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bsdtar(1)

NAME

     tar -- manipulate tape archives

SYNOPSIS

     tar [bundled-flags <args>] [<file> | <pattern> ...]
     tar {-c} [options] [files | directories]
     tar {-r | -u} -f archive-file [options] [files | directories]
     tar {-t | -x} [options] [patterns]

DESCRIPTION

     tar creates and manipulates streaming archive files.

     The first synopsis form shows a ``bundled'' option word.  This usage is
     provided for compatibility with historical implementations.  See COMPATI-
     BILITY below for details.

     The other synopsis forms show the preferred usage.  The first option to
     tar is a mode indicator from the following list:
     -c      Create a new archive containing the specified items.
     -r      Like -c, but new entries are appended to the archive.  Note that
	     this only works on uncompressed archives stored in regular files.
	     The -f option is required.
     -t      List archive contents to stdout.
     -u      Like -r, but new entries are added only if they have a modifica-
	     tion date newer than the corresponding entry in the archive.
	     Note that this only works on uncompressed archives stored in reg-
	     ular files.  The -f option is required.
     -x      Extract to disk from the archive.	If a file with the same name
	     appears more than once in the archive, each copy will be
	     extracted, with later copies overwriting (replacing) earlier
	     copies.

     In -c, -r, or -u mode, each specified file or directory is added to the
     archive in the order specified on the command line.  By default, the con-
     tents of each directory are also archived.

     In extract or list mode, the entire command line is read and parsed
     before the archive is opened.  The pathnames or patterns on the command
     line indicate which items in the archive should be processed.  Patterns
     are shell-style globbing patterns as documented in XXXX.

OPTIONS

     Unless specifically stated otherwise, options are applicable in all oper-
     ating modes.

     @archive
	     (c and r mode only) The specified archive is opened and the
	     entries in it will be appended to the current archive.  As a sim-
	     ple example,
		   tar -c -f - newfile @original.tar
	     writes a new archive to standard output containing a file newfile
	     and all of the entries from original.tar.	In contrast,
		   tar -c -f - newfile original.tar
	     creates a new archive with only two entries.  Similarly,
		   tar -czf - --format pax @-
	     reads an archive from standard input (whose format will be deter-
	     mined automatically) and converts it into a gzip-compressed pax-

     -C directory
	     In c and r mode, this changes the directory before adding the
	     following files.  In x mode, change directories after opening the
	     archive but before extracting entries from the archive.

     --check-links (-W check-links)
	     (c and r modes only) Issue a warning message unless all links to
	     each file are archived.

     --exclude pattern (-W exclude=pattern)
	     Do not process files or directories that match the specified pat-
	     tern.  Note that exclusions take precedence over patterns or
	     filenames specified on the command line.

     --format format (-W format=format)
	     (c mode only) Use the specified format for the created archive.
	     Supported formats include ``cpio'', ``pax'', ``shar'', and
	     ``ustar''.  Other formats may also be supported; see
	     libarchive-formats(5) for more information about currently-sup-
	     ported formats.

     -f file
	     Read the archive from or write the archive to the specified file.
	     The filename can be - for standard input or standard output.  If
	     not specified, the default tape device will be used.  (On
	     FreeBSD, the default tape device is /dev/sa0.)

     --fast-read (-W fast-read)
	     (x and t mode only) Extract or list only the first archive entry
	     that matches each pattern or filename operand.  Exit as soon as
	     each specified pattern or filename has been matched.  By default,
	     the archive is always read to the very end, since there can be
	     multiple entries with the same name and, by convention, later
	     entries overwrite earlier entries.  This option is provided as a
	     performance optimization.

     -H      (c and r mode only) Symbolic links named on the command line will
	     be followed; the target of the link will be archived, not the
	     link itself.

     -h      (c and r mode only) Synonym for -L.

     --include pattern (-W include=pattern)
	     Process only files or directories that match the specified pat-
	     tern.  Note that exclusions specified with --exclude take prece-
	     dence over inclusions.  If no inclusions are explicitly speci-
	     fied, all entries are processed by default.  The --include option
	     is especially useful when filtering archives.  For example, the
	     command
		   tar -c -f new.tar --include='*foo*' @old.tgz
	     creates a new archive new.tar containing only the entries from
	     old.tgz containing the string `foo'.

     -j      (c mode only) Compress the resulting archive with bzip2(1).  In
	     extract or list modes, this option is ignored.  Note that, unlike
	     other tar implementations, this implementation recognizes bzip2
	     compression automatically when reading archives.

     -l      If POSIXLY_CORRECT is specified in the environment, this is a
	     synonym for the --check-links option.  Otherwise, an error will
	     be displayed.  Users who desire behavior compatible with GNU tar
	     should use the --one-file-system option instead.

     -m      (x mode only) Do not extract modification time.  By default, the
	     modification time is set to the time stored in the archive.

     -n      (c, r, u modes only) Do not recursively archive the contents of
	     directories.

     --nodump (-W nodump)
	     (c and r modes only) Honor the nodump file flag by skipping this
	     file.

     -O      (x, t modes only) In extract (-x) mode, files will be written to
	     standard out rather than being extracted to disk.	In list (-t)
	     mode, the file listing will be written to stderr rather than the
	     usual stdout.

     -o      (x mode only) Use the user and group of the user running the pro-
	     gram rather than those specified in the archive.  Note that this
	     has no significance unless -p is specified, and the program is
	     being run by the root user.  In this case, the file modes and
	     flags from the archive will be restored, but ACLs or owner infor-
	     mation in the archive will be discarded.

     -P      Preserve pathnames.  By default, absolute pathnames (those that
	     begin with a / character) have the leading slash removed both
	     when creating archives and extracting from them.  Also, tar will
	     refuse to extract archive entries whose pathnames contain .. or
	     whose target directory would be altered by a symlink.  This
	     option suppresses these behaviors.

     -p      (x mode only) Preserve file permissions.  Attempt to restore the
	     full permissions, including owner, file modes, file flags and
	     ACLs, if available, for each item extracted from the archive.  By
	     default, newly-created files are owned by the user running tar,
	     the file mode is restored for newly-created regular files, and
	     all other types of entries receive default permissions.  If tar
	     is being run by root, the default is to restore the owner unless
	     the -o option is also specified.

     -T filename
	     (c mode only) Read names to be archived from filename.  Names are
	     terminated by newlines.  The special name ``-C'' will cause the
	     current directory to be changed to the directory specified on the
	     following line.

     -U      (x mode only) Unlink files before creating them.  Without this
	     option, tar overwrites existing files, which preserves existing
	     hardlinks.  With this option, existing hardlinks will be broken,
	     as will any symlink that would affect the location of an
	     extracted file.

     -v      Produce verbose output.  In create and extract modes, tar will
	     list each file name as it is read from or written to the archive.

     -w      Ask for confirmation for every action.

     -X filename
	     Read a list of exclusion patterns from the specified file.  See
	     --exclude for more information about the handling of exclusions.

     -y      (c mode only) Compress the resulting archive with bzip2(1).  In
	     extract or list modes, this option is ignored.  Note that, unlike
	     other tar implementations, this implementation recognizes bzip2
	     compression automatically when reading archives.

     -z      (c mode only) Compress the resulting archive with gzip(1).  In
	     extract or list modes, this option is ignored.  Note that, unlike
	     other tar implementations, this implementation recognizes gzip
	     compression automatically when reading archives.

ENVIRONMENT

     The following environment variables affect the execution of tar:

     LANG	The locale to use.  See environ(7) for more information.

     POSIXLY_CORRECT
		If this environment variable is defined, the -l option will be
		interpreted in accordance with ISO/IEC 9945-1:1996
		(``POSIX.1'').

     TAPE	The default tape device.  The -f option overrides this.

     TZ 	The timezone to use when displaying dates.  See environ(7) for
		more information.

FILES

     /dev/sa0	The default tape device, if not overridden by the TAPE envi-
		ronment variable or the -f option.

EXIT STATUS

     The tar utility exits 0 on success, and >0 if an error occurs.

EXAMPLES

     The following creates a new archive called file.tar that contains two
     files source.c and source.h:
	   tar -czf file.tar source.c source.h

     To view a detailed table of contents for this archive:
	   tar -tvf file.tar

     To extract all entries from the archive on the default tape drive:
	   tar -x

     In create mode, the list of files and directories to be archived can also
     include directory change instructions of the form -Cfoo/baz and archive
     inclusions of the form @archive-file.  For example, the command line
	   tar -c -f new.tar foo1 @old.tgz -C/tmp foo2
     will create a new archive new.tar.  tar will read the file foo1 from the
     current directory and add it to the output archive.  It will then read
     each entry from old.tgz and add those entries to the output archive.
     Finally, it will switch to the /tmp directory and add foo2 to the output

	   tar tbf 32 file.tar
     specifies three flags t, b, and f.  The b and f flags both require argu-
     ments, so there must be two additional items on the command line.	The 32
     is the argument to the b flag, and file.tar is the argument to the f
     flag.

     The mode options c, r, t, u, and x and the options b, f, l, m, o, v, and
     w comply with SUSv2.

     For maximum portability, scripts that invoke tar should use the bundled-
     argument format above, should limit themselves to the c, t, and x modes,
     and the b, f, m, v, and w options.

     On systems that support getopt_long(), additional long options are avail-
     able to improve compatibility with other tar implementations.

SECURITY

     Certain security issues are common to many archiving programs, including
     tar.  In particular, carefully-crafted archives can request that tar
     extract files to locations outside of the target directory.  This can
     potentially be used to cause unwitting users to overwrite files they did
     not intend to overwrite.  If the archive is being extracted by the supe-
     ruser, any file on the system can potentially be overwritten.  There are
     three ways this can happen.  Although tar has mechanisms to protect
     against each one, savvy users should be aware of the implications:

     o	     Archive entries can have absolute pathnames.  By default, tar
	     removes the leading / character from filenames before restoring
	     them to guard against this problem.

     o	     Archive entries can have pathnames that include .. components.
	     By default, tar will not extract files containing .. components
	     in their pathname.

     o	     Archive entries can exploit symbolic links to restore files to
	     other directories.  An archive can restore a symbolic link to
	     another directory, then use that link to restore a file into that
	     directory.  To guard against this, tar checks each extracted path
	     for symlinks.  If the final path element is a symlink, it will be
	     removed and replaced with the archive entry.  If -U is specified,
	     any intermediate symlink will also be unconditionally removed.
	     If neither -U nor -P is specified, tar will refuse to extract the
	     entry.
     To protect yourself, you should be wary of any archives that come from
     untrusted sources.  You should examine the contents of an archive with
	   tar -tf filename
     before extraction.  You should use the -k option to ensure that tar will
     not overwrite any existing files or the -U option to remove any pre-
     existing files.  You should generally not extract archives while running
     with super-user privileges.  Note that the -P option to tar disables the
     security checks above and allows you to extract an archive while preserv-
     ing any absolute pathnames, .. components, or symlinks to other directo-
     ries.

SEE ALSO

     bzip2(1), cpio(1), gzip(1), mt(1), pax(1), shar(1), libarchive(3),
     libarchive-formats(5), tar(5)

     The ustar and pax interchange file formats are defined by IEEE Std
     1003.1-2001 (``POSIX.1'') for the pax command.

HISTORY

     A tar command appeared in Seventh Edition Unix.  There have been numerous
     other implementations, many of which extended the file format.  John
     Gilmore's pdtar public-domain implementation (circa November, 1987) was
     quite influential, and formed the basis of GNU tar.  GNU tar was included
     as the standard system tar in FreeBSD beginning with FreeBSD 1.0.

     This is a complete re-implementation based on the libarchive(3) library.

BUGS

     POSIX and GNU violently disagree about the meaning of the -l option.
     Because of the potential for disaster if someone expects one behavior and
     gets the other, the -l option is deliberately broken in this implementa-
     tion.

     The -C dir option may differ from historic implementations.

     All archive output is written in correctly-sized blocks, even if the out-
     put is being compressed.  Whether or not the last output block is padded
     to a full block size varies depending on the format and the output
     device.  For tar and cpio formats, the last block of output is padded to
     a full block size if the output is being written to standard output or to
     a character or block device such as a tape drive.	If the output is being
     written to a regular file, the last block will not be padded.  Many com-
     pressors, including gzip(1) and bzip2(1), complain about the null padding
     when decompressing an archive created by tar, although they still extract
     it correctly.

     The compression and decompression is implemented internally, so there may
     be insignificant differences between the compressed output generated by
	   tar -czf - file
     and that generated by
	   tar -cf - file | gzip

     The default should be to read and write archives to the standard I/O
     paths, but tradition (and POSIX) dictates otherwise.

     The r and u modes require that the archive be uncompressed and located in
     a regular file on disk.  Other archives can be modified using c mode with
     the @archive-file extension.

     To archive a file called @foo or -foo you must specify it as ./@foo or
     ./-foo, respectively.

     In create mode, a leading ./ is always removed.  A leading / is stripped
     unless the -P option is specified.

     There needs to be better support for file selection on both create and
     extract.

     There is not yet any support for multi-volume archives or for archiving
     sparse files.

     Converting between dissimilar archive formats (such as tar and cpio)
     using the @- convention can cause hard link information to be lost.

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