Provided by: bsdtar_3.1.2-11build1_amd64 bug

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.  This implementation can extract from
     tar, pax, cpio, zip, jar, ar, xar, rpm, 7-zip, and ISO 9660 cdrom images and can create tar,
     pax, cpio, ar, zip, 7-zip, and shar archives.

     The first synopsis form shows a “bundled” option word.  This usage is provided for
     compatibility with historical implementations.  See COMPATIBILITY 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.  The long option form is
             --create.
     -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.  The long
             option form is --append.
     -t      List archive contents to stdout.  The long option form is --list.
     -u      Like -r, but new entries are added only if they have a modification date newer than
             the corresponding entry in the archive.  Note that this only works on uncompressed
             archives stored in regular files.  The -f option is required.  The long form is
             --update.
     -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.  The long option form is --extract.

     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 contents 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 tcsh(1).

OPTIONS

     Unless specifically stated otherwise, options are applicable in all operating 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 simple 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 determined automatically)
             and converts it into a gzip-compressed pax-format archive on stdout.  In this way,
             tar can be used to convert archives from one format to another.

     -a, --auto-compress
             (c mode only) Use the archive suffix to decide a set of the format and the
             compressions.  As a simple example,
                   tar -a -cf archive.tgz source.c source.h
             creates a new archive with restricted pax format and gzip compression,
                   tar -a -cf archive.tar.bz2.uu source.c source.h
             creates a new archive with restricted pax format and bzip2 compression and uuencode
             compression,
                   tar -a -cf archive.zip source.c source.h
             creates a new archive with zip format,
                   tar -a -jcf archive.tgz source.c source.h
             ignores the “-j” option, and creates a new archive with restricted pax format and
             gzip compression,
                   tar -a -jcf archive.xxx source.c source.h
             if it is unknown suffix or no suffix, creates a new archive with restricted pax
             format and bzip2 compression.

     -B, --read-full-blocks
             Ignored for compatibility with other tar(1) implementations.

     -b blocksize, --block-size blocksize
             Specify the block size, in 512-byte records, for tape drive I/O.  As a rule, this
             argument is only needed when reading from or writing to tape drives, and usually not
             even then as the default block size of 20 records (10240 bytes) is very common.

     -C directory, --cd directory, --directory 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.

     --chroot
             (x mode only) chroot() to the current directory after processing any -C options and
             before extracting any files.

     --disable-copyfile
             Mac OS X specific.  Disable the use of copyfile(3).

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

     --format format
             (c, r, u 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-supported
             formats.  In r and u modes, when extending an existing archive, the format specified
             here must be compatible with the format of the existing archive on disk.

     -f file, --file file
             Read the archive from or write the archive to the specified file.  The filename can
             be - for standard input or standard output.  The default varies by system; on
             FreeBSD, the default is /dev/sa0; on Linux, the default is /dev/st0.

     --gid id
             Use the provided group id number.  On extract, this overrides the group id in the
             archive; the group name in the archive will be ignored.  On create, this overrides
             the group id read from disk; if --gname is not also specified, the group name will
             be set to match the group id.

     --gname name
             Use the provided group name.  On extract, this overrides the group name in the
             archive; if the provided group name does not exist on the system, the group id (from
             the archive or from the --gid option) will be used instead.  On create, this sets
             the group name that will be stored in the archive; the name will not be verified
             against the system group database.

     -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.

     -I      Synonym for -T.

     --help  Show usage.

     --hfsCompression
             (x mode only) Mac OS X specific(v10.6 or later). Compress extracted regular files
             with HFS+ compression.

     --include pattern
             Process only files or directories that match the specified pattern.  Note that
             exclusions specified with --exclude take precedence over inclusions.  If no
             inclusions are explicitly specified, 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, --xz
             (c mode only) Compress the resulting archive with xz(1).  In extract or list modes,
             this option is ignored.  Note that, unlike other tar implementations, this
             implementation recognizes XZ compression automatically when reading archives.

     -j, --bzip, --bzip2, --bunzip2
             (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.

     -k, --keep-old-files
             (x mode only) Do not overwrite existing files.  In particular, if a file appears
             more than once in an archive, later copies will not overwrite earlier copies.

     --keep-newer-files
             (x mode only) Do not overwrite existing files that are newer than the versions
             appearing in the archive being extracted.

     -L, --dereference
             (c and r mode only) All symbolic links will be followed.  Normally, symbolic links
             are archived as such.  With this option, the target of the link will be archived
             instead.

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

     --lrzip
             (c mode only) Compress the resulting archive with lrzip(1).  In extract or list
             modes, this option is ignored.

     --lzma  (c mode only) Compress the resulting archive with the original LZMA algorithm.  Use
             of this option is discouraged and new archives should be created with --xz instead.
             Note that, unlike other tar implementations, this implementation recognizes LZMA
             compression automatically when reading archives.

     --lzop  (c mode only) Compress the resulting archive with lzop(1).  In extract or list
             modes, this option is ignored.

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

     -n, --norecurse, --no-recursion
             (c, r, u modes only) Do not recursively archive the contents of directories.

     --newer date
             (c, r, u modes only) Only include files and directories newer than the specified
             date.  This compares ctime entries.

     --newer-mtime date
             (c, r, u modes only) Like --newer, except it compares mtime entries instead of ctime
             entries.

     --newer-than file
             (c, r, u modes only) Only include files and directories newer than the specified
             file.  This compares ctime entries.

     --newer-mtime-than file
             (c, r, u modes only) Like --newer-than, except it compares mtime entries instead of
             ctime entries.

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

     --nopreserveHFSCompression
             (x mode only) Mac OS X specific(v10.6 or later). Do not compress extracted regular
             files which were compressed with HFS+ compression before archived.  By default,
             compress the regular files again with HFS+ compression.

     --null  (use with -I or -T) Filenames or patterns are separated by null characters, not by
             newlines.  This is often used to read filenames output by the -print0 option to
             find(1).

     --no-same-owner
             (x mode only) Do not extract owner and group IDs.  This is the reverse of
             --same-owner and the default behavior if tar is run as non-root.

     --no-same-permissions
             (x mode only) Do not extract full permissions (SGID, SUID, sticky bit, ACLs,
             extended attributes or extended file flags).  This is the reverse of -p and the
             default behavior if tar is run as non-root.

     --numeric-owner
             This is equivalent to --uname "" --gname "".  On extract, it causes user and group
             names in the archive to be ignored in favor of the numeric user and group ids.  On
             create, it causes user and group names to not be stored in the archive.

     -O, --to-stdout
             (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) Use the user and group of the user running the program 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 information in
             the archive will be discarded.

     -o      (c, r, u mode) A synonym for --format ustar

     --older date
             (c, r, u modes only) Only include files and directories older than the specified
             date.  This compares ctime entries.

     --older-mtime date
             (c, r, u modes only) Like --older, except it compares mtime entries instead of ctime
             entries.

     --older-than file
             (c, r, u modes only) Only include files and directories older than the specified
             file.  This compares ctime entries.

     --older-mtime-than file
             (c, r, u modes only) Like --older-than, except it compares mtime entries instead of
             ctime entries.

     --one-file-system
             (c, r, and u modes) Do not cross mount points.

     --options options
             Select optional behaviors for particular modules.  The argument is a text string
             containing comma-separated keywords and values.  These are passed to the modules
             that handle particular formats to control how those formats will behave.  Each
             option has one of the following forms:
             key=value
                     The key will be set to the specified value in every module that supports it.
                     Modules that do not support this key will ignore it.
             key     The key will be enabled in every module that supports it.  This is
                     equivalent to key=1.
             !key    The key will be disabled in every module that supports it.
             module:key=value, module:key, module:!key
                     As above, but the corresponding key and value will be provided only to
                     modules whose name matches module.
             The currently supported modules and keys are:
             iso9660:joliet
                     Support Joliet extensions.  This is enabled by default, use !joliet or
                     iso9660:!joliet to disable.
             iso9660:rockridge
                     Support Rock Ridge extensions.  This is enabled by default, use !rockridge
                     or iso9660:!rockridge to disable.
             gzip:compression-level
                     A decimal integer from 1 to 9 specifying the gzip compression level.
             gzip:timestamp
                     Store timestamp. This is enabled by default, use !timestamp or
                     gzip:!timestamp to disable.
             lrzip:compression=type
                     Use type as compression method.  Supported values are bzip2, gzip, lzo
                     (ultra fast), and zpaq (best, extremely slow).
             lrzip:compression-level
                     A decimal integer from 1 to 9 specifying the lrzip compression level.
             lzop:compression-level
                     A decimal integer from 1 to 9 specifying the lzop compression level.
             xz:compression-level
                     A decimal integer from 0 to 9 specifying the xz compression level.
             mtree:keyword
                     The mtree writer module allows you to specify which mtree keywords will be
                     included in the output.  Supported keywords include: cksum, device, flags,
                     gid, gname, indent, link, md5, mode, nlink, rmd160, sha1, sha256, sha384,
                     sha512, size, time, uid, uname.  The default is equivalent to: “device,
                     flags, gid, gname, link, mode, nlink, size, time, type, uid, uname”.
             mtree:all
                     Enables all of the above keywords.  You can also use mtree:!all to disable
                     all keywords.
             mtree:use-set
                     Enable generation of /set lines in the output.
             mtree:indent
                     Produce human-readable output by indenting options and splitting lines to
                     fit into 80 columns.
             zip:compression=type
                     Use type as compression method.  Supported values are store (uncompressed)
                     and deflate (gzip algorithm).
             If a provided option is not supported by any module, that is a fatal error.

     -P, --absolute-paths
             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, --insecure, --preserve-permissions
             (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.  This is the default, if tar is being run by root and
             can be overridden by also specifying --no-same-owner and --no-same-permissions.

     --posix
             (c, r, u mode only) Synonym for --format pax

     -q, --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.

     -S      (x mode only) Extract files as sparse files.  For every block on disk, check first
             if it contains only NULL bytes and seek over it otherwise.  This works similar to
             the conv=sparse option of dd.

     -s pattern
             Modify file or archive member names according to pattern.  The pattern has the
             format /old/new/[ghHprRsS] where old is a basic regular expression, new is the
             replacement string of the matched part, and the optional trailing letters modify how
             the replacement is handled.  If old is not matched, the pattern is skipped.  Within
             new, ~ is substituted with the match, \1 to \9 with the content of the corresponding
             captured group.  The optional trailing g specifies that matching should continue
             after the matched part and stop on the first unmatched pattern.  The optional
             trailing s specifies that the pattern applies to the value of symbolic links.  The
             optional trailing p specifies that after a successful substitution the original path
             name and the new path name should be printed to standard error.  Optional trailing
             H, R, or S characters suppress substitutions for hardlink targets, regular
             filenames, or symlink targets, respectively.  Optional trailing h, r, or s
             characters enable substitutions for hardlink targets, regular filenames, or symlink
             targets, respectively.  The default is hrs which applies substitutions to all names.
             In particular, it is never necessary to specify h, r, or s.

     --same-owner
             (x mode only) Extract owner and group IDs.  This is the reverse of --no-same-owner
             and the default behavior if tar is run as root.

     --strip-components count
             Remove the specified number of leading path elements.  Pathnames with fewer elements
             will be silently skipped.  Note that the pathname is edited after checking
             inclusion/exclusion patterns but before security checks.

     -T filename, --files-from filename
             In x or t mode, tar will read the list of names to be extracted from filename.  In c
             mode, tar will read names to be archived from filename.  The special name “-C” on a
             line by itself will cause the current directory to be changed to the directory
             specified on the following line.  Names are terminated by newlines unless --null is
             specified.  Note that --null also disables the special handling of lines containing
             “-C”.  Note:  If you are generating lists of files using find(1), you probably want
             to use -n as well.

     --totals
             (c, r, u mode only) After archiving all files, print a summary to stderr.

     -U, --unlink, --unlink-first
             (x mode only) Unlink files before creating them.  This can be a minor performance
             optimization if most files already exist, but can make things slower if most files
             do not already exist.  This flag also causes tar to remove intervening directory
             symlinks instead of reporting an error.  See the SECURITY section below for more
             details.

     --uid id
             Use the provided user id number and ignore the user name from the archive.  On
             create, if --uname is not also specified, the user name will be set to match the
             user id.

     --uname name
             Use the provided user name.  On extract, this overrides the user name in the
             archive; if the provided user name does not exist on the system, it will be ignored
             and the user id (from the archive or from the --uid option) will be used instead.
             On create, this sets the user name that will be stored in the archive; the name is
             not verified against the system user database.

     --use-compress-program program
             Pipe the input (in x or t mode) or the output (in c mode) through program instead of
             using the builtin compression support.

     -v, --verbose
             Produce verbose output.  In create and extract modes, tar will list each file name
             as it is read from or written to the archive.  In list mode, tar will produce output
             similar to that of ls(1).  Additional -v options will provide additional detail.

     --version
             Print version of tar and libarchive, and exit.

     -w, --confirmation, --interactive
             Ask for confirmation for every action.

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

     -z, --gunzip, --gzip
             (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:

     TAR_READER_OPTIONS
                The default options for format readers and compression readers.  The --options
                option overrides this.

     TAR_WRITER_OPTIONS
                The default options for format writers and compression writers.  The --options
                option overrides this.

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

     TAPE       The default device.  The -f option overrides this.  Please see the description of
                the -f option above for more details.

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

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.gz that contains two files source.c and
     source.h:
           tar -czf file.tar.gz source.c source.h

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

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

     To examine the contents of an ISO 9660 cdrom image:
           tar -tf image.iso

     To move file hierarchies, invoke tar as
           tar -cf - -C srcdir . | tar -xpf - -C destdir
     or more traditionally
           cd srcdir ; tar -cf - . | (cd destdir ; tar -xpf -)

     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 archive.

     An input file in mtree(5) format can be used to create an output archive with arbitrary
     ownership, permissions, or names that differ from existing data on disk:

           $ cat input.mtree
           #mtree
           usr/bin uid=0 gid=0 mode=0755 type=dir
           usr/bin/ls uid=0 gid=0 mode=0755 type=file content=myls
           $ tar -cvf output.tar @input.mtree

     The --newer and --newer-mtime switches accept a variety of common date and time
     specifications, including “12 Mar 2005 7:14:29pm”, “2005-03-12 19:14”, “5 minutes ago”, and
     “19:14 PST May 1”.

     The --options argument can be used to control various details of archive generation or
     reading.  For example, you can generate mtree output which only contains type, time, and uid
     keywords:
           tar -cf file.tar --format=mtree --options='!all,type,time,uid' dir
     or you can set the compression level used by gzip or xz compression:
           tar -czf file.tar --options='compression-level=9'.
     For more details, see the explanation of the archive_read_set_options() and
     archive_write_set_options() API calls that are described in archive_read(3) and
     archive_write(3).

COMPATIBILITY

     The bundled-arguments format is supported for compatibility with historic implementations.
     It consists of an initial word (with no leading - character) in which each character
     indicates an option.  Arguments follow as separate words.  The order of the arguments must
     match the order of the corresponding characters in the bundled command word.  For example,
           tar tbf 32 file.tar
     specifies three flags t, b, and f.  The b and f flags both require arguments, 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.

     Additional long options are provided 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
     superuser, 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:

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

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

     ·       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 preserving any
     absolute pathnames, .. components, or symlinks to other directories.

SEE ALSO

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

STANDARDS

     There is no current POSIX standard for the tar command; it appeared in ISO/IEC 9945-1:1996
     (“POSIX.1”) but was dropped from IEEE Std 1003.1-2001 (“POSIX.1”).  The options supported by
     this implementation were developed by surveying a number of existing tar implementations as
     well as the old POSIX specification for tar and the current POSIX specification for pax.

     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, which was released in January, 1979.  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.  It was first
     released with FreeBSD 5.4 in May, 2005.

BUGS

     This program follows ISO/IEC 9945-1:1996 (“POSIX.1”) for the definition of the -l option.
     Note that GNU tar prior to version 1.15 treated -l as a synonym for the --one-file-system
     option.

     The -C dir option may differ from historic implementations.

     All archive output is written in correctly-sized blocks, even if the output 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 compressors, 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.  (This is a consequence of the incompatible ways
     that different archive formats store hardlink information.)