tar(1)tar(1)NAMEtar - Manipulates tape archives
SYNOPSIStar function_key[bBfFEhilLmpPsSvVwzn] [n | o] [option_argument...] [-e
exception]... [-C directory]... [file...]
tar -function_key[options] [option_argument]... [n | o] [option_argu‐
ment...] [-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
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
tar: XCU5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
FUNCTION KEYS
[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.
OPTIONS
[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 ar‐
chives. 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 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; nei‐
ther 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 infor‐
mation 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 ker‐
nel 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 origi‐
nal 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 immedi‐
ately following this option contains a list of file names sepa‐
rated 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 (ver‐
bose) 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 begin‐
ning 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 extrac‐
tion 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 inter‐
spersed within the list of file names. All other options must be spec‐
ified together (with no separating spaces) before -e, -C, and the file
list. For all options that require arguments, the arguments must fol‐
low the string of options and be ordered in the same way as the speci‐
fied options.
[Tru64 UNIX] Previous restrictions on the tar command's ability to
properly handle blocked archives have been lifted.
DESCRIPTION
The tar command is used to save and restore data from traditional for‐
mat 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
[Tru64 UNIX] You must have the tape command authorization to import or
export data to removable media (magnetic tapes, and so on). A full dis‐
cussion of security restrictions is contained in the sU_NOMAP. You can‐
not directly access device files used for import and export on the
trusted system.
[Tru64 UNIX] Do not use the tar command to transfer directory hierar‐
chies; use the mltape command instead.
NOTES
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 func‐
tion 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 re‐
write, 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 previ‐
ously written archives. [Tru64 UNIX] Socket files are ignored while
archiving through thetar.
EXIT STATUS
The following exit values are returned: Successful completion. An
error occurred.
EXAMPLES
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/log‐
file -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 ar‐
chive 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 con‐
tents, 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
The following environment variables affect the execution of tar: Pro‐
vides 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 vari‐
ables contain an invalid setting, the utility behaves as if none of the
variables had been defined. If set to a non-empty string value, over‐
rides 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 multi‐
byte characters in arguments). Determines the locale for the format
and contents of diagnostic messages written to standard error. Deter‐
mines the format of date and time strings output when listing the con‐
tents 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.
FILES
Device name used with the n option. Temporary file used with the u
function.
SEE ALSO
Commands: cpio(1), pax(1)
Functions: chdir(2), umask(2)
Files: tar(4)
Standards: standards(5)
Security
tar(1)
