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NAME

tar - manipulate tape archives

CONTENTS

Synopsis
Description
Options
Environment
Files
Exit Status
Examples
Compatibility
Security
See Also
Standards
History
Bugs

SYNOPSIS

tar [bundled-flags<args>] [<file|<pattern...>>] tar
.Brq Fl c [options] [files | directories] tar
.Brq Fl r | Fl u -f archive-file [options] [files | directories] tar
.Brq Fl t | Fl 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 COMPATIBILITY 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 modification date newer than the corresponding entry in the archive. Note that this only works on uncompressed archives stored in regular 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 contents 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 operating 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 simple example,

-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,

-c -f - newfile original.tar

creates a new archive with only two entries. Similarly,

-czf ---format pax @ -

reads an archive from standard input (whose format will be determined automatically) and converts it into a gzip-compressed pax-format archive on stdout. In this way, tar can be used to convert 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 pattern. 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-supported 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 pattern. Note that exclusions specified with --exclude take precedence over inclusions. If no inclusions are explicitly specified, all entries are processed by default. The --include option is especially useful when filtering archives. For example, the command

-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. Normally, 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 program 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 information 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 inclusion/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 specified 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 systems 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 -p1003.1-96.
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 environment variable or the -f option.

EXIT STATUS


.Ex -std

EXAMPLES

The following creates a new archive called file.tar that contains two files source.c and source.h:

-czf file.tar source.c source.h

To view a detailed table of contents for this archive:

-tvf file.tar

To extract all entries from the archive on the default tape drive:

-x

To move file hierarchies, invoke tar as

-cf --C srcdir . |-xpBf --C destdir

or more traditionally

cd srcdir ;-cf - . |( cd destdir ;-xpBf -)

In create mode, the list of files and directories to be archived can also include directory change instructions of the form -C foo/baz and archive inclusions of the form @ archive-file. For example, the command line

-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 - character) 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,

tbf 32 file.tar

specifies three flags t, b, and f. The b and f flags both require arguments, 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 available 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 superuser, 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:
  • Archive entries can have absolute pathnames. By default, tar removes the leading / character from filenames before restoring them to guard against this problem.
  • Archive entries can have pathnames that include .. components. By default, tar will not extract files containing .. components in their pathname.
  • 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

-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 preserving any absolute pathnames, .. components, or symlinks to other directories.

SEE ALSO

bzip2(1), cpio(1), gzip(1), mt(1), pax(1), shar(1), libarchive(3), libarchive-formats(5), tar(5)

STANDARDS

HISTORY

libarchive(3)

BUGS

gzip(1) bzip2(1),


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