.\"	$OpenBSD: tar.1,v 1.39 2002/06/09 05:33:42 todd Exp $
.\"
.\" Copyright (c) 1996 SigmaSoft, Th. Lockert
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
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.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"      This product includes software developed by SigmaSoft, Th. Lockert.
.\" 4. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\"	$OpenBSD: tar.1,v 1.39 2002/06/09 05:33:42 todd Exp $
.\"
.Dd February 7, 2001
.Dt TAR 1
.Os
.Sh NAME
.Nm tar
.Nd tape archiver
.Sh SYNOPSIS
.Nm tar
.Sm off
.Oo \&- Oc {crtux} Op befhmopqsvwzHLOPXZ014578
.Sm on
.Op Ar blocksize
.Op Ar archive
.Op Ar replstr
.\" XXX how to do this right?
.Op Fl C Ar directory
.Op Fl I Ar file
.Op Ar file ...
.Sh DESCRIPTION
The
.Nm
command creates, adds files to, or extracts files from an
archive file in
.Dq tar
format.
A tar archive is often stored on a magnetic tape, but can be
stored equally well on a floppy, CD-ROM, or in a regular disk file.
.Pp
One of the following flags must be present:
.Bl -tag -width Ar
.It Fl c
Create new archive, or overwrite an existing archive,
adding the specified files to it.
.It Fl r
Append the named new files to existing archive.
Note that this will only work on media on which an end-of-file mark
can be overwritten.
.It Fl t
List contents of archive.
If any files are named on the
command line, only those files will be listed.
.It Fl u
Alias for
.Fl r .
.It Fl x
Extract files from archive.
If any files are named on the
command line, only those files will be extracted from the
archive.
If more than one copy of a file exists in the
archive, later copies will overwrite earlier copies during
extraction.
The file mode and modification time are preserved
if possible.
The file mode is subject to modification by the
.Xr umask 2 .
.El
.Pp
In addition to the flags mentioned above, any of the following
flags may be used:
.Bl -tag -width Ar
.It Fl b Ar "blocking factor"
Set blocking factor to use for the archive.
.Nm
uses 512 byte blocks.
The default is 20, the maximum is 126.
Archives with a blocking factor larger than 63 violate the
.Tn POSIX
standard and will not be portable to all systems.
.It Fl e
Stop after the first error.
.It Fl f Ar archive
Filename where the archive is stored.
Defaults to
.Pa /dev/rst0 .
.It Fl h
Follow symbolic links as if they were normal files
or directories.
In extract mode this means that a directory entry in the archive
will not overwrite an existing symbolic link, but rather what the
link ultimately points to.
.It Fl m
Do not preserve modification time.
.It Fl O
Write old-style (non-POSIX) archives.
.It Fl o
Don't write directory information that the older (V7) style
.Nm
is unable to decode.
This implies the
.Fl O
flag.
.It Fl p
Preserve user and group ID as well as file mode regardless of
the current
.Xr umask 2 .
The setuid and setgid bits are only preserved if the user is
the superuser.
Only meaningful in conjunction with the
.Fl x
flag.
.It Fl q
Select the first archive member that matches each
.Ar pattern
operand.
No more than one archive member is matched for each
.Ar pattern .
When members of type directory are matched, the file hierarchy rooted at that
directory is also matched.
.It Fl s Ar replstr
Modify the file or archive member names specified by the
.Ar pattern
or
.Ar file
operands according to the substitution expression
.Ar replstr ,
using the syntax of the
.Xr ed 1
utility regular expressions.
The format of these regular expressions are:
.Dl /old/new/[gp]
As in
.Xr ed 1 ,
.Cm old
is a basic regular expression and
.Cm new
can contain an ampersand (&), \\n (where n is a digit) back-references,
or subexpression matching.
The
.Cm old
string may also contain
.Dv <newline>
characters.
Any non-null character can be used as a delimiter (/ is shown here).
Multiple
.Fl s
expressions can be specified.
The expressions are applied in the order they are specified on the
command line, terminating with the first successful substitution.
The optional trailing
.Cm g
continues to apply the substitution expression to the pathname substring
which starts with the first character following the end of the last successful
substitution.
The first unsuccessful substitution stops the operation of the
.Cm g
option.
The optional trailing
.Cm p
will cause the final result of a successful substitution to be written to
.Dv standard error
in the following format:
.Dl <original pathname> >> <new pathname>
File or archive member names that substitute to the empty string
are not selected and will be skipped.
.It Fl v
Verbose operation mode.
.It Fl w
Interactively rename files.
This option causes
.Nm
to prompt the user for the filename to use when storing or
extracting files in an archive.
.It Fl z
Compress archive using gzip.
.It Fl C Ar directory
This is a positional argument which sets the working directory for the
following files.
When extracting, files will be extracted into
the specified directory; when creating, the specified files will be matched
from the directory.
.It Fl H
Follow symlinks given on command line only.
.It Fl L
Follow all symlinks.
In extract mode this means that a directory entry in the archive
will not overwrite an existing symbolic link, but rather what the
link ultimately points to.
.It Fl P
Do not strip leading slashes
.Pq Sq /
from pathnames.
The default is to strip leading slashes.
.It Fl I Ar file
This is a positional argument which reads the names of files to
archive or extract from the given file, one per line.
.It Fl X
Do not cross mount points in the file system.
.It Fl Z
Compress archive using compress.
.El
.Pp
The options
.Op Fl 014578
can be used to select one of the compiled-in backup devices,
.Pa /dev/rstN .
.Sh EXAMPLES
.Cm $ tar c bonvole sekve
.Pp
Creates an archive on the default tape drive, containing the files named
.Pa bonvole
and
.Pa sekve
.
.Pp
.Cm $ tar zcf foriru.tar.gz bonvole sekve
.Pp
Outputs a
.Xr gzip 1
compressed archive containing the files
.Pa bonvole
and
.Pa sekve
to a file called
.Pa foriru.tar.gz
.Pp
.Cm $ tar zcvf backup.tar.gz *.c
.Pp
Verbosely creates an archive, called
.Pa backup.tar.gz
, of all files matching the shell
.Xr glob 3
function
.Pa *.c
.Pp
.Cm $ tar tvzf backup.tar.gz '*.jpeg'
.Pp
Verbosely lists, but does not extract, all files ending in
.Pa .jpeg
from an compressed archive named
.Pa backup.tar.gz .
Note that the glob pattern has been quoted to avoid expansion by the shell.
.Pp
For more detailed examples, see
.Xr pax 1
.Pp
.Sh DIAGNOSTICS
.Nm
will exit with one of the following values:
.Bl -tag -width 2n
.It 0
All files were processed successfully.
.It 1
An error occurred.
.El
.Pp
Whenever
.Nm
cannot create a file or a link when extracting an archive or cannot
find a file while writing an archive, or cannot preserve the user
ID, group ID, file mode, or access and modification times when the
.Fl p
option is specified, a diagnostic message is written to standard
error and a non-zero exit value will be returned, but processing
will continue.
In the case where
.Nm
cannot create a link to a file,
.Nm
will not create a second copy of the file.
.Pp
If the extraction of a file from an archive is prematurely terminated
by a signal or error,
.Nm
may have only partially extracted the file the user wanted.
Additionally, the file modes of extracted files and directories may
have incorrect file bits, and the modification and access times may
be wrong.
.Pp
If the creation of an archive is prematurely terminated by a signal
or error,
.Nm
may have only partially created the archive which may violate the
specific archive format specification.
.Sh FILES
.Bl -tag -width "/dev/rst0"
.It Pa /dev/rst0
default archive name
.El
.Sh ENVIRONMENT
.Bl -tag -width Fl
.It Ev TMPDIR
Path in which to store temporary files.
.It Ev TAPE
Default tape device to use instead of
.Pa /dev/rst0 .
.El
.Sh SEE ALSO
.Xr cpio 1 ,
.Xr pax 1
.Sh AUTHORS
Keith Muller at the University of California, San Diego.
.Sh HISTORY
A
.Nm
command first appeared in
.At v7 .
.Sh CAVEATS
The
.Fl L
flag is not portable to other versions of
.Nm
where it may have a different meaning.