TAR

Section: User Commands (1)
Updated: 5 November 1987
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NAME

tar - tape (or other media) file archiver  

SYNOPSIS

tar -[BcdDhiklmopRstvxzZ] [-b N] [-f F] [-T F] [ filename or regexp ... ]  

DESCRIPTION

tar provides a way to store many files into a single archive, which can be kept in another Unix file, stored on an I/O device such as tape, floppy, cartridge, or disk, sent over a network, or piped to another program. It is useful for making backup copies, or for packaging up a set of files to move them to another system.

tar has existed since Version 7 Unix with very little change. It has been proposed as the standard format for interchange of files among systems that conform to the IEEE P1003 ``Portable Operating System'' standard.

This version of tar supports some of the extensions which were proposed in the P1003 draft standards, including owner and group names, and support for named pipes, fifos, contiguous files, and block and character devices.

When reading an archive, this version of tar continues after finding an error. Previous versions required the `i' option to ignore checksum errors.  

OPTIONS

tar options can be specified in either of two ways. The usual Unix conventions can be used: each option is preceded by `-'; arguments directly follow each option; multiple options can be combined behind one `-' as long as they take no arguments. For compatability with the Unix tar program, the options may also be specified as ``keyletters,'' wherein all the option letters occur in the first argument to tar, with no `-', and their arguments, if any, occur in the second, third, ... arguments. Examples:

Normal: tar -f arcname -cv file1 file2

Old: tar fcv arcname file1 file2

At least one of the -c, -t, -d, or -x options must be included. The rest are optional.

Files to be operated upon are specified by a list of file names, which follows the option specifications (or can be read from a file by the -T option). Specifying a directory name causes that directory and all the files it contains to be (recursively) processed. If a full path name is specified when creating an archive, it will be written to the archive without the initial "/", to allow the files to be later read into a different place than where they were dumped from, and a warning will be printed. If files are extracted from an archive which contains full path names, they will be extracted relative to the current directory and a warning message printed.

When extracting or listing files, the ``file names'' are treated as regular expressions, using mostly the same syntax as the shell. The shell actually matches each substring between ``/''s separately, while tar matches the entire string at once, so some anomalies will occur; e.g. ``*'' or ``?'' can match a ``/''. To specify a regular expression as an argument to tar, quote it so the shell will not expand it.

-a
Set the archived bit of the file as it is added to the archive. (Amiga only)
-A
Do not add the file to the archive if its archived bit is set. Applies only to regular files, directories are always dumped (Amiga only)
-b N
Specify a blocking factor for the archive. The block size will be N x 512 bytes. Larger blocks typically run faster and let you fit more data on a tape. The default blocking factor is set when tar is compiled, and is typically 20. There is no limit to the maximum block size, as long as enough memory can be allocated for it, and as long as the device containing the archive can read or write that block size.
-B
When reading an archive, reblock it as we read it. Normally, tar reads each block with a single read(2) system call. This does not work when reading from a pipe or network socket under Berkeley Unix; read(2) only gives as much data as has arrived at the moment. With this option, it will do multiple read(2)s to fill out to a record boundary, rather than reporting an error. This option is default when reading an archive from standard input, or over a network.
-c
Create an archive from a list of files.
-d
Diff an archive against the files in the file system. Reports differences in file size, mode, uid, gid, and contents. If a file exists on the tape, but not in the file system, that is reported. This option needs further work to be really useful.
-D
When creating an archive, only dump each directory itself; don't dump all the files inside the directory. In conjunction with find(1), this is useful in creating incremental dumps for archival backups, similar to those produced by dump(8).
-f F
Specify the filename of the archive. If the specified filename is ``-'', the archive is read from the standard input or written to the standard output. If the -f option is not used, and the environment variable TAPE exists, its value will be used; otherwise, a default archive name (which was picked when tar was compiled) is used. The default is normally set to the ``first'' tape drive or other transportable I/O medium on the system.
If the filename contains a colon before a slash, it is interpreted as a ``hostname:/file/name'' pair. tar will invoke the commands rsh and dd to access the specified file or device on the system hostname. If you need to do something unusual like rsh with a different user name, use ``-f -'' and pipe it to rsh manually.
-h
When creating an archive, if a symbolic link is encountered, dump the file or directory to which it points, rather than dumping it as a symbolic link. (Does not apply to Amiga)
-i
When reading an archive, ignore blocks of zeros in the archive. Normally a block of zeros indicates the end of the archive, but in a damaged archive, or one which was created by appending several archives, this option allows tar to continue. It is not on by default because there is garbage written after the zeroed blocks by the Unix tar program. Note that with this option set, tar will read all the way to the end of the file, eliminating problems with multi-file tapes.
-k
When extracting files from an archive, keep existing files, rather than overwriting them with the version from the archive.
-l
When dumping the contents of a directory to an archive, stay within the local file system of that directory. This option only affects the files dumped because they are in a dumped directory; files named on the command line are always dumped, and they can be from various file systems. This is useful for making ``full dump'' archival backups of a file system, as with the dump(8) command. Files which are skipped due to this option are mentioned on the standard error.
-m
When extracting files from an archive, set each file's modified timestamp to the current time, rather than extracting each file's modified timestamp from the archive.
-o
When creating an archive, write an old format archive, which does not include information about directories, pipes, fifos, contiguous files, or device files, and specifies file ownership by uid's and gid's rather than by user names and group names. In most cases, a ``new'' format archive can be read by an ``old'' tar program without serious trouble, so this option should seldom be needed.
-p
When extracting files from an archive, restore them to the same permissions that they had in the archive. If -p is not specified, the current umask limits the permissions of the extracted files. See umask(2). (Does not apply to Amiga version, permission always completely restored)
-R
With each message that tar produces, print the record number within the archive where the message occurred. This option is especially useful when reading damaged archives, since it helps to pinpoint the damaged section.
-s
When specifying a list of filenames to be listed or extracted from an archive, the -s flag specifies that the list is sorted into the same order as the tape. This allows a large list to be used, even on small machines, because the entire list need not be read into memory at once. Such a sorted list can easily be created by running ``tar -t'' on the archive and editing its output.
-t
List a table of contents of an existing archive. If file names are specified, just list files matching the specified names. The listing appears on the standard output.
-T F
Rather than specifying file names or regular expressions as arguments to the tar command, this option specifies that they should be read from the file F, one per line. If the file name specified is ``-'', the list is read from the standard input. This option, in conjunction with the -s option, allows an arbitrarily large list of files to be processed, and allows the list to be piped to tar.
-v
Be verbose about the files that are being processed or listed. Normally, archive creation, file extraction, and differencing are silent, and archive listing just gives file names. The -v option causes an ``ls -l''-like listing to be produced. The output from -v appears on the standard output except when creating an archive (since the new archive might be on standard output), where it goes to the standard error output.
-x
Extract files from an existing archive. If file names are specified, just extract files matching the specified names, otherwise extract all the files in the archive.
-z or -Z
The archive should be compressed as it is written, or decompressed as it is read, using the compress(1) program. This option works on I/O devices and over the network, as well as on disk files; data to or from such devices is reblocked using a ``dd'' command to enforce the specified (or default) block size. The default compression parameters are used; if you need to override them, avoid the ``z'' option and compress it yourself. (Not currently supported on Amiga)
 

SEE ALSO

shar(1), tar(5), compress(1), ar(1), arc(1), cpio(1), dump(8), restore(8), restor(8), rsh(1), dd(1), find(1)  

BUGS

The r, u, w, X, l, F, C, and digit options of Unix tar are not supported.

Multiple-tape (or floppy) archives should be supported, but so far no clean way has been implemented.

A bug in the Bourne Shell usually causes an extra newline to be written to the standard error when using compressed or remote archives.

A bug in ``dd'' prevents turning off the ``x+y records in/out'' messages on the standard error when ``dd'' is used to reblock or transport an archive.

 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
SEE ALSO
BUGS
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Time: 22:58:44 GMT, January 09, 2023