Number of the checkpoint.
@vrindex TAR_SUBCOMMAND, checkpoint script environment
@item TAR_SUBCOMMAND
-A short option describing the operation @command{tar} is executing
+A short option describing the operation @command{tar} is executing.
@xref{Operations}, for a complete list of subcommand options.
@vrindex TAR_FORMAT, checkpoint script environment
@option{--files-from}.
@table @option
-@opindex null
+@xopindex{null, described}
@item --null
Only consider @code{NUL} terminated file names, instead of files that
terminate in a newline.
+
+@xopindex{no-null, described}
+@item --no-null
+Undo the effect of any previous @option{--null} option.
@end table
The @option{--null} option is just like the one in @acronym{GNU}
$ @kbd{tar -c -v --null --files-from=long-files --file=big.tar}
@end smallexample
-@FIXME{say anything else here to conclude the section?}
+The @option{--no-null} option can be used if you need to read both
+zero-terminated and newline-terminated files on the same command line.
+For example, if @file{flist} is a newline-terminated file, then the
+following command can be used to combine it with the above command:
+
+@smallexample
+@group
+$ @kbd{find . -size +800 -print0 |
+ tar -c -f big.tar --null -T - --no-null -T flist}
+@end group
+@end smallexample
+
+This example uses short options for typographic reasons, to avoid
+very long lines.
+
+@GNUTAR is able to automatically detect null-terminated file lists, so
+it is safe to use them even without the @option{--null} option. In
+this case @command{tar} will print a warning and continue reading such
+a file as if @option{--null} were actually given:
+
+@smallexample
+@group
+$ @kbd{find . -size +800 -print0 | tar -c -f big.tar -T -}
+tar: -: file name read contains nul character
+@end group
+@end smallexample
+
+The null terminator, however, remains in effect only for this
+particular file, any following @option{-T} options will assume
+newline termination. Of course, the null autodetection applies
+to these eventual surplus @option{-T} options as well.
@node exclude
@section Excluding Some Files
@cindex CVS, excluding files
@cindex SVN, excluding files
@cindex git, excluding files
+@cindex Bazaar, excluding files
+@cindex Arch, excluding files
+@cindex Mercurial, excluding files
+@cindex Darcs, excluding files
@table @option
@opindex exclude-vcs
@item --exclude-vcs
-Exclude files and directories used by some version control systems.
+Exclude files and directories used by following version control
+systems: @samp{CVS}, @samp{RCS}, @samp{SCCS}, @samp{SVN}, @samp{Arch},
+@samp{Bazaar}, @samp{Mercurial}, and @samp{Darcs}.
@end table
As of version @value{VERSION}, the following files are excluded:
@item @file{=RELEASE-ID}
@item @file{=meta-update}
@item @file{=update}
+@item @file{.bzr}
+@item @file{.bzrignore}
+@item @file{.bzrtags}
+@item @file{.hg}
+@item @file{.hgignore}
+@item @file{.hgrags}
+@item @file{_darcs}
@end itemize
@findex exclude-caches
@command{Tar} archives contain detailed information about files stored
in them and full file names are part of that information. When
-storing file to an archive, its file name is recorded in the archive
+storing file to an archive, its file name is recorded in it,
along with the actual file contents. When restoring from an archive,
a file is created on disk with exactly the same name as that stored
in the archive. In the majority of cases this is the desired behavior
cases it is desirable to store files under differing names in the
archive.
-@GNUTAR{} provides two options for these needs.
+@GNUTAR{} provides several options for these needs.
@table @option
@opindex strip-components
two leading components (@file{usr/} and @file{include/}) off the file
name.
-If you add to the above invocation @option{--verbose} (@option{-v})
-option, you will note that the verbose listing still contains the
+If you add the @option{--verbose} (@option{-v}) option to the invocation
+above, you will note that the verbose listing still contains the
full file name, with the two removed components still in place. This
can be inconvenient, so @command{tar} provides a special option for
altering this behavior:
@end group
@end smallexample
-Notice that in both cases the file is @file{stdlib.h} extracted to the
+Notice that in both cases the file @file{stdlib.h} is extracted to the
current working directory, @option{--show-transformed-names} affects
only the way its name is displayed.
@table @option
@opindex transform
+@opindex xform
@item --transform=@var{expression}
+@itemx --xform=@var{expression}
Modify file names using supplied @var{expression}.
@end table
@var{regexp} and @var{replace} are described in detail in
@ref{The "s" Command, The "s" Command, The `s' Command, sed, GNU sed}.
+Any delimiter can be used in lieue of @samp{/}, the only requirement being
+that it be used consistently throughout the expression. For example,
+the following two expressions are equivalent:
+
+@smallexample
+@group
+s/one/two/
+s,one,two,
+@end group
+@end smallexample
+
+Changing delimiters is often useful when the @var{regex} contains
+slashes. For example, it is more convenient to write @code{s,/,-,} than
+@code{s/\//-/}.
+
As in @command{sed}, you can give several replace expressions,
separated by a semicolon.
@item @var{number}
Only replace the @var{number}th match of the @var{regexp}.
-Note: the @var{posix} standard does not specify what should happen
+Note: the @acronym{POSIX} standard does not specify what should happen
when you mix the @samp{g} and @var{number} modifiers. @GNUTAR{}
follows the GNU @command{sed} implementation in this regard, so
the interaction is defined to be: ignore matches before the
@end table
-Any delimiter can be used in lieue of @samp{/}, the only requirement being
-that it be used consistently throughout the expression. For example,
-the following two expressions are equivalent:
+In addition, several @dfn{transformation scope} flags are supported,
+that control to what files transformations apply. These are:
+
+@table @samp
+@item r
+Apply transformation to regular archive members.
+
+@item R
+Do not apply transformation to regular archive members.
+
+@item s
+Apply transformation to symbolic link targets.
+
+@item S
+Do not apply transformation to symbolic link targets.
+
+@item h
+Apply transformation to hard link targets.
+
+@item H
+Do not apply transformation to hard link targets.
+@end table
+
+Default is @samp{rsh}, which means to apply tranformations to both archive
+members and targets of symbolic and hard links.
+
+Default scope flags can also be changed using @samp{flags=} statement
+in the transform expression. The flags set this way remain in force
+until next @samp{flags=} statement or end of expression, whichever
+occurs first. For example:
@smallexample
-@group
-s/one/two/
-s,one,two,
-@end group
+ --transform 'flags=S;s|^|/usr/local/|'
@end smallexample
-Changing delimiters is often useful when the @var{regex} contains
-slashes. For example, it is more convenient to write @code{s,/,-,} than
-@code{s/\//-/}.
-
Here are several examples of @option{--transform} usage:
@enumerate
$ @kbd{tar --transform='s,/*[^/]*/[^/]*/,,' -x -f arch.tar}
@end smallexample
+@item Convert each file name to lower case:
+
+@smallexample
+$ @kbd{tar --transform 's/.*/\L&/' -x -f arch.tar}
+@end smallexample
+
@item Prepend @file{/prefix/} to each file name:
@smallexample
$ @kbd{tar --transform 's,^,/prefix/,' -x -f arch.tar}
@end smallexample
-@item Convert each file name to lower case:
+@item Archive the @file{/lib} directory, prepending @samp{/usr/local}
+to each archive member:
@smallexample
-$ @kbd{tar --transform 's/.*/\L&/' -x -f arch.tar}
+$ @kbd{tar --transform 's,^,/usr/local/,S' -c -f arch.tar /lib}
@end smallexample
-
@end enumerate
+Notice the use of flags in the last example. The @file{/lib}
+directory often contains many symbolic links to files within it.
+It may look, for example, like this:
+
+@smallexample
+$ @kbd{ls -l}
+drwxr-xr-x root/root 0 2008-07-08 16:20 /lib/
+-rwxr-xr-x root/root 1250840 2008-05-25 07:44 /lib/libc-2.3.2.so
+lrwxrwxrwx root/root 0 2008-06-24 17:12 /lib/libc.so.6 -> libc-2.3.2.so
+...
+@end smallexample
+
+Using the expression @samp{s,^,/usr/local/,} would mean adding
+@samp{/usr/local} to both regular archive members and to link
+targets. In this case, @file{/lib/libc.so.6} would become:
+
+@smallexample
+ /usr/local/lib/libc.so.6 -> /usr/local/libc-2.3.2.so
+@end smallexample
+
+This is definitely not desired. To avoid this, the @samp{S} flag
+are used, which excludes symbolic link targets from filename
+transformations. The result is:
+
+@smallexample
+$ @kbd{tar --transform 's,^,/usr/local/,S', -c -v -f arch.tar \
+ --show-transformed /lib}
+drwxr-xr-x root/root 0 2008-07-08 16:20 /usr/local/lib/
+-rwxr-xr-x root/root 1250840 2008-05-25 07:44 /usr/local/lib/libc-2.3.2.so
+lrwxrwxrwx root/root 0 2008-06-24 17:12 /usr/local/lib/libc.so.6 ->
+libc-2.3.2.so
+@end smallexample
+
Unlike @option{--strip-components}, @option{--transform} can be used
in any @GNUTAR{} operation mode. For example, the following command
adds files to the archive while replacing the leading @file{usr/}
For example:
@smallexample
-$ @kbd{(cd / && tar -c -f archive.tar home)}
-# @i{or}:
-$ @kbd{tar -c -f archive.tar -C / home}
+$ @kbd{tar -c -f archive.tar -C / home}
@end smallexample
@include getdate.texi
@cindex Compressed archives
@cindex Storing archives in compressed format
+@cindex gzip
+@cindex bzip2
+@cindex lzma
+@cindex lzop
+@cindex compress
@GNUTAR{} is able to create and read compressed archives. It supports
-@command{gzip}, @command{bzip2} and @command{lzma} compression
+@command{gzip}, @command{bzip2}, @command{lzma} and @command{lzop} 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
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,
-@option{--lzma} to create an @asis{LZMA} compressed archive and
+@option{-J} (@option{--lzma}) to create an @asis{LZMA} compressed
+archive, @option{--lzop} to create an @asis{LSOP} archive, and
@option{-Z} (@option{--compress}) to use @command{compress} program.
For example:
$ @kbd{tar xf archive.tar.gz}
@end smallexample
+The format recognition algorithm is based on @dfn{signatures}, a
+special byte sequences in the beginning of file, that are specific for
+certain compression formats. If this approach fails, @command{tar}
+falls back to using archive name suffix to determine its format
+(@xref{auto-compress}, for a list of recognized suffixes).
+
The only case when you have to specify a decompression option while
reading the archive is when reading from a pipe or from a tape drive
that does not support random access. However, in this case @GNUTAR{}
@item --auto-compress
@itemx -a
Select a compression program to use by the archive file name
-suffix. The following suffixes are recognized:
+suffix. The following suffixes are recognized:
@multitable @columnfractions 0.3 0.6
@headitem Suffix @tab Compression program
@item @samp{.tbz} @tab @command{bzip2}
@item @samp{.lzma} @tab @command{lzma}
@item @samp{.tlz} @tab @command{lzma}
+@item @samp{.lzo} @tab @command{lzop}
@end multitable
@opindex gzip
@opindex lzma
@item --lzma
+@itemx -J
Filter the archive through @command{lzma}. Otherwise like @option{--gzip}.
+@opindex lzop
+@item --lzop
+Filter the archive through @command{lzop}. Otherwise like
+@option{--gzip}.
+
@opindex compress
@opindex uncompress
@item -Z
projects / tar / blobdiff