tar (gnutar)

Create, add files to, or extract files from an archive file in gnutar format, called a tarfile. Tape ARchiver; manipulate "tar" archive files.

Syntax
       tar [[-]function] [options] filenames...

       tar [[-]function] [options] -C directory-name...

   Command-line arguments that specify files to add to, extract from,
   or list from an archive may  be given as shell pattern matching strings.

FUNCTIONS
       Exactly one of the following functions must be specified.
       (append, create, difference, replace, table of contents, update, and extract)
     -A
     --catenate
     --concatenate  Append the contents of named file, which must itself be a
		    gnutar archive, to the end of the archive (erasing the old
		    end-of-archive block).  This has the effect of adding the
		    files contained in the named file to the first archive,
		    rather than adding the second archive as an element of the
		    first.  Note: This option requires a rewritable tarfile,
		    and therefore does not work on quarter-inch cartridge
		    tapes.  (see notes below)
     -c
     --create	    Create a new archive (or truncates an old one) and writes
		    the named files to it.
     -d
     --diff
     --compare	    Find differences between files in the archive and corre-
		    sponding files in the file system.

     --delete	    Delete named files from the archive.  (Does not work on
		    quarter-inch tapes).
     -r
     --append	    Append files to the end of an archive.  (Does not work on
		    quarter-inch tapes).
     -t
     --list	    List the contents of an archive; if filename arguments are
		    given, only those files are listed, otherwise the entire
		    table of contents is listed.
     -u
     --update	    Append the named files if the on-disk version has a modi-
		    fication date more recent than their copy in the archive
		    (if any).  Does not work on quarter-inch tapes.
     -x
     --extract
     --get	    Extract files from an archive.  The owner, modification
		    time, and file permissions are restored, if possible.  If
		    no file arguments are given, extract all the files in the
		    archive.  If a filename argument matches the name of a
		    directory on the tape, that directory and its contents are
		    extracted (as well as all directories under that direc-
		    tory).  If the archive contains multiple entries corre-
		    sponding to the same file (see the --append command
		    above), the last one extracted will overwrite all earlier
		    versions.

You can specify an argument for the `--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') option whenever you use `tar'; this option determines the name of the archive file that `tar' will work on.

If you don't specify this argument, then `tar' will use a default, usually some physical tape drive attached to your machine. If there is no tape drive attached, or the default is not meaningful, then `tar' will print an error message. The error message might look roughly like one of the following:

     tar: can't open /dev/rmt8 : No such device or address
     tar: can't open /dev/rsmt0 : I/O error

To avoid confusion, we recommend that you always specify an archive file name by using `--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') when writing your `tar' commands.

     --verbose' (`-v') shows details about the results of running `tar'.

This can be especially useful when the results might not be obvious. For example, if you want to see the progress of `tar' as it writes files into the archive, you can use the `--verbose' option. In the beginning, you may find it useful to use `--verbose' at all times; when you are more accustomed to `tar', you will likely want to use it at certain times but not at others.

Sometimes, a single instance of `--verbose' on the command line will show a full, `ls' style listing of an archive or files, giving sizes, owners, and similar information. Other times, `--verbose' will only show files or members that the particular operation is operating on at the time. In the latter case, you can use `--verbose' twice in a command to get a listing such as that in the former case.

Options

The other options to gnutar may be combined arbitrarily; single-letter options may be bundled in with the command word. Verbose options which take arguments will be followed by the argument; single-letter options will consume successive command line arguments (see the EXAMPLES below).
gnutar will properly handle option arguments passed either with or without a leading `=` (i.e. either --option=arg or --option arg).

     --help		     Prints a message listing and briefly describing
			     all the command options to gnutar.
     --atime-preserve	     Restore the access times on files which are writ-
			     ten to tape (note that this will change the
			     inode-change time!).
     -b
     --block-size number
     --blocking-factor number
     --record-size size	     Sets the block size for reading or writing to
			     number * 512-byte blocks.	Or sets block size for
			     reading or writing to size bytes which must be a
			     multiple of 512.
     -B
     --read-full-records     Re-assemble short reads into full records (for
			     reading 4.2BSD pipes).
     --backup control	     Backup files before removal.  Optionally, the
			     user can specify a control argument to control
			     how gnutar performs the backups.  Supported val-
			     ues are listed bellow in the ENVIRONMENT section.
     --suffix suffix	     Backup files before removal.  Override the normal
			     backup suffix (default: '~'), using suffix
			     instead.
     -C directory
     --directory directory   Change to directory before processing the remain-
			     ing arguments. (see notes below)

     --checkpoint	     Print number of buffer reads/writes while read-
			     ing/writing the archive.

     -f [hostname:]file
     --file [hostname:]file  Read or write the specified file (default is
			     /dev/sa0).	 If a hostname is specified, gnutar

			     will use rmt(8) to read or write the specified
			     file on a remote machine.	`-' may be used as a
			     filename, for reading or writing to/from
			     stdin/stdout.

     --force-local	     Archive file is local even if it has a colon.

     -F file
     --info-script file
     --new-volume-script file
			     Run a script at the end of each archive volume
			     (implies -M).
     -G
     --incremental	     Create/list/extract old GNU-format incremental
			     backup.
     -g file
     --listed-incremental file
			     Create/list/extract new GNU-format incremental
			     backup.
     --group name	     Force group as group for added files.
     -h
     --dereference	     Don't write symlinks as symlinks; write the data
			     of the files they name.
     -i
     --ignore-zeros	     Ignore blocks of zeroes in archive (usually means
			     End-Of-File).
     --ignore-failed-read    Don't exit with non-zero status on unreadable
			     files.
     -j
     --bzip2		     Filter the archive through bzip2(1).
     -k
     --keep-old-files	     Keep files which already exist on disk; don't
			     overwrite them from the archive.
     -K file
     --starting-file file    Begin at file in the archive.
     -l
     --one-file-system	     Stay in local file system when creating an
			     archive (do not cross mount points).
     -L number
     --tape-length number    Change tapes after writing number * 1024 bytes.
     --mode changes	     Force changes to file mode of added files.
     -m
     --modification-time     Don't extract file modified time.
     -M
     --multi-volume	     Create/list/extract multi-volume archive.
     --no-recursion	     Don't recurse into subdirectories when creating.
     --volno-file file	     File name with volume number to start with.
     -N date
     --after-date date
     --newer date	     Only store files with creation time newer than
			     date.
     --newer-mtime date	     Only store files with modification time newer
			     than date.
     --no-same-owner	     Do not preserve ownership when extracting files.
			     Extract them all as owned by the current user.
     --no-same-permissions   Do not extract permission information.  Extract
			     them using the default permissions for the cur-
			     rent user.
     --numeric-owner	     Use numbers instead of names for owner/group
			     names.
     -o
     --old-archive
     --portability	     Write a V7 format archive, rather than POSIX for-
			     mat.
     -O
     --to-stdout	     Extract files to standard output.
     --owner name	     Force name as owner for added files.
     --overwrite	     Overwrite existing files when extracting.
     --overwrite-dir	     Overwrite directory metadata when extracting.
     -p
     --same-permissions
     --preserve-permissions  Extract all permission information.
     --preserve		     Has the effect of -p -s.
     -P
     --absolute-names	     Don't strip leading `/' from file names.
     --posix		     Instructs gnutar to create a POSIX compliant
			     `tar' archive.
     -R
     --block-number	     Show record number within archive with each mes-
			     sage.
     --remove-files	     Remove files after adding them to the archive.
     --rsh-command command   Use command instead of rsh for remote
			     archives/files.
     -s
     --same-order
     --preserve-order	     List of names to extract is sorted to match
			     archive.
     --same-owner	     Try to preserve ownership when extracting files.
     --show-omitted-dirs     Show directories which were omitted while pro-
			     cessing the archive.
     -S
     --sparse		     Handle `sparse' files efficiently.
     -T file
     --files-from file	     Get names of files to extract or create from
			     file, one per line.
     --null		     Modifies behavior of -T to expect null-terminated
			     names; disables -C.
     --totals		     Prints total bytes written with --create.
     -U
     --unlink-first	     Unlink files before creating them.
     --recursive-unlink	     Empty hierarchies prior to extracting directory.
     -v
     --verbose		     Lists files written to archive with --create or
			     extracted with --extract; lists file protection
			     information along with file names with --list.
     -V volume-name
     --label volume-name     Create archive with the given volume-name.	 When
			     used with list or extract, volume-name is used as
			     a globing pattern.
     --version		     Print gnutar program version number.
     -w
     --interactive
     --confirmation	     Ask for confirmation for every action.
     -W
     --verify		     Attempt to verify the archive after writing it.
     --exclude pattern	     Exclude files matching the pattern (don't extract
			     them, don't add them, don't list them).
     -X file
     --exclude-from file     Exclude files listed in file.
     --anchored		     Exclude patterns match file name start (default).
     --no-anchored	     Exclude patterns match after any /.
     --ignore-case	     Exclude patterns ignore case.
     --no-ignore-case	     Exclude patterns are case sensitive (default).
     --wildcards	     Exclude patterns use wildcards (default).
     --no-wildcards	     Exclude patterns are plain strings.
     --wildcards-match-slash
			     Exclude pattern wildcards match '/' (default).
     --no-wildcards-match-slash
			     Exclude pattern wildcards do not match '/'.
     -Z
     --compress
     --uncompress	     Filter the archive through compress(1).
     -z
     --gzip
     --ungzip
     --gunzip		     Filter the archive through gzip(1).
     --use-compress-program program
			     Filter the archive through program (which must
			     accept -d to mean `decompress').
     -[0-7][lmh]	     Specify tape drive and density.

Examples

To tar and zip a file

  tar -czvf MyArchive.tgz Source_file 
or in full
  tar --create --gzip --verbose --file=MyArchive.tgz Source_file

To tar a folder (with all sub-folders and files)

  tar czf /volumes/myexternaldrive/backup01.tgz myfolder

The reverse process to extract the file

  tar -xzvf MyArchive.tgz Source_file 
or
  tar --extract --gunzip --verbose --file=MyArchive.tgz Source_file

  tar xzvf /volumes/myexternaldrive/backup01.tgz myfolder/subfolder/thefiletorestore

To extract all the C sources and headers from an archive named
backup.tar, type

  tar xf backup.tar '*.[ch]'

Note that the pattern must be quoted to prevent the shell from attempting
to expand it according the files in the current working directory (the
shell does not have access to the list of files in the archive, of
course).

To move file hierarchies, use a command line like this:

  tar -cf - -C srcdir . | tar xpf - -C destdir

To create a compressed archive on diskette, using gzip(1), use a command-
line like
  tar --block-compress -z -c -v -f /dev/fd1a -b 36 tar/

     Note that you cannot mix bundled flags and --style flags; you can use
     single-letter flags in the manner above, rather than having to type
	   tar --block-compress --gzip --verbose --file /dev/fd1a --block-size
	   20 tar/

     The above-created diskette can be listed with
	   tar tvfbz /dev/fd1a 36

To join two gnutar archives into a single archive, use

   tar Af archive1.tar archive2.tar

which will add the files contained in archive2.tar onto the end of
archive1.tar (note that this can't be done by simply typing

   cat archive2.tar >> archive1.tar

because of the end-of-file block at the end of a gnutar archive).

To archive all files from the directory srcdir, which were modified after
Feb. 9th 1997, 13:00 h, use

   tar -c -f backup.tar --newer-mtime 'Feb 9 13:15 1997' srcdir/

Other possible time specifications are `02/09/97 13:15', `1997-02-09
13:15', `13:15 9 Feb 1997', `9 Feb 1997 13:15', `Feb. 9, 1997 1:15pm',
`09-Feb', `3 weeks ago' or `May first Sunday'.  To specify the correct
time zone use either e.g. `13:15 CEST' or `13:15+200'.

Notes

Always tar -t before tar -x to check if the archive contents have been placed inside one subdirectory or will just spill all over the current directory.

The -C feature does not work like historical gnutar programs, and is probably untrustworthy.

The -A command should work to join an arbitrary number of gnutar archives together, but it does not; attempting to do so leaves the end-of-archive blocks in place for the second and subsequent archives.

The gnutar file format is a semi fixed width field format, and the field for device numbers were designed for 16 bit (8 major, 8 minor) and can not absorb our 32 bit (8 major, 16+8 minor) numbers.

Environment Variables

     POSIXLY_CORRECT  Normally, gnutar will process flag arguments that appear
		      in the file list.	 If set in the environment, this
		      causes gnutar to consider the first non-flag argument to
		      terminate flag processing, as per the POSIX specification.

     SHELL	      In interactive mode, a permissible response to the
		      prompt is to request to spawn a subshell, which will be
		      /bin/sh unless the SHELL variable is set.

     SIMPLE_BACKUP_SUFFIX
		      Sets the backup suffix used by gnutar.  Default is '~'.

     TAPE	      Changes gnutar's default tape drive /dev/sa0 (which is still
		      overridden by the -f flag).

     TAR_OPTIONS      The environment variable TAR_OPTIONS can hold a set of
		      default options for gnutar.  These options are inter-
		      preted first and can be overwritten by explicit command
		      line parameters.

     TAR_RSH	      The TAR_RSH environment variable allows you to override
		      the default shell used as the transport for gnutar.

     VERSION_CONTROL  Sets the backup method used by gnutar.  Possible values:

		      t, numbered      Make numbered backups

		      nil, existing    Numbered if numbered backups exist,
				       simple otherwise

		      never, simple    Always make simple backups
				
		      Default behaviour is 'existing'.

"To disarm the bomb simply enter a valid tar command on your first try. No Googling" ~ XKCD

Related:

tar man page - Apple.com
bzip2(1)
compress - compress and expand data
gzip - Compress or decompress files
pax(1)
rmt - remote magtape protocol module
info tar


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