NAME

tar − tape file archiver

SYNOPSIS

tar [ key ] [ files ]

DESCRIPTION

Tar saves and restores files on magnetic tape.  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 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. 

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.  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.  The owner, modification time, and mode 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 earlier ones. 

t The names of the specified files are listed each time that they occur on the tape.  If no files argument is given, all the names 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. 

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 tape is mounted.  The default is 1. 

v Normally, tar does its work silently.  The v (verbose) 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 tape entries than just the name. 

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 /dev/mt?.  If the name of the file is −, 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 tape records.  The default is 1, the maximum is 20.  This option should only be used with raw magnetic tape archives (see f above).  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 specified, no error messages are printed. 

m tells tar to not restore the modification times.  The modification time of the file will be the time of extraction. 

FILES

/dev/mt? 
/tmp/tar∗

DIAGNOSTICS

Complaints about bad key characters and tape read/write errors. 
Complaints if enough memory is not available to hold the link tables.

BUGS

There is no way to ask for the n-th occurrence of a file.
Tape errors are handled ungracefully.
The u option can be slow. 
The b option should not be used with archives that are going to be updated.  The current magnetic tape driver cannot backspace raw magnetic tape.  If the archive is on a disk file, the b option should not be used at all, because updating an archive stored on disk can destroy it. 
The current limit on file-name length is 100 characters.