tar(1) tar(1)NAME tar - copy files to or from a tar archive SYNOPSIS tar [key] [file...] DESCRIPTION tar saves and restores files within an archive, which fre- quently is magnetic tape media or floppy disks. Its actions are controlled by the key argument. The key is a string of characters containing a maximum of one function letter and possibly one or more function modifiers. Other arguments to the command are files (or directory names) specifying which files are to be dumped or restored. In all cases, appearance of a directory name refers to the files and (recursively) subdirectories of that directory. tar does not follow symbolic links. The function portion of the key is specified by one of the following letters: r The named files are written on the end of the tape. This may not work on all media. It requires the abili- ty to ``seek''. The c function implies this function. x The named files are extracted from the tape. If a named file matches a directory whose contents had been written onto the tape, this directory is (recursively) extracted. If a named file on tape does not exist on the system, the file is created with the same mode as the one on tape, except that the set-user-ID and set- group-ID bits are not set unless you are superuser. If the files exist, their modes are not changed except for the bits described above. The owner, group, and modif- ication time are restored (if possible). If no files argument is given, the entire content of the tape is extracted. Note that if several files with the same name are on the tape, the last one overwrites all ear- lier ones. t The names of all the files on the tape are listed. u The named files are added to the tape if they are not already there or have been modified since last written on that tape. c Create a new tape; writing begins at the beginning of the tape, instead of after the last file. This command implies the r function. April, 1990 1
tar(1) tar(1)The following characters may be used in addition to the letter that selects the desired function. ns Where n is a tape drive number (0,...,7), and s is the density (l - low (800 bpi), m - medium (1600 bpi), or h - high (6250 bpi)). This modifier selects the drive on which the tape is mounted. The default is 0m. i Causes tar to ignore symbolic links. v Normally, tar does its work silently. The v (verbose) flag option causes it to type the name of each file it treats, preceded by the function letter. With the t function, v gives, in addition to the name, information about the tape entries. w 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 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 /dev/mt/0m. If the name of the file is -, tar writes to the standard output or reads from the standard input, whichever is appropriate. Thus, tar may be used as the head or tail of a pipeline. tar may 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 tape records. The default is 1, the maximum is 20. This flag option should only be used with raw magnetic tape archives (see f). The block size is determined automatically when reading tapes (key letters x and t). l Tells tar to complain if it cannot resolve all of the links to the files being dumped. If l is not speci- fied, 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 ex- traction. o Causes extracted files to take on the user and group identifier of the user running the program rather than those on the tape. If more than one flag is used that requires an argument, the arguments must be supplied in the same order that the flags 2 April, 1990
tar(1) tar(1)were specified. This version of tar is capable of writing more than one tape or disk. The user will be prompted to change media when necessary. The next two flag options are used for tapes; the last is for disks. d Causes tar to use the next argument as the tape's den- sity. The default density is 1600 bpi. s Causes tar to use the next argument as the tape's length in feet. The default length is 2300 feet. B Causes tar to use the next argument as the number of 512-byte blocks on the disk. EXAMPLES cd fromdir; tar cf - . | (cd todir; tar xf -) will copy directories from one directory tree (fromdir) to another (todir). FILES /usr/bin/tar /dev/rmt/* /dev/mt/* /tmp/tar* /bin/mkdir build directories during recovery /bin/pwd get working directory name SEE ALSO ar(1), cpio(1), dd(1), tp(1), dump.bsd(1M), tar(4). DIAGNOSTICS Complaints about bad key characters and tape read/write er- rors. Complaints that enough memory is not available to hold the link tables. BUGS There is no way to ask for the nth occurrence of a file. Tape errors are handled ungracefully. The u flag option can be slow. The b flag option should not be used with archives that are going to be updated. The current magnetic tape driver can- not backspace raw magnetic tape. If the archive is on a disk file, the b flag option should not be used at all, be- cause updating an archive stored on disk can destroy it. The current limit on filename length is 100 characters. Empty directories are skipped when creating a tar archive. Note that tar c0m is not the same as tar cm0. tar is unable to archive special devices. April, 1990 3