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BSDTAR(1) FreeBSD General Commands Manual BSDTAR(1)
NAME
tar -- manipulate tape archives
SYNOPSIS
tar [bundled-flags ] [<file> | <pattern> ...]
tar {-c} [options] [files | directories]
tar {-r | -u} -f archive-file [options] [files | directories]
tar {-t | -x} [options] [patterns]
DESCRIPTION
tar creates and manipulates streaming archive files.
The first synopsis form shows a ``bundled'' option word. This usage is
provided for compatibility with historical implementations. See COMPATI-
BILITY below for details.
The other synopsis forms show the preferred usage. The first option to
tar is a mode indicator from the following list:
-c Create a new archive containing the specified items.
-r Like -c, but new entries are appended to the archive. Note that
this only works on uncompressed archives stored in regular files.
The -f option is required.
-t List archive contents to stdout.
-u Like -r, but new entries are added only if they have a modifica-
tion date newer than the corresponding entry in the archive.
Note that this only works on uncompressed archives stored in reg-
ular files. The -f option is required.
-x Extract to disk from the archive. If a file with the same name
appears more than once in the archive, each copy will be
extracted, with later copies overwriting (replacing) earlier
copies.
In -c, -r, or -u mode, each specified file or directory is added to the
archive in the order specified on the command line. By default, the con-
tents of each directory are also archived.
In extract or list mode, the entire command line is read and parsed
before the archive is opened. The pathnames or patterns on the command
line indicate which items in the archive should be processed. Patterns
are shell-style globbing patterns as documented in tcsh(1).
OPTIONS
Unless specifically stated otherwise, options are applicable in all oper-
ating modes.
@archive
(c and r mode only) The specified archive is opened and the
entries in it will be appended to the current archive. As a sim-
ple example,
tar -c -f - newfile @original.tar
writes a new archive to standard output containing a file newfile
and all of the entries from original.tar. In contrast,
tar -c -f - newfile original.tar
creates a new archive with only two entries. Similarly,
tar -czf - --format pax @-
reads an archive from standard input (whose format will be deter-
mined automatically) and converts it into a gzip-compressed pax-
format archive on stdout. In this way, tar can be used to con-
vert archives from one format to another.
-b blocksize
Specify the block size, in 512-byte records, for tape drive I/O.
As a rule, this argument is only needed when reading from or
writing to tape drives, and usually not even then as the default
block size of 20 records (10240 bytes) is very common.
-C directory
In c and r mode, this changes the directory before adding the
following files. In x mode, change directories after opening the
archive but before extracting entries from the archive.
--check-links (-W check-links)
(c and r modes only) Issue a warning message unless all links to
each file are archived.
--exclude pattern (-W exclude=pattern)
Do not process files or directories that match the specified pat-
tern. Note that exclusions take precedence over patterns or
filenames specified on the command line.
--format format (-W format=format)
(c mode only) Use the specified format for the created archive.
Supported formats include ``cpio'', ``pax'', ``shar'', and
``ustar''. Other formats may also be supported; see
libarchive-formats(5) for more information about currently-sup-
ported formats.
-f file
Read the archive from or write the archive to the specified file.
The filename can be - for standard input or standard output. If
not specified, the default tape device will be used. (On
FreeBSD, the default tape device is /dev/sa0.)
--fast-read (-W fast-read)
(x and t mode only) Extract or list only the first archive entry
that matches each pattern or filename operand. Exit as soon as
each specified pattern or filename has been matched. By default,
the archive is always read to the very end, since there can be
multiple entries with the same name and, by convention, later
entries overwrite earlier entries. This option is provided as a
performance optimization.
-H (c and r mode only) Symbolic links named on the command line will
be followed; the target of the link will be archived, not the
link itself.
-h (c and r mode only) Synonym for -L.
-I Synonym for -T.
--include pattern (-W include=pattern)
Process only files or directories that match the specified pat-
tern. Note that exclusions specified with --exclude take prece-
dence over inclusions. If no inclusions are explicitly speci-
fied, all entries are processed by default. The --include option
is especially useful when filtering archives. For example, the
command
tar -c -f new.tar --include='*foo*' @old.tgz
creates a new archive new.tar containing only the entries from
old.tgz containing the string `foo'.
-j (c mode only) Compress the resulting archive with bzip2(1). In
extract or list modes, this option is ignored. Note that, unlike
other tar implementations, this implementation recognizes bzip2
compression automatically when reading archives.
-k (x mode only) Do not overwrite existing files. In particular, if
a file appears more than once in an archive, later copies will
not overwrite earlier copies.
-L (c and r mode only) All symbolic links will be followed. Nor-
mally, symbolic links are archived as such. With this option,
the target of the link will be archived instead.
-l If POSIXLY_CORRECT is specified in the environment, this is a
synonym for the --check-links option. Otherwise, an error will
be displayed. Users who desire behavior compatible with GNU tar
should use the --one-file-system option instead.
-m (x mode only) Do not extract modification time. By default, the
modification time is set to the time stored in the archive.
-n (c, r, u modes only) Do not recursively archive the contents of
directories.
--newer date (-W newer=date)
(c, r, u modes only) Only include files and directories newer
than the specified date. This compares ctime entries.
--newer-mtime date (-W newer-mtime=date)
(c, r, u modes only) Like --newer, except it compares mtime
entries instead of ctime entries.
--newer-than file (-W newer-than=file)
(c, r, u modes only) Only include files and directories newer
than the specified file. This compares ctime entries.
--newer-mtime-than file (-W newer-mtime-than=file)
(c, r, u modes only) Like --newer-than, except it compares mtime
entries instead of ctime entries.
--nodump (-W nodump)
(c and r modes only) Honor the nodump file flag by skipping this
file.
--null (-W null)
(use with -I, -T, or -X) Filenames or patterns are separated by
null characters, not by newlines. This is often used to read
filenames output by the -print0 option to find(1).
-O (x, t modes only) In extract (-x) mode, files will be written to
standard out rather than being extracted to disk. In list (-t)
mode, the file listing will be written to stderr rather than the
usual stdout.
-o (x mode only) Use the user and group of the user running the pro-
gram rather than those specified in the archive. Note that this
has no significance unless -p is specified, and the program is
being run by the root user. In this case, the file modes and
flags from the archive will be restored, but ACLs or owner infor-
mation in the archive will be discarded.
--one-file-system (-W one-file-system)
(c, r, and u modes) Do not cross mount points.
-P Preserve pathnames. By default, absolute pathnames (those that
begin with a / character) have the leading slash removed both
when creating archives and extracting from them. Also, tar will
refuse to extract archive entries whose pathnames contain .. or
whose target directory would be altered by a symlink. This
option suppresses these behaviors.
-p (x mode only) Preserve file permissions. Attempt to restore the
full permissions, including owner, file modes, file flags and
ACLs, if available, for each item extracted from the archive. By
default, newly-created files are owned by the user running tar,
the file mode is restored for newly-created regular files, and
all other types of entries receive default permissions. If tar
is being run by root, the default is to restore the owner unless
the -o option is also specified.
--strip-components count (-W strip-components=count)
(x and t mode only) Remove the specified number of leading path
elements. Pathnames with fewer elements will be silently
skipped. Note that the pathname is edited after checking inclu-
sion/exclusion patterns but before security checks.
-T filename
In x or t mode, tar will read the list of names to be extracted
from filename. In c mode, tar will read names to be archived
from filename. The special name ``-C'' on a line by itself will
cause the current directory to be changed to the directory speci-
fied on the following line. Names are terminated by newlines
unless --null is specified. Note that --null also disables the
special handling of lines containing ``-C''.
-U (x mode only) Unlink files before creating them. Without this
option, tar overwrites existing files, which preserves existing
hardlinks. With this option, existing hardlinks will be broken,
as will any symlink that would affect the location of an
extracted file.
-v Produce verbose output. In create and extract modes, tar will
list each file name as it is read from or written to the archive.
In list mode, tar will produce output similar to that of ls(1).
Additional -v options will provide additional detail.
-W longopt=value
Long options (preceded by --) are only supported directly on sys-
tems that have the getopt_long(3) function. The -W option can be
used to access long options on systems that do not support this
function.
-w Ask for confirmation for every action.
-X filename
Read a list of exclusion patterns from the specified file. See
--exclude for more information about the handling of exclusions.
-y (c mode only) Compress the resulting archive with bzip2(1). In
extract or list modes, this option is ignored. Note that, unlike
other tar implementations, this implementation recognizes bzip2
compression automatically when reading archives.
-z (c mode only) Compress the resulting archive with gzip(1). In
extract or list modes, this option is ignored. Note that, unlike
other tar implementations, this implementation recognizes gzip
compression automatically when reading archives.
ENVIRONMENT
The following environment variables affect the execution of tar:
LANG The locale to use. See environ(7) for more information.
POSIXLY_CORRECT
If this environment variable is defined, the -l option will be
interpreted in accordance with ISO/IEC 9945-1:1996
(``POSIX.1'').
TAPE The default tape device. The -f option overrides this.
TZ The timezone to use when displaying dates. See environ(7) for
more information.
FILES
/dev/sa0 The default tape device, if not overridden by the TAPE envi-
ronment variable or the -f option.
EXIT STATUS
The tar utility exits 0 on success, and >0 if an error occurs.
EXAMPLES
The following creates a new archive called file.tar that contains two
files source.c and source.h:
tar -czf file.tar source.c source.h
To view a detailed table of contents for this archive:
tar -tvf file.tar
To extract all entries from the archive on the default tape drive:
tar -x
To move file hierarchies, invoke tar as
tar -cf - -C srcdir . | tar -xpBf - -C destdir
or more traditionally
cd srcdir ; tar -cf - . | (cd destdir ; tar -xpBf -)
In create mode, the list of files and directories to be archived can also
include directory change instructions of the form -Cfoo/baz and archive
inclusions of the form @archive-file. For example, the command line
tar -c -f new.tar foo1 @old.tgz -C/tmp foo2
will create a new archive new.tar. tar will read the file foo1 from the
current directory and add it to the output archive. It will then read
each entry from old.tgz and add those entries to the output archive.
Finally, it will switch to the /tmp directory and add foo2 to the output
archive.
The --newer and --newer-mtime switches accept a variety of common date
and time specifications, including ``12 Mar 2005 7:14:29pm'',
``2005-03-12 19:14'', ``5 minutes ago'', and ``19:14 PST May 1''.
COMPATIBILITY
The bundled-arguments format is supported for compatibility with historic
implementations. It consists of an initial word (with no leading - char-
acter) in which each character indicates an option. Arguments follow as
separate words. The order of the arguments must match the order of the
corresponding characters in the bundled command word. For example,
tar tbf 32 file.tar
specifies three flags t, b, and f. The b and f flags both require argu-
ments, so there must be two additional items on the command line. The 32
is the argument to the b flag, and file.tar is the argument to the f
flag.
The mode options c, r, t, u, and x and the options b, f, l, m, o, v, and
w comply with SUSv2.
For maximum portability, scripts that invoke tar should use the bundled-
argument format above, should limit themselves to the c, t, and x modes,
and the b, f, m, v, and w options.
On systems that support getopt_long(), additional long options are avail-
able to improve compatibility with other tar implementations.
SECURITY
Certain security issues are common to many archiving programs, including
tar. In particular, carefully-crafted archives can request that tar
extract files to locations outside of the target directory. This can
potentially be used to cause unwitting users to overwrite files they did
not intend to overwrite. If the archive is being extracted by the supe-
ruser, any file on the system can potentially be overwritten. There are
three ways this can happen. Although tar has mechanisms to protect
against each one, savvy users should be aware of the implications:
o Archive entries can have absolute pathnames. By default, tar
removes the leading / character from filenames before restoring
them to guard against this problem.
o Archive entries can have pathnames that include .. components.
By default, tar will not extract files containing .. components
in their pathname.
o Archive entries can exploit symbolic links to restore files to
other directories. An archive can restore a symbolic link to
another directory, then use that link to restore a file into that
directory. To guard against this, tar checks each extracted path
for symlinks. If the final path element is a symlink, it will be
removed and replaced with the archive entry. If -U is specified,
any intermediate symlink will also be unconditionally removed.
If neither -U nor -P is specified, tar will refuse to extract the
entry.
To protect yourself, you should be wary of any archives that come from
untrusted sources. You should examine the contents of an archive with
tar -tf filename
before extraction. You should use the -k option to ensure that tar will
not overwrite any existing files or the -U option to remove any pre-
existing files. You should generally not extract archives while running
with super-user privileges. Note that the -P option to tar disables the
security checks above and allows you to extract an archive while preserv-
ing any absolute pathnames, .. components, or symlinks to other directo-
ries.
SEE ALSO
bzip2(1), cpio(1), gzip(1), mt(1), pax(1), shar(1), libarchive(3),
libarchive-formats(5), tar(5)
STANDARDS
There is no current POSIX standard for the tar command; it appeared in
ISO/IEC 9945-1:1996 (``POSIX.1'') but was dropped from IEEE Std
1003.1-2001 (``POSIX.1''). The options used by this implementation were
developed by surveying a number of existing tar implementations as well
as the old POSIX specification for tar and the current POSIX specifica-
tion for pax.
The ustar and pax interchange file formats are defined by IEEE Std
1003.1-2001 (``POSIX.1'') for the pax command.
HISTORY
A tar command appeared in Seventh Edition Unix. There have been numerous
other implementations, many of which extended the file format. John
Gilmore's pdtar public-domain implementation (circa November, 1987) was
quite influential, and formed the basis of GNU tar. GNU tar was included
as the standard system tar in FreeBSD beginning with FreeBSD 1.0.
This is a complete re-implementation based on the libarchive(3) library.
BUGS
POSIX and GNU violently disagree about the meaning of the -l option.
Because of the potential for disaster if someone expects one behavior and
gets the other, the -l option is deliberately broken in this implementa-
tion.
The -C dir option may differ from historic implementations.
All archive output is written in correctly-sized blocks, even if the out-
put is being compressed. Whether or not the last output block is padded
to a full block size varies depending on the format and the output
device. For tar and cpio formats, the last block of output is padded to
a full block size if the output is being written to standard output or to
a character or block device such as a tape drive. If the output is being
written to a regular file, the last block will not be padded. Many com-
pressors, including gzip(1) and bzip2(1), complain about the null padding
when decompressing an archive created by tar, although they still extract
it correctly.
The compression and decompression is implemented internally, so there may
be insignificant differences between the compressed output generated by
tar -czf - file
and that generated by
tar -cf - file | gzip
The default should be to read and write archives to the standard I/O
paths, but tradition (and POSIX) dictates otherwise.
The r and u modes require that the archive be uncompressed and located in
a regular file on disk. Other archives can be modified using c mode with
the @archive-file extension.
To archive a file called @foo or -foo you must specify it as ./@foo or
./-foo, respectively.
In create mode, a leading ./ is always removed. A leading / is stripped
unless the -P option is specified.
There needs to be better support for file selection on both create and
extract.
There is not yet any support for multi-volume archives or for archiving
sparse files.
Converting between dissimilar archive formats (such as tar and cpio)
using the @- convention can cause hard link information to be lost.
(This is a consequence of the incompatible ways that different archive
formats store hardlink information.)
There are alternative long options for many of the short options that are
deliberately not documented.
FreeBSD 6.1 April 13, 2004 FreeBSD 6.1
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