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pax.1p (125851B)

    

  1. '\" et
  2. .TH PAX "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. pax
  12. \(em portable archive interchange
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. pax \fB[\fR-dv\fB] [\fR-c|-n\fB] [\fR-H|-L\fB] [\fR-o \fIoptions\fB] [\fR-f \fIarchive\fB] [\fR-s \fIreplstr\fB]\fR...
  17.     \fB[\fIpattern\fR...\fB]\fR
  18. .P
  19. pax -r\fB[\fR-c|-n\fB] [\fR-dikuv\fB] [\fR-H|-L\fB] [\fR-f \fIarchive\fB] [\fR-o \fIoptions\fB]\fR... \fB[\fR-p \fIstring\fB]\fR...
  20.     \fB[\fR-s \fIreplstr\fB]\fR... \fB[\fIpattern\fR...\fB]\fR
  21. .P
  22. pax -w \fB[\fR-dituvX\fB] [\fR-H|-L\fB] [\fR-b \fIblocksize\fB] [[\fR-a\fB] [\fR-f \fIarchive\fB]] [\fR-o \fIoptions\fB]\fR...
  23.     \fB[\fR-s \fIreplstr\fB]\fR... \fB[\fR-x \fIformat\fB] [\fIfile\fR...\fB]\fR
  24. .P
  25. pax -r -w \fB[\fR-diklntuvX\fB] [\fR-H|-L\fB] [\fR-o \fIoptions\fB]\fR... \fB[\fR-p \fIstring\fB]\fR...
  26.     \fB[\fR-s \fIreplstr\fB]\fR... \fB[\fIfile\fR...\fB] \fIdirectory\fR
  27. .fi
  28. .SH DESCRIPTION
  29. The
  30. .IR pax
  31. utility shall read, write, and write lists of the members of archive
  32. files and copy directory hierarchies. A variety of archive formats
  33. shall be supported; see the
  34. .BR \-x
  35. .IR format
  36. option.
  37. .P
  38. The action to be taken depends on the presence of the
  39. .BR \-r
  40. and
  41. .BR \-w
  42. options. The four combinations of
  43. .BR \-r
  44. and
  45. .BR \-w
  46. are referred to as the four modes of operation:
  47. .BR list ,
  48. .BR read ,
  49. .BR write ,
  50. and
  51. .BR copy
  52. modes, corresponding respectively to the four forms shown in the
  53. SYNOPSIS section.
  54. .IP "\fBlist\fP" 10
  55. In
  56. .BR list
  57. mode (when neither
  58. .BR \-r
  59. nor
  60. .BR \-w
  61. are specified),
  62. .IR pax
  63. shall write the names of the members of the archive file read from the
  64. standard input, with pathnames matching the specified patterns, to
  65. standard output. If a named file is of type directory, the file
  66. hierarchy rooted at that file shall be listed as well.
  67. .IP "\fBread\fP" 10
  68. In
  69. .BR read
  70. mode (when
  71. .BR \-r
  72. is specified, but
  73. .BR \-w
  74. is not),
  75. .IR pax
  76. shall extract the members of the archive file read from the standard
  77. input, with pathnames matching the specified patterns. If an extracted
  78. file is of type directory, the file hierarchy rooted at that file shall
  79. be extracted as well. The extracted files shall be created performing
  80. pathname resolution with the directory in which
  81. .IR pax
  82. was invoked as the current working directory.
  83. .RS 10 
  84. .P
  85. If an attempt is made to extract a directory when the directory
  86. already exists, this shall not be considered an error. If
  87. an attempt is made to extract a FIFO when the FIFO already exists,
  88. this shall not be considered an error.
  89. .P
  90. The ownership, access, and modification times, and file mode of the
  91. restored files are discussed under the
  92. .BR \-p
  93. option.
  94. .RE
  95. .IP "\fBwrite\fP" 10
  96. In
  97. .BR write
  98. mode (when
  99. .BR \-w
  100. is specified, but
  101. .BR \-r
  102. is not),
  103. .IR pax
  104. shall write the contents of the
  105. .IR file
  106. operands to the standard output in an archive format. If no
  107. .IR file
  108. operands are specified, a list of files to copy, one per line, shall be
  109. read from the standard input and each entry in this list shall be
  110. processed as if it had been a
  111. .IR file
  112. operand on the command line. A file of type directory shall include
  113. all of the files in the file hierarchy rooted at the file.
  114. .IP "\fBcopy\fP" 10
  115. In
  116. .BR copy
  117. mode (when both
  118. .BR \-r
  119. and
  120. .BR \-w
  121. are specified),
  122. .IR pax
  123. shall copy the
  124. .IR file
  125. operands to the destination directory.
  126. .RS 10 
  127. .P
  128. If no
  129. .IR file
  130. operands are specified, a list of files to copy, one per line, shall be
  131. read from the standard input. A file of type directory shall include
  132. all of the files in the file hierarchy rooted at the file.
  133. .P
  134. The effect of the
  135. .BR copy
  136. shall be as if the copied files were written to a
  137. .IR pax
  138. format archive file and then subsequently extracted, except that
  139. copying of sockets may be supported even if archiving them in write
  140. mode is not supported, and that there may be hard links between the
  141. original and the copied files. If the destination directory is a
  142. subdirectory of one of the files to be copied, the results
  143. are unspecified. If the destination directory is a file of a
  144. type not defined by the System Interfaces volume of POSIX.1\(hy2017, the results are implementation-defined;
  145. otherwise, it shall be an error for the file named by the
  146. .IR directory
  147. operand not to exist, not be writable by the user, or not be a file of
  148. type directory.
  149. .RE
  150. .P
  151. In
  152. .BR read
  153. or
  154. .BR copy
  155. modes, if intermediate directories are necessary to extract an archive
  156. member,
  157. .IR pax
  158. shall perform actions equivalent to the
  159. \fImkdir\fR()
  160. function defined in the System Interfaces volume of POSIX.1\(hy2017, called with the following arguments:
  161. .IP " *" 4
  162. The intermediate directory used as the
  163. .IR path
  164. argument
  165. .IP " *" 4
  166. The value of the bitwise-inclusive OR of S_IRWXU, S_IRWXG, and S_IRWXO
  167. as the
  168. .IR mode
  169. argument
  170. .P
  171. If any specified
  172. .IR pattern
  173. or
  174. .IR file
  175. operands are not matched by at least one file or archive member,
  176. .IR pax
  177. shall write a diagnostic message to standard error for each one that
  178. did not match and exit with a non-zero exit status.
  179. .P
  180. The archive formats described in the EXTENDED DESCRIPTION section shall
  181. be automatically detected on input. The default output archive format
  182. shall be implementation-defined.
  183. .P
  184. A single archive can span multiple files. The
  185. .IR pax
  186. utility shall determine, in an implementation-defined manner, what
  187. file to read or write as the next file.
  188. .P
  189. If the selected archive format supports the specification of linked files,
  190. it shall be an error if these files cannot be linked when the archive
  191. is extracted. For archive formats that do not store file contents with
  192. each name that causes a hard link, if the file that contains the data
  193. is not extracted during this
  194. .IR pax
  195. session, either the data shall be restored from the original file, or a
  196. diagnostic message shall be displayed with the name of a file that can
  197. be used to extract the data. In traversing directories,
  198. .IR pax
  199. shall detect infinite loops; that is, entering a previously visited
  200. directory that is an ancestor of the last file visited. When it detects
  201. an infinite loop,
  202. .IR pax
  203. shall write a diagnostic message to standard error and shall
  204. terminate.
  205. .SH OPTIONS
  206. The
  207. .IR pax
  208. utility shall conform to the Base Definitions volume of POSIX.1\(hy2017,
  209. .IR "Section 12.2" ", " "Utility Syntax Guidelines",
  210. except that the order of presentation of the
  211. .BR \-o ,
  212. .BR \-p ,
  213. and
  214. .BR \-s
  215. options is significant.
  216. .P
  217. The following options shall be supported:
  218. .IP "\fB\-r\fP" 10
  219. Read an archive file from standard input.
  220. .IP "\fB\-w\fP" 10
  221. Write files to the standard output in the specified archive format.
  222. .IP "\fB\-a\fP" 10
  223. Append files to the end of the archive. It is implementation-defined
  224. which devices on the system support appending. Additional file formats
  225. unspecified by this volume of POSIX.1\(hy2017 may impose restrictions on appending.
  226. .IP "\fB\-b\ \fIblocksize\fR" 10
  227. Block the output at a positive decimal integer number of bytes per
  228. write to the archive file. Devices and archive formats may impose
  229. restrictions on blocking. Blocking shall be automatically determined on
  230. input. Conforming applications shall not specify a
  231. .IR blocksize
  232. value larger than 32\|256. Default blocking when creating archives
  233. depends on the archive format. (See the
  234. .BR \-x
  235. option below.)
  236. .IP "\fB\-c\fP" 10
  237. Match all file or archive members except those specified by the
  238. .IR pattern
  239. or
  240. .IR file
  241. operands.
  242. .IP "\fB\-d\fP" 10
  243. Cause files of type directory being copied or archived or archive
  244. members of type directory being extracted or listed to match only the
  245. file or archive member itself and not the file hierarchy rooted at the
  246. file.
  247. .IP "\fB\-f\ \fIarchive\fR" 10
  248. Specify the pathname of the input or output archive, overriding the
  249. default standard input (in
  250. .BR list
  251. or
  252. .BR read
  253. modes) or standard output (\c
  254. .BR write
  255. mode).
  256. .IP "\fB\-H\fP" 10
  257. If a symbolic link referencing a file of type directory is specified on
  258. the command line,
  259. .IR pax
  260. shall archive the file hierarchy rooted in the file referenced by the
  261. link, using the name of the link as the root of the file hierarchy.
  262. Otherwise, if a symbolic link referencing a file of any other file type
  263. which
  264. .IR pax
  265. can normally archive is specified on the command line, then
  266. .IR pax
  267. shall archive the file referenced by the link, using the name of the
  268. link. The default behavior, when neither
  269. .BR \-H
  270. or
  271. .BR \-L
  272. are specified, shall be to archive the symbolic link itself.
  273. .IP "\fB\-i\fP" 10
  274. Interactively rename files or archive members. For each archive member
  275. matching a
  276. .IR pattern
  277. operand or file matching a
  278. .IR file
  279. operand, a prompt shall be written to the file
  280. .BR /dev/tty .
  281. The prompt shall contain the name of the file or archive member, but
  282. the format is otherwise unspecified. A line shall then be read from
  283. .BR /dev/tty .
  284. If this line is blank, the file or archive member shall be skipped. If
  285. this line consists of a single period, the file or archive member shall
  286. be processed with no modification to its name. Otherwise, its name
  287. shall be replaced with the contents of the line. The
  288. .IR pax
  289. utility shall immediately exit with a non-zero exit status if
  290. end-of-file is encountered when reading a response or if
  291. .BR /dev/tty
  292. cannot be opened for reading and writing.
  293. .RS 10 
  294. .P
  295. The results of extracting a hard link to a file that has been renamed
  296. during extraction are unspecified.
  297. .RE
  298. .IP "\fB\-k\fP" 10
  299. Prevent the overwriting of existing files.
  300. .IP "\fB\-l\fP" 10
  301. (The letter ell.) In
  302. .BR copy
  303. mode, hard links shall be made between the source and destination file
  304. hierarchies whenever possible. If specified in conjunction with
  305. .BR \-H
  306. or
  307. .BR \-L ,
  308. when a symbolic link is encountered, the hard link created in the
  309. destination file hierarchy shall be to the file referenced by the
  310. symbolic link. If specified when neither
  311. .BR \-H
  312. nor
  313. .BR \-L
  314. is specified, when a symbolic link is encountered, the implementation
  315. shall create a hard link to the symbolic link in the source file
  316. hierarchy or copy the symbolic link to the destination.
  317. .IP "\fB\-L\fP" 10
  318. If a symbolic link referencing a file of type directory is specified on
  319. the command line or encountered during the traversal of a file
  320. hierarchy,
  321. .IR pax
  322. shall archive the file hierarchy rooted in the file referenced by the
  323. link, using the name of the link as the root of the file hierarchy.
  324. Otherwise, if a symbolic link referencing a file of any other file type
  325. which
  326. .IR pax
  327. can normally archive is specified on the command line or encountered
  328. during the traversal of a file hierarchy,
  329. .IR pax
  330. shall archive the file referenced by the link, using the name of the
  331. link. The default behavior, when neither
  332. .BR \-H
  333. or
  334. .BR \-L
  335. are specified, shall be to archive the symbolic link itself.
  336. .IP "\fB\-n\fP" 10
  337. Select the first archive member that matches each
  338. .IR pattern
  339. operand. No more than one archive member shall be matched for each
  340. pattern (although members of type directory shall still match the file
  341. hierarchy rooted at that file).
  342. .IP "\fB\-o\ \fIoptions\fR" 10
  343. Provide information to the implementation to modify the algorithm for
  344. extracting or writing files. The value of
  345. .IR options
  346. shall consist of one or more
  347. <comma>-separated
  348. keywords of the form:
  349. .RS 10 
  350. .sp
  351. .RS 4
  352. .nf
  354. \fIkeyword\fB[[\fR:\fB]\fR=\fIvalue\fB][\fR,\fIkeyword\fB[[\fR:\fB]\fR=\fIvalue\fB]\fR, ...\fB]\fR
  355. .fi
  356. .P
  357. .RE
  358. .P
  359. Some keywords apply only to certain file formats, as indicated with
  360. each description. Use of keywords that are inapplicable to the file
  361. format being processed produces undefined results.
  362. .P
  363. Keywords in the
  364. .IR options
  365. argument shall be a string that would be a valid portable filename as
  366. described in the Base Definitions volume of POSIX.1\(hy2017,
  367. .IR "Section 3.282" ", " "Portable Filename Character Set".
  368. .TP 10
  369. .BR Note:
  370. Keywords are not expected to be filenames, merely to follow the same
  371. character composition rules as portable filenames.
  372. .P
  373. .P
  374. Keywords can be preceded with white space. The
  375. .IR value
  376. field shall consist of zero or more characters; within
  377. .IR value ,
  378. the application shall precede any literal
  379. <comma>
  380. with a
  381. <backslash>,
  382. which shall be ignored, but preserves the
  383. <comma>
  384. as part of
  385. .IR value .
  386. A
  387. <comma>
  388. as the final character, or a
  389. <comma>
  390. followed solely by white space as the final characters, in
  391. .IR options
  392. shall be ignored. Multiple
  393. .BR \-o
  394. options can be specified; if keywords given to these multiple
  395. .BR \-o
  396. options conflict, the keywords and values appearing later in command
  397. line sequence shall take precedence and the earlier shall be silently
  398. ignored. The following keyword values of
  399. .IR options
  400. shall be supported for the file formats as indicated:
  401. .IP "\fBdelete\fR=\fIpattern\fR" 6
  402. .br
  403. (Applicable only to the
  404. .BR \-x
  405. .BR pax
  406. format.) When used in
  407. .BR write
  408. or
  409. .BR copy
  410. mode,
  411. .IR pax
  412. shall omit from extended header records that it produces any keywords
  413. matching the string pattern. When used in
  414. .BR read
  415. or
  416. .BR list
  417. mode,
  418. .IR pax
  419. shall ignore any keywords matching the string pattern in the extended
  420. header records. In both cases, matching shall be performed using the
  421. pattern matching notation described in
  422. .IR "Section 2.13.1" ", " "Patterns Matching a Single Character"
  423. and
  424. .IR "Section 2.13.2" ", " "Patterns Matching Multiple Characters".
  425. For example:
  426. .RS 6 
  427. .sp
  428. .RS 4
  429. .nf
  431. -o \fBdelete\fR=\fIsecurity\fR.*
  432. .fi
  433. .P
  434. .RE
  435. .P
  436. would suppress security-related information. See
  437. .IR "pax Extended Header"
  438. for extended header record keyword usage.
  439. .P
  440. When multiple
  441. .BR \-o \c
  442. .BR delete=pattern
  443. options are specified, the patterns shall be additive; all keywords
  444. matching the specified string patterns shall be omitted from extended
  445. header records that
  446. .IR pax
  447. produces.
  448. .RE
  449. .IP "\fBexthdr.name\fR=\fIstring\fR" 6
  450. .br
  451. (Applicable only to the
  452. .BR \-x
  453. .BR pax
  454. format.) This keyword allows user control over the name that is written
  455. into the
  456. .BR ustar
  457. header blocks for the extended header produced under the circumstances
  458. described in
  459. .IR "pax Header Block".
  460. The name shall be the contents of
  461. .IR string ,
  462. after the following character substitutions have been made:
  463. .TS
  464. center box tab(!);
  465. cB | cB
  466. cB | cB
  467. lf5 | lw(3.8i).
  468. \fIstring\fP
  469. Includes:!Replaced by:
  470. _
  471. %d!T{
  472. The directory name of the file, equivalent to the result of the
  473. .IR dirname
  474. utility on the translated pathname.
  475. T}
  476. %f!T{
  477. The filename of the file, equivalent to the result of the
  478. .IR basename
  479. utility on the translated pathname.
  480. T}
  481. %p!T{
  482. The process ID of the
  483. .IR pax
  484. process.
  485. T}
  486. %%!T{
  487. A
  488. .BR '%' 
  489. character.
  490. T}
  491. .TE
  492. .RS 6 
  493. .P
  494. Any other
  495. .BR '%' 
  496. characters in
  497. .IR string
  498. produce undefined results.
  499. .P
  500. If no
  501. .BR \-o
  502. .BR exthdr.name=string
  503. is specified,
  504. .IR pax
  505. shall use the following default value:
  506. .sp
  507. .RS 4
  508. .nf
  510. %d/PaxHeaders.%p/%f
  511. .fi
  512. .P
  513. .RE
  514. .RE
  515. .IP "\fBglobexthdr.name\fR=\fIstring\fR" 6
  516. .br
  517. (Applicable only to the
  518. .BR \-x
  519. .BR pax
  520. format.) When used in
  521. .BR write
  522. or
  523. .BR copy
  524. mode with the appropriate options,
  525. .IR pax
  526. shall create global extended header records with
  527. .BR ustar
  528. header blocks that will be treated as regular files by previous
  529. versions of
  530. .IR pax .
  531. This keyword allows user control over the name that is written into the
  532. .BR ustar
  533. header blocks for global extended header records. The name shall be the
  534. contents of string, after the following character substitutions have
  535. been made:
  536. .TS
  537. center box tab(!);
  538. cB | cB
  539. cB | cB
  540. lf5 | lw(3.8i).
  541. \fIstring\fP
  542. Includes:!Replaced by:
  543. _
  544. %n!T{
  545. An integer that represents the sequence number of the global extended
  546. header record in the archive, starting at 1.
  547. T}
  548. %p!T{
  549. The process ID of the
  550. .IR pax
  551. process.
  552. T}
  553. %%!T{
  554. A
  555. .BR '%' 
  556. character.
  557. T}
  558. .TE
  559. .RS 6 
  560. .P
  561. Any other
  562. .BR '%' 
  563. characters in
  564. .IR string
  565. produce undefined results.
  566. .P
  567. If no
  568. .BR \-o
  569. .BR globexthdr.name=string
  570. is specified,
  571. .IR pax
  572. shall use the following default value:
  573. .sp
  574. .RS 4
  575. .nf
  577. $TMPDIR/GlobalHead.%p.%n
  578. .fi
  579. .P
  580. .RE
  581. .P
  582. where $\c
  583. .IR TMPDIR
  584. represents the value of the
  585. .IR TMPDIR
  586. environment variable. If
  587. .IR TMPDIR
  588. is not set,
  589. .IR pax
  590. shall use
  591. .BR /tmp .
  592. .RE
  593. .IP "\fBinvalid\fR=\fIaction\fR" 6
  594. .br
  595. (Applicable only to the
  596. .BR \-x
  597. .BR pax
  598. format.) This keyword allows user control over the action
  599. .IR pax
  600. takes upon encountering values in an extended header record that, in
  601. .BR read
  602. or
  603. .BR copy
  604. mode, are invalid in the destination hierarchy or, in
  605. .BR list
  606. mode, cannot be written in the codeset and current locale of the
  607. implementation. The following are invalid values that shall be
  608. recognized by
  609. .IR pax :
  610. .RS 6 
  611. .IP -- 4
  612. In
  613. .BR read
  614. or
  615. .BR copy
  616. mode, a filename or link name that contains character encodings
  617. invalid in the destination hierarchy. (For example, the name may
  618. contain embedded NULs.)
  619. .IP -- 4
  620. In
  621. .BR read
  622. or
  623. .BR copy
  624. mode, a filename or link name that is longer than the maximum allowed
  625. in the destination hierarchy (for either a pathname component or the
  626. entire pathname).
  627. .IP -- 4
  628. In
  629. .BR list
  630. mode, any character string value (filename, link name, user name, and
  631. so on) that cannot be written in the codeset and current locale of the
  632. implementation.
  633. .P
  634. The following mutually-exclusive values of the
  635. .IR action
  636. argument are supported:
  637. .IP "\fBbinary\fR" 10
  638. In
  639. .BR write
  640. mode,
  641. .IR pax
  642. shall generate a
  643. .BR hdrcharset = BINARY
  644. extended header record for each file with a filename, link name, group
  645. name, owner name, or any other field in an extended header record that
  646. cannot be translated to the UTF\(hy8 codeset, allowing the archive to
  647. contain the files with unencoded extended header record values. In
  648. .BR read
  649. or
  650. .BR copy
  651. mode,
  652. .IR pax
  653. shall use the values specified in the header without translation,
  654. regardless of whether this may overwrite an existing file with a valid
  655. name. In
  656. .BR list
  657. mode,
  658. .IR pax
  659. shall behave identically to the
  660. .BR bypass
  661. action.
  662. .IP "\fBbypass\fR" 10
  663. In
  664. .BR read
  665. or
  666. .BR copy
  667. mode,
  668. .IR pax
  669. shall bypass the file, causing no change to the destination hierarchy.
  670. In
  671. .BR list
  672. mode,
  673. .IR pax
  674. shall write all requested valid values for the file, but its method for
  675. writing invalid values is unspecified.
  676. .IP "\fBrename\fR" 10
  677. In
  678. .BR read
  679. or
  680. .BR copy
  681. mode,
  682. .IR pax
  683. shall act as if the
  684. .BR \-i
  685. option were in effect for each file with invalid filename or link name
  686. values, allowing the user to provide a replacement name interactively.
  687. In
  688. .BR list
  689. mode,
  690. .IR pax
  691. shall behave identically to the
  692. .BR bypass
  693. action.
  694. .IP "\fBUTF\(hy8\fR" 10
  695. When used in
  696. .BR read ,
  697. .BR copy ,
  698. or
  699. .BR list
  700. mode and a filename, link name, owner name, or any other field in an
  701. extended header record cannot be translated from the
  702. .BR pax
  703. UTF\(hy8 codeset format to the codeset and current locale of the
  704. implementation,
  705. .IR pax
  706. shall use the actual UTF\(hy8 encoding for the name. If a
  707. .BR hdrcharset
  708. extended header record is in effect for this file, the character set
  709. specified by that record shall be used instead of UTF\(hy8. If a
  710. .BR hdrcharset = BINARY
  711. extended header record is in effect for this file, no translation shall
  712. be performed.
  713. .IP "\fBwrite\fR" 10
  714. In
  715. .BR read
  716. or
  717. .BR copy
  718. mode,
  719. .IR pax
  720. shall write the file, translating the name, regardless of whether this
  721. may overwrite an existing file with a valid name. In
  722. .BR list
  723. mode,
  724. .IR pax
  725. shall behave identically to the
  726. .BR bypass
  727. action.
  728. .P
  729. If no
  730. .BR \-o
  731. .BR invalid=option
  732. is specified,
  733. .IR pax
  734. shall act as if
  735. .BR \-o \c
  736. .BR invalid=bypass
  737. were specified. Any overwriting of existing files that may be allowed
  738. by the
  739. .BR \-o \c
  740. .BR invalid=
  741. actions shall be subject to permission (\c
  742. .BR \-p )
  743. and modification time (\c
  744. .BR \-u )
  745. restrictions, and shall be suppressed if the
  746. .BR \-k
  747. option is also specified.
  748. .RE
  749. .IP "\fBlinkdata\fP" 6
  750. .br
  751. (Applicable only to the
  752. .BR \-x
  753. .BR pax
  754. format.) In
  755. .BR write
  756. mode,
  757. .IR pax
  758. shall write the contents of a file to the archive even when that file
  759. is merely a hard link to a file whose contents have already been
  760. written to the archive.
  761. .IP "\fBlistopt\fR=\fIformat\fP" 6
  762. .br
  763. This keyword specifies the output format of the table of contents
  764. produced when the
  765. .BR \-v
  766. option is specified in
  767. .BR list
  768. mode. See
  769. .IR "List Mode Format Specifications".
  770. To avoid ambiguity, the
  771. .BR listopt=format
  772. shall be the only or final
  773. .BR keyword=value
  774. pair in a
  775. .BR \-o
  776. option-argument; all characters in the remainder of the option-argument
  777. shall be considered part of the format string. When multiple
  778. .BR \-o \c
  779. .BR listopt=format
  780. options are specified, the format strings shall be considered a single,
  781. concatenated string, evaluated in command line order.
  782. .IP "\fBtimes\fR" 6
  783. .br
  784. (Applicable only to the
  785. .BR \-x
  786. .IR pax
  787. format.) When used in
  788. .BR write
  789. or
  790. .BR copy
  791. mode,
  792. .IR pax
  793. shall include
  794. .BR atime
  795. and
  796. .BR mtime
  797. extended header records for each file. See
  798. .IR "pax Extended Header File Times".
  799. .P
  800. In addition to these keywords, if the
  801. .BR \-x
  802. .IR pax
  803. format is specified, any of the keywords and values defined in
  804. .IR "pax Extended Header",
  805. including implementation extensions, can be used in
  806. .BR \-o
  807. option-arguments, in either of two modes:
  808. .IP "\fBkeyword\fR=\fIvalue\fR" 6
  809. .br
  810. When used in
  811. .BR write
  812. or
  813. .BR copy
  814. mode, these keyword/value pairs shall be included at the beginning of
  815. the archive as
  816. .BR typeflag
  817. .BR g
  818. global extended header records. When used in
  819. .BR read
  820. or
  821. .BR list
  822. mode, these keyword/value pairs shall act as if they had been at the
  823. beginning of the archive as
  824. .BR typeflag
  825. .BR g
  826. global extended header records.
  827. .IP "\fBkeyword\fR:=\fIvalue\fR" 6
  828. .br
  829. When used in
  830. .BR write
  831. or
  832. .BR copy
  833. mode, these keyword/value pairs shall be included as records at the
  834. beginning of a
  835. .BR typeflag
  836. .BR x
  837. extended header for each file. (This shall be equivalent to the
  838. <equals-sign>
  839. form except that it creates no
  840. .BR typeflag
  841. .BR g
  842. global extended header records.) When used in
  843. .BR read
  844. or
  845. .BR list
  846. mode, these keyword/value pairs shall act as if they were included as
  847. records at the end of each extended header; thus, they shall override
  848. any global or file-specific extended header record keywords of the same
  849. names. For example, in the command:
  850. .RS 6 
  851. .sp
  852. .RS 4
  853. .nf
  855. pax -r -o "
  856. gname:=mygroup,
  857. " <archive
  858. .fi
  859. .P
  860. .RE
  861. .P
  862. the group name will be forced to a new value for all files read from
  863. the archive.
  864. .RE
  865. .P
  866. The precedence of
  867. .BR \-o
  868. keywords over various fields in the archive is described in
  869. .IR "pax Extended Header Keyword Precedence".
  870. If the
  871. .BR \-o
  872. .BR delete =\c
  873. .IR pattern ,
  874. .BR \-o
  875. .BR keyword =\c
  876. .IR value ,
  877. or
  878. .BR \-o
  879. .BR keyword :=\c
  880. .IR value
  881. options are used to override or remove any extended header data needed
  882. to find files in an archive (e.g.,
  883. .BR "-o delete=size"
  884. for a file whose size cannot be represented in a
  885. .BR ustar
  886. header or
  887. .BR "-o size=100"
  888. for a file whose size is not 100 bytes), the behavior is undefined.
  889. .RE
  890. .IP "\fB\-p\ \fIstring\fR" 10
  891. Specify one or more file characteristic options (privileges). The
  892. .IR string
  893. option-argument shall be a string specifying file characteristics to be
  894. retained or discarded on extraction. The string shall consist of the
  895. specification characters
  896. .BR a ,
  897. .BR e ,
  898. .BR m ,
  899. .BR o ,
  900. and
  901. .BR p .
  902. Other implementation-defined characters can be included. Multiple
  903. characteristics can be concatenated within the same string and multiple
  904. .BR \-p
  905. options can be specified. The meaning of the specification characters
  906. are as follows:
  907. .RS 10 
  908. .IP "\fRa\fP" 6
  909. Do not preserve file access times.
  910. .IP "\fRe\fP" 6
  911. Preserve the user ID, group ID, file mode bits (see the Base Definitions volume of POSIX.1\(hy2017,
  912. .IR "Section 3.169" ", " "File Mode Bits"),
  913. access time, modification time, and any other implementation-defined
  914. file characteristics.
  915. .IP "\fRm\fP" 6
  916. Do not preserve file modification times.
  917. .IP "\fRo\fP" 6
  918. Preserve the user ID and group ID.
  919. .IP "\fRp\fP" 6
  920. Preserve the file mode bits. Other implementation-defined file mode
  921. attributes may be preserved.
  922. .P
  923. In the preceding list, ``preserve'' indicates that an attribute stored
  924. in the archive shall be given to the extracted file, subject to the
  925. permissions of the invoking process. The access and modification times
  926. of the file shall be preserved unless otherwise specified with the
  927. .BR \-p
  928. option or not stored in the archive. All attributes that are not
  929. preserved shall be determined as part of the normal file creation
  930. action (see
  931. .IR "Section 1.1.1.4" ", " "File Read" ", " "Write" ", " "and Creation").
  932. .P
  933. If neither the
  934. .BR e
  935. nor the
  936. .BR o
  937. specification character is specified, or the user ID and group ID are
  938. not preserved for any reason,
  939. .IR pax
  940. shall not set the S_ISUID and S_ISGID bits of the file mode.
  941. .P
  942. If the preservation of any of these items fails for any reason,
  943. .IR pax
  944. shall write a diagnostic message to standard error. Failure to preserve
  945. these items shall affect the final exit status, but shall not cause the
  946. extracted file to be deleted.
  947. .P
  948. If file characteristic letters in any of the
  949. .IR string
  950. option-arguments are duplicated or conflict with each other, the ones
  951. given last shall take precedence. For example, if
  952. .BR \-p
  953. .BR eme
  954. is specified, file modification times are preserved.
  955. .RE
  956. .IP "\fB\-s\ \fIreplstr\fR" 10
  957. Modify file or archive member names named by
  958. .IR pattern
  959. or
  960. .IR file
  961. operands according to the substitution expression
  962. .IR replstr ,
  963. using the syntax of the
  964. .IR ed
  965. utility. The concepts of ``address'' and ``line'' are meaningless in
  966. the context of the
  967. .IR pax
  968. utility, and shall not be supplied. The format shall be:
  969. .RS 10 
  970. .sp
  971. .RS 4
  972. .nf
  974. -s /\fIold\fR/\fInew\fR/\fB[\fRgp\fB]\fR
  975. .fi
  976. .P
  977. .RE
  978. .P
  979. where as in
  980. .IR ed ,
  981. .IR old
  982. is a basic regular expression and
  983. .IR new
  984. can contain an
  985. <ampersand>,
  986. .BR '\en' 
  987. (where
  988. .IR n
  989. is a digit) back-references, or subexpression matching. The
  990. .IR old
  991. string shall also be permitted to contain
  992. <newline>
  993. characters.
  994. .P
  995. Any non-null character can be used as a delimiter (\c
  996. .BR '/' 
  997. shown here). Multiple
  998. .BR \-s
  999. expressions can be specified; the expressions shall be applied in the
  1000. order specified, terminating with the first successful substitution.
  1001. The optional trailing
  1002. .BR 'g' 
  1003. is as defined in the
  1004. .IR ed
  1005. utility. The optional trailing
  1006. .BR 'p' 
  1007. shall cause successful substitutions to be written to standard error.
  1008. File or archive member names that substitute to the empty string shall
  1009. be ignored when reading and writing archives.
  1010. .RE
  1011. .IP "\fB\-t\fP" 10
  1012. When reading files from the file system, and if the user has the
  1013. permissions required by
  1014. \fIutime\fR()
  1015. to do so, set the access time of each file read to the access time that
  1016. it had before being read by
  1017. .IR pax .
  1018. .IP "\fB\-u\fP" 10
  1019. Ignore files that are older (having a less recent file modification
  1020. time) than a pre-existing file or archive member with the same name.
  1021. In
  1022. .BR read
  1023. mode, an archive member with the same name as a file in the file system
  1024. shall be extracted if the archive member is newer than the file. In
  1025. .BR write
  1026. mode, an archive file member with the same name as a file in the file
  1027. system shall be superseded if the file is newer than the archive
  1028. member. If
  1029. .BR \-a
  1030. is also specified, this is accomplished by appending to the archive;
  1031. otherwise, it is unspecified whether this is accomplished by actual
  1032. replacement in the archive or by appending to the archive. In
  1033. .BR copy
  1034. mode, the file in the destination hierarchy shall be replaced by the
  1035. file in the source hierarchy or by a link to the file in the source
  1036. hierarchy if the file in the source hierarchy is newer.
  1037. .IP "\fB\-v\fP" 10
  1038. In
  1039. .BR list
  1040. mode, produce a verbose table of contents (see the STDOUT section).
  1041. Otherwise, write archive member pathnames to standard error (see the
  1042. STDERR section).
  1043. .IP "\fB\-x\ \fIformat\fR" 10
  1044. Specify the output archive format. The
  1045. .IR pax
  1046. utility shall support the following formats:
  1047. .RS 10 
  1048. .IP "\fBcpio\fR" 10
  1049. The
  1050. .BR cpio
  1051. interchange format; see the EXTENDED DESCRIPTION section. The default
  1052. .IR blocksize
  1053. for this format for character special archive files shall be 5\|120.
  1054. Implementations shall support all
  1055. .IR blocksize
  1056. values less than or equal to 32\|256 that are multiples of 512.
  1057. .IP "\fBpax\fR" 10
  1058. The
  1059. .BR pax
  1060. interchange format; see the EXTENDED DESCRIPTION section. The default
  1061. .IR blocksize
  1062. for this format for character special archive files shall be 5\|120.
  1063. Implementations shall support all
  1064. .IR blocksize
  1065. values less than or equal to 32\|256 that are multiples of 512.
  1066. .IP "\fBustar\fR" 10
  1067. The
  1068. .BR tar
  1069. interchange format; see the EXTENDED DESCRIPTION section. The default
  1070. .IR blocksize
  1071. for this format for character special archive files shall be 10\|240.
  1072. Implementations shall support all
  1073. .IR blocksize
  1074. values less than or equal to 32\|256 that are multiples of 512.
  1075. .P
  1076. Implementation-defined formats shall specify a default block size as
  1077. well as any other block sizes supported for character special archive
  1078. files.
  1079. .P
  1080. Any attempt to append to an archive file in a format different from the
  1081. existing archive format shall cause
  1082. .IR pax
  1083. to exit immediately with a non-zero exit status.
  1084. .RE
  1085. .IP "\fB\-X\fP" 10
  1086. When traversing the file hierarchy specified by a pathname,
  1087. .IR pax
  1088. shall not descend into directories that have a different device ID (\c
  1089. .IR st_dev ;
  1090. see the System Interfaces volume of POSIX.1\(hy2017,
  1091. \fIstat\fR()).
  1092. .P
  1093. Specifying more than one of the mutually-exclusive options
  1094. .BR \-H
  1095. and
  1096. .BR \-L
  1097. shall not be considered an error and the last option specified shall
  1098. determine the behavior of the utility.
  1099. .P
  1100. The options that operate on the names of files or archive members (\c
  1101. .BR \-c ,
  1102. .BR \-i ,
  1103. .BR \-n ,
  1104. .BR \-s ,
  1105. .BR \-u ,
  1106. and
  1107. .BR \-v )
  1108. shall interact as follows. In
  1109. .BR read
  1110. mode, the archive members shall be selected based on the user-specified
  1111. .IR pattern
  1112. operands as modified by the
  1113. .BR \-c ,
  1114. .BR \-n ,
  1115. and
  1116. .BR \-u
  1117. options. Then, any
  1118. .BR \-s
  1119. and
  1120. .BR \-i
  1121. options shall modify, in that order, the names of the selected files.
  1122. The
  1123. .BR \-v
  1124. option shall write names resulting from these modifications.
  1125. .P
  1126. In
  1127. .BR write
  1128. mode, the files shall be selected based on the user-specified
  1129. pathnames as modified by the
  1130. .BR \-n
  1131. and
  1132. .BR \-u
  1133. options. Then, any
  1134. .BR \-s
  1135. and
  1136. .BR \-i
  1137. options shall modify, in that order, the names of these selected files.
  1138. The
  1139. .BR \-v
  1140. option shall write names resulting from these modifications.
  1141. .P
  1142. If both the
  1143. .BR \-u
  1144. and
  1145. .BR \-n
  1146. options are specified,
  1147. .IR pax
  1148. shall not consider a file selected unless it is newer than the file to
  1149. which it is compared.
  1150. .SS "List Mode Format Specifications"
  1151. .P
  1152. In
  1153. .BR list
  1154. mode with the
  1155. .BR \-o
  1156. .BR listopt=format
  1157. option, the
  1158. .IR format
  1159. argument shall be applied for each selected file. The
  1160. .IR pax
  1161. utility shall append a
  1162. <newline>
  1163. to the
  1164. .BR listopt
  1165. output for each selected file. The
  1166. .IR format
  1167. argument shall be used as the
  1168. .IR format
  1169. string described in the Base Definitions volume of POSIX.1\(hy2017,
  1170. .IR "Chapter 5" ", " "File Format Notation",
  1171. with the exceptions 1. through 6. defined in the EXTENDED DESCRIPTION
  1172. section of
  1173. .IR printf ,
  1174. plus the following exceptions:
  1175. .IP 7. 6
  1176. The sequence (\c
  1177. .IR keyword )
  1178. can occur before a format conversion specifier. The conversion
  1179. argument is defined by the value of
  1180. .IR keyword .
  1181. The implementation shall support the following keywords:
  1182. .RS 6 
  1183. .IP -- 4
  1184. Any of the Field Name entries in
  1185. .IR "Table 4-14, ustar Header Block"
  1186. and
  1187. .IR "Table 4-16, Octet-Oriented cpio Archive Entry".
  1188. The implementation may support the
  1189. .IR cpio
  1190. keywords without the leading
  1191. .BR c_
  1192. in addition to the form required by
  1193. .IR "Table 4-16, Octet-Oriented cpio Archive Entry".
  1194. .IP -- 4
  1195. Any keyword defined for the extended header in
  1196. .IR "pax Extended Header".
  1197. .IP -- 4
  1198. Any keyword provided as an implementation-defined extension within
  1199. the extended header defined in
  1200. .IR "pax Extended Header".
  1201. .P
  1202. For example, the sequence
  1203. .BR \(dq%(charset)s\(dq 
  1204. is the string value of the name of the character set in the extended
  1205. header.
  1206. .P
  1207. The result of the keyword conversion argument shall be the value from
  1208. the applicable header field or extended header, without any trailing
  1209. NULs.
  1210. .P
  1211. All keyword values used as conversion arguments shall be translated
  1212. from the UTF\(hy8 encoding (or alternative encoding specified by any
  1213. .BR hdrcharset
  1214. extended header record) to the character set appropriate for the local
  1215. file system, user database, and so on, as applicable.
  1216. .RE
  1217. .IP 8. 6
  1218. An additional conversion specifier character,
  1219. .BR T ,
  1220. shall be used to specify time formats. The
  1221. .BR T
  1222. conversion specifier character can be preceded by the sequence (\c
  1223. .IR keyword= \c
  1224. .IR subformat ),
  1225. where
  1226. .IR subformat
  1227. is a date format as defined by
  1228. .IR date
  1229. operands. The default
  1230. .IR keyword
  1231. shall be
  1232. .BR mtime
  1233. and the default subformat shall be:
  1234. .RS 6 
  1235. .sp
  1236. .RS 4
  1237. .nf
  1239. %b %e %H:%M %Y
  1240. .fi
  1241. .P
  1242. .RE
  1243. .RE
  1244. .IP 9. 6
  1245. An additional conversion specifier character,
  1246. .BR M ,
  1247. shall be used to specify the file mode string as defined in
  1248. .IR ls
  1249. Standard Output. If (\c
  1250. .IR keyword )
  1251. is omitted, the
  1252. .BR mode
  1253. keyword shall be used. For example,
  1254. .BR %.1M
  1255. writes the single character corresponding to the <\fIentry\ type\fP>
  1256. field of the
  1257. .IR ls
  1258. .BR \-l
  1259. command.
  1260. .IP 10. 6
  1261. An additional conversion specifier character,
  1262. .BR D ,
  1263. shall be used to specify the device for block or special files, if
  1264. applicable, in an implementation-defined format. If not applicable,
  1265. and (\c
  1266. .IR keyword )
  1267. is specified, then this conversion shall be equivalent to
  1268. \fR%(\fIkeyword\fR)u\fR. If not applicable, and (\c
  1269. .IR keyword )
  1270. is omitted, then this conversion shall be equivalent to
  1271. <space>.
  1272. .IP 11. 6
  1273. An additional conversion specifier character,
  1274. .BR F ,
  1275. shall be used to specify a pathname. The
  1276. .BR F
  1277. conversion character can be preceded by a sequence of
  1278. <comma>-separated
  1279. keywords:
  1280. .RS 6 
  1281. .sp
  1282. .RS 4
  1283. .nf
  1285. (\fIkeyword\fB[\fR,\fIkeyword\fB]\fR ... )
  1286. .fi
  1287. .P
  1288. .RE
  1289. .P
  1290. The values for all the keywords that are non-null shall be concatenated
  1291. together, each separated by a
  1292. .BR '/' .
  1293. The default shall be (\c
  1294. .BR path )
  1295. if the keyword
  1296. .BR path
  1297. is defined; otherwise, the default shall be (\c
  1298. .BR prefix ,\c
  1299. .BR name ).
  1300. .RE
  1301. .IP 12. 6
  1302. An additional conversion specifier character,
  1303. .BR L ,
  1304. shall be used to specify a symbolic link expansion. If the current
  1305. file is a symbolic link, then
  1306. .BR %L
  1307. shall expand to:
  1308. .RS 6 
  1309. .sp
  1310. .RS 4
  1311. .nf
  1313. "%s -> %s", <\fIvalue of keyword\fR>, <\fIcontents of link\fR>
  1314. .fi
  1315. .P
  1316. .RE
  1317. .P
  1318. Otherwise, the
  1319. .BR %L
  1320. conversion specification shall be the equivalent of
  1321. .BR %F .
  1322. .RE
  1323. .SH OPERANDS
  1324. The following operands shall be supported:
  1325. .IP "\fIdirectory\fR" 10
  1326. The destination directory pathname for
  1327. .BR copy
  1328. mode.
  1329. .IP "\fIfile\fR" 10
  1330. A pathname of a file to be copied or archived.
  1331. .IP "\fIpattern\fR" 10
  1332. A pattern matching one or more pathnames of archive members. A pattern
  1333. must be given in the name-generating notation of the pattern matching
  1334. notation in
  1335. .IR "Section 2.13" ", " "Pattern Matching Notation",
  1336. including the filename expansion rules in
  1337. .IR "Section 2.13.3" ", " "Patterns Used for Filename Expansion".
  1338. The default, if no
  1339. .IR pattern
  1340. is specified, is to select all members in the archive.
  1341. .SH STDIN
  1342. In
  1343. .BR write
  1344. mode, the standard input shall be used only if no
  1345. .IR file
  1346. operands are specified. It shall be a file containing a list of
  1347. pathnames, each terminated by a
  1348. <newline>
  1349. character.
  1350. .P
  1351. In
  1352. .BR list
  1353. and
  1354. .BR read
  1355. modes, if
  1356. .BR \-f
  1357. is not specified, the standard input shall be an archive file.
  1358. .P
  1359. Otherwise, the standard input shall not be used.
  1360. .SH "INPUT FILES"
  1361. The input file named by the
  1362. .IR archive
  1363. option-argument, or standard input when the archive is read from there,
  1364. shall be a file formatted according to one of the specifications in the
  1365. EXTENDED DESCRIPTION section or some other implementation-defined
  1366. format.
  1367. .P
  1368. The file
  1369. .BR /dev/tty
  1370. shall be used to write prompts and read responses.
  1371. .SH "ENVIRONMENT VARIABLES"
  1372. The following environment variables shall affect the execution of
  1373. .IR pax :
  1374. .IP "\fILANG\fP" 10
  1375. Provide a default value for the internationalization variables that are
  1376. unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
  1377. .IR "Section 8.2" ", " "Internationalization Variables"
  1378. the precedence of internationalization variables used to determine the
  1379. values of locale categories.)
  1380. .IP "\fILC_ALL\fP" 10
  1381. If set to a non-empty string value, override the values of all the
  1382. other internationalization variables.
  1383. .IP "\fILC_COLLATE\fP" 10
  1384. .br
  1385. Determine the locale for the behavior of ranges, equivalence classes,
  1386. and multi-character collating elements used in the pattern matching
  1387. expressions for the
  1388. .IR pattern
  1389. operand, the basic regular expression for the
  1390. .BR \-s
  1391. option, and the extended regular expression defined for the
  1392. .BR yesexpr
  1393. locale keyword in the
  1394. .IR LC_MESSAGES
  1395. category.
  1396. .IP "\fILC_CTYPE\fP" 10
  1397. Determine the locale for the interpretation of sequences of bytes of
  1398. text data as characters (for example, single-byte as opposed to
  1399. multi-byte characters in arguments and input files), the behavior of
  1400. character classes used in the extended regular expression defined for
  1401. the
  1402. .BR yesexpr
  1403. locale keyword in the
  1404. .IR LC_MESSAGES
  1405. category, and pattern matching.
  1406. .IP "\fILC_MESSAGES\fP" 10
  1407. .br
  1408. Determine the locale used to process affirmative responses, and the
  1409. locale used to affect the format and contents of diagnostic messages
  1410. and prompts written to standard error.
  1411. .IP "\fILC_TIME\fP" 10
  1412. Determine the format and contents of date and time strings when the
  1413. .BR \-v
  1414. option is specified.
  1415. .IP "\fINLSPATH\fP" 10
  1416. Determine the location of message catalogs for the processing of
  1417. .IR LC_MESSAGES .
  1418. .IP "\fITMPDIR\fP" 10
  1419. Determine the pathname that provides part of the default global
  1420. extended header record file, as described for the
  1421. .BR \-o
  1422. .BR globexthdr=
  1423. keyword in the OPTIONS section.
  1424. .IP "\fITZ\fP" 10
  1425. Determine the timezone used to calculate date and time strings when the
  1426. .BR \-v
  1427. option is specified. If
  1428. .IR TZ
  1429. is unset or null, an unspecified default timezone shall be used.
  1430. .SH "ASYNCHRONOUS EVENTS"
  1431. Default.
  1432. .SH STDOUT
  1433. In
  1434. .BR write
  1435. mode, if
  1436. .BR \-f
  1437. is not specified, the standard output shall be the archive formatted
  1438. according to one of the specifications in the EXTENDED DESCRIPTION
  1439. section, or some other implementation-defined format (see
  1440. .BR \-x
  1441. .IR format ).
  1442. .P
  1443. In
  1444. .BR list
  1445. mode, when the
  1446. .BR \-o \c
  1447. .BR listopt =\c
  1448. .IR format
  1449. has been specified, the selected archive members shall be written to
  1450. standard output using the format described under
  1451. .IR "List Mode Format Specifications".
  1452. In
  1453. .BR list
  1454. mode without the
  1455. .BR \-o \c
  1456. .BR listopt =\c
  1457. .IR format
  1458. option, the table of contents of the selected archive members shall
  1459. be written to standard output using the following format:
  1460. .sp
  1461. .RS 4
  1462. .nf
  1464. "%s\en", <\fIpathname\fR>
  1465. .fi
  1466. .P
  1467. .RE
  1468. .P
  1469. If the
  1470. .BR \-v
  1471. option is specified in
  1472. .BR list
  1473. mode, the table of contents of the selected archive members shall be
  1474. written to standard output using the following formats.
  1475. .P
  1476. For pathnames representing hard links to previous members of the
  1477. archive:
  1478. .sp
  1479. .RS 4
  1480. .nf
  1482. "%s == %s\en", <\fIls\fR -l \fIlisting\fR>, <\fIlinkname\fR>
  1483. .fi
  1484. .P
  1485. .RE
  1486. .P
  1487. For all other pathnames:
  1488. .sp
  1489. .RS 4
  1490. .nf
  1492. "%s\en", <\fIls\fR -l \fIlisting\fR>
  1493. .fi
  1494. .P
  1495. .RE
  1496. .P
  1497. where <\fIls\ \fR\-l\ \fIlisting\fR> shall be the format specified by
  1498. the
  1499. .IR ls
  1500. utility with the
  1501. .BR \-l
  1502. option. When writing pathnames in this format, it is unspecified what
  1503. is written for fields for which the underlying archive format does not
  1504. have the correct information, although the correct number of
  1505. <blank>-separated
  1506. fields shall be written.
  1507. .P
  1508. In
  1509. .BR list
  1510. mode, standard output shall not be buffered more than a pathname
  1511. (plus any associated information and a
  1512. <newline>
  1513. terminator) at a time.
  1514. .SH STDERR
  1515. If
  1516. .BR \-v
  1517. is specified in
  1518. .BR read ,
  1519. .BR write ,
  1520. or
  1521. .BR copy
  1522. modes,
  1523. .IR pax
  1524. shall write the pathnames it processes to the standard error output
  1525. using the following format:
  1526. .sp
  1527. .RS 4
  1528. .nf
  1530. "%s\en", <\fIpathname\fR>
  1531. .fi
  1532. .P
  1533. .RE
  1534. .P
  1535. These pathnames shall be written as soon as processing is begun on the
  1536. file or archive member, and shall be flushed to standard error. The
  1537. trailing
  1538. <newline>,
  1539. which shall not be buffered, is written when the file has been read or
  1540. written.
  1541. .P
  1542. If the
  1543. .BR \-s
  1544. option is specified, and the replacement string has a trailing
  1545. .BR 'p' ,
  1546. substitutions shall be written to standard error in the following
  1547. format:
  1548. .sp
  1549. .RS 4
  1550. .nf
  1552. "%s >> %s\en", <\fIoriginal pathname\fR>, <\fInew pathname\fR>
  1553. .fi
  1554. .P
  1555. .RE
  1556. .P
  1557. In all operating modes of
  1558. .IR pax ,
  1559. optional messages of unspecified format concerning the input archive
  1560. format and volume number, the number of files, blocks, volumes, and
  1561. media parts as well as other diagnostic messages may be written to
  1562. standard error.
  1563. .P
  1564. In all formats, for both standard output and standard error, it is
  1565. unspecified how non-printable characters in pathnames or link names
  1566. are written.
  1567. .P
  1568. When using the
  1569. .BR \-x \c
  1570. .BR pax
  1571. archive format, if a filename, link name, group name, owner name, or
  1572. any other field in an extended header record cannot be translated
  1573. between the codeset in use for that extended header record and the
  1574. character set of the current locale,
  1575. .IR pax
  1576. shall write a diagnostic message to standard error, shall process the
  1577. file as described for the
  1578. .BR \-o
  1579. .BR invalid=
  1580. option, and then shall continue processing with the next file.
  1581. .SH "OUTPUT FILES"
  1582. In
  1583. .BR read
  1584. mode, the extracted output files shall be of the archived file type.
  1585. In
  1586. .BR copy
  1587. mode, the copied output files shall be the type of the file being
  1588. copied. In either mode, existing files in the destination hierarchy
  1589. shall be overwritten only when all permission (\c
  1590. .BR \-p ),
  1591. modification time (\c
  1592. .BR \-u ),
  1593. and invalid-value (\c
  1594. .BR \-o \c
  1595. .BR invalid= )
  1596. tests allow it.
  1597. .P
  1598. In
  1599. .BR write
  1600. mode, the output file named by the
  1601. .BR \-f
  1602. option-argument shall be a file formatted according to one of the
  1603. specifications in the EXTENDED DESCRIPTION section, or some other
  1604. implementation-defined format.
  1605. .SH "EXTENDED DESCRIPTION"
  1606. .SS "pax Interchange Format"
  1607. .P
  1608. A
  1609. .IR pax
  1610. archive tape or file produced in the
  1611. .BR \-x \c
  1612. .BR pax
  1613. format shall contain a series of blocks. The physical layout of the
  1614. archive shall be identical to the
  1615. .BR ustar
  1616. format described in
  1617. .IR "ustar Interchange Format".
  1618. Each file archived shall be represented by the following sequence:
  1619. .IP " *" 4
  1620. An optional header block with extended header records. This header
  1621. block is of the form described in
  1622. .IR "pax Header Block",
  1623. with a
  1624. .IR typeflag
  1625. value of
  1626. .BR x
  1627. or
  1628. .BR g .
  1629. The extended header records, described in
  1630. .IR "pax Extended Header",
  1631. shall be included as the data for this header block.
  1632. .IP " *" 4
  1633. A header block that describes the file. Any fields in the preceding
  1634. optional extended header shall override the associated fields in
  1635. this header block for this file.
  1636. .IP " *" 4
  1637. Zero or more blocks that contain the contents of the file.
  1638. .P
  1639. At the end of the archive file there shall be two 512-byte blocks
  1640. filled with binary zeros, interpreted as an end-of-archive indicator.
  1641. .P
  1642. A schematic of an example archive with global extended header records
  1643. and two actual files is shown in
  1644. .IR "Figure 4-1, pax Format Archive Example".
  1645. In the example, the second file in the archive has no extended header
  1646. preceding it, presumably because it has no need for extended
  1647. attributes.
  1648. .sp
  1649. .ce 1
  1650. \fBFigure 4-1: pax Format Archive Example\fR
  1651. .SS "pax Header Block"
  1652. .P
  1653. The
  1654. .BR pax
  1655. header block shall be identical to the
  1656. .BR ustar
  1657. header block described in
  1658. .IR "ustar Interchange Format",
  1659. except that two additional
  1660. .IR typeflag
  1661. values are defined:
  1662. .IP "\fRx\fP" 6
  1663. Represents extended header records for the following file in the
  1664. archive (which shall have its own
  1665. .BR ustar
  1666. header block). The format of these extended header records shall be as
  1667. described in
  1668. .IR "pax Extended Header".
  1669. .IP "\fRg\fR" 6
  1670. Represents global extended header records for the following files in
  1671. the archive. The format of these extended header records shall be as
  1672. described in
  1673. .IR "pax Extended Header".
  1674. Each value shall affect all subsequent files that do not override that
  1675. value in their own extended header record and until another global
  1676. extended header record is reached that provides another value for the
  1677. same field. The
  1678. .IR typeflag
  1679. .BR g
  1680. global headers should not be used with interchange media that could
  1681. suffer partial data loss in transporting the archive.
  1682. .P
  1683. For both of these types, the
  1684. .IR size
  1685. field shall be the size of the extended header records in octets. The
  1686. other fields in the header block are not meaningful to this version of
  1687. the
  1688. .IR pax
  1689. utility. However, if this archive is read by a
  1690. .IR pax
  1691. utility conforming to the ISO\ POSIX\(hy2:\|1993 standard, the header block fields are used to
  1692. create a regular file that contains the extended header records as
  1693. data. Therefore, header block field values should be selected to
  1694. provide reasonable file access to this regular file.
  1695. .P
  1696. A further difference from the
  1697. .BR ustar
  1698. header block is that data blocks for files of
  1699. .IR typeflag
  1700. 1 (the digit one) (hard link) may be included, which means that the
  1701. size field may be greater than zero. Archives created by
  1702. .IR pax
  1703. .BR \-o
  1704. .BR linkdata
  1705. shall include these data blocks with the hard links.
  1706. .SS "pax Extended Header"
  1707. .P
  1708. A
  1709. .BR pax
  1710. extended header contains values that are inappropriate for the
  1711. .BR ustar
  1712. header block because of limitations in that format: fields requiring a
  1713. character encoding other than that described in the ISO/IEC\ 646:\|1991 standard, fields
  1714. representing file attributes not described in the
  1715. .BR ustar
  1716. header, and fields whose format or length do not fit the requirements
  1717. of the
  1718. .BR ustar
  1719. header. The values in an extended header add attributes to the
  1720. following file (or files; see the description of the
  1721. .IR typeflag
  1722. .BR g
  1723. header block) or override values in the following header block(s), as
  1724. indicated in the following list of keywords.
  1725. .P
  1726. An extended header shall consist of one or more records, each
  1727. constructed as follows:
  1728. .sp
  1729. .RS 4
  1730. .nf
  1732. "%d %s=%s\en", <\fIlength\fR>, <\fIkeyword\fR>, <\fIvalue\fR>
  1733. .fi
  1734. .P
  1735. .RE
  1736. .P
  1737. The extended header records shall be encoded according to the ISO/IEC\ 10646\(hy1:\|2000 standard
  1738. UTF\(hy8 encoding. The <\fIlength\fP> field,
  1739. <blank>,
  1740. <equals-sign>,
  1741. and
  1742. <newline>
  1743. shown shall be limited to the portable character set, as encoded in
  1744. UTF\(hy8. The <\fIkeyword\fP> fields can be any UTF\(hy8 characters.
  1745. The <\fIlength\fP> field shall be the decimal length of the extended
  1746. header record in octets, including the trailing
  1747. <newline>.
  1748. If there is a
  1749. .BR hdrcharset
  1750. extended header in effect for a file, the
  1751. .IR value
  1752. field for any
  1753. .BR gname ,
  1754. .BR linkpath ,
  1755. .BR path ,
  1756. and
  1757. .BR uname
  1758. extended header records shall be encoded using the character set
  1759. specified by the
  1760. .BR hdrcharset
  1761. extended header record; otherwise, the
  1762. .IR value
  1763. field shall be encoded using UTF\(hy8. The
  1764. .IR value
  1765. field for all other keywords specified by POSIX.1\(hy2008 shall be
  1766. encoded using UTF\(hy8.
  1767. .P
  1768. The <\fIkeyword\fP> field shall be one of the entries from the
  1769. following list or a keyword provided as an implementation extension.
  1770. Keywords consisting entirely of lowercase letters, digits, and periods
  1771. are reserved for future standardization. A keyword shall not include an
  1772. <equals-sign>.
  1773. (In the following list, the notations ``file(s)'' or ``block(s)'' is used
  1774. to acknowledge that a keyword affects the following single file after a
  1775. .IR typeflag
  1776. .BR x
  1777. extended header, but possibly multiple files after
  1778. .IR typeflag
  1779. .BR g .
  1780. Any requirements in the list for
  1781. .IR pax
  1782. to include a record when in
  1783. .BR write
  1784. or
  1785. .BR copy
  1786. mode shall apply only when such a record has not already been provided
  1787. through the use of the
  1788. .BR \-o
  1789. option. When used in
  1790. .BR copy
  1791. mode,
  1792. .IR pax
  1793. shall behave as if an archive had been created with applicable extended
  1794. header records and then extracted.)
  1795. .IP "\fBatime\fP" 10
  1796. The file access time for the following file(s), equivalent to the value
  1797. of the
  1798. .IR st_atime
  1799. member of the
  1800. .BR stat
  1801. structure for a file, as described by the
  1802. \fIstat\fR()
  1803. function. The access time shall be restored if the process has
  1804. appropriate privileges required to do so. The format of the
  1805. <\fIvalue\fP> shall be as described in
  1806. .IR "pax Extended Header File Times".
  1807. .IP "\fBcharset\fP" 10
  1808. The name of the character set used to encode the data in the following
  1809. file(s). The entries in the following table are defined to refer to
  1810. known standards; additional names may be agreed on between the
  1811. originator and recipient.
  1812. .TS
  1813. center box tab(!);
  1814. cB | cB
  1815. lf5 | l.
  1816. <value>!Formal Standard
  1817. _
  1818. ISO-IR 646 1990!ISO/IEC 646:\|1990
  1819. ISO-IR 8859 1 1998!ISO/IEC 8859\(hy1:\|1998
  1820. ISO-IR 8859 2 1999!ISO/IEC 8859\(hy2:\|1999
  1821. ISO-IR 8859 3 1999!ISO/IEC 8859\(hy3:\|1999
  1822. ISO-IR 8859 4 1998!ISO/IEC 8859\(hy4:\|1998
  1823. ISO-IR 8859 5 1999!ISO/IEC 8859\(hy5:\|1999
  1824. ISO-IR 8859 6 1999!ISO/IEC 8859\(hy6:\|1999
  1825. ISO-IR 8859 7 1987!ISO/IEC 8859\(hy7:\|1987
  1826. ISO-IR 8859 8 1999!ISO/IEC 8859\(hy8:\|1999
  1827. ISO-IR 8859 9 1999!ISO/IEC 8859\(hy9:\|1999
  1828. ISO-IR 8859 10 1998!ISO/IEC 8859\(hy10:\|1998
  1829. ISO-IR 8859 13 1998!ISO/IEC 8859\(hy13:\|1998
  1830. ISO-IR 8859 14 1998!ISO/IEC 8859\(hy14:\|1998
  1831. ISO-IR 8859 15 1999!ISO/IEC 8859\(hy15:\|1999
  1832. ISO-IR 10646 2000!ISO/IEC 10646:\|2000
  1833. ISO-IR 10646 2000 UTF-8!ISO/IEC 10646, UTF-8 encoding
  1834. BINARY!None.
  1835. .TE
  1836. .RS 10 
  1837. .P
  1838. The encoding is included in an extended header for information only;
  1839. when
  1840. .IR pax
  1841. is used as described in POSIX.1\(hy2008, it shall not translate the file data
  1842. into any other encoding. The
  1843. .BR BINARY
  1844. entry indicates unencoded binary data.
  1845. .P
  1846. When used in
  1847. .BR write
  1848. or
  1849. .BR copy
  1850. mode, it is implementation-defined whether
  1851. .IR pax
  1852. includes a
  1853. .BR charset
  1854. extended header record for a file.
  1855. .RE
  1856. .IP "\fBcomment\fP" 10
  1857. A series of characters used as a comment. All characters in the
  1858. <\fIvalue\fP> field shall be ignored by
  1859. .IR pax .
  1860. .IP "\fBgid\fP" 10
  1861. The group ID of the group that owns the file, expressed as a decimal
  1862. number using digits from the ISO/IEC\ 646:\|1991 standard. This record shall override the
  1863. .IR gid
  1864. field in the following header block(s). When used in
  1865. .BR write
  1866. or
  1867. .BR copy
  1868. mode,
  1869. .IR pax
  1870. shall include a
  1871. .IR gid
  1872. extended header record for each file whose group ID is greater than
  1873. 2\|097\|151 (octal 7\|777\|777).
  1874. .IP "\fBgname\fP" 10
  1875. The group of the file(s), formatted as a group name in the group
  1876. database. This record shall override the
  1877. .IR gid
  1878. and
  1879. .IR gname
  1880. fields in the following header block(s), and any
  1881. .IR gid
  1882. extended header record. When used in
  1883. .BR read ,
  1884. .BR copy ,
  1885. or
  1886. .BR list
  1887. mode,
  1888. .IR pax
  1889. shall translate the name from the encoding in the header record to
  1890. the character set appropriate for the group database on the
  1891. receiving system. If any of the characters cannot be
  1892. translated, and if neither the
  1893. .BR \-o \c
  1894. .BR invalid=UTF\(hy8
  1895. option nor the
  1896. .BR \-o \c
  1897. .BR invalid=binary
  1898. option is specified, the results are implementation-defined.
  1899. When used in
  1900. .BR write
  1901. or
  1902. .BR copy
  1903. mode,
  1904. .IR pax
  1905. shall include a
  1906. .BR gname
  1907. extended header record for each file whose group name cannot be
  1908. represented entirely with the letters and digits of the portable
  1909. character set.
  1910. .IP "\fBhdrcharset\fR" 10
  1911. The name of the character set used to encode the value field of the
  1912. .BR gname ,
  1913. .BR linkpath ,
  1914. .BR path ,
  1915. and
  1916. .BR uname
  1917. .IR pax
  1918. extended header records. The entries in the following table are defined
  1919. to refer to known standards; additional names may be agreed between the
  1920. originator and the recipient.
  1921. .br
  1922. .TS
  1923. center box tab(!);
  1924. cB | cB
  1925. lf5 | l.
  1926. <value>!Formal Standard
  1927. _
  1928. ISO-IR 10646 2000 UTF-8!ISO/IEC 10646, UTF-8 encoding
  1929. BINARY!None.
  1930. .TE
  1931. .RS 10 
  1932. .P
  1933. If no
  1934. .BR hdrcharset
  1935. extended header record is specified, the default character set used to
  1936. encode all values in extended header records shall be the ISO/IEC\ 10646\(hy1:\|2000 standard
  1937. UTF\(hy8 encoding.
  1938. .P
  1939. The
  1940. .BR BINARY
  1941. entry indicates that all values recorded in extended headers for
  1942. affected files are unencoded binary data from the underlying system.
  1943. .RE
  1944. .IP "\fBlinkpath\fP" 10
  1945. The pathname of a link being created to another file, of any type,
  1946. previously archived. This record shall override the
  1947. .IR linkname
  1948. field in the following
  1949. .BR ustar
  1950. header block(s). The following
  1951. .BR ustar
  1952. header block shall determine the type of link created. If
  1953. .IR typeflag
  1954. of the following header block is 1, it shall be a hard link. If
  1955. .IR typeflag
  1956. is 2, it shall be a symbolic link and the
  1957. .BR linkpath
  1958. value shall be the contents of the symbolic link. The
  1959. .IR pax
  1960. utility shall translate the name of the link (contents of the symbolic
  1961. link) from the encoding in the header to the character set appropriate
  1962. for the local file system. When used in
  1963. .BR write
  1964. or
  1965. .BR copy
  1966. mode,
  1967. .IR pax
  1968. shall include a
  1969. .BR linkpath
  1970. extended header record for each link whose pathname cannot be
  1971. represented entirely with the members of the portable character set
  1972. other than NUL.
  1973. .IP "\fBmtime\fP" 10
  1974. The file modification time of the following file(s), equivalent to the
  1975. value of the
  1976. .IR st_mtime
  1977. member of the
  1978. .BR stat
  1979. structure for a file, as described in the
  1980. \fIstat\fR()
  1981. function. This record shall override the
  1982. .IR mtime
  1983. field in the following header block(s). The modification time shall be
  1984. restored if the process has appropriate privileges required to do
  1985. so. The format of the <\fIvalue\fP> shall be as described in
  1986. .IR "pax Extended Header File Times".
  1987. .IP "\fBpath\fP" 10
  1988. The pathname of the following file(s). This record shall override the
  1989. .IR name
  1990. and
  1991. .IR prefix
  1992. fields in the following header block(s). The
  1993. .IR pax
  1994. utility shall translate the pathname of the file from the encoding in
  1995. the header to the character set appropriate for the local file system.
  1996. .RS 10 
  1997. .P
  1998. When used in
  1999. .BR write
  2000. or
  2001. .BR copy
  2002. mode,
  2003. .IR pax
  2004. shall include a
  2005. .IR path
  2006. extended header record for each file whose pathname cannot be
  2007. represented entirely with the members of the portable character set
  2008. other than NUL.
  2009. .RE
  2010. .IP "\fBrealtime.\fIany\fR" 10
  2011. The keywords prefixed by ``realtime.'' are reserved for future
  2012. standardization.
  2013. .IP "\fBsecurity.\fIany\fR" 10
  2014. The keywords prefixed by ``security.'' are reserved for future
  2015. standardization.
  2016. .IP "\fBsize\fP" 10
  2017. The size of the file in octets, expressed as a decimal number using
  2018. digits from the ISO/IEC\ 646:\|1991 standard. This record shall override the
  2019. .IR size
  2020. field in the following header block(s). When used in
  2021. .BR write
  2022. or
  2023. .BR copy
  2024. mode,
  2025. .IR pax
  2026. shall include a
  2027. .IR size
  2028. extended header record for each file with a size value greater than
  2029. 8\|589\|934\|591 (octal 77\|777\|777\|777).
  2030. .IP "\fBuid\fP" 10
  2031. The user ID of the file owner, expressed as a decimal number using
  2032. digits from the ISO/IEC\ 646:\|1991 standard. This record shall override the
  2033. .IR uid
  2034. field in the following header block(s). When used in
  2035. .BR write
  2036. or
  2037. .BR copy
  2038. mode,
  2039. .IR pax
  2040. shall include a
  2041. .IR uid
  2042. extended header record for each file whose owner ID is greater than
  2043. 2\|097\|151 (octal 7\|777\|777).
  2044. .IP "\fBuname\fP" 10
  2045. The owner of the following file(s), formatted as a user name in the
  2046. user database. This record shall override the
  2047. .IR uid
  2048. and
  2049. .IR uname
  2050. fields in the following header block(s), and any
  2051. .IR uid
  2052. extended header record. When used in
  2053. .BR read ,
  2054. .BR copy ,
  2055. or
  2056. .BR list
  2057. mode,
  2058. .IR pax
  2059. shall translate the name from the encoding in the header record to the
  2060. character set appropriate for the user database on the receiving
  2061. system. If any of the characters cannot be translated, and if neither
  2062. the
  2063. .BR \-o \c
  2064. .BR invalid=UTF\(hy8
  2065. option nor the
  2066. .BR \-o \c
  2067. .BR invalid=binary
  2068. option is specified, the results are implementation-defined.
  2069. When used in
  2070. .BR write
  2071. or
  2072. .BR copy
  2073. mode,
  2074. .IR pax
  2075. shall include a
  2076. .BR uname
  2077. extended header record for each file whose user name cannot be
  2078. represented entirely with the letters and digits of the portable
  2079. character set.
  2080. .P
  2081. If the <\fIvalue\fP> field is zero length, it shall delete any header
  2082. block field, previously entered extended header value, or global
  2083. extended header value of the same name.
  2084. .P
  2085. If a keyword in an extended header record (or in a
  2086. .BR \-o
  2087. option-argument) overrides or deletes a corresponding field in the
  2088. .BR ustar
  2089. header block,
  2090. .IR pax
  2091. shall ignore the contents of that header block field.
  2092. .P
  2093. Unlike the
  2094. .BR ustar
  2095. header block fields, NULs shall not delimit <\fIvalue\fP>s; all
  2096. characters within the <\fIvalue\fP> field shall be considered data for
  2097. the field. None of the length limitations of the
  2098. .BR ustar
  2099. header block fields in
  2100. .IR "Table 4-14, ustar Header Block"
  2101. shall apply to the extended header records.
  2102. .SS "pax Extended Header Keyword Precedence"
  2103. .P
  2104. This section describes the precedence in which the various header
  2105. records and fields and command line options are selected to apply to a
  2106. file in the archive. When
  2107. .IR pax
  2108. is used in
  2109. .BR read
  2110. or
  2111. .BR list
  2112. modes, it shall determine a file attribute in the following sequence:
  2113. .IP " 1." 4
  2114. If
  2115. .BR \-o \c
  2116. .BR delete=keyword-prefix
  2117. is used, the affected attributes shall be determined from step 7., if
  2118. applicable, or ignored otherwise.
  2119. .IP " 2." 4
  2120. If
  2121. .BR \-o \c
  2122. .IR keyword :=
  2123. is used, the affected attributes shall be ignored.
  2124. .IP " 3." 4
  2125. If
  2126. .BR \-o \c
  2127. .BR keyword:=value
  2128. is used, the affected attribute shall be assigned the value.
  2129. .IP " 4." 4
  2130. If there is a
  2131. .IR typeflag
  2132. .BR x
  2133. extended header record, the affected attribute shall be assigned the
  2134. <\fIvalue\fP>. When extended header records conflict, the last one
  2135. given in the header shall take precedence.
  2136. .IP " 5." 4
  2137. If
  2138. .BR \-o \c
  2139. .BR keyword=value
  2140. is used, the affected attribute shall be assigned the value.
  2141. .IP " 6." 4
  2142. If there is a
  2143. .IR typeflag
  2144. .BR g
  2145. global extended header record, the affected attribute shall be assigned
  2146. the <\fIvalue\fP>. When global extended header records conflict, the
  2147. last one given in the global header shall take precedence.
  2148. .IP " 7." 4
  2149. Otherwise, the attribute shall be determined from the
  2150. .BR ustar
  2151. header block.
  2152. .SS "pax Extended Header File Times"
  2153. .P
  2154. The
  2155. .IR pax
  2156. utility shall write an
  2157. .BR mtime
  2158. record for each file in
  2159. .BR write
  2160. or
  2161. .BR copy
  2162. modes if the file's modification time cannot be represented exactly in
  2163. the
  2164. .BR ustar
  2165. header logical record described in
  2166. .IR "ustar Interchange Format".
  2167. This can occur if the time is out of
  2168. .BR ustar
  2169. range, or if the file system of the underlying implementation supports
  2170. non-integer time granularities and the time is not an integer. All of
  2171. these time records shall be formatted as a decimal representation of
  2172. the time in seconds since the Epoch. If a
  2173. <period>
  2174. (\c
  2175. .BR '.' )
  2176. decimal point character is present, the digits to the right of the
  2177. point shall represent the units of a subsecond timing granularity,
  2178. where the first digit is tenths of a second and each subsequent digit
  2179. is a tenth of the previous digit. In
  2180. .BR read
  2181. or
  2182. .BR copy
  2183. mode, the
  2184. .IR pax
  2185. utility shall truncate the time of a file to the greatest value that is
  2186. not greater than the input header file time. In
  2187. .BR write
  2188. or
  2189. .BR copy
  2190. mode, the
  2191. .IR pax
  2192. utility shall output a time exactly if it can be represented exactly as
  2193. a decimal number, and otherwise shall generate only enough digits so
  2194. that the same time shall be recovered if the file is extracted on a
  2195. system whose underlying implementation supports the same time
  2196. granularity.
  2197. .SS "ustar Interchange Format"
  2198. .P
  2199. A
  2200. .BR ustar
  2201. archive tape or file shall contain a series of logical records. Each
  2202. logical record shall be a fixed-size logical record of 512 octets (see
  2203. below). Although this format may be thought of as being stored on
  2204. 9-track industry-standard 12.7 mm (0.5 in) magnetic tape, other types of
  2205. transportable media are not excluded. Each file archived shall be
  2206. represented by a header logical record that describes the file,
  2207. followed by zero or more logical records that give the contents of the
  2208. file. At the end of the archive file there shall be two 512-octet
  2209. logical records filled with binary zeros, interpreted as an
  2210. end-of-archive indicator.
  2211. .P
  2212. The logical records may be grouped for physical I/O operations, as
  2213. described under the
  2214. .BR \-b \c
  2215. .IR blocksize
  2216. and
  2217. .BR \-x
  2218. .BR ustar
  2219. options. Each group of logical records may be written with a single
  2220. operation equivalent to the
  2221. \fIwrite\fR()
  2222. function. On magnetic tape, the result of this write shall be a single
  2223. tape physical block. The last physical block shall always be the full
  2224. size, so logical records after the two zero logical records may contain
  2225. undefined data.
  2226. .P
  2227. The header logical record shall be structured as shown in the following
  2228. table. All lengths and offsets are in decimal.
  2229. .br
  2230. .sp
  2231. .ce 1
  2232. \fBTable 4-14: ustar Header Block\fR
  2233. .TS
  2234. center box tab(@);
  2235. cB | cB | cB
  2236. lI | n | n.
  2237. Field Name@Octet Offset@Length (in Octets)
  2238. _
  2239. name@0@100
  2240. mode@100@8
  2241. uid@108@8
  2242. gid@116@8
  2243. size@124@12
  2244. mtime@136@12
  2245. chksum@148@8
  2246. typeflag@156@1
  2247. linkname@157@100
  2248. magic@257@6
  2249. version@263@2
  2250. uname@265@32
  2251. gname@297@32
  2252. devmajor@329@8
  2253. devminor@337@8
  2254. prefix@345@155
  2255. .TE
  2256. .P
  2257. All characters in the header logical record shall be represented in the
  2258. coded character set of the ISO/IEC\ 646:\|1991 standard. For maximum portability between
  2259. implementations, names should be selected from characters represented
  2260. by the portable filename character set as octets with the most
  2261. significant bit zero. If an implementation supports the use of
  2262. characters outside of
  2263. <slash>
  2264. and the portable filename character set in names for files, users, and
  2265. groups, one or more implementation-defined encodings of these characters
  2266. shall be provided for interchange purposes.
  2267. .P
  2268. However, the
  2269. .IR pax
  2270. utility shall never create filenames on the local system that cannot
  2271. be accessed via the procedures described in POSIX.1\(hy2008. If a filename is
  2272. found on the medium that would create an invalid filename, it is
  2273. implementation-defined whether the data from the file is stored on the
  2274. file hierarchy and under what name it is stored. The
  2275. .IR pax
  2276. utility may choose to ignore these files as long as it produces an
  2277. error indicating that the file is being ignored.
  2278. .P
  2279. Each field within the header logical record is contiguous; that is,
  2280. there is no padding used. Each character on the archive medium shall be
  2281. stored contiguously.
  2282. .P
  2283. The fields
  2284. .IR magic ,
  2285. .IR uname ,
  2286. and
  2287. .IR gname
  2288. are character strings each terminated by a NUL character. The fields
  2289. .IR name ,
  2290. .IR linkname ,
  2291. and
  2292. .IR prefix
  2293. are NUL-terminated character strings except when all characters in the
  2294. array contain non-NUL characters including the last character. The
  2295. .IR version
  2296. field is two octets containing the characters
  2297. .BR \(dq00\(dq 
  2298. (zero-zero). The
  2299. .IR typeflag
  2300. contains a single character. All other fields are leading zero-filled
  2301. octal numbers using digits from the ISO/IEC\ 646:\|1991 standard IRV. Each numeric field is
  2302. terminated by one or more
  2303. <space>
  2304. or NUL characters.
  2305. .P
  2306. The
  2307. .IR name
  2308. and the
  2309. .IR prefix
  2310. fields shall produce the pathname of the file. A new pathname shall
  2311. be formed, if
  2312. .IR prefix
  2313. is not an empty string (its first character is not NUL), by
  2314. concatenating
  2315. .IR prefix
  2316. (up to the first NUL character), a
  2317. <slash>
  2318. character, and
  2319. .IR name ;
  2320. otherwise,
  2321. .IR name
  2322. is used alone. In either case,
  2323. .IR name
  2324. is terminated at the first NUL character. If
  2325. .IR prefix
  2326. begins with a NUL character, it shall be ignored. In this manner,
  2327. pathnames of at most 256 characters can be supported. If a pathname
  2328. does not fit in the space provided,
  2329. .IR pax
  2330. shall notify the user of the error, and shall not store any part of the
  2331. file\(emheader or data\(emon the medium.
  2332. .P
  2333. The
  2334. .IR linkname
  2335. field, described below, shall not use the
  2336. .IR prefix
  2337. to produce a pathname. As such, a
  2338. .IR linkname
  2339. is limited to 100 characters. If the name does not fit in the space
  2340. provided,
  2341. .IR pax
  2342. shall notify the user of the error, and shall not attempt to store the
  2343. link on the medium.
  2344. .P
  2345. The
  2346. .IR mode
  2347. field provides 12 bits encoded in the ISO/IEC\ 646:\|1991 standard octal digit representation.
  2348. The encoded bits shall represent the following values:
  2349. .br
  2350. .sp
  2351. .ce 1
  2352. \fBTable: ustar \fImode\fP Field\fR
  2353. .TS
  2354. tab(!) center box;
  2355. cB | cB | cB
  2356. n | l | l.
  2357. Bit Value!POSIX.1\(hy2008 Bit!Description
  2358. _
  2359. 04\|000!S_ISUID!Set UID on execution.
  2360. 02\|000!S_ISGID!Set GID on execution.
  2361. 01\|000!<reserved>!Reserved for future standardization.
  2362. 00\|400!S_IRUSR!Read permission for file owner class.
  2363. 00\|200!S_IWUSR!Write permission for file owner class.
  2364. 00\|100!S_IXUSR!Execute/search permission for file owner class.
  2365. 00\|040!S_IRGRP!Read permission for file group class.
  2366. 00\|020!S_IWGRP!Write permission for file group class.
  2367. 00\|010!S_IXGRP!Execute/search permission for file group class.
  2368. 00\|004!S_IROTH!Read permission for file other class.
  2369. 00\|002!S_IWOTH!Write permission for file other class.
  2370. 00\|001!S_IXOTH!Execute/search permission for file other class.
  2371. .TE
  2372. .P
  2373. When appropriate privileges are required to set one of these mode bits,
  2374. and the user restoring the files from the archive does not have
  2375. appropriate privileges, the mode bits for which the user does not have
  2376. appropriate privileges shall be ignored. Some of the mode bits in the
  2377. archive format are not mentioned elsewhere in this volume of POSIX.1\(hy2017. If the
  2378. implementation does not support those bits, they may be ignored.
  2379. .P
  2380. The
  2381. .IR uid
  2382. and
  2383. .IR gid
  2384. fields are the user and group ID of the owner and group of the file,
  2385. respectively.
  2386. .P
  2387. The
  2388. .IR size
  2389. field is the size of the file in octets. If the
  2390. .IR typeflag
  2391. field is set to specify a file to be of type 1 (a link) or 2 (a
  2392. symbolic link), the
  2393. .IR size
  2394. field shall be specified as zero. If the
  2395. .IR typeflag
  2396. field is set to specify a file of type 5 (directory), the
  2397. .IR size
  2398. field shall be interpreted as described under the definition of that
  2399. record type. No data logical records are stored for types 1, 2, or 5.
  2400. If the
  2401. .IR typeflag
  2402. field is set to 3 (character special file), 4 (block special file), or
  2403. 6 (FIFO), the meaning of the
  2404. .IR size
  2405. field is unspecified by this volume of POSIX.1\(hy2017, and no data logical records shall be
  2406. stored on the medium. Additionally, for type 6, the
  2407. .IR size
  2408. field shall be ignored when reading. If the
  2409. .IR typeflag
  2410. field is set to any other value, the number of logical records written
  2411. following the header shall be (\c
  2412. .IR size +511)/512,
  2413. ignoring any fraction in the result of the division.
  2414. .P
  2415. The
  2416. .IR mtime
  2417. field shall be the modification time of the file at the time it was
  2418. archived. It is the ISO/IEC\ 646:\|1991 standard representation of the octal value of the
  2419. modification time obtained from the
  2420. \fIstat\fR()
  2421. function.
  2422. .P
  2423. The
  2424. .IR chksum
  2425. field shall be the ISO/IEC\ 646:\|1991 standard IRV representation of the octal value of the
  2426. simple sum of all octets in the header logical record. Each octet in
  2427. the header shall be treated as an unsigned value. These values shall be
  2428. added to an unsigned integer, initialized to zero, the precision of
  2429. which is not less than 17 bits. When calculating the checksum, the
  2430. .IR chksum
  2431. field is treated as if it were all
  2432. <space>
  2433. characters.
  2434. .P
  2435. The
  2436. .IR typeflag
  2437. field specifies the type of file archived. If a particular
  2438. implementation does not recognize the type, or the user does not have
  2439. appropriate privileges to create that type, the file shall be extracted
  2440. as if it were a regular file if the file type is defined to have a
  2441. meaning for the
  2442. .IR size
  2443. field that could cause data logical records to be written on the medium
  2444. (see the previous description for
  2445. .IR size ).
  2446. If conversion to a regular file occurs, the
  2447. .IR pax
  2448. utility shall produce an error indicating that the conversion took
  2449. place. All of the
  2450. .IR typeflag
  2451. fields shall be coded in the ISO/IEC\ 646:\|1991 standard IRV:
  2452. .IP "\fR0\fR" 8
  2453. Represents a regular file. For backwards-compatibility, a
  2454. .IR typeflag
  2455. value of binary zero (\c
  2456. .BR '\e0' )
  2457. should be recognized as meaning a regular file when extracting files
  2458. from the archive. Archives written with this version of the archive
  2459. file format create regular files with a
  2460. .IR typeflag
  2461. value of the ISO/IEC\ 646:\|1991 standard IRV
  2462. .BR '0' .
  2463. .IP "\fR1\fR" 8
  2464. Represents a file linked to another file, of any type, previously
  2465. archived. Such files are identified by having the same device
  2466. and file serial numbers, and pathnames that refer to different
  2467. directory entries. All such files shall be archived as linked files.
  2468. The linked-to name is specified in the
  2469. .IR linkname
  2470. field with a NUL-character terminator if it is less than 100 octets in
  2471. length.
  2472. .IP "\fR2\fR" 8
  2473. Represents a symbolic link. The contents of the symbolic link shall be
  2474. stored in the
  2475. .IR linkname
  2476. field.
  2477. .IP "\fR3,4\fR" 8
  2478. Represent character special files and block special files respectively.
  2479. In this case the
  2480. .IR devmajor
  2481. and
  2482. .IR devminor
  2483. fields shall contain information defining the device, the format of
  2484. which is unspecified by this volume of POSIX.1\(hy2017. Implementations may map the device
  2485. specifications to their own local specification or may ignore the
  2486. entry.
  2487. .IP "\fR5\fR" 8
  2488. Specifies a directory or subdirectory. On systems where disk allocation
  2489. is performed on a directory basis, the
  2490. .IR size
  2491. field shall contain the maximum number of octets (which may be rounded
  2492. to the nearest disk block allocation unit) that the directory may hold.
  2493. A
  2494. .IR size
  2495. field of zero indicates no such limiting. Systems that do not support
  2496. limiting in this manner should ignore the
  2497. .IR size
  2498. field.
  2499. .IP "\fR6\fR" 8
  2500. Specifies a FIFO special file. Note that the archiving of a FIFO file
  2501. archives the existence of this file and not its contents.
  2502. .IP "\fR7\fR" 8
  2503. Reserved to represent a file to which an implementation has associated
  2504. some high-performance attribute. Implementations without such
  2505. extensions should treat this file as a regular file (type 0).
  2506. .IP "\fRA\(hyZ\fR" 8
  2507. The letters
  2508. .BR 'A' 
  2509. to
  2510. .BR 'Z' ,
  2511. inclusive, are reserved for custom implementations. All other values
  2512. are reserved for future versions of this standard.
  2513. .P
  2514. It is unspecified whether files with pathnames that refer to the same
  2515. directory entry are archived as linked files or as separate files. If
  2516. they are archived as linked files, this means that attempting to
  2517. extract both pathnames from the resulting archive will always cause an
  2518. error (unless the
  2519. .BR \-u
  2520. option is used) because the link cannot be created.
  2521. .P
  2522. It is unspecified whether files with the same device and file serial
  2523. numbers being appended to an archive are treated as linked files to
  2524. members that were in the archive before the append.
  2525. .P
  2526. Attempts to archive a socket shall produce a diagnostic message when
  2527. .BR ustar
  2528. interchange format is used, but may be allowed when
  2529. .BR pax
  2530. interchange format is used. Handling of other file types is
  2531. implementation-defined.
  2532. .P
  2533. The
  2534. .IR magic
  2535. field is the specification that this archive was output in this archive
  2536. format. If this field contains
  2537. .BR ustar
  2538. (the five characters from the ISO/IEC\ 646:\|1991 standard IRV shown followed by NUL), the
  2539. .IR uname
  2540. and
  2541. .IR gname
  2542. fields shall contain the ISO/IEC\ 646:\|1991 standard IRV representation of the owner and
  2543. group of the file, respectively (truncated to fit, if necessary). When
  2544. the file is restored by a privileged, protection-preserving version of
  2545. the utility, the user and group databases shall be scanned for these
  2546. names. If found, the user and group IDs contained within these files
  2547. shall be used rather than the values contained within the
  2548. .IR uid
  2549. and
  2550. .IR gid
  2551. fields.
  2552. .SS "cpio Interchange Format"
  2553. .P
  2554. The octet-oriented
  2555. .BR cpio
  2556. archive format shall be a series of entries, each comprising a header
  2557. that describes the file, the name of the file, and then the contents of
  2558. the file.
  2559. .P
  2560. An archive may be recorded as a series of fixed-size blocks of octets.
  2561. This blocking shall be used only to make physical I/O more efficient.
  2562. The last group of blocks shall always be at the full size.
  2563. .P
  2564. For the octet-oriented
  2565. .BR cpio
  2566. archive format, the individual entry information shall be in the order
  2567. indicated and described by the following table; see also the
  2568. .IR <cpio.h> 
  2569. header.
  2570. .br
  2571. .sp
  2572. .ce 1
  2573. \fBTable 4-16: Octet-Oriented cpio Archive Entry\fR
  2574. .TS
  2575. center box tab(!);
  2576. cB | cB | cB
  2577. lI | n | l.
  2578. Header Field Name!Length (in Octets)!Interpreted as
  2579. _
  2580. c_magic!6!Octal number
  2581. c_dev!6!Octal number
  2582. c_ino!6!Octal number
  2583. c_mode!6!Octal number
  2584. c_uid!6!Octal number
  2585. c_gid!6!Octal number
  2586. c_nlink!6!Octal number
  2587. c_rdev!6!Octal number
  2588. c_mtime!11!Octal number
  2589. c_namesize!6!Octal number
  2590. c_filesize!11!Octal number
  2591. _
  2592. .T&
  2593. cB | cB | cB
  2594. lI lI l.
  2595. Filename Field Name!Length!Interpreted as
  2596. _
  2597. c_name!c_namesize!Pathname string
  2598. _
  2599. .T&
  2600. cB | cB | cB
  2601. lI lI l.
  2602. File Data Field Name!Length!Interpreted as
  2603. _
  2604. c_filedata!c_filesize!Data
  2605. .TE
  2606. .SS "cpio Header"
  2607. .P
  2608. For each file in the archive, a header as defined previously shall be
  2609. written. The information in the header fields is written as streams of
  2610. the ISO/IEC\ 646:\|1991 standard characters interpreted as octal numbers. The octal numbers
  2611. shall be extended to the necessary length by appending the ISO/IEC\ 646:\|1991 standard IRV
  2612. zeros at the most-significant-digit end of the number; the result is
  2613. written to the most-significant digit of the stream of octets first.
  2614. The fields shall be interpreted as follows:
  2615. .IP "\fIc_magic\fR" 10
  2616. Identify the archive as being a transportable archive by containing the
  2617. identifying value
  2618. .BR \(dq070707\(dq .
  2619. .IP "\fIc_dev\fR,\ \fIc_ino\fR" 10
  2620. Contains values that uniquely identify the file within the archive
  2621. (that is, no files contain the same pair of
  2622. .IR c_dev
  2623. and
  2624. .IR c_ino
  2625. values unless they are links to the same file). The values shall be
  2626. determined in an unspecified manner.
  2627. .IP "\fIc_mode\fR" 10
  2628. Contains the file type and access permissions as defined in the
  2629. following table.
  2630. .br
  2631. .sp
  2632. .ce 1
  2633. \fBTable 4-17: Values for cpio c_mode Field\fR
  2634. .TS
  2635. center box tab(@);
  2636. cB | cB | cB
  2637. l | n | l.
  2638. File Permissions Name@Value@Indicates
  2639. _
  2640. C_IRUSR@000\|400@Read by owner
  2641. C_IWUSR@000\|200@Write by owner
  2642. C_IXUSR@000\|100@Execute by owner
  2643. C_IRGRP@000\|040@Read by group
  2644. C_IWGRP@000\|020@Write by group
  2645. C_IXGRP@000\|010@Execute by group
  2646. C_IROTH@000\|004@Read by others
  2647. C_IWOTH@000\|002@Write by others
  2648. C_IXOTH@000\|001@Execute by others
  2649. C_ISUID@004\|000@Set \fIuid\fP
  2650. C_ISGID@002\|000@Set \fIgid\fP
  2651. C_ISVTX@001\|000@Reserved
  2652. _
  2653. .T&
  2654. cB | cB | cB
  2655. l | n | l.
  2656. File Type Name@Value@Indicates
  2657. _
  2658. C_ISDIR@040\|000@Directory
  2659. C_ISFIFO@010\|000@FIFO
  2660. C_ISREG@0100\|000@Regular file
  2661. C_ISLNK@0120\|000@Symbolic link
  2662. .RS 10 
  2663. .P
  2664. C_ISBLK@060\|000@Block special file
  2665. C_ISCHR@020\|000@Character special file
  2666. C_ISSOCK@0140\|000@Socket
  2667. .P
  2668. C_ISCTG@0110\|000@Reserved
  2669. .TE
  2670. .P
  2671. Directories, FIFOs, symbolic links, and regular files shall be
  2672. supported on a system conforming to this volume of POSIX.1\(hy2017; additional values defined
  2673. previously are reserved for compatibility with existing systems.
  2674. Additional file types may be supported; however, such files should not
  2675. be written to archives intended to be transported to other systems.
  2676. .RE
  2677. .IP "\fIc_uid\fR" 10
  2678. Contains the user ID of the owner.
  2679. .IP "\fIc_gid\fR" 10
  2680. Contains the group ID of the group.
  2681. .IP "\fIc_nlink\fR" 10
  2682. Contains a number greater than or equal to the number of links in the
  2683. archive referencing the file. If the
  2684. .BR \-a
  2685. option is used to append to a
  2686. .IR cpio
  2687. archive, then the
  2688. .IR pax
  2689. utility need not account for the files in the existing part of the
  2690. archive when calculating the
  2691. .IR c_nlink
  2692. values for the appended part of the archive, and need not alter the
  2693. .IR c_nlink
  2694. values in the existing part of the archive if additional files with the
  2695. same
  2696. .IR c_dev
  2697. and
  2698. .IR c_ino
  2699. values are appended to the archive.
  2700. .IP "\fIc_rdev\fR" 10
  2701. Contains implementation-defined information for character or block
  2702. special files.
  2703. .IP "\fIc_mtime\fR" 10
  2704. Contains the latest time of modification of the file at the time the
  2705. archive was created.
  2706. .IP "\fIc_namesize\fR" 10
  2707. Contains the length of the pathname, including the terminating NUL
  2708. character.
  2709. .IP "\fIc_filesize\fR" 10
  2710. Contains the length in octets of the data section following the
  2711. header structure.
  2712. .SS "cpio Filename"
  2713. .P
  2714. The
  2715. .IR c_name
  2716. field shall contain the pathname of the file. The length of this field
  2717. in octets is the value of
  2718. .IR c_namesize .
  2719. .P
  2720. If a filename is found on the medium that would create an invalid
  2721. pathname, it is implementation-defined whether the data from the file
  2722. is stored on the file hierarchy and under what name it is stored.
  2723. .P
  2724. All characters shall be represented in the ISO/IEC\ 646:\|1991 standard IRV. For maximum
  2725. portability between implementations, names should be selected from
  2726. characters represented by the portable filename character set as
  2727. octets with the most significant bit zero. If an implementation
  2728. supports the use of characters outside the portable filename character
  2729. set in names for files, users, and groups, one or more
  2730. implementation-defined encodings of these characters shall be provided
  2731. for interchange purposes. However, the
  2732. .IR pax
  2733. utility shall never create filenames on the local system that cannot
  2734. be accessed via the procedures described previously in this volume of POSIX.1\(hy2017. If a
  2735. filename is found on the medium that would create an invalid filename,
  2736. it is implementation-defined whether the data from the file is stored on
  2737. the local file system and under what name it is stored. The
  2738. .IR pax
  2739. utility may choose to ignore these files as long as it produces an
  2740. error indicating that the file is being ignored.
  2741. .SS "cpio File Data"
  2742. .P
  2743. Following
  2744. .IR c_name ,
  2745. there shall be
  2746. .IR c_filesize
  2747. octets of data. Interpretation of such data occurs in a manner
  2748. dependent on the file. For regular files, the data shall consist
  2749. of the contents of the file. For symbolic links, the data shall
  2750. consist of the contents of the symbolic link. If
  2751. .IR c_filesize
  2752. is zero, no data shall be contained in
  2753. .IR c_filedata .
  2754. .P
  2755. When restoring from an archive:
  2756. .IP " *" 4
  2757. If the user does not have appropriate privileges to create a file of
  2758. the specified type,
  2759. .IR pax
  2760. shall ignore the entry and write an error message to standard error.
  2761. .IP " *" 4
  2762. Only regular files and symbolic links have data to be restored. Presuming
  2763. a regular file meets any selection criteria that might be imposed on
  2764. the format-reading utility by the user, such data shall be restored.
  2765. .IP " *" 4
  2766. If a user does not have appropriate privileges to set a particular mode
  2767. flag, the flag shall be ignored. Some of the mode flags in the archive
  2768. format are not mentioned elsewhere in this volume of POSIX.1\(hy2017. If the implementation does
  2769. not support those flags, they may be ignored.
  2770. .SS "cpio Special Entries"
  2771. .P
  2772. FIFO special files, directories, and the trailer shall be recorded with
  2773. .IR c_filesize
  2774. equal to zero. Symbolic links shall be recorded with
  2775. .IR c_filesize
  2776. equal to the length of the contents of the symbolic link.
  2777. For other special files,
  2778. .IR c_filesize
  2779. is unspecified by this volume of POSIX.1\(hy2017. The header for the next file entry in the
  2780. archive shall be written directly after the last octet of the file
  2781. entry preceding it. A header denoting the filename
  2782. .BR TRAILER!!!
  2783. shall indicate the end of the archive; the contents of octets in the
  2784. last block of the archive following such a header are undefined.
  2785. .SH "EXIT STATUS"
  2786. The following exit values shall be returned:
  2787. .IP "\00" 6
  2788. All files were processed successfully.
  2789. .IP >0 6
  2790. An error occurred.
  2791. .SH "CONSEQUENCES OF ERRORS"
  2792. If
  2793. .IR pax
  2794. cannot create a file or a link when reading an archive or cannot find a
  2795. file when writing an archive, or cannot preserve the user ID, group ID,
  2796. or file mode when the
  2797. .BR \-p
  2798. option is specified, a diagnostic message shall be written to standard
  2799. error and a non-zero exit status shall be returned, but processing
  2800. shall continue. In the case where
  2801. .IR pax
  2802. cannot create a link to a file,
  2803. .IR pax
  2804. shall not, by default, create a second copy of the file.
  2805. .P
  2806. If the extraction of a file from an archive is prematurely terminated
  2807. by a signal or error,
  2808. .IR pax
  2809. may have only partially extracted the file or (if the
  2810. .BR \-n
  2811. option was not specified) may have extracted a file of the same name as
  2812. that specified by the user, but which is not the file the user wanted.
  2813. Additionally, the file modes of extracted directories may have
  2814. additional bits from the S_IRWXU mask set as well as incorrect
  2815. modification and access times.
  2816. .LP
  2817. .IR "The following sections are informative."
  2818. .SH "APPLICATION USAGE"
  2819. Caution is advised when using the
  2820. .BR \-a
  2821. option to append to a
  2822. .IR cpio
  2823. format archive. If any of the files being appended happen to be given
  2824. the same
  2825. .IR c_dev
  2826. and
  2827. .IR c_ino
  2828. values as a file in the existing part of the archive, then they may be
  2829. treated as links to that file on extraction. Thus, it is risky to use
  2830. .BR \-a
  2831. with
  2832. .IR cpio
  2833. format except when it is done on the same system that the original
  2834. archive was created on, and with the same
  2835. .IR pax
  2836. utility, and in the knowledge that there has been little or no file
  2837. system activity since the original archive was created that could lead
  2838. to any of the files appended being given the same
  2839. .IR c_dev
  2840. and
  2841. .IR c_ino
  2842. values as an unrelated file in the existing part of the archive. Also,
  2843. when (intentionally) appending additional links to a file in the
  2844. existing part of the archive, the
  2845. .IR c_nlink
  2846. values in the modified archive can be smaller than the number of links
  2847. to the file in the archive, which may mean that the links are not
  2848. preserved on extraction.
  2849. .P
  2850. The
  2851. .BR \-p
  2852. (privileges) option was invented to reconcile differences between
  2853. historical
  2854. .IR tar
  2855. and
  2856. .IR cpio
  2857. implementations. In particular, the two utilities use
  2858. .BR \-m
  2859. in diametrically opposed ways. The
  2860. .BR \-p
  2861. option also provides a consistent means of extending the ways in which
  2862. future file attributes can be addressed, such as for enhanced security
  2863. systems or high-performance files. Although it may seem complex, there
  2864. are really two modes that are most commonly used:
  2865. .IP "\fB\-p\ e\fR" 8
  2866. ``Preserve everything''. This would be used by the historical
  2867. superuser, someone with all appropriate privileges, to preserve all
  2868. aspects of the files as they are recorded in the archive. The
  2869. .BR e
  2870. flag is the sum of
  2871. .BR o
  2872. and
  2873. .BR p ,
  2874. and other implementation-defined attributes.
  2875. .IP "\fB\-p\ p\fR" 8
  2876. ``Preserve'' the file mode bits. This would be used by the user with
  2877. regular privileges who wished to preserve aspects of the file other
  2878. than the ownership. The file times are preserved by default, but two
  2879. other flags are offered to disable these and use the time of
  2880. extraction.
  2881. .P
  2882. The one pathname per line format of standard input precludes
  2883. pathnames containing
  2884. <newline>
  2885. characters. Although such pathnames violate the portable filename
  2886. guidelines, they may exist and their presence may inhibit usage of
  2887. .IR pax
  2888. within shell scripts. This problem is inherited from historical archive
  2889. programs. The problem can be avoided by listing filename arguments on
  2890. the command line instead of on standard input.
  2891. .P
  2892. It is almost certain that appropriate privileges are required for
  2893. .IR pax
  2894. to accomplish parts of this volume of POSIX.1\(hy2017. Specifically, creating files of type
  2895. block special or character special, restoring file access times unless
  2896. the files are owned by the user (the
  2897. .BR \-t
  2898. option), or preserving file owner, group, and mode (the
  2899. .BR \-p
  2900. option) all probably require appropriate privileges.
  2901. .P
  2902. In
  2903. .BR read
  2904. mode, implementations are permitted to overwrite files when the archive
  2905. has multiple members with the same name. This may fail if permissions
  2906. on the first version of the file do not permit it to be overwritten.
  2907. .P
  2908. The
  2909. .BR cpio
  2910. and
  2911. .BR ustar
  2912. formats can only support files up to 8\|589\|934\|592 bytes
  2913. (8 \(** 2^30) in size.
  2914. .P
  2915. When archives containing binary header information are listed , the
  2916. filenames printed may cause strange behavior on some terminals.
  2917. .P
  2918. When all of the following are true:
  2919. .IP " 1." 4
  2920. A file of type directory is being placed into an archive.
  2921. .IP " 2." 4
  2922. The
  2923. .BR ustar
  2924. archive format is being used.
  2925. .IP " 3." 4
  2926. The pathname of the directory is less than or equal to 155 bytes long
  2927. (it will fit in the
  2928. .IR prefix
  2929. field in the
  2930. .BR ustar
  2931. header block).
  2932. .IP " 4." 4
  2933. The last component of the pathname of the directory is longer than 100
  2934. bytes long (it will not fit in the
  2935. .IR name
  2936. field in the
  2937. .BR ustar
  2938. header block).
  2939. .P
  2940. some implementations of the
  2941. .IR pax
  2942. utility will place the entire directory pathname in the
  2943. .IR prefix
  2944. field, set the
  2945. .IR name
  2946. field to an empty string, and place the directory in the archive.
  2947. Other implementations of the
  2948. .IR pax
  2949. utility will give an error under these conditions because the
  2950. .IR name
  2951. field is not large enough to hold the last component of the directory name.
  2952. This standard allows either behavior. However, when extracting a directory
  2953. from a
  2954. .BR ustar
  2955. format archive, this standard requires that all implementations be able
  2956. to extract a directory even if the
  2957. .IR name
  2958. field contains an empty string as long as the
  2959. .IR prefix
  2960. field does not also contain an empty string.
  2961. .SH EXAMPLES
  2962. The following command:
  2963. .sp
  2964. .RS 4
  2965. .nf
  2967. pax -w -f /dev/rmt/1m .
  2968. .fi
  2969. .P
  2970. .RE
  2971. .P
  2972. copies the contents of the current directory to tape drive 1, medium
  2973. density (assuming historical System V device naming procedures\(emthe
  2974. historical BSD device name would be
  2975. .BR /dev/rmt9 ).
  2976. .P
  2977. The following commands:
  2978. .sp
  2979. .RS 4
  2980. .nf
  2982. mkdir \fInewdir\fR
  2983. pax -rw \fIolddir newdir\fR
  2984. .fi
  2985. .P
  2986. .RE
  2987. .P
  2988. copy the
  2989. .IR olddir
  2990. directory hierarchy to
  2991. .IR newdir .
  2992. .sp
  2993. .RS 4
  2994. .nf
  2996. pax -r -s \(aq,\(ha//*usr//*,,\(aq -f a.pax
  2997. .fi
  2998. .P
  2999. .RE
  3000. .P
  3001. reads the archive
  3002. .BR a.pax ,
  3003. with all files rooted in
  3004. .BR /usr
  3005. in the archive extracted relative to the current directory.
  3006. .P
  3007. Using the option:
  3008. .sp
  3009. .RS 4
  3010. .nf
  3012. -o listopt="%M %(atime)T %(size)D %(name)s"
  3013. .fi
  3014. .P
  3015. .RE
  3016. .P
  3017. overrides the default output description in Standard Output and instead
  3018. writes:
  3019. .sp
  3020. .RS 4
  3021. .nf
  3023. -rw-rw--- Jan 12 15:53 2003 1492 /usr/foo/bar
  3024. .fi
  3025. .P
  3026. .RE
  3027. .P
  3028. Using the options:
  3029. .sp
  3030. .RS 4
  3031. .nf
  3033. -o listopt=\(aq%L\et%(size)D\en%.7\(aq \e
  3034. -o listopt=\(aq(name)s\en%(atime)T\en%T\(aq
  3035. .fi
  3036. .P
  3037. .RE
  3038. .P
  3039. overrides the default output description in Standard Output and instead
  3040. writes:
  3041. .sp
  3042. .RS 4
  3043. .nf
  3045. /usr/foo/bar -> /tmp   1492
  3046. /usr/fo
  3047. Jan 12 15:53 1991
  3048. Jan 31 15:53 2003
  3049. .fi
  3050. .P
  3051. .RE
  3052. .SH RATIONALE
  3053. The
  3054. .IR pax
  3055. utility was new for the ISO\ POSIX\(hy2:\|1993 standard. It represents a peaceful
  3056. compromise between advocates of the historical
  3057. .IR tar
  3058. and
  3059. .IR cpio
  3060. utilities.
  3061. .P
  3062. A fundamental difference between
  3063. .IR cpio
  3064. and
  3065. .IR tar
  3066. was in the way directories were treated. The
  3067. .IR cpio
  3068. utility did not treat directories differently from other files, and to
  3069. select a directory and its contents required that each file in the
  3070. hierarchy be explicitly specified. For
  3071. .IR tar ,
  3072. a directory matched every file in the file hierarchy it rooted.
  3073. .P
  3074. The
  3075. .IR pax
  3076. utility offers both interfaces; by default, directories map into the
  3077. file hierarchy they root. The
  3078. .BR \-d
  3079. option causes
  3080. .IR pax
  3081. to skip any file not explicitly referenced, as
  3082. .IR cpio
  3083. historically did. The
  3084. .IR tar
  3085. .BR \- \c
  3086. .IR style
  3087. behavior was chosen as the default because it was believed that this
  3088. was the more common usage and because
  3089. .IR tar
  3090. is the more commonly available interface, as it was historically
  3091. provided on both System V and BSD implementations.
  3092. .P
  3093. The data interchange format specification in this volume of POSIX.1\(hy2017 requires that
  3094. processes with ``appropriate privileges'' shall always restore the
  3095. ownership and permissions of extracted files exactly as archived. If
  3096. viewed from the historic equivalence between superuser and
  3097. ``appropriate privileges'', there are two problems
  3098. with this requirement. First, users running as superusers may
  3099. unknowingly set dangerous permissions on extracted files. Second, it is
  3100. needlessly limiting, in that superusers cannot extract files and own
  3101. them as superuser unless the archive was created by the superuser. (It
  3102. should be noted that restoration of ownerships and permissions for the
  3103. superuser, by default, is historical practice in
  3104. .IR cpio ,
  3105. but not in
  3106. .IR tar .)
  3107. In order to avoid these two problems, the
  3108. .IR pax
  3109. specification has an additional ``privilege'' mechanism, the
  3110. .BR \-p
  3111. option. Only a
  3112. .IR pax
  3113. invocation with the privileges needed, and which has the
  3114. .BR \-p
  3115. option set using the
  3116. .BR e
  3117. specification character, has appropriate privileges to restore
  3118. full ownership and permission information.
  3119. .P
  3120. Note also that this volume of POSIX.1\(hy2017 requires that the file ownership and access
  3121. permissions shall be set, on extraction, in the same fashion as the
  3122. \fIcreat\fR()
  3123. function when provided with the mode stored in the archive. This means
  3124. that the file creation mask of the user is applied to the file
  3125. permissions.
  3126. .P
  3127. Users should note that directories may be created by
  3128. .IR pax
  3129. while extracting files with permissions that are different from those
  3130. that existed at the time the archive was created. When extracting
  3131. sensitive information into a directory hierarchy that no longer exists,
  3132. users are encouraged to set their file creation mask appropriately to
  3133. protect these files during extraction.
  3134. .P
  3135. The table of contents output is written to standard output to
  3136. facilitate pipeline processing.
  3137. .P
  3138. An early proposal had hard links displaying for all pathnames. This
  3139. was removed because it complicates the output of the case where
  3140. .BR \-v
  3141. is not specified and does not match historical
  3142. .IR cpio
  3143. usage. The hard-link information is available in the
  3144. .BR \-v
  3145. display.
  3146. .P
  3147. The description of the
  3148. .BR \-l
  3149. option allows implementations to make hard links to symbolic links.
  3150. Earlier versions of this standard did not specify any way to create a
  3151. hard link to a symbolic link, but many implementations provided this
  3152. capability as an extension. If there are hard links to symbolic links
  3153. when an archive is created, the implementation is required to archive
  3154. the hard link in the archive (unless
  3155. .BR \-H
  3156. or
  3157. .BR \-L
  3158. is specified). When in
  3159. .BR read
  3160. mode and in
  3161. .BR copy
  3162. mode, implementations supporting hard links to symbolic links should
  3163. use them when appropriate.
  3164. .P
  3165. The archive formats inherited from the POSIX.1\(hy1990 standard have certain restrictions
  3166. that have been brought along from historical usage. For example, there
  3167. are restrictions on the length of pathnames stored in the archive.
  3168. When
  3169. .IR pax
  3170. is used in
  3171. .BR copy (\c
  3172. .BR \-rw )
  3173. mode (copying directory hierarchies), the ability to use extensions
  3174. from the
  3175. .BR \-x \c
  3176. .BR pax
  3177. format overcomes these restrictions.
  3178. .P
  3179. The default
  3180. .IR blocksize
  3181. value of 5\|120 bytes for
  3182. .IR cpio
  3183. was selected because it is one of the standard block-size values for
  3184. .IR cpio ,
  3185. set when the
  3186. .BR \-B
  3187. option is specified. (The other default block-size value for
  3188. .IR cpio
  3189. is 512 bytes, and this was considered to be too small.) The default
  3190. block value of 10\|240 bytes for
  3191. .IR tar
  3192. was selected because that is the standard block-size value for BSD
  3193. .IR tar .
  3194. The maximum block size of 32\|256 bytes (2\s-3\u15\d\s+3\-512 bytes)
  3195. is the largest multiple of 512 bytes that fits into a signed 16-bit
  3196. tape controller transfer register. There are known limitations in some
  3197. historical systems that would prevent larger blocks from being
  3198. accepted. Historical values were chosen to improve compatibility with
  3199. historical scripts using
  3200. .IR dd
  3201. or similar utilities to manipulate archives. Also, default block sizes
  3202. for any file type other than character special file has been deleted
  3203. from this volume of POSIX.1\(hy2017 as unimportant and not likely to affect the structure of the
  3204. resulting archive.
  3205. .P
  3206. Implementations are permitted to modify the block-size value based on
  3207. the archive format or the device to which the archive is being
  3208. written. This is to provide implementations with the opportunity to
  3209. take advantage of special types of devices, and it should not be used
  3210. without a great deal of consideration as it almost certainly decreases
  3211. archive portability.
  3212. .P
  3213. The intended use of the
  3214. .BR \-n
  3215. option was to permit extraction of one or more files from the archive
  3216. without processing the entire archive. This was viewed by the standard
  3217. developers as offering significant performance advantages over
  3218. historical implementations. The
  3219. .BR \-n
  3220. option in early proposals had three effects; the first was to cause
  3221. special characters in patterns to not be treated specially. The second
  3222. was to cause only the first file that matched a pattern to be
  3223. extracted. The third was to cause
  3224. .IR pax
  3225. to write a diagnostic message to standard error when no file was found
  3226. matching a specified pattern. Only the second behavior is retained by
  3227. this volume of POSIX.1\(hy2017, for many reasons. First, it is in general not acceptable for a
  3228. single option to have multiple effects. Second, the ability to make
  3229. pattern matching characters act as normal characters
  3230. is useful for parts of
  3231. .IR pax
  3232. other than file extraction. Third, a finer degree of control over the
  3233. special characters is useful because users may wish to normalize only a
  3234. single special character in a single filename. Fourth, given a more
  3235. general escape mechanism, the previous behavior of the
  3236. .BR \-n
  3237. option can be easily obtained using the
  3238. .BR \-s
  3239. option or a
  3240. .IR sed
  3241. script. Finally, writing a diagnostic message when a pattern specified
  3242. by the user is unmatched by any file is useful behavior in all cases.
  3243. .P
  3244. In this version, the
  3245. .BR \-n
  3246. was removed from the
  3247. .BR copy
  3248. mode synopsis of
  3249. .IR pax ;
  3250. it is inapplicable because there are no pattern operands specified in
  3251. this mode.
  3252. .P
  3253. There is another method than
  3254. .IR pax
  3255. for copying subtrees in POSIX.1\(hy2008 described as part of the
  3256. .IR cp
  3257. utility. Both methods are historical practice:
  3258. .IR cp
  3259. provides a simpler, more intuitive interface, while
  3260. .IR pax
  3261. offers a finer granularity of control. Each provides additional
  3262. functionality to the other; in particular,
  3263. .IR pax
  3264. maintains the hard-link structure of the hierarchy while
  3265. .IR cp
  3266. does not. It is the intention of the standard developers that the
  3267. results be similar (using appropriate option combinations in both
  3268. utilities). The results are not required to be identical; there seemed
  3269. insufficient gain to applications to balance the difficulty of
  3270. implementations having to guarantee that the results would be exactly
  3271. identical.
  3272. .P
  3273. A single archive may span more than one file. It is suggested that
  3274. implementations provide informative messages to the user on standard
  3275. error whenever the archive file is changed.
  3276. .P
  3277. The
  3278. .BR \-d
  3279. option (do not create intermediate directories not listed in the
  3280. archive) found in early proposals was originally provided as a
  3281. complement to the historic
  3282. .BR \-d
  3283. option of
  3284. .IR cpio .
  3285. It has been deleted.
  3286. .P
  3287. The
  3288. .BR \-s
  3289. option in early proposals specified a subset of the substitution
  3290. command from the
  3291. .IR ed
  3292. utility. As there was no reason for only a subset to be supported, the
  3293. .BR \-s
  3294. option is now compatible with the current
  3295. .IR ed
  3296. specification. Since the delimiter can be any non-null character, the
  3297. following usage with single
  3298. <space>
  3299. characters is valid:
  3300. .sp
  3301. .RS 4
  3302. .nf
  3304. pax -s " foo bar " ...
  3305. .fi
  3306. .P
  3307. .RE
  3308. .P
  3309. The
  3310. .BR \-t
  3311. description is worded so as to note that this may cause the access time
  3312. update caused by some other activity (which occurs while the file is
  3313. being read) to be overwritten.
  3314. .P
  3315. The default behavior of
  3316. .IR pax
  3317. with regard to file modification times is the same as historical
  3318. implementations of
  3319. .IR tar .
  3320. It is not the historical behavior of
  3321. .IR cpio .
  3322. .P
  3323. Because the
  3324. .BR \-i
  3325. option uses
  3326. .BR /dev/tty ,
  3327. utilities without a controlling terminal are not able to use this
  3328. option.
  3329. .P
  3330. The
  3331. .BR \-y
  3332. option, found in early proposals, has been deleted because a line
  3333. containing a single
  3334. <period>
  3335. for the
  3336. .BR \-i
  3337. option has equivalent functionality. The special lines for the
  3338. .BR \-i
  3339. option (a single
  3340. <period>
  3341. and the empty line) are historical practice in
  3342. .IR cpio .
  3343. .P
  3344. In early drafts, a
  3345. .BR \-e \c
  3346. .IR charmap
  3347. option was included to increase portability of files between systems
  3348. using different coded character sets. This option was omitted because
  3349. it was apparent that consensus could not be formed for it. In this
  3350. version, the use of UTF\(hy8 should be an adequate substitute.
  3351. .P
  3352. The ISO\ POSIX\(hy2:\|1993 standard and ISO\ POSIX\(hy1 standard requirements for
  3353. .IR pax ,
  3354. however, made it very difficult to create a single archive containing
  3355. files created using extended characters provided by different locales.
  3356. This version adds the
  3357. .BR hdrcharset
  3358. keyword to make it possible to archive files in these cases without
  3359. dropping files due to translation errors.
  3360. .P
  3361. Translating filenames and other attributes from a locale's encoding to
  3362. UTF\(hy8 and then back again can lose information, as the resulting
  3363. filename might not be byte-for-byte equivalent to the original. To
  3364. avoid this problem, users can specify the
  3365. .BR \-o
  3366. .BR hdrcharset=binary
  3367. option, which will cause the resulting archive to use binary
  3368. format for all names and attributes. Such archives are not portable
  3369. among hosts that use different native encodings (e.g., EBCDIC
  3370. \fIversus\fR ASCII-based encodings), but they will allow interchange
  3371. among the vast majority of POSIX file systems in practical use. Also,
  3372. the
  3373. .BR \-o
  3374. .BR hdrcharset=binary
  3375. option will cause
  3376. .IR pax
  3377. in
  3378. .BR copy
  3379. mode to behave more like other standard utilities such as
  3380. .IR cp .
  3381. .P
  3382. If the values specified by the
  3383. .BR \-o
  3384. .BR exthdr.name=value ,
  3385. .BR \-o
  3386. .BR globexthdr.name=value ,
  3387. or by
  3388. .BR $TMPDIR
  3389. (if
  3390. .BR \-o
  3391. .BR globexthdr.name
  3392. is not specified) require a character encoding other than that
  3393. described in the ISO/IEC\ 646:\|1991 standard, a
  3394. .BR path
  3395. extended header record will have to be created for the file. If a
  3396. .BR hdrcharset
  3397. extended header record is active for such headers, it will determine
  3398. the codeset used for the value field in these extended
  3399. .BR path
  3400. header records. These
  3401. .BR path
  3402. extended header records always need to be created when writing an
  3403. archive even if
  3404. .BR hdrcharset=binary
  3405. has been specified and would contain the same (binary) data that
  3406. appears in the
  3407. .BR ustar
  3408. header record prefix and
  3409. .IR name
  3410. fields. (In other words, an extended header
  3411. .BR path
  3412. record is always required to be generated if the
  3413. .IR prefix
  3414. or
  3415. .IR name
  3416. fields contain non-ASCII characters even when
  3417. .BR hdrcharset=binary
  3418. is also in effect for that file.)
  3419. .P
  3420. The
  3421. .BR \-k
  3422. option was added to address international concerns about the dangers
  3423. involved in the character set transformations of
  3424. .BR \-e
  3425. (if the target character set were different from the source, the
  3426. filenames might be transformed into names matching existing files) and
  3427. also was made more general to protect files transferred between file
  3428. systems with different
  3429. {NAME_MAX}
  3430. values (truncating a filename on a smaller system might also
  3431. inadvertently overwrite existing files). As stated, it prevents any
  3432. overwriting, even if the target file is older than the source. This
  3433. version adds more granularity of options to solve this problem by
  3434. introducing the
  3435. .BR \-o \c
  3436. .BR invalid=option \c
  3437. \(emspecifically the
  3438. .BR UTF\(hy8
  3439. and
  3440. .BR binary
  3441. actions. (Note that an existing file is still subject to overwriting in
  3442. this case. The
  3443. .BR \-k
  3444. option closes that loophole.)
  3445. .P
  3446. Some of the file characteristics referenced in this volume of POSIX.1\(hy2017 might not be
  3447. supported by some archive formats. For example, neither the
  3448. .BR tar
  3449. nor
  3450. .BR cpio
  3451. formats contain the file access time. For this reason, the
  3452. .BR e
  3453. specification character has been provided, intended to cause all file
  3454. characteristics specified in the archive to be retained.
  3455. .P
  3456. It is required that extracted directories, by default, have their
  3457. access and modification times and permissions set to the values
  3458. specified in the archive. This has obvious problems in that the
  3459. directories are almost certainly modified after being extracted and
  3460. that directory permissions may not permit file creation. One possible
  3461. solution is to create directories with the mode specified in the
  3462. archive, as modified by the
  3463. .IR umask
  3464. of the user, with sufficient permissions to allow file creation. After
  3465. all files have been extracted,
  3466. .IR pax
  3467. would then reset the access and modification times and permissions as
  3468. necessary.
  3469. .P
  3470. The list-mode formatting description borrows heavily from the one
  3471. defined by the
  3472. .IR printf
  3473. utility. However, since there is no separate operand list to get
  3474. conversion arguments, the format was extended to allow specifying the
  3475. name of the conversion argument as part of the conversion
  3476. specification.
  3477. .P
  3478. The
  3479. .BR T
  3480. conversion specifier allows time fields to be displayed in any of
  3481. the date formats. Unlike the
  3482. .IR ls
  3483. utility,
  3484. .IR pax
  3485. does not adjust the format when the date is less than six months in the
  3486. past. This makes parsing the output more predictable.
  3487. .P
  3488. The
  3489. .BR D
  3490. conversion specifier handles the ability to display the major/minor
  3491. or file size, as with
  3492. .IR ls ,
  3493. by using \fR%\-8(\fIsize\fR)D\fR.
  3494. .P
  3495. The
  3496. .BR L
  3497. conversion specifier handles the
  3498. .IR ls
  3499. display for symbolic links.
  3500. .P
  3501. Conversion specifiers were added to generate existing known types used
  3502. for
  3503. .IR ls .
  3504. .SS "pax Interchange Format"
  3505. .P
  3506. The new POSIX data interchange format was developed primarily to
  3507. satisfy international concerns that the
  3508. .BR ustar
  3509. and
  3510. .BR cpio
  3511. formats did not provide for file, user, and group names encoded in
  3512. characters outside a subset of the ISO/IEC\ 646:\|1991 standard. The standard developers
  3513. realized that this new POSIX data interchange format should be very
  3514. extensible because there were other requirements they foresaw in the
  3515. near future:
  3516. .IP " *" 4
  3517. Support international character encodings and locale information
  3518. .IP " *" 4
  3519. Support security information (ACLs, and so on)
  3520. .IP " *" 4
  3521. Support future file types, such as realtime or contiguous files
  3522. .IP " *" 4
  3523. Include data areas for implementation use
  3524. .IP " *" 4
  3525. Support systems with words larger than 32 bits and timers with
  3526. subsecond granularity
  3527. .P
  3528. The following were not goals for this format because these are better
  3529. handled by separate utilities or are inappropriate for a portable
  3530. format:
  3531. .IP " *" 4
  3532. Encryption
  3533. .IP " *" 4
  3534. Compression
  3535. .IP " *" 4
  3536. Data translation between locales and codesets
  3537. .IP " *" 4
  3538. .IR inode
  3539. storage
  3540. .P
  3541. The format chosen to support the goals is an extension of the
  3542. .BR ustar
  3543. format. Of the two formats previously available, only the
  3544. .BR ustar
  3545. format was selected for extensions because:
  3546. .IP " *" 4
  3547. It was easier to extend in an upwards-compatible way. It offered version
  3548. flags and header block type fields with room for future
  3549. standardization. The
  3550. .BR cpio
  3551. format, while possessing a more flexible file naming methodology, could
  3552. not be extended without breaking some theoretical implementation
  3553. or using a dummy filename that could be a legitimate filename.
  3554. .IP " *" 4
  3555. Industry experience since the original ``\c
  3556. .IR tar
  3557. wars'' fought in developing the ISO\ POSIX\(hy1 standard has clearly been in favor of the
  3558. .BR ustar
  3559. format, which is generally the default output format selected for
  3560. .IR pax
  3561. implementations on new systems.
  3562. .P
  3563. The new format was designed with one additional goal in mind:
  3564. reasonable behavior when an older
  3565. .IR tar
  3566. or
  3567. .IR pax
  3568. utility happened to read an archive. Since the POSIX.1\(hy1990 standard mandated that a
  3569. ``format-reading utility'' had to treat unrecognized
  3570. .IR typeflag
  3571. values as regular files, this allowed the format to include all the
  3572. extended information in a pseudo-regular file that preceded each real
  3573. file. An option is given that allows the archive creator to set up
  3574. reasonable names for these files on the older systems. Also, the
  3575. normative text suggests that reasonable file access values be used for
  3576. this
  3577. .BR ustar
  3578. header block. Making these header files inaccessible for convenient
  3579. reading and deleting would not be reasonable. File permissions of 600
  3580. or 700 are suggested.
  3581. .P
  3582. The
  3583. .BR ustar
  3584. .IR typeflag
  3585. field was used to accommodate the additional functionality of the new
  3586. format rather than magic or version because the POSIX.1\(hy1990 standard (and, by
  3587. reference, the previous version of
  3588. .IR pax ),
  3589. mandated the behavior of the format-reading utility when it encountered
  3590. an unknown
  3591. .IR typeflag ,
  3592. but was silent about the other two fields.
  3593. .P
  3594. Early proposals for the first version of this standard contained a proposed
  3595. archive format that was based on compatibility with the standard for
  3596. tape files (ISO\ 1001, similar to the format used historically on many
  3597. mainframes and minicomputers). This format was overly complex and required
  3598. considerable overhead in volume and header records. Furthermore, the
  3599. standard developers felt that it would not be acceptable to the community
  3600. of POSIX developers, so it was later changed to be a format more closely
  3601. related to historical practice on POSIX systems.
  3602. .P
  3603. The prefix and name split of pathnames in
  3604. .BR ustar
  3605. was replaced by the single path extended header record for simplicity.
  3606. .P
  3607. The concept of a global extended header (\c
  3608. .IR typeflag \c
  3609. .BR g )
  3610. was controversial. If this were applied to an archive being recorded on
  3611. magnetic tape, a few unreadable blocks at the beginning of the tape
  3612. could be a serious problem; a utility attempting to extract as many
  3613. files as possible from a damaged archive could lose a large percentage
  3614. of file header information in this case. However, if the archive were
  3615. on a reliable medium, such as a CD\(hyROM, the global extended header
  3616. offers considerable potential size reductions by eliminating redundant
  3617. information. Thus, the text warns against using the global method for
  3618. unreliable media and provides a method for implanting global
  3619. information in the extended header for each file, rather than in the
  3620. .IR typeflag
  3621. .BR g
  3622. records.
  3623. .P
  3624. No facility for data translation or filtering on a per-file basis is
  3625. included because the standard developers could not invent an interface
  3626. that would allow this in an efficient manner. If a filter, such as
  3627. encryption or compression, is to be applied to all the files, it is
  3628. more efficient to apply the filter to the entire archive as a single
  3629. file. The standard developers considered interfaces that would invoke a
  3630. shell script for each file going into or out of the archive, but the
  3631. system overhead in this approach was considered to be too high.
  3632. .P
  3633. One such approach would be to have
  3634. .BR filter=
  3635. records that give a pathname for an executable. When the program is
  3636. invoked, the file and archive would be open for standard input/output
  3637. and all the header fields would be available as environment variables
  3638. or command-line arguments. The standard developers did discuss such
  3639. schemes, but they were omitted from POSIX.1\(hy2008 due to concerns about
  3640. excessive overhead. Also, the program itself would need to be in the
  3641. archive if it were to be used portably.
  3642. .P
  3643. There is currently no portable means of identifying the character
  3644. set(s) used for a file in the file system. Therefore,
  3645. .IR pax
  3646. has not been given a mechanism to generate charset records
  3647. automatically. The only portable means of doing this is for the user to
  3648. write the archive using the
  3649. .BR \-o \c
  3650. .BR charset=string
  3651. command line option. This assumes that all of the files in the archive
  3652. use the same encoding. The ``implementation-defined'' text is
  3653. included to allow for a system that can identify the encodings used for
  3654. each of its files.
  3655. .P
  3656. The table of standards that accompanies the charset record description
  3657. is acknowledged to be very limited. Only a limited number of character
  3658. set standards is reasonable for maximal interchange. Any character set
  3659. is, of course, possible by prior agreement. It was suggested that
  3660. EBCDIC be listed, but it was omitted because it is not defined by a
  3661. formal standard. Formal standards, and then only those with reasonably
  3662. large followings, can be included here, simply as a matter of
  3663. practicality. The <\fIvalue\fP>s represent names of officially
  3664. registered character sets in the format required by the ISO\ 2375:\|1985 standard.
  3665. .P
  3666. The normal
  3667. <comma>
  3668. or
  3669. <blank>-separated
  3670. list rules are not followed in the case of keyword options to allow
  3671. ease of argument parsing for
  3672. .IR getopts .
  3673. .P
  3674. Further information on character encodings is in
  3675. .IR "pax Archive Character Set Encoding/Decoding".
  3676. .P
  3677. The standard developers have reserved keyword name space for vendor
  3678. extensions. It is suggested that the format to be used is:
  3679. .sp
  3680. .RS 4
  3681. .nf
  3683. \fIVENDOR.keyword\fR
  3684. .fi
  3685. .P
  3686. .RE
  3687. .P
  3688. where
  3689. .IR VENDOR
  3690. is the name of the vendor or organization in all uppercase letters. It
  3691. is further suggested that the keyword following the
  3692. <period>
  3693. be named differently than any of the standard keywords so that it could
  3694. be used for future standardization, if appropriate, by omitting the
  3695. .IR VENDOR
  3696. prefix.
  3697. .P
  3698. The <\fIlength\fP> field in the extended header record was included to
  3699. make it simpler to step through the records, even if a record contains
  3700. an unknown format (to a particular
  3701. .IR pax )
  3702. with complex interactions of special characters. It also provides a
  3703. minor integrity checkpoint within the records to aid a program
  3704. attempting to recover files from a damaged archive.
  3705. .P
  3706. There are no extended header versions of the
  3707. .IR devmajor
  3708. and
  3709. .IR devminor
  3710. fields because the unspecified format
  3711. .BR ustar
  3712. header field should be sufficient. If they are not, vendor-specific
  3713. extended keywords (such as
  3714. .IR VENDOR.devmajor )
  3715. should be used.
  3716. .P
  3717. Device and
  3718. .IR i -number
  3719. labeling of files was not adopted from
  3720. .IR cpio ;
  3721. files are interchanged strictly on a symbolic name basis, as in
  3722. .BR ustar .
  3723. .P
  3724. Just as with the
  3725. .BR ustar
  3726. format descriptions, the new format makes no special arrangements for
  3727. multi-volume archives. Each of the
  3728. .IR pax
  3729. archive types is assumed to be inside a single POSIX file and splitting
  3730. that file over multiple volumes (diskettes, tape cartridges, and so
  3731. on), processing their labels, and mounting each in the proper sequence
  3732. are considered to be implementation details that cannot be described
  3733. portably.
  3734. .P
  3735. The
  3736. .BR pax
  3737. format is intended for interchange, not only for backup on a single
  3738. (family of) systems. It is not as densely packed as might be possible
  3739. for backup:
  3740. .IP " *" 4
  3741. It contains information as coded characters that could be coded in
  3742. binary.
  3743. .IP " *" 4
  3744. It identifies extended records with name fields that could be omitted
  3745. in favor of a fixed-field layout.
  3746. .IP " *" 4
  3747. It translates names into a portable character set and identifies
  3748. locale-related information, both of which are probably unnecessary for
  3749. backup.
  3750. .P
  3751. The requirements on restoring from an archive are slightly different
  3752. from the historical wording, allowing for non-monolithic privilege to
  3753. bring forward as much as possible. In particular, attributes such as
  3754. ``high performance file'' might be broadly but not universally granted
  3755. while set-user-ID or
  3756. \fIchown\fR()
  3757. might be much more restricted. There is no implication in POSIX.1\(hy2008 that
  3758. the security information be honored after it is restored to the file
  3759. hierarchy, in spite of what might be improperly inferred by the silence
  3760. on that topic. That is a topic for another standard.
  3761. .P
  3762. Links are recorded in the fashion described here because a link can be
  3763. to any file type. It is desirable in general to be able to restore part
  3764. of an archive selectively and restore all of those files completely. If
  3765. the data is not associated with each link, it is not possible to do
  3766. this. However, the data associated with a file can be large, and when
  3767. selective restoration is not needed, this can be a significant burden.
  3768. The archive is structured so that files that have no associated data
  3769. can always be restored by the name of any link name of any link, and
  3770. the user may choose whether data is recorded with each instance of a
  3771. file that contains data. The format permits mixing of both types of
  3772. links in a single archive; this can be done for special needs, and
  3773. .IR pax
  3774. is expected to interpret such archives on input properly, despite the
  3775. fact that there is no
  3776. .IR pax
  3777. option that would force this mixed case on output. (When
  3778. .BR \-o
  3779. .BR linkdata
  3780. is used, the output must contain the duplicate data, but the
  3781. implementation is free to include it or omit it when
  3782. .BR \-o
  3783. .BR linkdata
  3784. is not used.)
  3785. .P
  3786. The time values are included as extended header records for those
  3787. implementations needing more than the eleven octal digits allowed by
  3788. the
  3789. .BR ustar
  3790. format. Portable file timestamps cannot be negative. If
  3791. .IR pax
  3792. encounters a file with a negative timestamp in
  3793. .BR copy
  3794. or
  3795. .BR write
  3796. mode, it can reject the file, substitute a non-negative timestamp, or
  3797. generate a non-portable timestamp with a leading
  3798. .BR '\-' .
  3799. Even though some implementations can support finer file-time
  3800. granularities than seconds, the normative text requires support only
  3801. for seconds since the Epoch because the ISO\ POSIX\(hy1 standard states them that way. The
  3802. .BR ustar
  3803. format includes only
  3804. .IR mtime ;
  3805. the new format adds
  3806. .IR atime
  3807. and
  3808. .IR ctime
  3809. for symmetry. The
  3810. .IR atime
  3811. access time restored to the file system will be affected by the
  3812. .BR \-p
  3813. .BR a
  3814. and
  3815. .BR \-p
  3816. .BR e
  3817. options. The
  3818. .IR ctime
  3819. creation time (actually
  3820. .IR inode
  3821. modification time) is described with appropriate privileges so that
  3822. it can be ignored when writing to the file system. POSIX does not
  3823. provide a portable means to change file creation time. Nothing is
  3824. intended to prevent a non-portable implementation of
  3825. .IR pax
  3826. from restoring the value.
  3827. .P
  3828. The
  3829. .IR gid ,
  3830. .IR size ,
  3831. and
  3832. .IR uid
  3833. extended header records were included to allow expansion beyond the
  3834. sizes specified in the regular
  3835. .IR tar
  3836. header. New file system architectures are emerging that will exhaust
  3837. the 12-digit size field. There are probably not many systems requiring
  3838. more than 8 digits for user and group IDs, but the extended header
  3839. values were included for completeness, allowing overrides for all of
  3840. the decimal values in the
  3841. .IR tar
  3842. header.
  3843. .P
  3844. The standard developers intended to describe the effective results of
  3845. .IR pax
  3846. with regard to file ownerships and permissions; implementations are not
  3847. restricted in timing or sequencing the restoration of such, provided
  3848. the results are as specified.
  3849. .P
  3850. Much of the text describing the extended headers refers to use in ``\c
  3851. .BR write
  3852. or
  3853. .BR copy
  3854. modes''. The
  3855. .BR copy
  3856. mode references are due to the normative text: ``The effect of the
  3857. copy shall be as if the copied files were written to an archive file
  3858. and then subsequently extracted .\|.\|.''. There is certainly no way to
  3859. test whether
  3860. .IR pax
  3861. is actually generating the extended headers in
  3862. .BR copy
  3863. mode, but the effects must be as if it had.
  3864. .SS "pax Archive Character Set Encoding/Decoding"
  3865. .P
  3866. There is a need to exchange archives of files between systems of
  3867. different native codesets. Filenames, group names, and user names must
  3868. be preserved to the fullest extent possible when an archive is read on
  3869. the receiving platform. Translation of the contents of files is not
  3870. within the scope of the
  3871. .IR pax
  3872. utility.
  3873. .P
  3874. There will also be the need to represent characters that are not
  3875. available on the receiving platform. These unsupported characters
  3876. cannot be automatically folded to the local set of characters due to
  3877. the chance of collisions. This could result in overwriting previous
  3878. extracted files from the archive or pre-existing files on the system.
  3879. .P
  3880. For these reasons, the codeset used to represent characters within the
  3881. extended header records of the
  3882. .IR pax
  3883. archive must be sufficiently rich to handle all commonly used character
  3884. sets. The fields requiring translation include, at a minimum,
  3885. filenames, user names, group names, and link pathnames. Implementations
  3886. may wish to have localized extended keywords that use non-portable
  3887. characters.
  3888. .P
  3889. The standard developers considered the following options:
  3890. .IP " *" 4
  3891. The archive creator specifies the well-defined name of the source
  3892. codeset. The receiver must then recognize the codeset name and perform
  3893. the appropriate translations to the destination codeset.
  3894. .IP " *" 4
  3895. The archive creator includes within the archive the character mapping
  3896. table for the source codeset used to encode extended header records.
  3897. The receiver must then read the character mapping table and perform the
  3898. appropriate translations to the destination codeset.
  3899. .IP " *" 4
  3900. The archive creator translates the extended header records in the
  3901. source codeset into a canonical form. The receiver must then perform
  3902. the appropriate translations to the destination codeset.
  3903. .P
  3904. The approach that incorporates the name of the source codeset poses the
  3905. problem of codeset name registration, and makes the archive useless to
  3906. .IR pax
  3907. archive decoders that do not recognize that codeset.
  3908. .P
  3909. Because parts of an archive may be corrupted, the standard developers
  3910. felt that including the character map of the source codeset was too
  3911. fragile. The loss of this one key component could result in making the
  3912. entire archive useless. (The difference between this and the global
  3913. extended header decision was that the latter has a
  3914. workaround\(emduplicating extended header records on unreliable
  3915. media\(embut this would be too burdensome for large character set
  3916. maps.)
  3917. .P
  3918. Both of the above approaches also put an undue burden on the
  3919. .IR pax
  3920. archive receiver to handle the cross-product of all source and
  3921. destination codesets.
  3922. .P
  3923. To simplify the translation from the source codeset to the canonical
  3924. form and from the canonical form to the destination codeset, the
  3925. standard developers decided that the internal representation should be
  3926. a stateless encoding. A stateless encoding is one where each codepoint
  3927. has the same meaning, without regard to the decoder being in a specific
  3928. state. An example of a stateful encoding would be the Japanese
  3929. Shift-JIS; an example of a stateless encoding would be the ISO/IEC\ 646:\|1991 standard
  3930. (equivalent to 7-bit ASCII).
  3931. .P
  3932. For these reasons, the standard developers decided to adopt a canonical
  3933. format for the representation of file information strings. The obvious,
  3934. well-endorsed candidate is the ISO/IEC\ 10646\(hy1:\|2000 standard (based in part on Unicode), which
  3935. can be used to represent the characters of virtually all standardized
  3936. character sets. The standard developers initially agreed upon using
  3937. UCS2 (16-bit Unicode) as the internal representation. This repertoire
  3938. of characters provides a sufficiently rich set to represent all
  3939. commonly-used codesets.
  3940. .P
  3941. However, the standard developers found that the 16-bit Unicode
  3942. representation had some problems. It forced the issue of standardizing
  3943. byte ordering. The 2-byte length of each character made the extended
  3944. header records twice as long for the case of strings coded entirely
  3945. from historical 7-bit ASCII. For these reasons, the standard developers
  3946. chose the UTF\(hy8 defined in the ISO/IEC\ 10646\(hy1:\|2000 standard. This multi-byte representation
  3947. encodes UCS2 or UCS4 characters reliably and deterministically,
  3948. eliminating the need for a canonical byte ordering. In addition, NUL
  3949. octets and other characters possibly confusing to POSIX file systems do
  3950. not appear, except to represent themselves. It was realized that
  3951. certain national codesets take up more space after the encoding, due to
  3952. their placement within the UCS range; it was felt that the usefulness
  3953. of the encoding of the names outweighs the disadvantage of size
  3954. increase for file, user, and group names.
  3955. .P
  3956. The encoding of UTF\(hy8 is as follows:
  3957. .sp
  3958. .RS 4
  3959. .nf
  3961. UCS4 Hex Encoding  UTF-8 Binary Encoding
  3962. .P
  3963. 00000000-0000007F  0xxxxxxx
  3964. 00000080-000007FF  110xxxxx 10xxxxxx
  3965. 00000800-0000FFFF  1110xxxx 10xxxxxx 10xxxxxx
  3966. 00010000-001FFFFF  11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
  3967. 00200000-03FFFFFF  111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
  3968. 04000000-7FFFFFFF  1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
  3969. .fi
  3970. .P
  3971. .RE
  3972. .P
  3973. where each
  3974. .BR 'x' 
  3975. represents a bit value from the character being translated.
  3976. .SS "ustar Interchange Format"
  3977. .P
  3978. The description of the
  3979. .BR ustar
  3980. format reflects numerous enhancements over pre-1988 versions of the
  3981. historical
  3982. .IR tar
  3983. utility. The goal of these changes was not only to provide the
  3984. functional enhancements desired, but also to retain compatibility
  3985. between new and old versions. This compatibility has been retained.
  3986. Archives written using the old archive format are compatible with the
  3987. new format.
  3988. .P
  3989. Implementors should be aware that the previous file format did not
  3990. include a mechanism to archive directory type files. For this reason,
  3991. the convention of using a filename ending with
  3992. <slash>
  3993. was adopted to specify a directory on the archive.
  3994. .P
  3995. The total size of the
  3996. .IR name
  3997. and
  3998. .IR prefix
  3999. fields have been set to meet the minimum requirements for
  4000. {PATH_MAX}.
  4001. If a pathname will fit within the
  4002. .IR name
  4003. field, it is recommended that the pathname be stored there without the
  4004. use of the
  4005. .IR prefix
  4006. field. Although the name field is known to be too small to contain
  4007. {PATH_MAX}
  4008. characters, the value was not changed in this version of the archive
  4009. file format to retain backwards-compatibility, and instead the prefix
  4010. was introduced. Also, because of the earlier version of the format,
  4011. there is no way to remove the restriction on the
  4012. .IR linkname
  4013. field being limited in size to just that of the
  4014. .IR name
  4015. field.
  4016. .P
  4017. The
  4018. .IR size
  4019. field is required to be meaningful in all implementation extensions,
  4020. although it could be zero. This is required so that the data blocks can
  4021. always be properly counted.
  4022. .P
  4023. It is suggested that if device special files need to be represented
  4024. that cannot be represented in the standard format, that one of the
  4025. extension types (\c
  4026. .BR A \(hy\c
  4027. .BR Z )
  4028. be used, and that the additional information for the special file be
  4029. represented as data and be reflected in the
  4030. .IR size
  4031. field.
  4032. .P
  4033. Attempting to restore a special file type, where it is converted to
  4034. ordinary data and conflicts with an existing filename, need not be
  4035. specially detected by the utility. If run as an ordinary user,
  4036. .IR pax
  4037. should not be able to overwrite the entries in, for example,
  4038. .BR /dev
  4039. in any case (whether the file is converted to another type or not). If
  4040. run as a privileged user, it should be able to do so, and it would be
  4041. considered a bug if it did not. The same is true of ordinary data files
  4042. and similarly named special files; it is impossible to anticipate the
  4043. needs of the user (who could really intend to overwrite the file), so
  4044. the behavior should be predictable (and thus regular) and rely on the
  4045. protection system as required.
  4046. .P
  4047. The value 7 in the
  4048. .IR typeflag
  4049. field is intended to define how contiguous files can be stored in a
  4050. .BR ustar
  4051. archive. POSIX.1\(hy2008 does not require the contiguous file extension, but does
  4052. define a standard way of archiving such files so that all conforming
  4053. systems can interpret these file types in a meaningful and consistent
  4054. manner. On a system that does not support extended file types, the
  4055. .IR pax
  4056. utility should do the best it can with the file and go on to the next.
  4057. .P
  4058. The file protection modes are those conventionally used by the
  4059. .IR ls
  4060. utility. This is extended beyond the usage in the ISO\ POSIX\(hy2 standard to support the
  4061. ``shared text'' or ``sticky'' bit. It is intended that the conformance
  4062. document should not document anything beyond the existence of and
  4063. support of such a mode. Further extensions are expected to these bits,
  4064. particularly with overloading the set-user-ID and set-group-ID flags.
  4065. .SS "cpio Interchange Format"
  4066. .P
  4067. The reference to appropriate privileges in the
  4068. .BR cpio
  4069. format refers to an error on standard output; the
  4070. .BR ustar
  4071. format does not make comparable statements.
  4072. .P
  4073. The model for this format was the historical System V
  4074. .IR cpio \c
  4075. .BR \-c
  4076. data interchange format. This model documents the portable version of
  4077. the
  4078. .BR cpio
  4079. format and not the binary version. It has the flexibility to transfer
  4080. data of any type described within POSIX.1\(hy2008, yet is extensible to transfer
  4081. data types specific to extensions beyond POSIX.1\(hy2008 (for example, contiguous
  4082. files). Because it describes existing practice, there is no question of
  4083. maintaining upwards-compatibility.
  4084. .SS "cpio Header"
  4085. .P
  4086. There has been some concern that the size of the
  4087. .IR c_ino
  4088. field of the header is too small to handle those systems that have very
  4089. large
  4090. .IR inode
  4091. numbers. However, the
  4092. .IR c_ino
  4093. field in the header is used strictly as a hard-link resolution
  4094. mechanism for archives. It is not necessarily the same value as the
  4095. .IR inode
  4096. number of the file in the location from which that file is extracted.
  4097. .P
  4098. The name
  4099. .IR c_magic
  4100. is based on historical usage.
  4101. .SS "cpio Filename"
  4102. .P
  4103. For most historical implementations of the
  4104. .IR cpio
  4105. utility,
  4106. {PATH_MAX}
  4107. octets can be used to describe the pathname without the addition of
  4108. any other header fields (the NUL character would be included in this
  4109. count).
  4110. {PATH_MAX}
  4111. is the minimum value for pathname size, documented as 256 bytes.
  4112. However, an implementation may use
  4113. .IR c_namesize
  4114. to determine the exact length of the pathname. With the current
  4115. description of the
  4116. .IR <cpio.h> 
  4117. header, this pathname size can be as large as a number that is
  4118. described in six octal digits.
  4119. .P
  4120. Two values are documented under the
  4121. .IR c_mode
  4122. field values to provide for extensibility for known file types:
  4123. .IP "\fB0110\ 000\fP" 10
  4124. Reserved for contiguous files. The implementation may treat the rest of
  4125. the information for this archive like a regular file. If this file type
  4126. is undefined, the implementation may create the file as a regular
  4127. file.
  4128. .P
  4129. This provides for extensibility of the
  4130. .BR cpio
  4131. format while allowing for the ability to read old archives. Files of an
  4132. unknown type may be read as ``regular files'' on some implementations.
  4133. On a system that does not support extended file types, the
  4134. .IR pax
  4135. utility should do the best it can with the file and go on to the next.
  4136. .SH "FUTURE DIRECTIONS"
  4137. None.
  4138. .SH "SEE ALSO"
  4139. .IR "Chapter 2" ", " "Shell Command Language",
  4140. .IR "\fIcp\fR\^",
  4141. .IR "\fIed\fR\^",
  4142. .IR "\fIgetopts\fR\^",
  4143. .IR "\fIls\fR\^",
  4144. .IR "\fIprintf\fR\^"
  4145. .P
  4146. The Base Definitions volume of POSIX.1\(hy2017,
  4147. .IR "Section 3.169" ", " "File Mode Bits",
  4148. .IR "Chapter 5" ", " "File Format Notation",
  4149. .IR "Chapter 8" ", " "Environment Variables",
  4150. .IR "Section 12.2" ", " "Utility Syntax Guidelines",
  4151. .IR "\fB<cpio.h>\fP",
  4152. .IR "\fB<tar.h>\fP"
  4153. .P
  4154. The System Interfaces volume of POSIX.1\(hy2017,
  4155. .IR "\fIchown\fR\^(\|)",
  4156. .IR "\fIcreat\fR\^(\|)",
  4157. .IR "\fIfstatat\fR\^(\|)",
  4158. .IR "\fImkdir\fR\^(\|)",
  4159. .IR "\fImkfifo\fR\^(\|)",
  4160. .IR "\fIutime\fR\^(\|)",
  4161. .IR "\fIwrite\fR\^(\|)"
  4162. .\"
  4163. .SH COPYRIGHT
  4164. Portions of this text are reprinted and reproduced in electronic form
  4165. from IEEE Std 1003.1-2017, Standard for Information Technology
  4166. -- Portable Operating System Interface (POSIX), The Open Group Base
  4167. Specifications Issue 7, 2018 Edition,
  4168. Copyright (C) 2018 by the Institute of
  4169. Electrical and Electronics Engineers, Inc and The Open Group.
  4170. In the event of any discrepancy between this version and the original IEEE and
  4171. The Open Group Standard, the original IEEE and The Open Group Standard
  4172. is the referee document. The original Standard can be obtained online at
  4173. http://www.opengroup.org/unix/online.html .
  4174. .PP
  4175. Any typographical or formatting errors that appear
  4176. in this page are most likely
  4177. to have been introduced during the conversion of the source files to
  4178. man page format. To report such errors, see
  4179. https://www.kernel.org/doc/man-pages/reporting_bugs.html .