TAR(1) INTERACTIVE UNIX System TAR(1)
NAME
tar - file archiver
SYNOPSIS
tar [ key ] [ files ]
DESCRIPTION
tar saves and restores files to and from an archive medium,
which is typically a storage device such as a floppy disk, a
tape, or a regular file. Its actions are controlled by the
key argument. The key is a string of characters containing
at most one function letter and possibly one or more func-
tion modifiers. Valid function letters are c, t, x, u, and
r. Other arguments to the command are files (or directory
names) specifying which files are to be backed up or
restored. In all cases, appearance of a directory name
refers to the files and (recursively) subdirectories of that
directory.
The function portion of the key is specified by one of the
following letters:
r The named files are written to the end of the
archive.
x The named files are extracted from the archive. If
a named file matches a directory whose contents have
been written onto the archive, this directory is
(recursively) extracted. The owner, modification
time, and mode are restored (if possible). If no
files argument is given, the contents of the archive
are extracted. Note that if several files with the
same name are on the archive, the last file
overwrites all earlier ones.
t The names of the specified files are listed each
time that they occur on the archive. If no files
argument is given, all the names on the archive are
listed.
u The named files are added to the archive if they are
not already there, or if they have been modified
since last written on that archive.
c Creates a new archive; writing begins at the begin-
ning of the archive, instead of after the last file.
e Prevents files from being split across volumes
(tapes or floppy disks). If there is not enough
room on the present volume for a given file, tar
prompts for a new volume. This is only valid when
the -k option is also specified on the command line.
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The following characters may be used in addition to the
letter that selects the desired function:
0,...,7 This modifier selects the drive on which the archive
is mounted. The default drive is 1.
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v Normally, tar does its work silently. The v (ver-
bose) option causes it to type the name of each file
it treats, preceded by the function letter. With
the t function, v gives more information about the
archive entries than just the name.
o Causes the extracted files to assume the owner and
group ID of the user running the program rather than
those on the archive tape.
w Causes tar to print the action to be taken, followed
by the name of the file, and then wait for the
user's confirmation. If a word beginning with `y'
is given, the action is performed. Any other input
means ``no.''
f Causes tar to use the next argument as the name of
the archive instead of the default device in
/etc/tar/default. If the name of the file is a dash
(-), tar writes to the standard output or reads from
the standard input, whichever is appropriate. Thus,
tar can be used as the head or tail of a pipeline.
Tar can also be used to move hierarchies with the
command:
cd fromdir; tar cf - . | (cd todir; tar xf -)
b Causes tar to use the next argument as the blocking
factor for archive records. The default is 2, the
maximum is 20. This option should only be used with
raw magnetic tape archives (see f above). The
number of bytes in a block is BSIZE as defined in
/usr/include/sys/param.h.
F Causes tar to use the next argument as the name of a
file from which succeeding arguments are taken. The
dash (-) is not a valid argument here.
l Tells tar to print an error message if it cannot
resolve all of the links to the files being backed
up. If l is not specified, no error messages are
printed.
m Tells tar not to restore the modification times.
The modification time of the file will be the time
of extraction.
k Causes tar to use the next argument as the size of
an archive volume in kilobytes. The minimum value
allowed is 250. This option is useful when the
archive is not intended for a magnetic tape device,
but for some fixed size device, such as floppy disk
(See f above). Very large files are split into
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``extents'' across volumes. When restoring from a
multivolume archive, tar only prompts for a new
volume if a split file has been partially restored.
n Indicates the archive device is not a magnetic tape.
The k option implies this. Listing and extracting
the contents of an archive are sped because tar can
seek over files it wishes to skip. Sizes are
printed in kilobytes instead of tape blocks.
p Indicates that files are extracted using their ori-
ginal permissions. It is possible that a non-
super-user may be unable to extract files because of
the permissions associated with the files or direc-
tories being extracted.
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EXAMPLES
If the name of a floppy disk device is /dev/dsk/f1q15dt, a
tar format file can be created on this device by typing
tar cvfk /dev/dsk/f1q15dt 360 files
where files are the names of files you want archived and 360
is the capacity of the floppy disk in kilobytes. Note that
arguments to key letters are given in the same order as the
key letters themselves; thus, the fk key letters have
corresponding arguments, /dev/dsk/f1q15dt and 360. Note
that if a file is a directory, the contents of the directory
are archived recursively. To print a listing of the
archive, type
tar tvf /dev/dsk/f1q15dt
At some later time you may want to extract the files from
the floppy archive. You can do this by typing
tar xvf /dev/dsk/f1q15dt
The above command extracts all files from the archive using
the same pathnames as those of the original archive. Because
of this behavior, it is best to save archive files with
relative pathnames rather than absolute ones since directory
permissions may not let you read the files into the speci-
fied absolute directories.
In the above examples, the v option is used to confirm the
reading or writing of archive files on the screen. Also, a
normal file could be substituted for the floppy device,
/dev/dsk/f1q15dt, in the examples.
FILES
/etc/default/tar Default devices
/tmp/tar*
SEE ALSO
cpio(1), ls(1).
DIAGNOSTICS
Prints an error message about bad key characters and archive
read/write errors.
Prints an error message if not enough memory is available to
hold the link tables.
NOTES
There is no way to ask for the nth occurrence of a file.
The u option can be slow.
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The b option should not be used with archives that are going
to be updated. If the archive is on a disk file, the b
option should not be used at all because updating an archive
stored on a disk can destroy it. To update (r or u option)
a tar archive, do not use raw magtape and do not use the b
option. This applies both when updating and when first
creating an archive.
The limit on filename length is 100 characters.
When archiving a directory that contains subdirectories, tar
will only access those subdirectories that are within 17
levels of nesting. Subdirectories at higher levels will be
ignored after tar displays an error message.
Systems with 1K byte file systems cannot specify raw disk
devices unless the b option is used to specify an even
number of blocks. This means that you cannot update a raw-
mode disk partition.
Don't do:
tar xfF - -
This would imply taking two things from the standard input
at the same time.
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