tar - Manipulates tape archives
tar function_key[bBfFEhilLmpPsSvVwzn] [n|o] [option_argument...] [-e exception]... [-C directory]... [file...]
tar -function_key[options] [option_argument]... [n|o] [option_argument...] [-e exception]... [-C directory]... [file...]
The tar command saves and restores multiple files on a single file (usually a magnetic tape, but it can be any file).
[Compaq] The syntax of the tar command has recently changed. The minus sign (-) at the beginning of a key/option set is no longer optional. If tar sees a minus sign in front of an option that requires an argument, tar expects the argument to follow the option immediately. In order to use the original tar syntax in existing scripts, you must remove the minus sign if more than one option requiring an argument is given. Consider this command in the old form: tar -xbfp 20 /dev/rmt1h
Under the new implementation, this command becomes tar xbfp 20 /dev/rmt1h
or tar -xb 20 -f /dev/rmt1h -p
Interfaces documented on this reference page conform to industry standards as follows:
tar: XPG4, XPG4-UNIX
Refer to the
reference page for more information
about industry standards and associated tags.
[Compaq] The function performed by
by one of the following key letters:
Creates a new archive. When writing to a tape device,
begins from the current tape position.
Writes the named files at the end of the specified archive.
If the archive is on tape,
expects that the tape is
currently positioned to the beginning of the archive.
Lists the contents of the archive. If the file argument does
not restrict the operation to one or more specific directories or files,
lists all of the file names in the archive.
Adds the named files to the tape, if the files are not already
there or if they were modified since last copied to the tape.
Extracts the named files from the tape. If a named file matches
a directory whose contents were written to the tape, this directory is (recursively)
extracted. The owner, modification time, and mode are restored (if possible).
If no file argument is given, the entire content of the tape is extracted.
If multiple entries specifying the same file are on the tape, the last one
overwrites all earlier ones.
[Compaq] The following options can be used with function keys: The tar command uses the next argument as the blocking factor for tape records. The default is 20 (larger values can be specified at the risk of creating a tape archive that some systems' tape drives might not be able to restore). Use this option only with raw magnetic tape archives. The block size is determined automatically when reading tapes (key letters x and t). [Compaq] Forces input and output blocking to the blocking factor (see the b option). The B option exists so that tar can work across a communications channel where the blocking cannot be maintained. [Compaq] The tar command uses the next argument, exception, as the name of the file to be excluded from the archive. Processes extended headers, allowing you to archive or extract extended UIDs and GIDs, long filenames, link-names, large files, and long user and group names The tar command uses the next argument as the name of the archive instead of /dev/rmtnh. (See the entry for the n option.) If the name of the file is - (dash), tar writes to standard output or reads from standard input, whichever is appropriate. Thus, tar can be used as the head or tail of a filter chain. The tar utility can also be used to move hierarchies with the command: cd fromdir; tar cf - . | (cd todir; tar xpf -) [Compaq] Checks certain file names before archiving. Source Code Control System (SCCS), Revision Control System (RCS), files named core, errs, a.out, and files ending in .o are not archived. [Compaq] Forces tar to follow symbolic links as if they were normal files or directories. Normally, tar does not follow symbolic links, but instead saves the link text in the archive. [Compaq] Ignores checksum errors. The tar command writes a file header containing a checksum for each file in the archive. When this option is not specified, the system verifies the contents of the header blocks by recomputing the checksum and stops with a directory checksum error when a mismatch occurs. When this option is specified, tar logs the error and then scans forward until it finds a valid header block. This permits restoring files from later volumes of a multivolume archive without reading earlier volumes. [Compaq] Tells tar to complain if it cannot resolve all of the links to the files dumped. If this option is not specified, no error messages are printed. [Compaq] Tries to create a symbolic link if tar is unsuccessful in its attempt to link (hard link) two files. Tells tar not to restore the modification times. The modification time is the time of extraction. This is always the case with symbolic links. [Compaq] Allows tar headers to be created with file names that cannot be null-terminated if they are exactly the maximum length (as specified in POSIX). This option is mutually exclusive with the o option (that is, new versus old). When specified, each of these options turns off the other; neither option is turned on by default, however. The o option is provided for backward compatibility. Specify this option if the archive is to be restored on a system with an older version of tar. On output, tar normally places information specifying owner and modes of directories in the archive. Former versions of tar, when encountering this information will give an error message of the following form: name: cannot create
[Compaq] Only the -e and -C options must be preceded by a - (dash) and can be specified more than once on a single command line or interspersed within the list of file names. All other options must be specified together (with no separating spaces) before -e, -C, and the file list. For all options that require arguments, the arguments must follow the string of options and be ordered in the same way as the specified options.
[Compaq] Previous restrictions on the
ability to properly handle blocked archives have been lifted.
The tar command is used to save and restore data from traditional format tar archives.
The actions of the tar command are controlled by a string containing, at most, one function key and possibly one or more options. Other arguments to tar are file or directory names specifying which files to dump or restore. In all cases, appearance of a directory name refers to the files and (recursively) subdirectories of that directory.
determines the locale's equivalent of
(for yes/no responses).
[Compaq] There is no way to ask for the
occurrence of a file.
[Compaq] Tape errors are handled ungracefully.
function can be slow.
[Compaq] The current limit on file name length is 256 bytes.
The current limit on file links (hard or soft) is 100 bytes.
[Compaq] There is no way selectively to follow symbolic links.
[Compaq] When extracting tapes created with the
functions, directory modification times
might not be set correctly.
[Compaq] After encountering tape write errors,
queries the operator about performing a rewrite. If the operator
requests a rewrite, a rewind is performed, followed by an attempt to rewrite
the data. In the event the no-rewind device is used, the user should always
load a new tape to avoid the possibility of overwriting previously written
The following exit values are returned:
An error occurred.
To create a tar archive to device /dev/rmt12, enter: tar cvfb /dev/rmt12 20 -e ./foo -C /usr/glenn . \ -e ./bar -e ./logs/logfile -C /usr/gaston .
The following environment variables affect the execution of
Provides a default value for the internationalization variables
that are unset or null. If
is unset or null, the corresponding value from the default locale is used.
If any of the internationalization variables contain an invalid setting, the
utility behaves as if none of the variables had been defined.
If set to a non-empty string value, overrides the values of
all the other internationalization variables.
Determines the locale for the interpretation of sequences
of bytes of text data as characters (for example, single-byte as opposed to
multibyte characters in arguments).
Determines the locale for the format and contents of diagnostic
messages written to standard error.
Determines the format of date and time strings output when
listing the contents of an archive.
Determines the location of message catalogs for the processing
Determines the time zone used with date and time strings.
Device name used with the
Temporary file used with the
Commands: cpio(1), pax(1)
Functions: chdir(2), umask(2)