NAME

tar − tape archiver

SYNOPSIS

tar [ key ] [ name ... ]

DESCRIPTION

Tar saves and restores files on magtape.  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 with contents which were 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 entries. 

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

u The named files are added to the tape if they are either not already listed 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. 

o On output, tar normally places information specifying owner and modes of directories in the archive.  Former versions of tar, when encountering this information, give error message of the following form
"<name>/: cannot create". 
This option suppresses the directory information.

p This option commands to restore files to their original modes, ignoring the present umask(2).  Setuid and sticky information is also restored to the super-user. 

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 performs 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 only the name. 

w Causes tar to print the action to be taken followed by file name, and then waits for user confirmation. If a word beginning with ‘y’ is given, the action is performed. Any other input specifies not to perform any action. 

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, depending on which action is appropriate; thus, tar can be used as the beginning or end of a filter chain.  Tar can also be used to move hierarchies with the following 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 20 (the maximum). 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 Commands tar to indicate if it cannot resolve all of the links to the files dumped. If l is not specified, no error messages are printed. 

m Commands tar to not restore the modification times.  The mod time is the time of extraction. 

Previous restrictions concerning tar’s inability to properly handle blocked archives have been eliminated.

FILES

/dev/rmt? 
/tmp/tar\(**

DIAGNOSTICS

Complaints about bad key characters and tape read/write errors. 
Complaints if not enough memory is 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.

4th Berkeley Distribution  —  %W%%Q%%Y%