.\" $NetBSD: tar.1,v 1.32 2011/06/19 07:34:24 wiz Exp $
.\"
.\" Copyright (c) 1996 SigmaSoft, Th. Lockert
.\" All rights reserved.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\"	OpenBSD: tar.1,v 1.28 2000/11/09 23:58:56 aaron Exp
.\"
.Dd June 18, 2011
.Dt TAR 1
.Os
.Sh NAME
.Nm tar
.Nd tape archiver
.Sh SYNOPSIS
.Nm tar
.Sm off
.Oo \&- Oc {crtux} Op Fl 014578befHhjklmOoPpqSvwXZz
.Sm on
.Op Ar archive
.Op Ar blocksize
.\" XXX how to do this right?
.Op Fl C Ar directory
.Op Fl s Ar replstr
.Op Fl T 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 , Fl Fl create
Create new archive, or overwrite an existing archive,
adding the specified files to it.
.It Fl r , Fl Fl append
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 , Fl Fl list
List contents of archive.
If any files are named on the
command line, only those files will be listed.
.It Fl u , Fl Fl update
Alias for
.Fl r .
.It Fl x , Fl Fl extract , Fl Fl get
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" , Fl Fl block-size 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 63 violate the
.Tn POSIX
standard and will not be portable to all systems.
.It Fl e
Stop after first error.
.It Fl f Ar archive , Fl Fl file Ar archive
Filename where the archive is stored.
Defaults to
.Pa /dev/rst0 .
If the archive is of the form:
.Ar [[user@]host:]file
then the archive will be processed using
.Xr rmt 8 .
.It Fl h , Fl Fl dereference
Follow symbolic links as if they were normal files
or directories.
.It Fl j, Fl Fl bzip2, Fl Fl bunzip2
Use
.Xr bzip2 1
for compression of the archive.
This option is a GNU extension.
.It Fl k , Fl Fl keep-old-files
Keep existing files; don't overwrite them from archive.
.It Fl l , Fl Fl one-file-system
Do not descend across mount points.
.\" should be '-X'
.It Fl m , Fl Fl modification-time
Do not preserve modification time.
.It Fl O
When creating and appending to an archive, write old-style (non-POSIX) archives.
When extracting from an archive, extract to standard output.
.It Fl o , Fl Fl portability , Fl Fl old-archive
Don't write directory information that the older (V7) style
.Nm
is unable to decode.
This implies the
.Fl O
flag.
.It Fl p , Fl Fl preserve-permissions , Fl Fl preserve
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 , Fl Fl fast-read
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 , Fl Fl sparse
This flag has no effect as
.Nm
always generates sparse files.
.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/[gps]
As in
.Xr ed 1 ,
.Cm old
is a basic regular expression and
.Cm new
can contain an ampersand (\*[Am]), \en (where n is a digit) back-references,
or subexpression matching.
The
.Cm old
string may also contain
.Aq 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 \*[Lt]original pathname\*[Gt] \*[Gt]\*[Gt] \*[Lt]new pathname\*[Gt]
File or archive member names that substitute to the empty string
are not selected and will be skipped.
The substitutions are applied by default to the destination hard and symbolic
links.
The optional trailing
.Cm s
prevents the substitutions from being performed on symbolic link destinations.
.It Fl v
Verbose operation mode.
.It Fl w , Fl Fl interactive , Fl Fl confirmation
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 Fl xz
Compress/decompress archive using 
.Xr xz  1 .
.It Fl z , Fl Fl gzip , Fl Fl gunzip
Compress/decompress archive using
.Xr gzip 1 .
.It Fl B , Fl Fl read-full-blocks
Reassemble small reads into full blocks (For reading from 4.2BSD pipes).
.It Fl C Ar directory , Fl Fl directory 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.
This argument and its parameter may also appear in a file list specified by
.Fl T .
.It Fl H
Only follow symlinks given on command line.
.Pp
Note SysVr3/i386 picked up ISC/SCO UNIX compatibility which implemented
.Dq Fl F Ar file
which was defined as obtaining a list of command line switches and files
on which to operate from the specified file,
but SunOS-5 uses
.Dq Fl I Ar file
because they use
.Sq Fl F
to mean something else.
We might someday provide SunOS-5 compatibility
but it makes little sense to confuse things with ISC/SCO compatibility.
.\".It Fl L
.\"Do not follow any symlinks (do the opposite of
.\".Fl h ).
.It Fl P , Fl Fl absolute-paths
Do not strip leading slashes
.Pq Sq /
from pathnames.
The default is to strip leading slashes.
.It Fl T Ar file , Fl Fl files-from Ar file
Read the names of files to archive or extract from the given file, one
per line.
A line may also specify the positional argument
.Dq Fl C Ar directory .
.It Fl X Ar file , Fl Fl exclude-from Ar file
Exclude files matching the shell glob patterns listed in the given file.
.\" exclude should be '-E' and '-X' should be one-file-system
.Pp
Note that it would be more standard to use this option to mean ``do not
cross filesystem mount points.''
.It Fl Z , Fl Fl compress , Fl Fl uncompress
Compress archive using compress.
.It Fl Fl strict
Do not enable GNU tar extensions such as long filenames and long link names.
.It Fl Fl atime-preserve
Preserve file access times.
.It Fl Fl chroot
.Fn chroot
to the current directory before extracting files.
Use with
.Fl x
and
.Fl h
to make absolute symlinks relative to the current directory.
.It Fl Fl unlink
Ignored, only accepted for compatibility with other
.Nm
implementations.
.Nm
always unlinks files before creating them.
.It Fl Fl use-compress-program Ar program
Use the named program as the program to decompress the input.
.It Fl Fl force-local
Do not interpret filenames that contain a
.Sq \&:
as remote files.
.It Fl Fl insecure
Normally
.Nm
ignores filenames that contain
.Dq ..
as a path component.
With this option, files that contain
.Dq ..
can be processed.
.It Fl Fl no-recursion
Cause files of type directory being copied or archived, or archive members of
type directory being extracted, to match only the directory file or archive
member and not the file hierarchy rooted at the directory.
.El
.Pp
The options
.Op Fl 014578
can be used to select one of the compiled-in backup devices,
.Pa /dev/rstN .
.Sh FILES
.Bl -tag -width "/dev/rst0"
.It Pa /dev/rst0
default archive name
.El
.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 SEE ALSO
.Xr cpio 1 ,
.Xr pax 1
.Sh HISTORY
A
.Nm
command first appeared in
.At v7 .
.Sh AUTHORS
Keith Muller at the University of California, San Diego.