TAR(1)			  BSD General Commands Manual			TAR(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.  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 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.  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 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.  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 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 tcsh(1).

OPTIONS

     Unless specifically stated otherwise, options are applicable in all oper‐

     ating modes.

     @archive

	     (c and r modes 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-

	     format archive on stdout.	In this way, tar can be used to con‐

	     vert archives from one format to another.

     -a, --auto-compress

	     (c mode only) Use the archive suffix to decide a set of the for‐

	     mat 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 com‐

	     pression,

		   tar -a -cf archive.tar.bz2.uu source.c source.h

	     creates a new archive with restricted pax format and bzip2 com‐

	     pression 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.

     --acls  (c, r, u, x modes only) Archive or extract POSIX.1e or NFSv4

	     ACLs. This is the reverse of --no-acls and the default behavior

	     in c, r, and u modes (except on Mac OS X) or if tar is run in x

	     mode as root. On Mac OS X this option translates extended ACLs to

	     NFSv4 ACLs. To store extended ACLs the --mac-metadata option is

	     preferred.

     -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.

     --clear-nochange-fflags

	     (x mode only) Before removing file system objects to replace

	     them, clear platform-specific file flags that might prevent

	     removal.

     --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.

     --fflags

	     (c, r, u, x modes only) Archive or extract file flags. This is

	     the reverse of --no-fflags and the default behavior in c, r, and

	     u modes or if tar is run in x mode as root.

     --format format

	     (c, r, u mode only) Use the specified format for the created ar‐

	     chive.  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.  In r and u modes, when extending an existing ar‐

	     chive, the format specified here must be compatible with the for‐

	     mat 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 modes 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 modes 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.

     --ignore-zeros

	     An alias of --options read_concatenated_archives for compatibil‐

	     ity with GNU tar.

     --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, --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 com‐

	     pression 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 modes only) All symbolic links will be followed.	Nor‐

	     mally, 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.

     --lz4   (c mode only) Compress the archive with lz4-compatible compres‐

	     sion before writing it.  In input mode, this option is ignored;

	     lz4 compression is recognized automatically on input.

     --lzma  (c mode only) Compress the resulting archive with the original

	     LZMA algorithm.  Use of this option is discouraged and new ar‐

	     chives 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.

     --mac-metadata

	     (c, r, u and x mode only) Mac OS X specific. Archive or extract

	     extended ACLs and extended attributes using copyfile(3) in Apple‐

	     Double format. This is the reverse of --no-mac-metadata.  and the

	     default behavior in c, r, and u modes or if tar is run in x mode

	     as root.

     -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+ compres‐

	     sion 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 file‐

	     names output by the -print0 option to find(1).

     --no-acls

	     (c, r, u, x modes only) Do not archive or extract POSIX.1e or

	     NFSv4 ACLs. This is the reverse of --acls and the default behav‐

	     ior if tar is run as non-root in x mode (on Mac OS X as any user

	     in c, r, u and x modes).

     --no-fflags

	     (c, r, u, x modes only) Do not archive or extract file flags.

	     This is the reverse of --fflags and the default behavior if tar

	     is run as non-root in x mode.

     --no-mac-metadata

	     (x mode only) Mac OS X specific. Do not archive or extract ACLs

	     and extended attributes using copyfile(3) in AppleDouble format.

	     This is the reverse of --mac-metadata.  and the default behavior

	     if tar is run as non-root in x mode.

     -n, --norecurse, --no-recursion

     --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.

     --no-xattrs

	     (c, r, u, x modes only) Do not archive or extract extended

	     attributes. This is the reverse of --xattrs and the default

	     behavior if tar is run as non-root in x mode.

     --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 mod‐

		     ule 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 com‐

		     pression 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 com‐

		     pression level.

	     lz4:compression-level

		     A decimal integer from 1 to 9 specifying the lzop com‐

		     pression level.

	     lz4:stream-checksum

		     Enable stream checksum. This is by default, use

		     lz4:!stream-checksum to disable.

	     lz4:block-checksum

		     Enable block checksum (Disabled by default).

	     lz4:block-size

		     A decimal integer from 4 to 7 specifying the lz4 compres‐

		     sion block size (7 is set by default).

	     lz4:block-dependence

		     Use the previous block of the block being compressed for

		     a compression dictionary to improve compression ratio.

	     lzop:compression-level

		     A decimal integer from 1 to 9 specifying the lzop com‐

		     pression level.

	     xz:compression-level

		     A decimal integer from 0 to 9 specifying the xz compres‐

		     sion level.

	     mtree:keyword

		     The mtree writer module allows you to specify which mtree

		     keywords will be included in the output.  Supported key‐

		     words include: cksum, device, flags, gid, gname, indent,

		     link, md5, mode, nlink, rmd160, sha1, sha256, sha384,

		     sha512, size, time, uid, uname.  The default is equiva‐

		     lent 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).

	     zip:encryption

		     Enable encryption using traditional zip encryption.

	     zip:encryption=type

		     Use type as encryption type.  Supported values are

		     zipcrypt (traditional zip encryption), aes128 (WinZip

		     AES-128 encryption) and aes256 (WinZip AES-256 encryp‐

		     tion).

	     read_concatenated_archives

		     Ignore zeroed blocks in the archive, which occurs when

		     multiple tar archives have been concatenated together.

		     Without this option, only the contents of the first con‐

		     catenated archive would be read.  This option is compara‐

		     ble to the -i, --ignore-zeros option of GNU tar.

	     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, ACLs, extended

	     attributes and extended file flags, if available, for each item

	     extracted from the archive. This is te reverse of

	     --no-same-permissions and the default if tar is being run by root

	     and can be partially overridden by also specifying --no-acls,

	     --no-fflags, --no-mac-metadata or --no-xattrs.

     --passphrase passphrase

	     The passphrase is used to extract or create an encrypted archive.

	     Currently, zip is the only supported format that supports encryp‐

	     tion.  You shouldn't use this option unless you realize how inse‐

	     cure use of this option is.

     --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 replace‐

	     ment 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 trail‐

	     ing 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 speci‐

	     fied 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 modes 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).

	     An additional -v option will also provide ls-like details in cre‐

	     ate and extract mode.

     --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.

     --xattrs

	     (c, r, u, x modes only) Archive or extract extended attributes.

	     This is the reverse of --no-xattrs and the default behavior in c,

	     r, and u modes or if tar is run in x mode as root.

     -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 read‐

		ers.  The --options option overrides this.

     TAR_WRITER_OPTIONS

		The default options for format writers and compression writ‐

		ers.  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 - char‐

     acter) 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 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.

     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 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:

     ·	     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 preserv‐

     ing any absolute pathnames, .. components, or symlinks to other directo‐

     ries.

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 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.

     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.)

BSD			       February 25, 2017			   BSD