1TAR(1) BSD General Commands Manual TAR(1)
2
4 tar — manipulate tape archives
5
7 tar [bundled-flags ⟨args⟩] [⟨file⟩ | ⟨pattern⟩ ...]
8 tar {-c} [options] [files | directories]
9 tar {-r | -u} -f archive-file [options] [files | directories]
10 tar {-t | -x} [options] [patterns]
11
13 tar creates and manipulates streaming archive files. This implementation
14 can extract from tar, pax, cpio, zip, jar, ar, xar, rpm, 7-zip, and ISO
15 9660 cdrom images and can create tar, pax, cpio, ar, zip, 7-zip, and shar
16 archives.
17 The first synopsis form shows a “bundled” option word. This usage is
19 provided for compatibility with historical implementations. See COMPATI‐
20 BILITY below for details.
21 The other synopsis forms show the preferred usage. The first option to
23 tar is a mode indicator from the following list:
24 -c Create a new archive containing the specified items. The long
25 option form is --create.
26 -r Like -c, but new entries are appended to the archive. Note that
27 this only works on uncompressed archives stored in regular files.
28 The -f option is required. The long option form is --append.
29 -t List archive contents to stdout. The long option form is --list.
30 -u Like -r, but new entries are added only if they have a modifica‐
31 tion date newer than the corresponding entry in the archive.
32 Note that this only works on uncompressed archives stored in reg‐
33 ular files. The -f option is required. The long form is
34 --update.
35 -x Extract to disk from the archive. If a file with the same name
36 appears more than once in the archive, each copy will be
37 extracted, with later copies overwriting (replacing) earlier
38 copies. The long option form is --extract.
39 In -c, -r, or -u mode, each specified file or directory is added to the
41 archive in the order specified on the command line. By default, the con‐
42 tents of each directory are also archived.
43 In extract or list mode, the entire command line is read and parsed
45 before the archive is opened. The pathnames or patterns on the command
46 line indicate which items in the archive should be processed. Patterns
47 are shell-style globbing patterns as documented in tcsh(1).
48
50 Unless specifically stated otherwise, options are applicable in all oper‐
51 ating modes.
52 @archive
54 (c and r mode only) The specified archive is opened and the
55 entries in it will be appended to the current archive. As a sim‐
56 ple example,
57 tar -c -f - newfile @original.tar
58 writes a new archive to standard output containing a file newfile
59 and all of the entries from original.tar. In contrast,
60 tar -c -f - newfile original.tar
61 creates a new archive with only two entries. Similarly,
62 tar -czf - --format pax @-
63 reads an archive from standard input (whose format will be deter‐
64 mined automatically) and converts it into a gzip-compressed pax-
65 format archive on stdout. In this way, tar can be used to con‐
66 vert archives from one format to another.
67 -a, --auto-compress
69 (c mode only) Use the archive suffix to decide a set of the for‐
70 mat and the compressions. As a simple example,
71 tar -a -cf archive.tgz source.c source.h
72 creates a new archive with restricted pax format and gzip com‐
73 pression,
74 tar -a -cf archive.tar.bz2.uu source.c source.h
75 creates a new archive with restricted pax format and bzip2 com‐
76 pression and uuencode compression,
77 tar -a -cf archive.zip source.c source.h
78 creates a new archive with zip format,
79 tar -a -jcf archive.tgz source.c source.h
80 ignores the “-j” option, and creates a new archive with
81 restricted pax format and gzip compression,
82 tar -a -jcf archive.xxx source.c source.h
83 if it is unknown suffix or no suffix, creates a new archive with
84 restricted pax format and bzip2 compression.
85 -B, --read-full-blocks
87 Ignored for compatibility with other tar(1) implementations.
88 -b blocksize, --block-size blocksize
90 Specify the block size, in 512-byte records, for tape drive I/O.
91 As a rule, this argument is only needed when reading from or
92 writing to tape drives, and usually not even then as the default
93 block size of 20 records (10240 bytes) is very common.
94 -C directory, --cd directory, --directory directory
96 In c and r mode, this changes the directory before adding the
97 following files. In x mode, change directories after opening the
98 archive but before extracting entries from the archive.
99 --chroot
101 (x mode only) chroot() to the current directory after processing
102 any -C options and before extracting any files.
103 --disable-copyfile
105 Mac OS X specific. Disable the use of copyfile(3).
106 --exclude pattern
108 Do not process files or directories that match the specified pat‐
109 tern. Note that exclusions take precedence over patterns or
110 filenames specified on the command line.
111 --format format
113 (c, r, u mode only) Use the specified format for the created ar‐
114 chive. Supported formats include “cpio”, “pax”, “shar”, and
115 “ustar”. Other formats may also be supported; see
116 libarchive-formats(5) for more information about currently-sup‐
117 ported formats. In r and u modes, when extending an existing ar‐
118 chive, the format specified here must be compatible with the for‐
119 mat of the existing archive on disk.
120 -f file, --file file
122 Read the archive from or write the archive to the specified file.
123 The filename can be - for standard input or standard output. The
124 default varies by system; on FreeBSD, the default is /dev/sa0; on
125 Linux, the default is /dev/st0.
126 --gid id
128 Use the provided group id number. On extract, this overrides the
129 group id in the archive; the group name in the archive will be
130 ignored. On create, this overrides the group id read from disk;
131 if --gname is not also specified, the group name will be set to
132 match the group id.
133 --gname name
135 Use the provided group name. On extract, this overrides the
136 group name in the archive; if the provided group name does not
137 exist on the system, the group id (from the archive or from the
138 --gid option) will be used instead. On create, this sets the
139 group name that will be stored in the archive; the name will not
140 be verified against the system group database.
141 -H (c and r mode only) Symbolic links named on the command line will
143 be followed; the target of the link will be archived, not the
144 link itself.
145 -h (c and r mode only) Synonym for -L.
147 -I Synonym for -T.
149 --help Show usage.
151 --hfsCompression
153 (x mode only) Mac OS X specific(v10.6 or later). Compress
154 extracted regular files with HFS+ compression.
155 --include pattern
157 Process only files or directories that match the specified pat‐
158 tern. Note that exclusions specified with --exclude take prece‐
159 dence over inclusions. If no inclusions are explicitly speci‐
160 fied, all entries are processed by default. The --include option
161 is especially useful when filtering archives. For example, the
162 command
163 tar -c -f new.tar --include='*foo*' @old.tgz
164 creates a new archive new.tar containing only the entries from
165 old.tgz containing the string ‘foo’.
166 -J, --xz
168 (c mode only) Compress the resulting archive with xz(1). In
169 extract or list modes, this option is ignored. Note that, unlike
170 other tar implementations, this implementation recognizes XZ com‐
171 pression automatically when reading archives.
172 -j, --bzip, --bzip2, --bunzip2
174 (c mode only) Compress the resulting archive with bzip2(1). In
175 extract or list modes, this option is ignored. Note that, unlike
176 other tar implementations, this implementation recognizes bzip2
177 compression automatically when reading archives.
178 -k, --keep-old-files
180 (x mode only) Do not overwrite existing files. In particular, if
181 a file appears more than once in an archive, later copies will
182 not overwrite earlier copies.
183 --keep-newer-files
185 (x mode only) Do not overwrite existing files that are newer than
186 the versions appearing in the archive being extracted.
187 -L, --dereference
189 (c and r mode only) All symbolic links will be followed. Nor‐
190 mally, symbolic links are archived as such. With this option,
191 the target of the link will be archived instead.
192 -l, --check-links
194 (c and r modes only) Issue a warning message unless all links to
195 each file are archived.
196 --lrzip
198 (c mode only) Compress the resulting archive with lrzip(1). In
199 extract or list modes, this option is ignored.
200 --lzma (c mode only) Compress the resulting archive with the original
202 LZMA algorithm. Use of this option is discouraged and new ar‐
203 chives should be created with --xz instead. Note that, unlike
204 other tar implementations, this implementation recognizes LZMA
205 compression automatically when reading archives.
206 --lzop (c mode only) Compress the resulting archive with lzop(1). In
208 extract or list modes, this option is ignored.
209 -m, --modification-time
211 (x mode only) Do not extract modification time. By default, the
212 modification time is set to the time stored in the archive.
213 -n, --norecurse, --no-recursion
215 (c, r, u modes only) Do not recursively archive the contents of
216 directories.
217 --newer date
219 (c, r, u modes only) Only include files and directories newer
220 than the specified date. This compares ctime entries.
221 --newer-mtime date
223 (c, r, u modes only) Like --newer, except it compares mtime
224 entries instead of ctime entries.
225 --newer-than file
227 (c, r, u modes only) Only include files and directories newer
228 than the specified file. This compares ctime entries.
229 --newer-mtime-than file
231 (c, r, u modes only) Like --newer-than, except it compares mtime
232 entries instead of ctime entries.
233 --nodump
235 (c and r modes only) Honor the nodump file flag by skipping this
236 file.
237 --nopreserveHFSCompression
239 (x mode only) Mac OS X specific(v10.6 or later). Do not compress
240 extracted regular files which were compressed with HFS+ compres‐
241 sion before archived. By default, compress the regular files
242 again with HFS+ compression.
243 --null (use with -I or -T) Filenames or patterns are separated by null
245 characters, not by newlines. This is often used to read file‐
246 names output by the -print0 option to find(1).
247 --no-same-owner
249 (x mode only) Do not extract owner and group IDs. This is the
250 reverse of --same-owner and the default behavior if tar is run as
251 non-root.
252 --no-same-permissions
254 (x mode only) Do not extract full permissions (SGID, SUID, sticky
255 bit, ACLs, extended attributes or extended file flags). This is
256 the reverse of -p and the default behavior if tar is run as non-
257 root.
258 --numeric-owner
260 This is equivalent to --uname "" --gname "". On extract, it
261 causes user and group names in the archive to be ignored in favor
262 of the numeric user and group ids. On create, it causes user and
263 group names to not be stored in the archive.
264 -O, --to-stdout
266 (x, t modes only) In extract (-x) mode, files will be written to
267 standard out rather than being extracted to disk. In list (-t)
268 mode, the file listing will be written to stderr rather than the
269 usual stdout.
270 -o (x mode) Use the user and group of the user running the program
272 rather than those specified in the archive. Note that this has
273 no significance unless -p is specified, and the program is being
274 run by the root user. In this case, the file modes and flags
275 from the archive will be restored, but ACLs or owner information
276 in the archive will be discarded.
277 -o (c, r, u mode) A synonym for --format ustar
279 --older date
281 (c, r, u modes only) Only include files and directories older
282 than the specified date. This compares ctime entries.
283 --older-mtime date
285 (c, r, u modes only) Like --older, except it compares mtime
286 entries instead of ctime entries.
287 --older-than file
289 (c, r, u modes only) Only include files and directories older
290 than the specified file. This compares ctime entries.
291 --older-mtime-than file
293 (c, r, u modes only) Like --older-than, except it compares mtime
294 entries instead of ctime entries.
295 --one-file-system
297 (c, r, and u modes) Do not cross mount points.
298 --options options
300 Select optional behaviors for particular modules. The argument
301 is a text string containing comma-separated keywords and values.
302 These are passed to the modules that handle particular formats to
303 control how those formats will behave. Each option has one of
304 the following forms:
305 key=value
306 The key will be set to the specified value in every mod‐
307 ule that supports it. Modules that do not support this
308 key will ignore it.
309 key The key will be enabled in every module that supports it.
310 This is equivalent to key=1.
311 !key The key will be disabled in every module that supports
312 it.
313 module:key=value, module:key, module:!key
314 As above, but the corresponding key and value will be
315 provided only to modules whose name matches module.
316 The currently supported modules and keys are:
317 iso9660:joliet
318 Support Joliet extensions. This is enabled by default,
319 use !joliet or iso9660:!joliet to disable.
320 iso9660:rockridge
321 Support Rock Ridge extensions. This is enabled by
322 default, use !rockridge or iso9660:!rockridge to disable.
323 gzip:compression-level
324 A decimal integer from 1 to 9 specifying the gzip com‐
325 pression level.
326 gzip:timestamp
327 Store timestamp. This is enabled by default, use
328 !timestamp or gzip:!timestamp to disable.
329 lrzip:compression=type
330 Use type as compression method. Supported values are
331 bzip2, gzip, lzo (ultra fast), and zpaq (best, extremely
332 slow).
333 lrzip:compression-level
334 A decimal integer from 1 to 9 specifying the lrzip com‐
335 pression level.
336 lzop:compression-level
337 A decimal integer from 1 to 9 specifying the lzop com‐
338 pression level.
339 xz:compression-level
340 A decimal integer from 0 to 9 specifying the xz compres‐
341 sion level.
342 mtree:keyword
343 The mtree writer module allows you to specify which mtree
344 keywords will be included in the output. Supported key‐
345 words include: cksum, device, flags, gid, gname, indent,
346 link, md5, mode, nlink, rmd160, sha1, sha256, sha384,
347 sha512, size, time, uid, uname. The default is equiva‐
348 lent to: “device, flags, gid, gname, link, mode, nlink,
349 size, time, type, uid, uname”.
350 mtree:all
351 Enables all of the above keywords. You can also use
352 mtree:!all to disable all keywords.
353 mtree:use-set
354 Enable generation of /set lines in the output.
355 mtree:indent
356 Produce human-readable output by indenting options and
357 splitting lines to fit into 80 columns.
358 zip:compression=type
359 Use type as compression method. Supported values are
360 store (uncompressed) and deflate (gzip algorithm).
361 If a provided option is not supported by any module, that is a
362 fatal error.
363 -P, --absolute-paths
365 Preserve pathnames. By default, absolute pathnames (those that
366 begin with a / character) have the leading slash removed both
367 when creating archives and extracting from them. Also, tar will
368 refuse to extract archive entries whose pathnames contain .. or
369 whose target directory would be altered by a symlink. This
370 option suppresses these behaviors.
371 -p, --insecure, --preserve-permissions
373 (x mode only) Preserve file permissions. Attempt to restore the
374 full permissions, including owner, file modes, file flags and
375 ACLs, if available, for each item extracted from the archive.
376 This is the default, if tar is being run by root and can be over‐
377 ridden by also specifying --no-same-owner and
378 --no-same-permissions.
379 --posix
381 (c, r, u mode only) Synonym for --format pax
382 -q, --fast-read
384 (x and t mode only) Extract or list only the first archive entry
385 that matches each pattern or filename operand. Exit as soon as
386 each specified pattern or filename has been matched. By default,
387 the archive is always read to the very end, since there can be
388 multiple entries with the same name and, by convention, later
389 entries overwrite earlier entries. This option is provided as a
390 performance optimization.
391 -S (x mode only) Extract files as sparse files. For every block on
393 disk, check first if it contains only NULL bytes and seek over it
394 otherwise. This works similar to the conv=sparse option of dd.
395 -s pattern
397 Modify file or archive member names according to pattern. The
398 pattern has the format /old/new/[ghHprRsS] where old is a basic
399 regular expression, new is the replacement string of the matched
400 part, and the optional trailing letters modify how the replace‐
401 ment is handled. If old is not matched, the pattern is skipped.
402 Within new, ~ is substituted with the match, \1 to \9 with the
403 content of the corresponding captured group. The optional trail‐
404 ing g specifies that matching should continue after the matched
405 part and stop on the first unmatched pattern. The optional
406 trailing s specifies that the pattern applies to the value of
407 symbolic links. The optional trailing p specifies that after a
408 successful substitution the original path name and the new path
409 name should be printed to standard error. Optional trailing H,
410 R, or S characters suppress substitutions for hardlink targets,
411 regular filenames, or symlink targets, respectively. Optional
412 trailing h, r, or s characters enable substitutions for hardlink
413 targets, regular filenames, or symlink targets, respectively.
414 The default is hrs which applies substitutions to all names. In
415 particular, it is never necessary to specify h, r, or s.
416 --same-owner
418 (x mode only) Extract owner and group IDs. This is the reverse
419 of --no-same-owner and the default behavior if tar is run as
420 root.
421 --strip-components count
423 Remove the specified number of leading path elements. Pathnames
424 with fewer elements will be silently skipped. Note that the
425 pathname is edited after checking inclusion/exclusion patterns
426 but before security checks.
427 -T filename, --files-from filename
429 In x or t mode, tar will read the list of names to be extracted
430 from filename. In c mode, tar will read names to be archived
431 from filename. The special name “-C” on a line by itself will
432 cause the current directory to be changed to the directory speci‐
433 fied on the following line. Names are terminated by newlines
434 unless --null is specified. Note that --null also disables the
435 special handling of lines containing “-C”. Note: If you are
436 generating lists of files using find(1), you probably want to use
437 -n as well.
438 --totals
440 (c, r, u mode only) After archiving all files, print a summary to
441 stderr.
442 -U, --unlink, --unlink-first
444 (x mode only) Unlink files before creating them. This can be a
445 minor performance optimization if most files already exist, but
446 can make things slower if most files do not already exist. This
447 flag also causes tar to remove intervening directory symlinks
448 instead of reporting an error. See the SECURITY section below
449 for more details.
450 --uid id
452 Use the provided user id number and ignore the user name from the
453 archive. On create, if --uname is not also specified, the user
454 name will be set to match the user id.
455 --uname name
457 Use the provided user name. On extract, this overrides the user
458 name in the archive; if the provided user name does not exist on
459 the system, it will be ignored and the user id (from the archive
460 or from the --uid option) will be used instead. On create, this
461 sets the user name that will be stored in the archive; the name
462 is not verified against the system user database.
463 --use-compress-program program
465 Pipe the input (in x or t mode) or the output (in c mode) through
466 program instead of using the builtin compression support.
467 -v, --verbose
469 Produce verbose output. In create and extract modes, tar will
470 list each file name as it is read from or written to the archive.
471 In list mode, tar will produce output similar to that of ls(1).
472 Additional -v options will provide additional detail.
473 --version
475 Print version of tar and libarchive, and exit.
476 -w, --confirmation, --interactive
478 Ask for confirmation for every action.
479 -X filename, --exclude-from filename
481 Read a list of exclusion patterns from the specified file. See
482 --exclude for more information about the handling of exclusions.
483 -y (c mode only) Compress the resulting archive with bzip2(1). In
485 extract or list modes, this option is ignored. Note that, unlike
486 other tar implementations, this implementation recognizes bzip2
487 compression automatically when reading archives.
488 -Z, --compress, --uncompress
490 (c mode only) Compress the resulting archive with compress(1).
491 In extract or list modes, this option is ignored. Note that,
492 unlike other tar implementations, this implementation recognizes
493 compress compression automatically when reading archives.
494 -z, --gunzip, --gzip
496 (c mode only) Compress the resulting archive with gzip(1). In
497 extract or list modes, this option is ignored. Note that, unlike
498 other tar implementations, this implementation recognizes gzip
499 compression automatically when reading archives.
500
502 The following environment variables affect the execution of tar:
503 TAR_READER_OPTIONS
505 The default options for format readers and compression read‐
506 ers. The --options option overrides this.
507 TAR_WRITER_OPTIONS
509 The default options for format writers and compression writ‐
510 ers. The --options option overrides this.
511 LANG The locale to use. See environ(7) for more information.
513 TAPE The default device. The -f option overrides this. Please see
515 the description of the -f option above for more details.
516 TZ The timezone to use when displaying dates. See environ(7) for
518 more information.
519
521 The tar utility exits 0 on success, and >0 if an error occurs.
522
524 The following creates a new archive called file.tar.gz that contains two
525 files source.c and source.h:
526 tar -czf file.tar.gz source.c source.h
527 To view a detailed table of contents for this archive:
529 tar -tvf file.tar.gz
530 To extract all entries from the archive on the default tape drive:
532 tar -x
533 To examine the contents of an ISO 9660 cdrom image:
535 tar -tf image.iso
536 To move file hierarchies, invoke tar as
538 tar -cf - -C srcdir . | tar -xpf - -C destdir
539 or more traditionally
540 cd srcdir ; tar -cf - . | (cd destdir ; tar -xpf -)
541 In create mode, the list of files and directories to be archived can also
543 include directory change instructions of the form -Cfoo/baz and archive
544 inclusions of the form @archive-file. For example, the command line
545 tar -c -f new.tar foo1 @old.tgz -C/tmp foo2
546 will create a new archive new.tar. tar will read the file foo1 from the
547 current directory and add it to the output archive. It will then read
548 each entry from old.tgz and add those entries to the output archive.
549 Finally, it will switch to the /tmp directory and add foo2 to the output
550 archive.
551 An input file in mtree(5) format can be used to create an output archive
553 with arbitrary ownership, permissions, or names that differ from existing
554 data on disk:
555 $ cat input.mtree
557 #mtree
558 usr/bin uid=0 gid=0 mode=0755 type=dir
559 usr/bin/ls uid=0 gid=0 mode=0755 type=file content=myls
560 $ tar -cvf output.tar @input.mtree
561 The --newer and --newer-mtime switches accept a variety of common date
563 and time specifications, including “12 Mar 2005 7:14:29pm”, “2005-03-12
564 19:14”, “5 minutes ago”, and “19:14 PST May 1”.
565 The --options argument can be used to control various details of archive
567 generation or reading. For example, you can generate mtree output which
568 only contains type, time, and uid keywords:
569 tar -cf file.tar --format=mtree --options='!all,type,time,uid' dir
570 or you can set the compression level used by gzip or xz compression:
571 tar -czf file.tar --options='compression-level=9'.
572 For more details, see the explanation of the archive_read_set_options()
573 and archive_write_set_options() API calls that are described in
574 archive_read(3) and archive_write(3).
575
577 The bundled-arguments format is supported for compatibility with historic
578 implementations. It consists of an initial word (with no leading - char‐
579 acter) in which each character indicates an option. Arguments follow as
580 separate words. The order of the arguments must match the order of the
581 corresponding characters in the bundled command word. For example,
582 tar tbf 32 file.tar
583 specifies three flags t, b, and f. The b and f flags both require argu‐
584 ments, so there must be two additional items on the command line. The 32
585 is the argument to the b flag, and file.tar is the argument to the f
586 flag.
587 The mode options c, r, t, u, and x and the options b, f, l, m, o, v, and
589 w comply with SUSv2.
590 For maximum portability, scripts that invoke tar should use the bundled-
592 argument format above, should limit themselves to the c, t, and x modes,
593 and the b, f, m, v, and w options.
594 Additional long options are provided to improve compatibility with other
596 tar implementations.
597
599 Certain security issues are common to many archiving programs, including
600 tar. In particular, carefully-crafted archives can request that tar
601 extract files to locations outside of the target directory. This can
602 potentially be used to cause unwitting users to overwrite files they did
603 not intend to overwrite. If the archive is being extracted by the supe‐
604 ruser, any file on the system can potentially be overwritten. There are
605 three ways this can happen. Although tar has mechanisms to protect
606 against each one, savvy users should be aware of the implications:
607 · Archive entries can have absolute pathnames. By default, tar
609 removes the leading / character from filenames before restoring
610 them to guard against this problem.
611 · Archive entries can have pathnames that include .. components.
613 By default, tar will not extract files containing .. components
614 in their pathname.
615 · Archive entries can exploit symbolic links to restore files to
617 other directories. An archive can restore a symbolic link to
618 another directory, then use that link to restore a file into that
619 directory. To guard against this, tar checks each extracted path
620 for symlinks. If the final path element is a symlink, it will be
621 removed and replaced with the archive entry. If -U is specified,
622 any intermediate symlink will also be unconditionally removed.
623 If neither -U nor -P is specified, tar will refuse to extract the
624 entry.
625 To protect yourself, you should be wary of any archives that come from
626 untrusted sources. You should examine the contents of an archive with
627 tar -tf filename
628 before extraction. You should use the -k option to ensure that tar will
629 not overwrite any existing files or the -U option to remove any pre-
630 existing files. You should generally not extract archives while running
631 with super-user privileges. Note that the -P option to tar disables the
632 security checks above and allows you to extract an archive while preserv‐
633 ing any absolute pathnames, .. components, or symlinks to other directo‐
634 ries.
635
637 bzip2(1), compress(1), cpio(1), gzip(1), mt(1), pax(1), shar(1), xz(1),
638 libarchive(3), libarchive-formats(5), tar(5)
639
641 There is no current POSIX standard for the tar command; it appeared in
642 ISO/IEC 9945-1:1996 (“POSIX.1”) but was dropped from IEEE Std 1003.1-2001
643 (“POSIX.1”). The options supported by this implementation were developed
644 by surveying a number of existing tar implementations as well as the old
645 POSIX specification for tar and the current POSIX specification for pax.
646 The ustar and pax interchange file formats are defined by IEEE Std
648 1003.1-2001 (“POSIX.1”) for the pax command.
649
651 A tar command appeared in Seventh Edition Unix, which was released in
652 January, 1979. There have been numerous other implementations, many of
653 which extended the file format. John Gilmore's pdtar public-domain
654 implementation (circa November, 1987) was quite influential, and formed
655 the basis of GNU tar. GNU tar was included as the standard system tar in
656 FreeBSD beginning with FreeBSD 1.0.
657 This is a complete re-implementation based on the libarchive(3) library.
659 It was first released with FreeBSD 5.4 in May, 2005.
660
662 This program follows ISO/IEC 9945-1:1996 (“POSIX.1”) for the definition
663 of the -l option. Note that GNU tar prior to version 1.15 treated -l as
664 a synonym for the --one-file-system option.
665 The -C dir option may differ from historic implementations.
667 All archive output is written in correctly-sized blocks, even if the out‐
669 put is being compressed. Whether or not the last output block is padded
670 to a full block size varies depending on the format and the output
671 device. For tar and cpio formats, the last block of output is padded to
672 a full block size if the output is being written to standard output or to
673 a character or block device such as a tape drive. If the output is being
674 written to a regular file, the last block will not be padded. Many com‐
675 pressors, including gzip(1) and bzip2(1), complain about the null padding
676 when decompressing an archive created by tar, although they still extract
677 it correctly.
678 The compression and decompression is implemented internally, so there may
680 be insignificant differences between the compressed output generated by
681 tar -czf - file
682 and that generated by
683 tar -cf - file | gzip
684 The default should be to read and write archives to the standard I/O
686 paths, but tradition (and POSIX) dictates otherwise.
687 The r and u modes require that the archive be uncompressed and located in
689 a regular file on disk. Other archives can be modified using c mode with
690 the @archive-file extension.
691 To archive a file called @foo or -foo you must specify it as ./@foo or
693 ./-foo, respectively.
694 In create mode, a leading ./ is always removed. A leading / is stripped
696 unless the -P option is specified.
697 There needs to be better support for file selection on both create and
699 extract.
700 There is not yet any support for multi-volume archives or for archiving
702 sparse files.
703 Converting between dissimilar archive formats (such as tar and cpio)
705 using the @- convention can cause hard link information to be lost.
706 (This is a consequence of the incompatible ways that different archive
707 formats store hardlink information.)
708BSD November 1, 2012 BSD