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).
Note
[Tru64 UNIX] 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/ntape/tape0
Under the new implementation, this command becomes tar
xbfp 20 /dev/ntape/tape0
or tar -xb 20 -f /dev/ntape/tape0 -p
Interfaces documented on this reference page conform to
industry standards as follows:
tar: XCU5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
[Tru64 UNIX] The function performed by tar is specified
by one of the following key letters: Creates a new
archive. When writing to a tape device, tar begins from
the current tape position. Writes the named files at the
end of the specified archive. If the archive is on tape,
tar 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, tar
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.
[Tru64 UNIX] 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). [Tru64
UNIX] 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. [Tru64 UNIX] 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/ntape/tapen. (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 -) [Tru64 UNIX] 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 are not archived. [Tru64
UNIX] 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. [Tru64 UNIX] 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. [Tru64
UNIX] 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. [Tru64
UNIX] 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. [Tru64 UNIX] Allows tar
headers to be created with file names that cannot be nullterminated
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
[Tru64 UNIX] This option suppresses the directory
information. It also prevents archiving special
files and FIFOs that earlier versions of tar would
not be able to extract properly. (Although anyone
can archive special files, only a user who has
mknod kernel authorization (who has superuser
authority) can extract them from the archives).
When o is used for reading, it causes the extracted
file to take on the User and Group ID (UID and GID)
of the user running the program, rather than those
of the tape. This is the default for the ordinary
user.
[Tru64 UNIX] This option is mutually exclusive
with the n option (that is, new vs. old). When
specified, each of these options turns off the
other; neither option is turned on by default, however.
[Tru64 UNIX] Restores files to their original
modes, ignoring the present umask. Set-user-ID
and sticky information will also be restored if the
user is superuser (has chown kernel authorization).
[Tru64 UNIX] Specifies the prefix that is to be
stripped off of the file names archived to or
extracted from tape. (See also the s option).
[Tru64 UNIX] Tells tar to strip off any leading
slashes from pathnames during extraction. This is
useful when restoring a tape that was created on a
system with a different file system structure.
(See also the P option.) [Tru64 UNIX] The named
file immediately following this option contains a
list of file names separated by newlines. This
list is added to (c function key, r function key)
or extracted from (x function key) the archive.
The -R option is incompatible with the -C option.
[Tru64 UNIX] Specifies the number of 512-byte
blocks per volume (first form), independent of the
tape blocking factor. You can also specify the
size of the tape in feet, and optionally density,
by using the second form. Feet are assumed to be
11 inches long to be conservative. This option
lets you deal more easily with multivolume tape
archives, where tar must be able to determine how
many blocks fit on each volume.
[Tru64 UNIX] Tape drives vary in density capabilities.
The density argument is used in the amount
of data that tar can fit on a tape. Normally tar
does its work silently. The v (verbose) option
makes tar print the name of each file it processes
as specified by the function key. With the t function
key, the verbose option gives more information
about the tape entries than just their names.
[Tru64 UNIX] Prevents any extended attributes from
being archived with associated files. This option
is particularly useful for archiving files that are
to be restored with previous versions of tar and
cpio. Causes tar to print the action to be taken
followed by the name of the file, and then to wait
for the user's confirmation. If a word beginning
with y, or the locale's definition of an affirmative
response, is given, the action is performed.
If any other input is given, the action is not performed.
[Tru64 UNIX] Positions the tape after the
EOF marker on extraction or listing. The z option
lets the user extract or list tapes that have multiple
archives on them one after the other without
error as a result of the tape not being positioned
correctly for the next extraction or listing.
[Tru64 UNIX] Selects /dev/ntape/tapen (the variable
n means 0-9) as the tape drive on which the
tape is mounted. The default is drive 0
(/dev/ntape/tape0). [Tru64 UNIX] Adds the following
argument to a list of exception strings that
prevent files whose names match exactly from being
archived. When used with the -C option, the list of
exceptions becomes relative to each new directory.
[Tru64 UNIX] If a file name is preceded by -C, tar
performs a chdir() to that file name. This allows
multiple directories not related by a close common
parent to be archived using short relative pathnames.
For example, to archive files from
/usr/include and from /etc, one might use the following
command line: tar c -C /usr/include . -C
/etc .
[Tru64 UNIX] Therefore, if you do not specify an
absolute file name, the file name is considered
relative to the previous -C directory. When you
specify this option multiple times on the command
line, make sure to specify subsequent -C directories
relative to the preceding -C directories.
[Tru64 UNIX] If an error occurs while trying to
change to the requested directory, subsequent file
names on the command line that are not absolute
(that is, have no leading / (slash)) are skipped
until the next -C option is specified.
[Tru64 UNIX] 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.
[Tru64 UNIX] Previous restrictions on the tar command's
ability to properly handle blocked archives have been
lifted.
The tar command is used to save and restore data from traditional
format tar archives.
[Tru64 UNIX] The actions of tar on a trusted system are
controlled by the way the Information System Security
Officer (ISSO) has set up the Device Assignment database.
Refer to the detailed description of import and export in
the Security.
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.
The LC_MESSAGES variable determines the locale's
equivalent of y or n (for yes/no responses).
Security Restrictions [Toc] [Back]
[Tru64 UNIX] You must have the tape command authorization
to import or export data to removable media (magnetic
tapes, and so on). A full discussion of security restrictions
is contained in the sU_NOMAP. You cannot directly
access device files used for import and export on the
trusted system.
[Tru64 UNIX] Do not use the tar command to transfer
directory hierarchies; use the mltape command instead.
The tar command is marked as LEGACY in XCU Issue 5.
[Tru64 UNIX] There is no way to ask for the nth occurrence
of a file. [Tru64 UNIX] Tape errors are handled
ungracefully. [Tru64 UNIX] The u function can be slow.
[Tru64 UNIX] The current limit on file name length is 256
bytes. The current limit on file links (hard or soft) is
100 bytes. [Tru64 UNIX] There is no way selectively to
follow symbolic links. [Tru64 UNIX] When extracting
tapes created with the r or u functions, directory modification
times might not be set correctly. [Tru64
UNIX] After encountering tape write errors, tar 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
archives. [Tru64 UNIX] Socket files are ignored while
archiving through thetar.
The following exit values are returned: Successful completion.
An error occurred.
To create a tar archive to device /dev/ntape/tape0, enter:
tar cvfb /dev/ntape/tape0 20 -e ./foo -C /usr/glenn . \ -e
./bar -e ./logs/logfile -C /usr/gaston .
The preceding command line specifies a blocking
factor of 20. The resulting archive contains all
files and directories in /usr/glenn except for file
and all files and directories in /usr/gaston except
for files To create a tar archive as a disk file,
enter: tar cvf /tmp/mybackup.tar -e $HOME/zeugma
$HOME
The preceding command line uses the f option to
create a tar archive named mybackup.tar in the /tmp
directory. The archive contains the user's home
directory and its contents, including all subdirectories
and files except the zeugma subdirectory and
its contents, which are excluded by the -e (exception)
option. The following example extracts one
directory 'APXUSRGD' (whose path in the supp.tar
archive is strips off the path prefix
(./DOCS/HTML/SUPPDOCS/) and stores the directory in
the users's current directory: tar Pxvf
./DOCS/HTML/SUPPDOCS/ supp.tar \ ./DOCS/HTML/SUPPDOCS/APXUSRGD
ENVIRONMENT VARIABLES [Toc] [Back] The following environment variables affect the execution
of tar: Provides a default value for the internationalization
variables that are unset or null. If LANG 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
of LC_MESSAGES. Determines the time zone used with date
and time strings.
Device name used with the n option. Temporary file used
with the u function.
Commands: cpio(1), pax(1)
Functions: chdir(2), umask(2)
Files: tar(4)
Standards: standards(5)
Security
tar(1)
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