GNU tar is an archiving program designed to store multiple files
in a single file (an archive), and to manipulate such archives.
The archive can be either a regular file or a device (e.g. a tape
drive, hence the name of the program, which stands for tape
archiver), which can be located either on the local or on a
remote machine.
Option styles
Options to GNU tar can be given in three different styles. In
traditional style, the first argument is a cluster of option
letters and all subsequent arguments supply arguments to those
options that require them. The arguments are read in the same
order as the option letters. Any command line words that remain
after all options has been processed are treated as non-optional
arguments: file or archive member names.
For example, the c option requires creating the archive, the v
option requests the verbose operation, and the f option takes an
argument that sets the name of the archive to operate upon. The
following command, written in the traditional style, instructs
tar to store all files from the directory /etc into the archive
file etc.tar verbosely listing the files being archived:
tar cfv etc.tar /etc
In UNIX or short-option style, each option letter is prefixed
with a single dash, as in other command line utilities. If an
option takes argument, the argument follows it, either as a
separate command line word, or immediately following the option.
However, if the option takes an optional argument, the argument
must follow the option letter without any intervening whitespace,
as in -g/tmp/snar.db.
Any number of options not taking arguments can be clustered
together after a single dash, e.g. -vkp. Options that take
arguments (whether mandatory or optional), can appear at the end
of such a cluster, e.g. -vkpf a.tar.
The example command above written in the short-option style could
look like:
tar -cvf etc.tar /etc
or
tar -c -v -f etc.tar /etc
In GNU or long-option style, each option begins with two dashes
and has a meaningful name, consisting of lower-case letters and
dashes. When used, the long option can be abbreviated to its
initial letters, provided that this does not create ambiguity.
Arguments to long options are supplied either as a separate
command line word, immediately following the option, or separated
from the option by an equals sign with no intervening whitespace.
Optional arguments must always use the latter method.
Here are several ways of writing the example command in this
style:
tar --create --file etc.tar --verbose /etc
or (abbreviating some options):
tar --cre --file=etc.tar --verb /etc
The options in all three styles can be intermixed, although doing
so with old options is not encouraged.
Operation mode
The options listed in the table below tell GNU tar what operation
it is to perform. Exactly one of them must be given. Meaning of
non-optional arguments depends on the operation mode requested.
-A, --catenate, --concatenate
Append archive to the end of another archive. The
arguments are treated as the names of archives to append.
All archives must be of the same format as the archive
they are appended to, otherwise the resulting archive
might be unusable with non-GNU implementations of tar.
Notice also that when more than one archive is given, the
members from archives other than the first one will be
accessible in the resulting archive only if using the -i
(--ignore-zeros) option.
Compressed archives cannot be concatenated.
-c, --create
Create a new archive. Arguments supply the names of the
files to be archived. Directories are archived
recursively, unless the --no-recursion option is given.
-d, --diff, --compare
Find differences between archive and file system. The
arguments are optional and specify archive members to
compare. If not given, the current working directory is
assumed.
--delete
Delete from the archive. The arguments supply names of
the archive members to be removed. At least one argument
must be given.
This option does not operate on compressed archives.
There is no short option equivalent.
-r, --append
Append files to the end of an archive. Arguments have the
same meaning as for -c (--create).
-t, --list
List the contents of an archive. Arguments are optional.
When given, they specify the names of the members to list.
--test-label
Test the archive volume label and exit. When used without
arguments, it prints the volume label (if any) and exits
with status 0. When one or more command line arguments
are given. tar compares the volume label with each
argument. It exits with code 0 if a match is found, and
with code 1 otherwise. No output is displayed, unless
used together with the -v (--verbose) option.
There is no short option equivalent for this option.
-u, --update
Append files which are newer than the corresponding copy
in the archive. Arguments have the same meaning as with
-c and -r options. Notice, that newer files don't replace
their old archive copies, but instead are appended to the
end of archive. The resulting archive can thus contain
several members of the same name, corresponding to various
versions of the same file.
-x, --extract, --get
Extract files from an archive. Arguments are optional.
When given, they specify names of the archive members to
be extracted.
--show-defaults
Show built-in defaults for various tar options and exit.
No arguments are allowed.
-?, --help
Display a short option summary and exit. No arguments
allowed.
--usage
Display a list of available options and exit. No
arguments allowed.
--version
Print program version and copyright information and exit.
