Go to the first, previous, next, last section, table of contents.
This chapter is about how one invokes the GNU
tar command, from
the command synopsis (see section 3.1 General Synopsis of
tar). There are numerous options,
and many styles for writing them. One mandatory option specifies
tar should perform (see section 3.4.1 Operations),
other options are meant to detail how this operation should be performed
(see section 3.4.2
tar Options). Non-option arguments are not always interpreted
the same way, depending on what the operation is.
You will find in this chapter everything about option styles and rules for
writing them (see section 3.3 The Three Option Styles). On the other hand, operations and options
are fully described elsewhere, in other chapters. Here, you will find
only synthetic descriptions for operations and options, together with
pointers to other parts of the
Some options are so special they are fully described right in this
chapter. They have the effect of inhibiting the normal operation of
tar or else, they globally alter the amount of feedback the user
receives about what is going on. These are the --help and
--version (see section 3.5 GNU
tar documentation), --verbose (-v) (see section 3.6 Checking
and --interactive (-w) options (see section 3.7 Asking for Confirmation During Operations).
tar program is invoked as either one of:
tar option... [name]... tar letter... [argument]... [option]... [name]...
The second form is for when old options are being used.
You can use
tar to store files in an archive, to extract them from
an archive, and to do other types of archive manipulation. The primary
tar, which is called the operation, specifies
which action to take. The other arguments to
tar are either
options, which change the way
tar performs an operation,
or file names or archive members, which specify the files or members
tar is to act on.
You can actually type in arguments in any order, even if in this manual
the options always precede the other arguments, to make examples easier
to understand. Further, the option stating the main operation mode
tar main command) is usually given first.
Each name in the synopsis above is interpreted as an archive member
name when the main command is one of --compare (--diff, -d), --delete,
--extract (--get, -x), --list (-t) or --update (-u). When naming
archive members, you must give the exact name of the member in the
archive, as it is printed by --list (-t). For --append (-r)
and --create (-c), these name arguments specify the names
of either files or directory hierarchies to place in the archive.
These files or hierarchies should already exist in the file system,
prior to the execution of the
tar interprets relative file names as being relative to the
tar will make all file names relative
(by removing leading slashes when archiving or restoring files),
unless you specify otherwise (using the --absolute-names (-P)
option). See section 6.8.2 Absolute File Names, for more information about
If you give the name of a directory as either a file name or a member
tar acts recursively on all the files and directories
beneath that directory. For example, the name `/' identifies all
the files in the filesystem to
The distinction between file names and archive member names is especially
important when shell globbing is used, and sometimes a source of confusion
for newcomers. See section 6.5 Wildcards Patterns and Matching, for more information about globbing.
The problem is that shells may only glob using existing files in the
file system. Only
tar itself may glob on archive members, so when
needed, you must ensure that wildcard characters reach
being interpreted by the shell first. Using a backslash before `*'
or `?', or putting the whole argument between quotes, is usually
sufficient for this.
Even if names are often specified on the command line, they can also be read from a text file in the file system, using the --files-from=file-of-names (-T file-of-names) option.
If you don't use any file name arguments, --append (-r),
--delete and --concatenate (--catenate, -A) will do nothing, while
--create (-c) will usually yield a diagnostic and inhibit
execution. The other operations of
tar (--list (-t),
--extract (--get, -x), --compare (--diff, -d), and --update (-u)) will act
on the entire contents of the archive.
Besides successful exits, GNU
tar may fail for many reasons.
Some reasons correspond to bad usage, that is, when the
command is improperly written.
Errors may be encountered later, while encountering an error
processing the archive or the files. Some errors are recoverable,
in which case the failure is delayed until
tar has completed
all its work. Some errors are such that it would not meaningful,
or at least risky, to continue processing:
tar then aborts
processing immediately. All abnormal exits, whether immediate or
delayed, should always be clearly diagnosed on
a line stating the nature of the error.
tar returns only a few exit statuses. I'm really
aiming simplicity in that area, for now. If you are not using the
--compare (--diff, -d) option, zero means that everything went well, besides
maybe innocuous warnings. Nonzero means that something went wrong.
Right now, as of today, "nonzero" is almost always 2, except for
remote operations, where it may be 128.
tar has a total of eight operating modes which allow you to
perform a variety of tasks. You are required to choose one operating
mode each time you employ the
tar program by specifying one, and
only one operation as an argument to the
tar command (two lists
of four operations each may be found at section 2.4 The Three Most Frequently Used Operations and
section 4.2.1 The Five Advanced
tar Operations). Depending on circumstances, you may also wish to
customize how the chosen operating mode behaves. For example, you may
wish to change the way the output looks, or the format of the files that
you wish to archive may require you to do something special in order to
make the archive look right.
You can customize and control
tar's performance by running
tar with one or more options (such as --verbose (-v), which
we used in the tutorial). As we said in the tutorial, options are
tar which are (as their name suggests) optional.
Depending on the operating mode, you may specify one or more options.
Different options will have different effects, but in general they all
change details of the operation, such as archive format, archive name,
or level of user interaction. Some options make sense with all
operating modes, while others are meaningful only with particular modes.
You will likely use some options frequently, while you will only use
others infrequently, or not at all. (A full list of options is
available in see section 3.4 All
tar options are case sensitive. For example, the
options `-T' and `-t' are different; the first requires an
argument for stating the name of a file providing a list of names,
while the second does not require an argument and is another way to
write --list (-t).
In addition to the eight operations, there are many options to
tar, and three different styles for writing both: long (mnemonic)
form, short form, and old style. These styles are discussed below.
Both the options and the operations can be written in any of these three
There are three styles for writing operations and options to the command
tar. The different styles were developed at
different times during the history of
tar. These styles will be
presented below, from the most recent to the oldest.
Some options must take an argument. (For example, --file=archive-name (-f archive-name) takes
the name of an archive file as an argument. If you do not supply an
archive file name,
tar will use a default, but this can be
confusing; thus, we recommend that you always supply a specific archive
file name.) Where you place the arguments generally depends on
which style of options you choose. We will detail specific information
relevant to each option style in the sections on the different option
styles, below. The differences are subtle, yet can often be very
important; incorrect option placement can cause you to overwrite a
number of important files. We urge you to note these differences, and
only use the option style(s) which makes the most sense to you until you
feel comfortable with the others.
Each option has at least one long (or mnemonic) name starting with two
dashes in a row, e.g. `--list'. The long names are more clear than
their corresponding short or old names. It sometimes happens that a
single mnemonic option has many different different names which are
synonymous, such as `--compare' and `--diff'. In addition,
long option names can be given unique abbreviations. For example,
`--cre' can be used in place of `--create' because there is no
other mnemonic option which begins with `cre'. (One way to find
this out is by trying it and seeing what happens; if a particular
abbreviation could represent more than one option,
tar will tell
you that that abbreviation is ambiguous and you'll know that that
abbreviation won't work. You may also choose to run `tar --help'
to see a list of options. Be aware that if you run
tar with a
unique abbreviation for the long name of an option you didn't want to
use, you are stuck;
tar will perform the command as ordered.)
Mnemonic options are meant to be obvious and easy to remember, and their meanings are generally easier to discern than those of their corresponding short options (see below). For example:
$ tar --create --verbose --blocking-factor=20 --file=/dev/rmt0
gives a fairly good set of hints about what the command does, even
for those not fully acquainted with
Mnemonic options which require arguments take those arguments
immediately following the option name; they are introduced by an equal
sign. For example, the `--file' option (which tells the name
tar archive) is given a file such as `archive.tar'
as argument by using the notation `--file=archive.tar' for the
Most options also have a short option name. Short options start with a single dash, and are followed by a single character, e.g. `-t' (which is equivalent to `--list'). The forms are absolutely identical in function; they are interchangeable.
The short option names are faster to type than long option names.
Short options which require arguments take their arguments immediately following the option, usually separated by white space. It is also possible to stick the argument right after the short option name, using no intervening space. For example, you might write `-f archive.tar' or `-farchive.tar' instead of using `--file=archive.tar'. Both `--file=archive-name' and `-f archive-name' denote the option which indicates a specific archive, here named `archive.tar'.
Short options' letters may be clumped together, but you are not
required to do this (as compared to old options; see below). When short
options are clumped as a set, use one (single) dash for them all, e.g.
tar -cvf'. Only the last option in such a set is allowed
to have an argument(1).
When the options are separated, the argument for each option which requires an argument directly follows that option, as is usual for Unix programs. For example:
$ tar -c -v -b 20 -f /dev/rmt0
If you reorder short options' locations, be sure to move any arguments that belong to them. If you do not move the arguments properly, you may end up overwriting files.
Like short options, old options are single letters. However, old options
must be written together as a single clumped set, without spaces separating
them or dashes preceding them(2). This set
of letters must be the first to appear on the command line, after the
tar program name and some white space; old options cannot appear
anywhere else. The letter of an old option is exactly the same letter as
the corresponding short option. For example, the old option `t' is
the same as the short option `-t', and consequently, the same as the
mnemonic option `--list'. So for example, the command `tar
cv' specifies the option `-v' in addition to the operation `-c'.
When options that need arguments are given together with the command, all the associated arguments follow, in the same order as the options. Thus, the example given previously could also be written in the old style as follows:
$ tar cvbf 20 /dev/rmt0
Here, `20' is the argument of `-b' and `/dev/rmt0' is the argument of `-f'.
On the other hand, this old style syntax makes it difficult to match option letters with their corresponding arguments, and is often confusing. In the command `tar cvbf 20 /dev/rmt0', for example, `20' is the argument for `-b', `/dev/rmt0' is the argument for `-f', and `-v' does not have a corresponding argument. Even using short options like in `tar -c -v -b 20 -f /dev/rmt0' is clearer, putting all arguments next to the option they pertain to.
If you want to reorder the letters in the old option argument, be sure to reorder any corresponding argument appropriately.
This old way of writing
tar options can surprise even experienced
users. For example, the two commands:
tar cfz archive.tar.gz file tar -cfz archive.tar.gz file
are quite different. The first example uses `archive.tar.gz' as the value for option `f' and recognizes the option `z'. The second example, however, uses `z' as the value for option `f'---probably not what was intended.
Old options are kept for compatibility with old versions of
This second example could be corrected in many ways, among which the following are equivalent:
tar -czf archive.tar.gz file tar -cf archive.tar.gz -z file tar cf archive.tar.gz -z file
As far as we know, all
tar programs, GNU and non-GNU, support
old options. GNU
tar supports them not only for historical
reasons, but also because many people are used to them. For
compatibility with Unix
tar, the first argument is always
treated as containing command and option letters even if it doesn't
start with `-'. Thus, `tar c' is equivalent to `tar
-c:' both of them specify the --create (-c) command to create an
All three styles may be intermixed in a single
tar command, so
long as the rules for each style are fully respected(3) version 1.11.6, a bug prevented intermixing old style options
with mnemonic options in some cases.}. Old style options and either of the
modern styles of options may be mixed within a single
However, old style options must be introduced as the first arguments only,
following the rule for old options (old options must appear directly
tar command and some white space). Modern options may
be given only after all arguments to the old options have been collected.
If this rule is not respected, a modern option might be falsely interpreted
as the value of the argument to one of the old style options.
For example, all the following commands are wholly equivalent, and illustrate the many combinations and orderings of option styles.
tar --create --file=archive.tar tar --create -f archive.tar tar --create -farchive.tar tar --file=archive.tar --create tar --file=archive.tar -c tar -c --file=archive.tar tar -c -f archive.tar tar -c -farchive.tar tar -cf archive.tar tar -cfarchive.tar tar -f archive.tar --create tar -f archive.tar -c tar -farchive.tar --create tar -farchive.tar -c tar c --file=archive.tar tar c -f archive.tar tar c -farchive.tar tar cf archive.tar tar f archive.tar --create tar f archive.tar -c tar fc archive.tar
On the other hand, the following commands are not equivalent to the previous set:
tar -f -c archive.tar tar -fc archive.tar tar -fcarchive.tar tar -farchive.tarc tar cfarchive.tar
These last examples mean something completely different from what the
user intended (judging based on the example in the previous set which
uses long options, whose intent is therefore very clear). The first
four specify that the
tar archive would be a file named
`-c', `c', `carchive.tar' or `archive.tarc',
respectively. The first two examples also specify a single non-option,
name argument having the value `archive.tar'. The last
example contains only old style option letters (repeating option
`c' twice), not all of which are meaningful (eg., `.',
`h', or `i'), with no argument value.
The coming manual sections contain an alphabetical listing of all
tar operations and options, with brief descriptions and cross
references to more in-depth explanations in the body of the manual.
They also contain an alphabetically arranged table of the short option
forms with their corresponding long option. You can use this table as
a reference for deciphering
tar commands in scripts.
tararchives to the end of the archive. See section 4.2.5 Combining Archives with
tararchive. See section 2.6 How to Create Archives.
tarstrips an initial `/' from member names. This option disables that behavior.
tarto preserve the access time field in a file's inode when dumping it. Due to limitations in the
utimessystem call, the modification time field is also preserved, which may cause problems if the file is simultaneously being modified by another program.
tarwill back them up using simple or numbered backups, depending upon backup-type.
tarprints error messages for read errors with the block number in the archive file.
taruses to blocking x 512 bytes per record.
tarto read or write archives through
tarto print periodic checkpoint messages as it reads through the archive. Its intended for when you want a visual indication that
taris still running, but don't want to see `--verbose' output.
tarwill use the
compressprogram when reading or writing the archive. This allows you to directly act on archives while saving space.
tarwill archive the file that a symbolic link points to, rather than archiving the symlink.
tarwill change its current directory to dir before performing any operations. When this option is used during archive creation, it is order sensitive.
tarwill skip files that match pattern.
tarwill use the list of patterns in the file file.
tarwill use the file archive as the
tararchive it performs operations on, rather than
tar's compilation dependent default.
tarwill use the contents of file as a list of archive members or files to operate on, in addition to those specified on the command-line.
tarto interpret the filename given to `--file' as a local file, even if it looks like a remote tape drive name.
tararchive will have a group id of group, rather than the group from the source file. group is first decoded as a group symbolic name, but if this interpretation fails, it has to be a decimal numeric group ID. Also see the comments for the --owner=user option.
tarto read or write archives through
tarto directly operate on several kinds of compressed archives transparently.
tarwill print out a short message summarizing the operations and options to
tarwill ignore zeroed blocks in the archive, which normally signals EOF. See section 4.4.1 Options to Help Read Archives.
tarthat it is working with an old GNU-format incremental backup archive. It is intended primarily for backwards compatibility only.
taris performing multi-tape backups, script-file is run at the end of each tape.
tarshould ask the user for confirmation before performing potentially destructive options, such as overwriting files.
tarto write name as a name record in the archive. When extracting or listing archives,
tarwill only operate on archives that have a label matching the pattern specified in name.
tarcreates is a new GNU-format incremental backup, using snapshot-file to determine which files to backup. With other operations, informs
tarthat the archive is in incremental format.
tarwill use permissions for the archive members, rather than the permissions from the files. The program
taroption share the same syntax for what permissions might be. See section `File permissions' in GNU file utilities. This reference also has useful information for those not being overly familiar with the Unix permission system. Of course, permissions might be plainly specified as an octal number. However, by using generic symbolic modifications to mode bits, this allows more flexibility. For example, the value `a+rw' adds read and write permissions for everybody, while retaining executable bits on directories or on any other file already marked as executable.
tarthat it should create or otherwise operate on a multi-volume
tarwill only add files that have changed since date.
tarwill only add files whose contents have changed (as opposed to just `--newer', which will also back up files for which any status information has changed).
tarwill not recurse into directories unless a directory is explicitly named as an argument to
tararchive. This the default behavior for ordinary users; this option has an effect only for the superuser.
taris using the `--files-from' option, this option instructs
tarto expect filenames terminated with NUL, so
tarcan correctly work with file names that contain newlines.
tarthat it should use numeric user and group IDs when creating a
tarfile, rather than names.
tarfrom recursing into directories that are on different file systems from the current directory.
tarshould use user as the owner of members when creating archives, instead of the user associated with the source file. user is first decoded as a user symbolic name, but if this interpretation fails, it has to be a decimal numeric user ID. There is no value indicating a missing number, and `0' usually means
root. Some people like to force `0' as the value to offer in their distributions for the owner of files, because the
rootuser is anonymous anyway, so that might as well be the owner of anonymous archives. This option does not affect extraction from archives.
tarto create an archive that is compatible with Unix V7
tarto create a POSIX compliant
taris extracting an archive, it normally subtracts the users' umask from the permissions specified in the archive and uses that number as the permissions to create the destination file. Specifying this option instructs
tarthat it should use the permissions directly from the archive. See section 4.4.2 Changing How
tarshould reblock its input, for reading from pipes on systems with buggy implementations. See section 4.4.1 Options to Help Read Archives.
tarto use size bytes per record when accessing the archive.
tarto remove the source file from the file system after appending it to an archive.
tarthat is should use cmd to communicate with remote devices.
tarwhen running on machines with small amounts of memory. It informs
tarthat the list of file arguments has already been sorted to match the order of files in the archive. See section 4.4.1 Options to Help Read Archives.
tarwill attempt to preserve the owner specified in the
tararchive with this option present. This is the default behavior for the superuser; this option has an effect only for ordinary users.
tarto mention directories its skipping over when operating on a
tarwill skip extracting files in the archive until it finds one that matches name. See section 4.4.3 Coping with Scarce Resources.
taruses when backing up files from the default `~'.
taris writing as being num x 1024 bytes long.
tarwill extract files to stdout rather than to the file system. See section 4.4.2 Changing How
tarto remove the corresponding file from the file system before extracting it from the archive. See section 4.4.2 Changing How
tarto access the archive through prog, which is presumed to be a compression program of some sort.
tarshould be more verbose about the operations its performing. This option can be specified multiple times for some operations to increase the amount of information displayed.
tarwill print an informational message about what version it is and a copyright message, some credits, and then exit.
tarwill keep track of which volume of a multi-volume archive its working in file.
Here is an alphabetized list of all of the short option forms, matching them with the equivalent long option.
Being careful, the first thing is really checking that you are using GNU
tar, indeed. The --version option will generate a message
giving confirmation that you are using GNU
tar, with the precise
version of GNU
tar you are using.
tar identifies itself
and prints the version number to the standard output, then immediately
exits successfully, without doing anything else, ignoring all other
options. For example, `tar --version' might return:
tar (GNU tar) 1.13.17
The first occurrence of `tar' in the result above is the program
name in the package (for example,
rmt is another program), while
the second occurrence of `tar' is the name of the package itself,
containing possibly many programs. The package is currently named
`tar', after the name of the main program it contains(4) and
tar packages into a single one
which would be called
paxutils. So, who knows if, one of this days,
the --version would not yield `tar (GNU paxutils) 3.2'}.
Another thing you might want to do is checking the spelling or meaning
of some particular
tar option, without resorting to this manual,
for once you have carefully read it. GNU
tar has a short help
feature, triggerable through the --help option. By using this
tar will print a usage message listing all available
options on standard output, then exit successfully, without doing
anything else and ignoring all other options. Even if this is only a
brief summary, it may be several screens long. So, if you are not
using some kind of scrollable window, you might prefer to use something
$ tar --help | less
presuming, here, that you like using
less for a pager. Other
popular pagers are
pg. If you know about some
keyword which interests you and do not want to read all the
--help output, another common idiom is doing:
tar --help | grep keyword
for getting only the pertinent lines.
The perceptive reader would have noticed some contradiction in the previous paragraphs. It is written that both --version and --help print something, and have all other options ignored. In fact, they cannot ignore each other, and one of them has to win. We do not specify which is stronger, here; experiment if you really wonder!
The short help output is quite succinct, and you might have to get back
to the full documentation for precise points. If you are reading this
paragraph, you already have the
tar manual in some form. This
manual is available in printed form, as a kind of small book. It may
printed out of the GNU
tar distribution, provided you have TeX
already installed somewhere, and a laser printer around. Just configure
the distribution, execute the command `make dvi', then print
`doc/tar.dvi' the usual way (contact your local guru to know how).
tar has been conveniently installed at your place, this
manual is also available in interactive, hypertextual form as an Info
file. Just call `info tar' or, if you do not have the
info program handy, use the Info reader provided within GNU
Emacs, calling `tar' from the main Info menu.
There is currently no
man page for GNU
tar. If you observe
man page on the system you are running, either it does not
long to GNU
tar, or it has not been produced by GNU. Currently,
tar documentation is provided in Texinfo format only, if we
except, of course, the short result of tar --help.
tar performs most operations without reporting any
information to the user except error messages. When using
with many options, particularly ones with complicated or
difficult-to-predict behavior, it is possible to make serious mistakes.
tar provides several options that make observing
easier. These options cause
tar to print information as it
progresses in its job, and you might want to use them just for being
more careful about what is going on, or merely for entertaining
yourself. If you have encountered a problem when operating on an
archive, however, you may need more information than just an error
message in order to solve the problem. The following options can be
helpful diagnostic tools.
Normally, the --list (-t) command to list an archive prints just
the file names (one per line) and the other commands are silent.
When used with most operations, the --verbose (-v) option causes
tar to print the name of each file or archive member as it
is processed. This and the other options which make
status information can be useful in monitoring
With --create (-c) or --extract (--get, -x), --verbose (-v) used once
just prints the names of the files or members as they are processed.
Using it twice causes
tar to print a longer listing (reminiscent
of `ls -l') for each member. Since --list (-t) already prints
the names of the members, --verbose (-v) used once with --list (-t)
tar to print an `ls -l' type listing of the files
in the archive. The following examples both extract members with
long list output:
$ tar --extract --file=archive.tar --verbose --verbose $ tar xvv archive.tar
Verbose output appears on the standard output except when an archive is
being written to the standard output, as with `tar --create
--file=- --verbose' (`tar cfv -', or even `tar cv'---if the
installer let standard output be the default archive). In that case
tar writes verbose output to the standard error stream.
The --totals option--which is only meaningful when used with
tar to print the total
amount written to the archive, after it has been fully created.
The --checkpoint option prints an occasional message
tar reads or writes the archive. In fact, it print
directory names while reading the archive. It is designed for
those who don't need the more detailed (and voluminous) output of
--block-number (-R), but do want visual confirmation that
is actually making forward progress.
The --show-omitted-dirs option, when reading an archive--with --list (-t) or --extract (--get, -x), for example--causes a message to be printed for each directory in the archive which is skipped. This happens regardless of the reason for skipping: the directory might not have been named on the command line (implicitly or explicitly), it might be excluded by the use of the --exclude=pattern option, or some other reason.
If --block-number (-R) is used,
tar prints, along with every
message it would normally produce, the block number within the archive
where the message was triggered. Also, supplementary messages are
triggered when reading blocks full of NULs, or when hitting end of file on
the archive. As of now, if the archive if properly terminated with a NUL
block, the reading of the file may stop before end of file is met, so the
position of end of file will not usually show when --block-number (-R)
is used. Note that GNU
tar drains the archive before exiting when
reading the archive from a pipe.
This option is especially useful when reading damaged archives, since it helps pinpoint the damaged sections. It can also be used with --list (-t) when listing a file-system backup tape, allowing you to choose among several backup tapes when retrieving a file later, in favor of the tape where the file appears earliest (closest to the front of the tape).
tar carries out a command without stopping for
further instructions. In some situations however, you may want to
exclude some files and archive members from the operation (for instance
if disk or storage space is tight). You can do this by excluding
certain files automatically (see section 6 Choosing Files and Names for
tar), or by performing
an operation interactively, using the --interactive (-w) option.
tar also accepts `--confirmation' for this option.
When the --interactive (-w) option is specified, before
reading, writing, or deleting files,
tar first prints a message
for each such file, telling what operation it intends to take, then asks
for confirmation on the terminal. The actions which require
confirmation include adding a file to the archive, extracting a file
from the archive, deleting a file from the archive, and deleting a file
from disk. To confirm the action, you must type a line of input
beginning with `y'. If your input line begins with anything other
tar skips that file.
tar is reading the archive from the standard input,
tar opens the file `/dev/tty' to support the interactive
Verbose output is normally sent to standard output, separate from
other error messages. However, if the archive is produced directly
on standard output, then verbose output is mixed with errors on
stderr. Producing the archive on standard output may be used
as a way to avoid using disk space, when the archive is soon to be
consumed by another process reading it, say. Some people felt the need
of producing an archive on stdout, still willing to segregate between
verbose output and error output. A possible approach would be using a
named pipe to receive the archive, and having the consumer process to
read from that named pipe. This has the advantage of letting standard
output free to receive verbose output, all separate from errors.
Go to the first, previous, next, last section, table of contents.