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.TH TAR 1
.SH NAME
tar  \-  tape archiver
.SH SYNOPSIS
.B tar
[ key ] [ [ option ] name ... ]
.SH DESCRIPTION
.I Tar
saves and restores files
on magtape (historic) or to/from archive files (aka 'tar-files').
Its actions are controlled by the
.I key
argument.
The
.I 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, or 
options which affect how
.B tar
processes the following files/directories. Such options are conveniently
capitalized. 
In all cases, appearance of a directory name refers to
the files and (recursively) subdirectories of that directory.
.PP
In addition to files and directories, 
.B tar
will also dump and restore (hard) links, symbolic links and devices.
.PP
In order to inadvertent overwrites, 
.B tar
will not store absolute pathnames, but remove the leading '/' if present. 
.PP
The function portion of
the key is specified by one of the following letters:
.TP 8
.B  r
The named files
are written
on the end of the tape.
The
.B c
function implies this.
.TP 8
.B  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.
.TP 8
.B  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.
.TP 8
.B  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.
.TP 8
.B  c
Create a new tape; writing begins on the beginning
of the tape instead of after the last file.
This command implies
.BR r .
.PP
The following characters may be used in addition to the letter
which selects the function desired.
.TP 10
.B  v
Normally
.I tar
does its work silently.
The
.B v
(verbose)
option causes it to type the name of each file it treats
preceded by the function letter.
With the
.B t
function,
.B v
gives more information about the
tape entries than just the name.
.TP 10
.B  w
causes
.I 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.
.TP 10
.B f
causes 
.I tar
to use the next argument as the name of the archive instead
of (the historic default) /dev/mt1. 
If the name of the file is `\-', tar writes to
standard output or reads from standard input, whichever is
appropriate. Thus,
.I tar
can be used as the head or tail of a filter chain.
.I Tar
can also be used to move hierarchies with the command
.B cd fromdir; tar cf - . | (cd todir; tar xf -)
.TP 10
.B b
causes
.I 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
.B f
above).
The block size is determined automatically when reading
tapes (key letters `x' and `t').
.TP 10
.B l
tells
.I 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.
.TP 10
.B m
tells
.I tar
to not restore the modification times.
The mod time
will be the time of extraction.
.TP 10
.B h
tells 
.I tar
to follow symlinks; archive and dump the files they point to.
.TP 10
.B o
tells
.I tar
to be compatible with very old versions which did not store directories on
the tape at all. Instead, they were created as needed when extracting.
.TP 10
.B p
tells 
.I tar
to use the saved permissions of extracted files and directories instead of the 
currently set
.IR umode ,
which is the default unnless the current user is
.IR root .
.PP
.SH OPTIONS
In addition to keys, 
.I tar
supports a few options which may appear anywhere on the command line, and apply to
the arguments appearing after the option and its parameter.
.TP 10
.BR \-C \ directory
Change ('chdir') to the specified directory before continuing. This option applies
only when writing (keys `c', `r' and `u') tapes/tar-files, using this option
with the `x' or `t' keys have no meaning and is an error.
The directory change not only affects where 
.I tar
looks for files and directories to store, but also to the filenames they are store 
under on the tape. Used with care and smartness, this allows 
.I tar
to create a tape/tar-file that extracts into a completely different tree than the source.
.TP 10
\ \ 
This option may be repeated any number of times on the command line and applies
to the file/directory arguments following the option.
.TP 10
.BR \-X \ file/dir
Exclude: When creating a tape/tar-file, exclude this file/directory. This is particularly
convenient for excluding mountpoints from a save-set. Currently, only one such exclusion
may be specified, and - again currently - this option only works when creating tapes/tar-files.
Eventually the parameter specified with the 
.B \-X
option will be a file containing a list of the files and directories to exclude.
.TP 10
\ 
As is the case with all saved files and directories, a leading '/' will be automatically 
removed from excluded files/directories too.
.SH FILES
/dev/mt1
.br
/tmp/tar*
.SH DIAGNOSTICS
Complaints about bad key characters and tape read/write errors.
.br
Complaints if enough memory is not available to hold
the link tables.
.SH BUGS
.nf
- There is no way to ask for the \fIn\fR-th occurrence of a file.
.br
- Tape errors are handled ungracefully.
.br
- The \fBu\fR option can be slow.
.br
- The \fBb\fR option should not be used with archives that are going to be
updated. The current magtape driver cannot backspace raw magtape. If the
archive is on a disk-file, the \fBb\fR option should not be used at all, as
updating an archive stored in this manner can destroy it.
.br
- The limit on file name length (saved path) is 100 characters.
.br
- The \fB-X\fR option is very limited.
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