NAME

tar − tape archiver

SYNOPSIS

tar [ key ] [ name ... ]

DESCRIPTION

Tar saves and restores files.  Tar may be used to transfer files between systems, or to save a collection of files into another file on the same system. 

Tar’s 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 file 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. 

x The named files are extracted from the tape.  If the 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 file argument is given, the entire content of the tape is extracted.  Note that if multiple entries specifying the same file are on the tape, the last one overwrites all earlier. 

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

u The named files are added to the tape if either they are not already there or have been modified since last put on the tape. 

c Create a new tape; writing begins on the beginning of the tape instead of after the last file.  This command implies r. 

The following characters may be used in addition to the letter which selects the function desired. 

0,...,7 This modifier selects an alternate drive on which the tape is mounted.  (The default is drive 0 at 1600 bpi, which is normally /dev/rmt8.) 

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 file name, then wait for user confirmation. If a word beginning with ’y’ is given, the action is performed. Any other input means don’t do it. 

f causes tar to use the next argument as the name of the archive instead of /dev/rmt?.  If the name of the file is ’−’, 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 Tar can also be used to move hierarchies (see EXAMPLE). 

b causes tar to use the next argument as the blocking factor for tape records.  The default is 20, the maximum is 40.  This option can be used to specify record length on raw magnetic tape archives or to cause more efficient data transfer on raw floppy disk archives.  If not specified, the block size is determined automatically when reading. 

l tells tar to complain if it cannot resolve all of the links to the files dumped. If this is not specified, no error messages are printed. 

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

Previous restrictions dealing with tar’s inability to properly handle blocked archives have been lifted.

EXAMPLE

cd fromdir; tar cf - . | (cd todir; tar xf -)

will copy directories from one directory tree to another. 

FILES

/dev/rmt? 
/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 current limit on file name length is 100 characters.

7th Edition  —  1/29/82