PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

PAX(1P)                   POSIX Programmer's Manual                  PAX(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       pax — portable archive interchange

SYNOPSIS         top

       pax [−dv] [−c|−n] [−H|−L] [−o options] [−f archive] [−s replstr]...
           [pattern...]

       pax −r[−c|−n] [−dikuv] [−H|−L] [−f archive] [−o options]... [−p string]...
           [−s replstr]... [pattern...]

       pax −w [−dituvX] [−H|−L] [−b blocksize] [[−a] [−f archive]] [−o options]...
           [−s replstr]... [−x format] [file...]

       pax −r −w [−diklntuvX] [−H|−L] [−o options]... [−p string]...
           [−s replstr]... [file...] directory

DESCRIPTION         top

       The pax utility shall read, write, and write lists of the members of
       archive files and copy directory hierarchies. A variety of archive
       formats shall be supported; see the −x format option.

       The action to be taken depends on the presence of the −r and −w
       options. The four combinations of −r and −w are referred to as the
       four modes of operation: list, read, write, and copy modes,
       corresponding respectively to the four forms shown in the SYNOPSIS
       section.

       list      In list mode (when neither −r nor −w are specified), pax
                 shall write the names of the members of the archive file
                 read from the standard input, with pathnames matching the
                 specified patterns, to standard output. If a named file is
                 of type directory, the file hierarchy rooted at that file
                 shall be listed as well.

       read      In read mode (when −r is specified, but −w is not), pax
                 shall extract the members of the archive file read from the
                 standard input, with pathnames matching the specified
                 patterns. If an extracted file is of type directory, the
                 file hierarchy rooted at that file shall be extracted as
                 well. The extracted files shall be created performing
                 pathname resolution with the directory in which pax was
                 invoked as the current working directory.

                 If an attempt is made to extract a directory when the
                 directory already exists, this shall not be considered an
                 error. If an attempt is made to extract a FIFO when the
                 FIFO already exists, this shall not be considered an error.

                 The ownership, access, and modification times, and file
                 mode of the restored files are discussed under the −p
                 option.

       write     In write mode (when −w is specified, but −r is not), pax
                 shall write the contents of the file operands to the
                 standard output in an archive format. If no file operands
                 are specified, a list of files to copy, one per line, shall
                 be read from the standard input and each entry in this list
                 shall be processed as if it had been a file operand on the
                 command line. A file of type directory shall include all of
                 the files in the file hierarchy rooted at the file.

       copy      In copy mode (when both −r and −w are specified), pax shall
                 copy the file operands to the destination directory.

                 If no file operands are specified, a list of files to copy,
                 one per line, shall be read from the standard input. A file
                 of type directory shall include all of the files in the
                 file hierarchy rooted at the file.

                 The effect of the copy shall be as if the copied files were
                 written to a pax format archive file and then subsequently
                 extracted, except that there may be hard links between the
                 original and the copied files. If the destination directory
                 is a subdirectory of one of the files to be copied, the
                 results are unspecified. If the destination directory is a
                 file of a type not defined by the System Interfaces volume
                 of POSIX.1‐2008, the results are implementation-defined;
                 otherwise, it shall be an error for the file named by the
                 directory operand not to exist, not be writable by the
                 user, or not be a file of type directory.

       In read or copy modes, if intermediate directories are necessary to
       extract an archive member, pax shall perform actions equivalent to
       the mkdir() function defined in the System Interfaces volume of
       POSIX.1‐2008, called with the following arguments:

        *  The intermediate directory used as the path argument

        *  The value of the bitwise-inclusive OR of S_IRWXU, S_IRWXG, and
           S_IRWXO as the mode argument

       If any specified pattern or file operands are not matched by at least
       one file or archive member, pax shall write a diagnostic message to
       standard error for each one that did not match and exit with a non-
       zero exit status.

       The archive formats described in the EXTENDED DESCRIPTION section
       shall be automatically detected on input. The default output archive
       format shall be implementation-defined.

       A single archive can span multiple files. The pax utility shall
       determine, in an implementation-defined manner, what file to read or
       write as the next file.

       If the selected archive format supports the specification of linked
       files, it shall be an error if these files cannot be linked when the
       archive is extracted. For archive formats that do not store file
       contents with each name that causes a hard link, if the file that
       contains the data is not extracted during this pax session, either
       the data shall be restored from the original file, or a diagnostic
       message shall be displayed with the name of a file that can be used
       to extract the data. In traversing directories, pax shall detect
       infinite loops; that is, entering a previously visited directory that
       is an ancestor of the last file visited. When it detects an infinite
       loop, pax shall write a diagnostic message to standard error and
       shall terminate.

OPTIONS         top

       The pax utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that
       the order of presentation of the −o, −p, and −s options is
       significant.

       The following options shall be supported:

       −r        Read an archive file from standard input.

       −w        Write files to the standard output in the specified archive
                 format.

       −a        Append files to the end of the archive. It is
                 implementation-defined which devices on the system support
                 appending. Additional file formats unspecified by this
                 volume of POSIX.1‐2008 may impose restrictions on
                 appending.

       −b blocksize
                 Block the output at a positive decimal integer number of
                 bytes per write to the archive file. Devices and archive
                 formats may impose restrictions on blocking. Blocking shall
                 be automatically determined on input. Conforming
                 applications shall not specify a blocksize value larger
                 than 32256. Default blocking when creating archives depends
                 on the archive format. (See the −x option below.)

       −c        Match all file or archive members except those specified by
                 the pattern or file operands.

       −d        Cause files of type directory being copied or archived or
                 archive members of type directory being extracted or listed
                 to match only the file or archive member itself and not the
                 file hierarchy rooted at the file.

       −f archive
                 Specify the pathname of the input or output archive,
                 overriding the default standard input (in list or read
                 modes) or standard output (write mode).

       −H        If a symbolic link referencing a file of type directory is
                 specified on the command line, pax shall archive the file
                 hierarchy rooted in the file referenced by the link, using
                 the name of the link as the root of the file hierarchy.
                 Otherwise, if a symbolic link referencing a file of any
                 other file type which pax can normally archive is specified
                 on the command line, then pax shall archive the file
                 referenced by the link, using the name of the link. The
                 default behavior, when neither −H or −L are specified,
                 shall be to archive the symbolic link itself.

       −i        Interactively rename files or archive members. For each
                 archive member matching a pattern operand or file matching
                 a file operand, a prompt shall be written to the file
                 /dev/tty.  The prompt shall contain the name of the file or
                 archive member, but the format is otherwise unspecified. A
                 line shall then be read from /dev/tty.  If this line is
                 blank, the file or archive member shall be skipped. If this
                 line consists of a single period, the file or archive
                 member shall be processed with no modification to its name.
                 Otherwise, its name shall be replaced with the contents of
                 the line. The pax utility shall immediately exit with a
                 non-zero exit status if end-of-file is encountered when
                 reading a response or if /dev/tty cannot be opened for
                 reading and writing.

                 The results of extracting a hard link to a file that has
                 been renamed during extraction are unspecified.

       −k        Prevent the overwriting of existing files.

       −l        (The letter ell.) In copy mode, hard links shall be made
                 between the source and destination file hierarchies
                 whenever possible. If specified in conjunction with −H or
                 −L, when a symbolic link is encountered, the hard link
                 created in the destination file hierarchy shall be to the
                 file referenced by the symbolic link. If specified when
                 neither −H nor −L is specified, when a symbolic link is
                 encountered, the implementation shall create a hard link to
                 the symbolic link in the source file hierarchy or copy the
                 symbolic link to the destination.

       −L        If a symbolic link referencing a file of type directory is
                 specified on the command line or encountered during the
                 traversal of a file hierarchy, pax shall archive the file
                 hierarchy rooted in the file referenced by the link, using
                 the name of the link as the root of the file hierarchy.
                 Otherwise, if a symbolic link referencing a file of any
                 other file type which pax can normally archive is specified
                 on the command line or encountered during the traversal of
                 a file hierarchy, pax shall archive the file referenced by
                 the link, using the name of the link. The default behavior,
                 when neither −H or −L are specified, shall be to archive
                 the symbolic link itself.

       −n        Select the first archive member that matches each pattern
                 operand. No more than one archive member shall be matched
                 for each pattern (although members of type directory shall
                 still match the file hierarchy rooted at that file).

       −o options
                 Provide information to the implementation to modify the
                 algorithm for extracting or writing files. The value of
                 options shall consist of one or more <comma>-separated
                 keywords of the form:

                     keyword[[:]=value][,keyword[[:]=value], ...]

                 Some keywords apply only to certain file formats, as
                 indicated with each description. Use of keywords that are
                 inapplicable to the file format being processed produces
                 undefined results.

                 Keywords in the options argument shall be a string that
                 would be a valid portable filename as described in the Base
                 Definitions volume of POSIX.1‐2008, Section 3.278, Portable
                 Filename Character Set.

                 Note:     Keywords are not expected to be filenames, merely
                           to follow the same character composition rules as
                           portable filenames.

                 Keywords can be preceded with white space. The value field
                 shall consist of zero or more characters; within value, the
                 application shall precede any literal <comma> with a
                 <backslash>, which shall be ignored, but preserves the
                 <comma> as part of value.  A <comma> as the final
                 character, or a <comma> followed solely by white space as
                 the final characters, in options shall be ignored. Multiple
                 −o options can be specified; if keywords given to these
                 multiple −o options conflict, the keywords and values
                 appearing later in command line sequence shall take
                 precedence and the earlier shall be silently ignored. The
                 following keyword values of options shall be supported for
                 the file formats as indicated:

                 delete=pattern
                       (Applicable only to the −x pax format.) When used in
                       write or copy mode, pax shall omit from extended
                       header records that it produces any keywords matching
                       the string pattern. When used in read or list mode,
                       pax shall ignore any keywords matching the string
                       pattern in the extended header records. In both
                       cases, matching shall be performed using the pattern
                       matching notation described in Section 2.13.1,
                       Patterns Matching a Single Character and Section
                       2.13.2, Patterns Matching Multiple Characters.  For
                       example:

                           −o delete=security.*

                       would suppress security-related information. See pax
                       Extended Header for extended header record keyword
                       usage.

                       When multiple −odelete=pattern options are specified,
                       the patterns shall be additive; all keywords matching
                       the specified string patterns shall be omitted from
                       extended header records that pax produces.

                 exthdr.name=string
                       (Applicable only to the −x pax format.) This keyword
                       allows user control over the name that is written
                       into the ustar header blocks for the extended header
                       produced under the circumstances described in pax
                       Header Block.  The name shall be the contents of
                       string, after the following character substitutions
                       have been made:

                       ┌──────────┬────────────────────────────────────────┐
                       │ string   │                                        │
                       │Includes: Replaced by:              │
                       ├──────────┼────────────────────────────────────────┤
                       │%d        │ The directory name of the file,        │
                       │          │ equivalent to the result of the        │
                       │          │ dirname utility on the translated      │
                       │          │ pathname.                              │
                       │%f        │ The filename of the file, equivalent   │
                       │          │ to the result of the basename utility  │
                       │          │ on the translated pathname.            │
                       │%p        │ The process ID of the pax process.     │
                       │%%        │ A '%' character.                       │
                       └──────────┴────────────────────────────────────────┘
                       Any other '%' characters in string produce undefined
                       results.

                       If no −o exthdr.name=string is specified, pax shall
                       use the following default value:

                           %d/PaxHeaders.%p/%f

                 globexthdr.name=string
                       (Applicable only to the −x pax format.) When used in
                       write or copy mode with the appropriate options, pax
                       shall create global extended header records with
                       ustar header blocks that will be treated as regular
                       files by previous versions of pax.  This keyword
                       allows user control over the name that is written
                       into the ustar header blocks for global extended
                       header records. The name shall be the contents of
                       string, after the following character substitutions
                       have been made:

                       ┌──────────┬────────────────────────────────────────┐
                       │ string   │                                        │
                       │Includes: Replaced by:              │
                       ├──────────┼────────────────────────────────────────┤
                       │%n        │ An integer that represents the         │
                       │          │ sequence number of the global extended │
                       │          │ header record in the archive, starting │
                       │          │ at 1.                                  │
                       │%p        │ The process ID of the pax process.     │
                       │%%        │ A '%' character.                       │
                       └──────────┴────────────────────────────────────────┘
                       Any other '%' characters in string produce undefined
                       results.

                       If no −o globexthdr.name=string is specified, pax
                       shall use the following default value:

                           $TMPDIR/GlobalHead.%p.%n

                       where $TMPDIR represents the value of the TMPDIR
                       environment variable. If TMPDIR is not set, pax shall
                       use /tmp.

                 invalid=action
                       (Applicable only to the −x pax format.) This keyword
                       allows user control over the action pax takes upon
                       encountering values in an extended header record
                       that, in read or copy mode, are invalid in the
                       destination hierarchy or, in list mode, cannot be
                       written in the codeset and current locale of the
                       implementation. The following are invalid values that
                       shall be recognized by pax:

                       --  In read or copy mode, a filename or link name
                           that contains character encodings invalid in the
                           destination hierarchy. (For example, the name may
                           contain embedded NULs.)

                       --  In read or copy mode, a filename or link name
                           that is longer than the maximum allowed in the
                           destination hierarchy (for either a pathname
                           component or the entire pathname).

                       --  In list mode, any character string value
                           (filename, link name, user name, and so on) that
                           cannot be written in the codeset and current
                           locale of the implementation.

                       The following mutually-exclusive values of the action
                       argument are supported:

                       binary    In write mode, pax shall generate a
                                 hdrcharset=BINARY extended header record
                                 for each file with a filename, link name,
                                 group name, owner name, or any other field
                                 in an extended header record that cannot be
                                 translated to the UTF‐8 codeset, allowing
                                 the archive to contain the files with
                                 unencoded extended header record values. In
                                 read or copy mode, pax shall use the values
                                 specified in the header without
                                 translation, regardless of whether this may
                                 overwrite an existing file with a valid
                                 name. In list mode, pax shall behave
                                 identically to the bypass action.

                       bypass    In read or copy mode, pax shall bypass the
                                 file, causing no change to the destination
                                 hierarchy.  In list mode, pax shall write
                                 all requested valid values for the file,
                                 but its method for writing invalid values
                                 is unspecified.

                       rename    In read or copy mode, pax shall act as if
                                 the −i option were in effect for each file
                                 with invalid filename or link name values,
                                 allowing the user to provide a replacement
                                 name interactively.  In list mode, pax
                                 shall behave identically to the bypass
                                 action.

                       UTF‐8     When used in read, copy, or list mode and a
                                 filename, link name, owner name, or any
                                 other field in an extended header record
                                 cannot be translated from the pax UTF‐8
                                 codeset format to the codeset and current
                                 locale of the implementation, pax shall use
                                 the actual UTF‐8 encoding for the name. If
                                 a hdrcharset extended header record is in
                                 effect for this file, the character set
                                 specified by that record shall be used
                                 instead of UTF‐8. If a hdrcharset=BINARY
                                 extended header record is in effect for
                                 this file, no translation shall be
                                 performed.

                       write     In read or copy mode, pax shall write the
                                 file, translating the name, regardless of
                                 whether this may overwrite an existing file
                                 with a valid name. In list mode, pax shall
                                 behave identically to the bypass action.

                       If no −o invalid=option is specified, pax shall act
                       as if −oinvalid=bypass were specified. Any
                       overwriting of existing files that may be allowed by
                       the −oinvalid= actions shall be subject to permission
                       (−p) and modification time (−u) restrictions, and
                       shall be suppressed if the −k option is also
                       specified.

                 linkdata
                       (Applicable only to the −x pax format.) In write
                       mode, pax shall write the contents of a file to the
                       archive even when that file is merely a hard link to
                       a file whose contents have already been written to
                       the archive.

                 listopt=format
                       This keyword specifies the output format of the table
                       of contents produced when the −v option is specified
                       in list mode. See List Mode Format Specifications.
                       To avoid ambiguity, the listopt=format shall be the
                       only or final keyword=value pair in a −o option-
                       argument; all characters in the remainder of the
                       option-argument shall be considered part of the
                       format string. When multiple −olistopt=format options
                       are specified, the format strings shall be considered
                       a single, concatenated string, evaluated in command
                       line order.

                 times
                       (Applicable only to the −x pax format.) When used in
                       write or copy mode, pax shall include atime and mtime
                       extended header records for each file. See pax
                       Extended Header File Times.

                 In addition to these keywords, if the −x pax format is
                 specified, any of the keywords and values defined in pax
                 Extended Header, including implementation extensions, can
                 be used in −o option-arguments, in either of two modes:

                 keyword=value
                       When used in write or copy mode, these keyword/value
                       pairs shall be included at the beginning of the
                       archive as typeflag g global extended header records.
                       When used in read or list mode, these keyword/value
                       pairs shall act as if they had been at the beginning
                       of the archive as typeflag g global extended header
                       records.

                 keyword:=value
                       When used in write or copy mode, these keyword/value
                       pairs shall be included as records at the beginning
                       of a typeflag x extended header for each file. (This
                       shall be equivalent to the <equals-sign> form except
                       that it creates no typeflag g global extended header
                       records.) When used in read or list mode, these
                       keyword/value pairs shall act as if they were
                       included as records at the end of each extended
                       header; thus, they shall override any global or file-
                       specific extended header record keywords of the same
                       names. For example, in the command:

                           pax −r −o "
                           gname:=mygroup,
                           " <archive

                       the group name will be forced to a new value for all
                       files read from the archive.

                 The precedence of −o keywords over various fields in the
                 archive is described in pax Extended Header Keyword
                 Precedence.

       −p string Specify one or more file characteristic options
                 (privileges). The string option-argument shall be a string
                 specifying file characteristics to be retained or discarded
                 on extraction. The string shall consist of the
                 specification characters a, e, m, o, and p.  Other
                 implementation-defined characters can be included. Multiple
                 characteristics can be concatenated within the same string
                 and multiple −p options can be specified. The meaning of
                 the specification characters are as follows:

                 a     Do not preserve file access times.

                 e     Preserve the user ID, group ID, file mode bits (see
                       the Base Definitions volume of POSIX.1‐2008, Section
                       3.169, File Mode Bits), access time, modification
                       time, and any other implementation-defined file
                       characteristics.

                 m     Do not preserve file modification times.

                 o     Preserve the user ID and group ID.

                 p     Preserve the file mode bits. Other implementation-
                       defined file mode attributes may be preserved.

                 In the preceding list, ``preserve'' indicates that an
                 attribute stored in the archive shall be given to the
                 extracted file, subject to the permissions of the invoking
                 process. The access and modification times of the file
                 shall be preserved unless otherwise specified with the −p
                 option or not stored in the archive. All attributes that
                 are not preserved shall be determined as part of the normal
                 file creation action (see Section 1.1.1.4, File Read,
                 Write, and Creation).

                 If neither the e nor the o specification character is
                 specified, or the user ID and group ID are not preserved
                 for any reason, pax shall not set the S_ISUID and S_ISGID
                 bits of the file mode.

                 If the preservation of any of these items fails for any
                 reason, pax shall write a diagnostic message to standard
                 error. Failure to preserve these items shall affect the
                 final exit status, but shall not cause the extracted file
                 to be deleted.

                 If file characteristic letters in any of the string option-
                 arguments are duplicated or conflict with each other, the
                 ones given last shall take precedence. For example, if −p
                 eme is specified, file modification times are preserved.

       −s replstr
                 Modify file or archive member names named by pattern or
                 file operands according to the substitution expression
                 replstr, using the syntax of the ed utility. The concepts
                 of ``address'' and ``line'' are meaningless in the context
                 of the pax utility, and shall not be supplied. The format
                 shall be:

                     −s /old/new/[gp]

                 where as in ed, old is a basic regular expression and new
                 can contain an <ampersand>, '\n' (where n is a digit) back-
                 references, or subexpression matching. The old string shall
                 also be permitted to contain <newline> characters.

                 Any non-null character can be used as a delimiter ('/'
                 shown here). Multiple −s expressions can be specified; the
                 expressions shall be applied in the order specified,
                 terminating with the first successful substitution.  The
                 optional trailing 'g' is as defined in the ed utility. The
                 optional trailing 'p' shall cause successful substitutions
                 to be written to standard error.  File or archive member
                 names that substitute to the empty string shall be ignored
                 when reading and writing archives.

       −t        When reading files from the file system, and if the user
                 has the permissions required by utime() to do so, set the
                 access time of each file read to the access time that it
                 had before being read by pax.

       −u        Ignore files that are older (having a less recent file
                 modification time) than a pre-existing file or archive
                 member with the same name.  In read mode, an archive member
                 with the same name as a file in the file system shall be
                 extracted if the archive member is newer than the file. In
                 write mode, an archive file member with the same name as a
                 file in the file system shall be superseded if the file is
                 newer than the archive member. If −a is also specified,
                 this is accomplished by appending to the archive;
                 otherwise, it is unspecified whether this is accomplished
                 by actual replacement in the archive or by appending to the
                 archive. In copy mode, the file in the destination
                 hierarchy shall be replaced by the file in the source
                 hierarchy or by a link to the file in the source hierarchy
                 if the file in the source hierarchy is newer.

       −v        In list mode, produce a verbose table of contents (see the
                 STDOUT section).  Otherwise, write archive member pathnames
                 to standard error (see the STDERR section).

       −x format Specify the output archive format. The pax utility shall
                 support the following formats:

                 cpio      The cpio interchange format; see the EXTENDED
                           DESCRIPTION section. The default blocksize for
                           this format for character special archive files
                           shall be 5120.  Implementations shall support all
                           blocksize values less than or equal to 32256 that
                           are multiples of 512.

                 pax       The pax interchange format; see the EXTENDED
                           DESCRIPTION section. The default blocksize for
                           this format for character special archive files
                           shall be 5120.  Implementations shall support all
                           blocksize values less than or equal to 32256 that
                           are multiples of 512.

                 ustar     The tar interchange format; see the EXTENDED
                           DESCRIPTION section. The default blocksize for
                           this format for character special archive files
                           shall be 10240.  Implementations shall support
                           all blocksize values less than or equal to 32256
                           that are multiples of 512.

                 Implementation-defined formats shall specify a default
                 block size as well as any other block sizes supported for
                 character special archive files.

                 Any attempt to append to an archive file in a format
                 different from the existing archive format shall cause pax
                 to exit immediately with a non-zero exit status.

       −X        When traversing the file hierarchy specified by a pathname,
                 pax shall not descend into directories that have a
                 different device ID (st_dev; see the System Interfaces
                 volume of POSIX.1‐2008, stat()).

       Specifying more than one of the mutually-exclusive options −H and −L
       shall not be considered an error and the last option specified shall
       determine the behavior of the utility.

       The options that operate on the names of files or archive members
       (−c, −i, −n, −s, −u, and −v) shall interact as follows. In read mode,
       the archive members shall be selected based on the user-specified
       pattern operands as modified by the −c, −n, and −u options. Then, any
       −s and −i options shall modify, in that order, the names of the
       selected files.  The −v option shall write names resulting from these
       modifications.

       In write mode, the files shall be selected based on the user-
       specified pathnames as modified by the −n and −u options. Then, any
       −s and −i options shall modify, in that order, the names of these
       selected files.  The −v option shall write names resulting from these
       modifications.

       If both the −u and −n options are specified, pax shall not consider a
       file selected unless it is newer than the file to which it is
       compared.

   List Mode Format Specifications
       In list mode with the −o listopt=format option, the format argument
       shall be applied for each selected file. The pax utility shall append
       a <newline> to the listopt output for each selected file. The format
       argument shall be used as the format string described in the Base
       Definitions volume of POSIX.1‐2008, Chapter 5, File Format Notation,
       with the exceptions 1. through 6. defined in the EXTENDED DESCRIPTION
       section of printf, plus the following exceptions:

       7.    The sequence (keyword) can occur before a format conversion
             specifier. The conversion argument is defined by the value of
             keyword.  The implementation shall support the following
             keywords:

             --  Any of the Field Name entries in Table 4-14, ustar Header
                 Block and Table 4-16, Octet-Oriented cpio Archive Entry.
                 The implementation may support the cpio keywords without
                 the leading c_ in addition to the form required by Table
                 4-16, Octet-Oriented cpio Archive Entry.

             --  Any keyword defined for the extended header in pax Extended
                 Header.

             --  Any keyword provided as an implementation-defined extension
                 within the extended header defined in pax Extended Header.

             For example, the sequence "%(charset)s" is the string value of
             the name of the character set in the extended header.

             The result of the keyword conversion argument shall be the
             value from the applicable header field or extended header,
             without any trailing NULs.

             All keyword values used as conversion arguments shall be
             translated from the UTF‐8 encoding (or alternative encoding
             specified by any hdrcharset extended header record) to the
             character set appropriate for the local file system, user
             database, and so on, as applicable.

       8.    An additional conversion specifier character, T, shall be used
             to specify time formats. The T conversion specifier character
             can be preceded by the sequence (keyword=subformat), where
             subformat is a date format as defined by date operands. The
             default keyword shall be mtime and the default subformat shall
             be:

                 %b %e %H:%M %Y

       9.    An additional conversion specifier character, M, shall be used
             to specify the file mode string as defined in ls Standard
             Output. If (keyword) is omitted, the mode keyword shall be
             used. For example, %.1M writes the single character
             corresponding to the <entry type> field of the ls −l command.

       10.   An additional conversion specifier character, D, shall be used
             to specify the device for block or special files, if
             applicable, in an implementation-defined format. If not
             applicable, and (keyword) is specified, then this conversion
             shall be equivalent to %(keyword)u. If not applicable, and
             (keyword) is omitted, then this conversion shall be equivalent
             to <space>.

       11.   An additional conversion specifier character, F, shall be used
             to specify a pathname. The F conversion character can be
             preceded by a sequence of <comma>-separated keywords:

                 (keyword[,keyword] ... )

             The values for all the keywords that are non-null shall be
             concatenated together, each separated by a '/'.  The default
             shall be (path) if the keyword path is defined; otherwise, the
             default shall be (prefix,name).

       12.   An additional conversion specifier character, L, shall be used
             to specify a symbolic link expansion. If the current file is a
             symbolic link, then %L shall expand to:

                 "%s −> %s", <value of keyword>, <contents of link>

             Otherwise, the %L conversion specification shall be the
             equivalent of %F.

OPERANDS         top

       The following operands shall be supported:

       directory The destination directory pathname for copy mode.

       file      A pathname of a file to be copied or archived.

       pattern   A pattern matching one or more pathnames of archive
                 members. A pattern must be given in the name-generating
                 notation of the pattern matching notation in Section 2.13,
                 Pattern Matching Notation, including the filename expansion
                 rules in Section 2.13.3, Patterns Used for Filename
                 Expansion.  The default, if no pattern is specified, is to
                 select all members in the archive.

STDIN         top

       In write mode, the standard input shall be used only if no file
       operands are specified. It shall be a file containing a list of
       pathnames, each terminated by a <newline> character.

       In list and read modes, if −f is not specified, the standard input
       shall be an archive file.

       Otherwise, the standard input shall not be used.

INPUT FILES         top

       The input file named by the archive option-argument, or standard
       input when the archive is read from there, shall be a file formatted
       according to one of the specifications in the EXTENDED DESCRIPTION
       section or some other implementation-defined format.

       The file /dev/tty shall be used to write prompts and read responses.

ENVIRONMENT VARIABLES         top

       The following environment variables shall affect the execution of
       pax:

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1‐2008, Section 8.2, Internationalization
                 Variables the precedence of internationalization variables
                 used to determine the values of locale categories.)

       LC_ALL    If set to a non-empty string value, override the values of
                 all the other internationalization variables.

       LC_COLLATE
                 Determine the locale for the behavior of ranges,
                 equivalence classes, and multi-character collating elements
                 used in the pattern matching expressions for the pattern
                 operand, the basic regular expression for the −s option,
                 and the extended regular expression defined for the yesexpr
                 locale keyword in the LC_MESSAGES category.

       LC_CTYPE  Determine the locale for the interpretation of sequences of
                 bytes of text data as characters (for example, single-byte
                 as opposed to multi-byte characters in arguments and input
                 files), the behavior of character classes used in the
                 extended regular expression defined for the yesexpr locale
                 keyword in the LC_MESSAGES category, and pattern matching.

       LC_MESSAGES
                 Determine the locale used to process affirmative responses,
                 and the locale used to affect the format and contents of
                 diagnostic messages and prompts written to standard error.

       LC_TIME   Determine the format and contents of date and time strings
                 when the −v option is specified.

       NLSPATH   Determine the location of message catalogs for the
                 processing of LC_MESSAGES.

       TMPDIR    Determine the pathname that provides part of the default
                 global extended header record file, as described for the −o
                 globexthdr= keyword in the OPTIONS section.

       TZ        Determine the timezone used to calculate date and time
                 strings when the −v option is specified. If TZ is unset or
                 null, an unspecified default timezone shall be used.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       In write mode, if −f is not specified, the standard output shall be
       the archive formatted according to one of the specifications in the
       EXTENDED DESCRIPTION section, or some other implementation-defined
       format (see −x format).

       In list mode, when the −olistopt=format has been specified, the
       selected archive members shall be written to standard output using
       the format described under List Mode Format Specifications.  In list
       mode without the −olistopt=format option, the table of contents of
       the selected archive members shall be written to standard output
       using the following format:

           "%s\n", <pathname>

       If the −v option is specified in list mode, the table of contents of
       the selected archive members shall be written to standard output
       using the following formats.

       For pathnames representing hard links to previous members of the
       archive:

           "%s == %s\n", <ls −l listing>, <linkname>

       For all other pathnames:

           "%s\n", <ls −l listing>

       where <ls −l listing> shall be the format specified by the ls utility
       with the −l option. When writing pathnames in this format, it is
       unspecified what is written for fields for which the underlying
       archive format does not have the correct information, although the
       correct number of <blank>-separated fields shall be written.

       In list mode, standard output shall not be buffered more than a
       pathname (plus any associated information and a <newline> terminator)
       at a time.

STDERR         top

       If −v is specified in read, write, or copy modes, pax shall write the
       pathnames it processes to the standard error output using the
       following format:

           "%s\n", <pathname>

       These pathnames shall be written as soon as processing is begun on
       the file or archive member, and shall be flushed to standard error.
       The trailing <newline>, which shall not be buffered, is written when
       the file has been read or written.

       If the −s option is specified, and the replacement string has a
       trailing 'p', substitutions shall be written to standard error in the
       following format:

           "%s >> %s\n", <original pathname>, <new pathname>

       In all operating modes of pax, optional messages of unspecified
       format concerning the input archive format and volume number, the
       number of files, blocks, volumes, and media parts as well as other
       diagnostic messages may be written to standard error.

       In all formats, for both standard output and standard error, it is
       unspecified how non-printable characters in pathnames or link names
       are written.

       When using the −xpax archive format, if a filename, link name, group
       name, owner name, or any other field in an extended header record
       cannot be translated between the codeset in use for that extended
       header record and the character set of the current locale, pax shall
       write a diagnostic message to standard error, shall process the file
       as described for the −o invalid= option, and then shall continue
       processing with the next file.

OUTPUT FILES         top

       In read mode, the extracted output files shall be of the archived
       file type.  In copy mode, the copied output files shall be the type
       of the file being copied. In either mode, existing files in the
       destination hierarchy shall be overwritten only when all permission
       (−p), modification time (−u), and invalid-value (−oinvalid=) tests
       allow it.

       In write mode, the output file named by the −f option-argument shall
       be a file formatted according to one of the specifications in the
       EXTENDED DESCRIPTION section, or some other implementation-defined
       format.

EXTENDED DESCRIPTION         top

   pax Interchange Format
       A pax archive tape or file produced in the −xpax format shall contain
       a series of blocks. The physical layout of the archive shall be
       identical to the ustar format described in ustar Interchange Format.
       Each file archived shall be represented by the following sequence:

        *  An optional header block with extended header records. This
           header block is of the form described in pax Header Block, with a
           typeflag value of x or g.  The extended header records, described
           in pax Extended Header, shall be included as the data for this
           header block.

        *  A header block that describes the file. Any fields in the
           preceding optional extended header shall override the associated
           fields in this header block for this file.

        *  Zero or more blocks that contain the contents of the file.

       At the end of the archive file there shall be two 512-byte blocks
       filled with binary zeros, interpreted as an end-of-archive indicator.

       A schematic of an example archive with global extended header records
       and two actual files is shown in Figure 4-1, pax Format Archive
       Example.  In the example, the second file in the archive has no
       extended header preceding it, presumably because it has no need for
       extended attributes.

                      Figure 4-1: pax Format Archive Example

   pax Header Block
       The pax header block shall be identical to the ustar header block
       described in ustar Interchange Format, except that two additional
       typeflag values are defined:

       x     Represents extended header records for the following file in
             the archive (which shall have its own ustar header block). The
             format of these extended header records shall be as described
             in pax Extended Header.

       g     Represents global extended header records for the following
             files in the archive. The format of these extended header
             records shall be as described in pax Extended Header.  Each
             value shall affect all subsequent files that do not override
             that value in their own extended header record and until
             another global extended header record is reached that provides
             another value for the same field. The typeflag g global headers
             should not be used with interchange media that could suffer
             partial data loss in transporting the archive.

       For both of these types, the size field shall be the size of the
       extended header records in octets. The other fields in the header
       block are not meaningful to this version of the pax utility. However,
       if this archive is read by a pax utility conforming to the
       ISO POSIX‐2:1993 standard, the header block fields are used to create
       a regular file that contains the extended header records as data.
       Therefore, header block field values should be selected to provide
       reasonable file access to this regular file.

       A further difference from the ustar header block is that data blocks
       for files of typeflag 1 (the digit one) (hard link) may be included,
       which means that the size field may be greater than zero. Archives
       created by pax −o linkdata shall include these data blocks with the
       hard links.

   pax Extended Header
       A pax extended header contains values that are inappropriate for the
       ustar header block because of limitations in that format: fields
       requiring a character encoding other than that described in the
       ISO/IEC 646:1991 standard, fields representing file attributes not
       described in the ustar header, and fields whose format or length do
       not fit the requirements of the ustar header. The values in an
       extended header add attributes to the following file (or files; see
       the description of the typeflag g header block) or override values in
       the following header block(s), as indicated in the following list of
       keywords.

       An extended header shall consist of one or more records, each
       constructed as follows:

           "%d %s=%s\n", <length>, <keyword>, <value>

       The extended header records shall be encoded according to the
       ISO/IEC 10646‐1:2000 standard UTF‐8 encoding. The <length> field,
       <blank>, <equals-sign>, and <newline> shown shall be limited to the
       portable character set, as encoded in UTF‐8. The <keyword> fields can
       be any UTF‐8 characters.  The <length> field shall be the decimal
       length of the extended header record in octets, including the
       trailing <newline>.  If there is a hdrcharset extended header in
       effect for a file, the value field for any gname, linkpath, path, and
       uname extended header records shall be encoded using the character
       set specified by the hdrcharset extended header record; otherwise,
       the value field shall be encoded using UTF‐8. The value field for all
       other keywords specified by POSIX.1‐2008 shall be encoded using
       UTF‐8.

       The <keyword> field shall be one of the entries from the following
       list or a keyword provided as an implementation extension.  Keywords
       consisting entirely of lowercase letters, digits, and periods are
       reserved for future standardization. A keyword shall not include an
       <equals-sign>.  (In the following list, the notations ``file(s)'' or
       ``block(s)'' is used to acknowledge that a keyword affects the
       following single file after a typeflag x extended header, but
       possibly multiple files after typeflag g.  Any requirements in the
       list for pax to include a record when in write or copy mode shall
       apply only when such a record has not already been provided through
       the use of the −o option. When used in copy mode, pax shall behave as
       if an archive had been created with applicable extended header
       records and then extracted.)

       atime     The file access time for the following file(s), equivalent
                 to the value of the st_atime member of the stat structure
                 for a file, as described by the stat() function. The access
                 time shall be restored if the process has appropriate
                 privileges required to do so. The format of the <value>
                 shall be as described in pax Extended Header File Times.

       charset   The name of the character set used to encode the data in
                 the following file(s). The entries in the following table
                 are defined to refer to known standards; additional names
                 may be agreed on between the originator and recipient.

                  ┌────────────────────────┬───────────────────────────────┐
                  │        <value>         Formal Standard        │
                  ├────────────────────────┼───────────────────────────────┤
                  │ISO-IR 646 1990         │ ISO/IEC 646:1990              │
                  │ISO-IR 8859 1 1998      │ ISO/IEC 8859‐1:1998           │
                  │ISO-IR 8859 2 1999      │ ISO/IEC 8859‐2:1999           │
                  │ISO-IR 8859 3 1999      │ ISO/IEC 8859‐3:1999           │
                  │ISO-IR 8859 4 1998      │ ISO/IEC 8859‐4:1998           │
                  │ISO-IR 8859 5 1999      │ ISO/IEC 8859‐5:1999           │
                  │ISO-IR 8859 6 1999      │ ISO/IEC 8859‐6:1999           │
                  │ISO-IR 8859 7 1987      │ ISO/IEC 8859‐7:1987           │
                  │ISO-IR 8859 8 1999      │ ISO/IEC 8859‐8:1999           │
                  │ISO-IR 8859 9 1999      │ ISO/IEC 8859‐9:1999           │
                  │ISO-IR 8859 10 1998     │ ISO/IEC 8859‐10:1998          │
                  │ISO-IR 8859 13 1998     │ ISO/IEC 8859‐13:1998          │
                  │ISO-IR 8859 14 1998     │ ISO/IEC 8859‐14:1998          │
                  │ISO-IR 8859 15 1999     │ ISO/IEC 8859‐15:1999          │
                  │ISO-IR 10646 2000       │ ISO/IEC 10646:2000            │
                  │ISO-IR 10646 2000 UTF-8 │ ISO/IEC 10646, UTF-8 encoding │
                  │BINARY                  │ None.                         │
                  └────────────────────────┴───────────────────────────────┘
                 The encoding is included in an extended header for
                 information only; when pax is used as described in
                 POSIX.1‐2008, it shall not translate the file data into any
                 other encoding. The BINARY entry indicates unencoded binary
                 data.

                 When used in write or copy mode, it is implementation-
                 defined whether pax includes a charset extended header
                 record for a file.

       comment   A series of characters used as a comment. All characters in
                 the <value> field shall be ignored by pax.

       gid       The group ID of the group that owns the file, expressed as
                 a decimal number using digits from the ISO/IEC 646:1991
                 standard. This record shall override the gid field in the
                 following header block(s). When used in write or copy mode,
                 pax shall include a gid extended header record for each
                 file whose group ID is greater than 2097151 (octal
                 7777777).

       gname     The group of the file(s), formatted as a group name in the
                 group database. This record shall override the gid and
                 gname fields in the following header block(s), and any gid
                 extended header record. When used in read, copy, or list
                 mode, pax shall translate the name from the encoding in the
                 header record to the character set appropriate for the
                 group database on the receiving system. If any of the
                 characters cannot be translated, and if neither the
                 −oinvalid=UTF‐8 option nor the −oinvalid=binary option is
                 specified, the results are implementation-defined.  When
                 used in write or copy mode, pax shall include a gname
                 extended header record for each file whose group name
                 cannot be represented entirely with the letters and digits
                 of the portable character set.

       hdrcharset
                 The name of the character set used to encode the value
                 field of the gname, linkpath, path, and uname pax extended
                 header records. The entries in the following table are
                 defined to refer to known standards; additional names may
                 be agreed between the originator and the recipient.

                  ┌────────────────────────┬───────────────────────────────┐
                  │        <value>         Formal Standard        │
                  ├────────────────────────┼───────────────────────────────┤
                  │ISO-IR 10646 2000 UTF-8 │ ISO/IEC 10646, UTF-8 encoding │
                  │BINARY                  │ None.                         │
                  └────────────────────────┴───────────────────────────────┘
                 If no hdrcharset extended header record is specified, the
                 default character set used to encode all values in extended
                 header records shall be the ISO/IEC 10646‐1:2000 standard
                 UTF‐8 encoding.

                 The BINARY entry indicates that all values recorded in
                 extended headers for affected files are unencoded binary
                 data from the underlying system.

       linkpath  The pathname of a link being created to another file, of
                 any type, previously archived. This record shall override
                 the linkname field in the following ustar header block(s).
                 The following ustar header block shall determine the type
                 of link created. If typeflag of the following header block
                 is 1, it shall be a hard link. If typeflag is 2, it shall
                 be a symbolic link and the linkpath value shall be the
                 contents of the symbolic link. The pax utility shall
                 translate the name of the link (contents of the symbolic
                 link) from the encoding in the header to the character set
                 appropriate for the local file system. When used in write
                 or copy mode, pax shall include a linkpath extended header
                 record for each link whose pathname cannot be represented
                 entirely with the members of the portable character set
                 other than NUL.

       mtime     The file modification time of the following file(s),
                 equivalent to the value of the st_mtime member of the stat
                 structure for a file, as described in the stat() function.
                 This record shall override the mtime field in the following
                 header block(s). The modification time shall be restored if
                 the process has appropriate privileges required to do so.
                 The format of the <value> shall be as described in pax
                 Extended Header File Times.

       path      The pathname of the following file(s). This record shall
                 override the name and prefix fields in the following header
                 block(s). The pax utility shall translate the pathname of
                 the file from the encoding in the header to the character
                 set appropriate for the local file system.

                 When used in write or copy mode, pax shall include a path
                 extended header record for each file whose pathname cannot
                 be represented entirely with the members of the portable
                 character set other than NUL.

       realtime.any
                 The keywords prefixed by ``realtime.'' are reserved for
                 future standardization.

       security.any
                 The keywords prefixed by ``security.'' are reserved for
                 future standardization.

       size      The size of the file in octets, expressed as a decimal
                 number using digits from the ISO/IEC 646:1991 standard.
                 This record shall override the size field in the following
                 header block(s). When used in write or copy mode, pax shall
                 include a size extended header record for each file with a
                 size value greater than 8589934591 (octal 77777777777).

       uid       The user ID of the file owner, expressed as a decimal
                 number using digits from the ISO/IEC 646:1991 standard.
                 This record shall override the uid field in the following
                 header block(s). When used in write or copy mode, pax shall
                 include a uid extended header record for each file whose
                 owner ID is greater than 2097151 (octal 7777777).

       uname     The owner of the following file(s), formatted as a user
                 name in the user database. This record shall override the
                 uid and uname fields in the following header block(s), and
                 any uid extended header record. When used in read, copy, or
                 list mode, pax shall translate the name from the encoding
                 in the header record to the character set appropriate for
                 the user database on the receiving system. If any of the
                 characters cannot be translated, and if neither the
                 −oinvalid=UTF‐8 option nor the −oinvalid=binary option is
                 specified, the results are implementation-defined.  When
                 used in write or copy mode, pax shall include a uname
                 extended header record for each file whose user name cannot
                 be represented entirely with the letters and digits of the
                 portable character set.

       If the <value> field is zero length, it shall delete any header block
       field, previously entered extended header value, or global extended
       header value of the same name.

       If a keyword in an extended header record (or in a −o option-
       argument) overrides or deletes a corresponding field in the ustar
       header block, pax shall ignore the contents of that header block
       field.

       Unlike the ustar header block fields, NULs shall not delimit
       <value>s; all characters within the <value> field shall be considered
       data for the field. None of the length limitations of the ustar
       header block fields in Table 4-14, ustar Header Block shall apply to
       the extended header records.

   pax Extended Header Keyword Precedence
       This section describes the precedence in which the various header
       records and fields and command line options are selected to apply to
       a file in the archive. When pax is used in read or list modes, it
       shall determine a file attribute in the following sequence:

        1. If −odelete=keyword-prefix is used, the affected attributes shall
           be determined from step 7., if applicable, or ignored otherwise.

        2. If −okeyword:= is used, the affected attributes shall be ignored.

        3. If −okeyword:=value is used, the affected attribute shall be
           assigned the value.

        4. If there is a typeflag x extended header record, the affected
           attribute shall be assigned the <value>. When extended header
           records conflict, the last one given in the header shall take
           precedence.

        5. If −okeyword=value is used, the affected attribute shall be
           assigned the value.

        6. If there is a typeflag g global extended header record, the
           affected attribute shall be assigned the <value>. When global
           extended header records conflict, the last one given in the
           global header shall take precedence.

        7. Otherwise, the attribute shall be determined from the ustar
           header block.

   pax Extended Header File Times
       The pax utility shall write an mtime record for each file in write or
       copy modes if the file's modification time cannot be represented
       exactly in the ustar header logical record described in ustar
       Interchange Format.  This can occur if the time is out of ustar
       range, or if the file system of the underlying implementation
       supports non-integer time granularities and the time is not an
       integer. All of these time records shall be formatted as a decimal
       representation of the time in seconds since the Epoch. If a <period>
       ('.')  decimal point character is present, the digits to the right of
       the point shall represent the units of a subsecond timing
       granularity, where the first digit is tenths of a second and each
       subsequent digit is a tenth of the previous digit. In read or copy
       mode, the pax utility shall truncate the time of a file to the
       greatest value that is not greater than the input header file time.
       In write or copy mode, the pax utility shall output a time exactly if
       it can be represented exactly as a decimal number, and otherwise
       shall generate only enough digits so that the same time shall be
       recovered if the file is extracted on a system whose underlying
       implementation supports the same time granularity.

   ustar Interchange Format
       A ustar archive tape or file shall contain a series of logical
       records. Each logical record shall be a fixed-size logical record of
       512 octets (see below). Although this format may be thought of as
       being stored on 9-track industry-standard 12.7 mm (0.5 in) magnetic
       tape, other types of transportable media are not excluded. Each file
       archived shall be represented by a header logical record that
       describes the file, followed by zero or more logical records that
       give the contents of the file. At the end of the archive file there
       shall be two 512-octet logical records filled with binary zeros,
       interpreted as an end-of-archive indicator.

       The logical records may be grouped for physical I/O operations, as
       described under the −bblocksize and −x ustar options. Each group of
       logical records may be written with a single operation equivalent to
       the write() function. On magnetic tape, the result of this write
       shall be a single tape physical block. The last physical block shall
       always be the full size, so logical records after the two zero
       logical records may contain undefined data.

       The header logical record shall be structured as shown in the
       following table. All lengths and offsets are in decimal.

                          Table 4-14: ustar Header Block

                 ┌───────────┬──────────────┬────────────────────┐
                 │Field Name Octet Offset Length (in Octets) │
                 ├───────────┼──────────────┼────────────────────┤
                 │name       │       0      │        100         │
                 │mode       │     100      │          8         │
                 │uid        │     108      │          8         │
                 │gid        │     116      │          8         │
                 │size       │     124      │         12         │
                 │mtime      │     136      │         12         │
                 │chksum     │     148      │          8         │
                 │typeflag   │     156      │          1         │
                 │linkname   │     157      │        100         │
                 │magic      │     257      │          6         │
                 │version    │     263      │          2         │
                 │uname      │     265      │         32         │
                 │gname      │     297      │         32         │
                 │devmajor   │     329      │          8         │
                 │devminor   │     337      │          8         │
                 │prefix     │     345      │        155         │
                 └───────────┴──────────────┴────────────────────┘
       All characters in the header logical record shall be represented in
       the coded character set of the ISO/IEC 646:1991 standard. For maximum
       portability between implementations, names should be selected from
       characters represented by the portable filename character set as
       octets with the most significant bit zero. If an implementation
       supports the use of characters outside of <slash> and the portable
       filename character set in names for files, users, and groups, one or
       more implementation-defined encodings of these characters shall be
       provided for interchange purposes.

       However, the pax utility shall never create filenames on the local
       system that cannot be accessed via the procedures described in
       POSIX.1‐2008. If a filename is found on the medium that would create
       an invalid filename, it is implementation-defined whether the data
       from the file is stored on the file hierarchy and under what name it
       is stored. The pax utility may choose to ignore these files as long
       as it produces an error indicating that the file is being ignored.

       Each field within the header logical record is contiguous; that is,
       there is no padding used. Each character on the archive medium shall
       be stored contiguously.

       The fields magic, uname, and gname are character strings each
       terminated by a NUL character. The fields name, linkname, and prefix
       are NUL-terminated character strings except when all characters in
       the array contain non-NUL characters including the last character.
       The version field is two octets containing the characters "00" (zero-
       zero). The typeflag contains a single character. All other fields are
       leading zero-filled octal numbers using digits from the
       ISO/IEC 646:1991 standard IRV. Each numeric field is terminated by
       one or more <space> or NUL characters.

       The name and the prefix fields shall produce the pathname of the
       file. A new pathname shall be formed, if prefix is not an empty
       string (its first character is not NUL), by concatenating prefix (up
       to the first NUL character), a <slash> character, and name;
       otherwise, name is used alone. In either case, name is terminated at
       the first NUL character. If prefix begins with a NUL character, it
       shall be ignored. In this manner, pathnames of at most 256 characters
       can be supported. If a pathname does not fit in the space provided,
       pax shall notify the user of the error, and shall not store any part
       of the file—header or data—on the medium.

       The linkname field, described below, shall not use the prefix to
       produce a pathname. As such, a linkname is limited to 100 characters.
       If the name does not fit in the space provided, pax shall notify the
       user of the error, and shall not attempt to store the link on the
       medium.

       The mode field provides 12 bits encoded in the ISO/IEC 646:1991
       standard octal digit representation.  The encoded bits shall
       represent the following values:

                              Table: ustar mode Field

  ┌──────────┬──────────────────┬─────────────────────────────────────────────────┐
  │Bit Value POSIX.1‐2008 Bit Description                   │
  ├──────────┼──────────────────┼─────────────────────────────────────────────────┤
  │  04000   │ S_ISUID          │ Set UID on execution.                           │
  │  02000   │ S_ISGID          │ Set GID on execution.                           │
  │  01000   │ <reserved>       │ Reserved for future standardization.            │
  │  00400   │ S_IRUSR          │ Read permission for file owner class.           │
  │  00200   │ S_IWUSR          │ Write permission for file owner class.          │
  │  00100   │ S_IXUSR          │ Execute/search permission for file owner class. │
  │  00040   │ S_IRGRP          │ Read permission for file group class.           │
  │  00020   │ S_IWGRP          │ Write permission for file group class.          │
  │  00010   │ S_IXGRP          │ Execute/search permission for file group class. │
  │  00004   │ S_IROTH          │ Read permission for file other class.           │
  │  00002   │ S_IWOTH          │ Write permission for file other class.          │
  │  00001   │ S_IXOTH          │ Execute/search permission for file other class. │
  └──────────┴──────────────────┴─────────────────────────────────────────────────┘
       When appropriate privileges are required to set one of these mode
       bits, and the user restoring the files from the archive does not have
       appropriate privileges, the mode bits for which the user does not
       have appropriate privileges shall be ignored. Some of the mode bits
       in the archive format are not mentioned elsewhere in this volume of
       POSIX.1‐2008. If the implementation does not support those bits, they
       may be ignored.

       The uid and gid fields are the user and group ID of the owner and
       group of the file, respectively.

       The size field is the size of the file in octets. If the typeflag
       field is set to specify a file to be of type 1 (a link) or 2 (a
       symbolic link), the size field shall be specified as zero. If the
       typeflag field is set to specify a file of type 5 (directory), the
       size field shall be interpreted as described under the definition of
       that record type. No data logical records are stored for types 1, 2,
       or 5.  If the typeflag field is set to 3 (character special file), 4
       (block special file), or 6 (FIFO), the meaning of the size field is
       unspecified by this volume of POSIX.1‐2008, and no data logical
       records shall be stored on the medium. Additionally, for type 6, the
       size field shall be ignored when reading. If the typeflag field is
       set to any other value, the number of logical records written
       following the header shall be (size+511)/512, ignoring any fraction
       in the result of the division.

       The mtime field shall be the modification time of the file at the
       time it was archived. It is the ISO/IEC 646:1991 standard
       representation of the octal value of the modification time obtained
       from the stat() function.

       The chksum field shall be the ISO/IEC 646:1991 standard IRV
       representation of the octal value of the simple sum of all octets in
       the header logical record. Each octet in the header shall be treated
       as an unsigned value. These values shall be added to an unsigned
       integer, initialized to zero, the precision of which is not less than
       17 bits. When calculating the checksum, the chksum field is treated
       as if it were all <space> characters.

       The typeflag field specifies the type of file archived. If a
       particular implementation does not recognize the type, or the user
       does not have appropriate privileges to create that type, the file
       shall be extracted as if it were a regular file if the file type is
       defined to have a meaning for the size field that could cause data
       logical records to be written on the medium (see the previous
       description for size).  If conversion to a regular file occurs, the
       pax utility shall produce an error indicating that the conversion
       took place. All of the typeflag fields shall be coded in the
       ISO/IEC 646:1991 standard IRV:

       0       Represents a regular file. For backwards-compatibility, a
               typeflag value of binary zero ('\0') should be recognized as
               meaning a regular file when extracting files from the
               archive. Archives written with this version of the archive
               file format create regular files with a typeflag value of the
               ISO/IEC 646:1991 standard IRV '0'.

       1       Represents a file linked to another file, of any type,
               previously archived. Such files are identified by having the
               same device and file serial numbers, and pathnames that refer
               to different directory entries. All such files shall be
               archived as linked files.  The linked-to name is specified in
               the linkname field with a NUL-character terminator if it is
               less than 100 octets in length.

       2       Represents a symbolic link. The contents of the symbolic link
               shall be stored in the linkname field.

       3,4     Represent character special files and block special files
               respectively.  In this case the devmajor and devminor fields
               shall contain information defining the device, the format of
               which is unspecified by this volume of POSIX.1‐2008.
               Implementations may map the device specifications to their
               own local specification or may ignore the entry.

       5       Specifies a directory or subdirectory. On systems where disk
               allocation is performed on a directory basis, the size field
               shall contain the maximum number of octets (which may be
               rounded to the nearest disk block allocation unit) that the
               directory may hold.  A size field of zero indicates no such
               limiting. Systems that do not support limiting in this manner
               should ignore the size field.

       6       Specifies a FIFO special file. Note that the archiving of a
               FIFO file archives the existence of this file and not its
               contents.

       7       Reserved to represent a file to which an implementation has
               associated some high-performance attribute. Implementations
               without such extensions should treat this file as a regular
               file (type 0).

       A‐Z     The letters 'A' to 'Z', inclusive, are reserved for custom
               implementations. All other values are reserved for future
               versions of this standard.

       It is unspecified whether files with pathnames that refer to the same
       directory entry are archived as linked files or as separate files. If
       they are archived as linked files, this means that attempting to
       extract both pathnames from the resulting archive will always cause
       an error (unless the −u option is used) because the link cannot be
       created.

       It is unspecified whether files with the same device and file serial
       numbers being appended to an archive are treated as linked files to
       members that were in the archive before the append.

       Attempts to archive a socket using ustar interchange format shall
       produce a diagnostic message. Handling of other file types is
       implementation-defined.

       The magic field is the specification that this archive was output in
       this archive format. If this field contains ustar (the five
       characters from the ISO/IEC 646:1991 standard IRV shown followed by
       NUL), the uname and gname fields shall contain the ISO/IEC 646:1991
       standard IRV representation of the owner and group of the file,
       respectively (truncated to fit, if necessary). When the file is
       restored by a privileged, protection-preserving version of the
       utility, the user and group databases shall be scanned for these
       names. If found, the user and group IDs contained within these files
       shall be used rather than the values contained within the uid and gid
       fields.

   cpio Interchange Format
       The octet-oriented cpio archive format shall be a series of entries,
       each comprising a header that describes the file, the name of the
       file, and then the contents of the file.

       An archive may be recorded as a series of fixed-size blocks of
       octets.  This blocking shall be used only to make physical I/O more
       efficient.  The last group of blocks shall always be at the full
       size.

       For the octet-oriented cpio archive format, the individual entry
       information shall be in the order indicated and described by the
       following table; see also the <cpio.h> header.

                   Table 4-16: Octet-Oriented cpio Archive Entry

           ┌─────────────────────┬────────────────────┬─────────────────┐
           │ Header Field Name   Length (in Octets) Interpreted as  │
           ├─────────────────────┼────────────────────┼─────────────────┤
           │c_magic              │          6         │ Octal number    │
           │c_dev                │          6         │ Octal number    │
           │c_ino                │          6         │ Octal number    │
           │c_mode               │          6         │ Octal number    │
           │c_uid                │          6         │ Octal number    │
           │c_gid                │          6         │ Octal number    │
           │c_nlink              │          6         │ Octal number    │
           │c_rdev               │          6         │ Octal number    │
           │c_mtime              │         11         │ Octal number    │
           │c_namesize           │          6         │ Octal number    │
           │c_filesize           │         11         │ Octal number    │
           ├─────────────────────┼────────────────────┼─────────────────┤
           │Filename Field Name  Length       Interpreted as  │
           ├─────────────────────┴────────────────────┴─────────────────┤
           │c_name                 c_namesize           Pathname string │
           ├─────────────────────┬────────────────────┬─────────────────┤
           │File Data Field Name Length       Interpreted as  │
           ├─────────────────────┴────────────────────┴─────────────────┤
           │c_filedata             c_filesize           Data            │
           └────────────────────────────────────────────────────────────┘
   cpio Header
       For each file in the archive, a header as defined previously shall be
       written. The information in the header fields is written as streams
       of the ISO/IEC 646:1991 standard characters interpreted as octal
       numbers. The octal numbers shall be extended to the necessary length
       by appending the ISO/IEC 646:1991 standard IRV zeros at the most-
       significant-digit end of the number; the result is written to the
       most-significant digit of the stream of octets first.  The fields
       shall be interpreted as follows:

       c_magic   Identify the archive as being a transportable archive by
                 containing the identifying value "070707".

       c_dev, c_ino
                 Contains values that uniquely identify the file within the
                 archive (that is, no files contain the same pair of c_dev
                 and c_ino values unless they are links to the same file).
                 The values shall be determined in an unspecified manner.

       c_mode    Contains the file type and access permissions as defined in
                 the following table.

                          Table 4-17: Values for cpio c_mode Field

                 ┌──────────────────────┬─────────┬────────────────────────┐
                 │File Permissions Name Value  Indicates        │
                 ├──────────────────────┼─────────┼────────────────────────┤
                 │C_IRUSR               │  000400 │ Read by owner          │
                 │C_IWUSR               │  000200 │ Write by owner         │
                 │C_IXUSR               │  000100 │ Execute by owner       │
                 │C_IRGRP               │  000040 │ Read by group          │
                 │C_IWGRP               │  000020 │ Write by group         │
                 │C_IXGRP               │  000010 │ Execute by group       │
                 │C_IROTH               │  000004 │ Read by others         │
                 │C_IWOTH               │  000002 │ Write by others        │
                 │C_IXOTH               │  000001 │ Execute by others      │
                 │C_ISUID               │  004000 │ Set uid                │
                 │C_ISGID               │  002000 │ Set gid                │
                 │C_ISVTX               │  001000 │ Reserved               │
                 ├──────────────────────┼─────────┼────────────────────────┤
                 │   File Type Name     Value  Indicates        │
                 ├──────────────────────┼─────────┼────────────────────────┤
                 │C_ISDIR               │  040000 │ Directory              │
                 │C_ISFIFO              │  010000 │ FIFO                   │
                 │C_ISREG               │ 0100000 │ Regular file           │
                 │C_ISLNK               │ 0120000 │ Symbolic link          │
                 │                      │         │                        │
                 │C_ISBLK               │  060000 │ Block special file     │
                 │C_ISCHR               │  020000 │ Character special file │
                 │C_ISSOCK              │ 0140000 │ Socket                 │
                 │                      │         │                        │
                 │C_ISCTG               │ 0110000 │ Reserved               │
                 └──────────────────────┴─────────┴────────────────────────┘
                 Directories, FIFOs, symbolic links, and regular files shall
                 be supported on a system conforming to this volume of
                 POSIX.1‐2008; additional values defined previously are
                 reserved for compatibility with existing systems.
                 Additional file types may be supported; however, such files
                 should not be written to archives intended to be
                 transported to other systems.

       c_uid     Contains the user ID of the owner.

       c_gid     Contains the group ID of the group.

       c_nlink   Contains a number greater than or equal to the number of
                 links in the archive referencing the file. If the −a option
                 is used to append to a cpio archive, then the pax utility
                 need not account for the files in the existing part of the
                 archive when calculating the c_nlink values for the
                 appended part of the archive, and need not alter the
                 c_nlink values in the existing part of the archive if
                 additional files with the same c_dev and c_ino values are
                 appended to the archive.

       c_rdev    Contains implementation-defined information for character
                 or block special files.

       c_mtime   Contains the latest time of modification of the file at the
                 time the archive was created.

       c_namesize
                 Contains the length of the pathname, including the
                 terminating NUL character.

       c_filesize
                 Contains the length in octets of the data section following
                 the header structure.

   cpio Filename
       The c_name field shall contain the pathname of the file. The length
       of this field in octets is the value of c_namesize.

       If a filename is found on the medium that would create an invalid
       pathname, it is implementation-defined whether the data from the file
       is stored on the file hierarchy and under what name it is stored.

       All characters shall be represented in the ISO/IEC 646:1991 standard
       IRV. For maximum portability between implementations, names should be
       selected from characters represented by the portable filename
       character set as octets with the most significant bit zero. If an
       implementation supports the use of characters outside the portable
       filename character set in names for files, users, and groups, one or
       more implementation-defined encodings of these characters shall be
       provided for interchange purposes. However, the pax utility shall
       never create filenames on the local system that cannot be accessed
       via the procedures described previously in this volume of
       POSIX.1‐2008. If a filename is found on the medium that would create
       an invalid filename, it is implementation-defined whether the data
       from the file is stored on the local file system and under what name
       it is stored. The pax utility may choose to ignore these files as
       long as it produces an error indicating that the file is being
       ignored.

   cpio File Data
       Following c_name, there shall be c_filesize octets of data.
       Interpretation of such data occurs in a manner dependent on the file.
       For regular files, the data shall consist of the contents of the
       file. For symbolic links, the data shall consist of the contents of
       the symbolic link. If c_filesize is zero, no data shall be contained
       in c_filedata.

       When restoring from an archive:

        *  If the user does not have appropriate privileges to create a file
           of the specified type, pax shall ignore the entry and write an
           error message to standard error.

        *  Only regular files and symbolic links have data to be restored.
           Presuming a regular file meets any selection criteria that might
           be imposed on the format-reading utility by the user, such data
           shall be restored.

        *  If a user does not have appropriate privileges to set a
           particular mode flag, the flag shall be ignored. Some of the mode
           flags in the archive format are not mentioned elsewhere in this
           volume of POSIX.1‐2008. If the implementation does not support
           those flags, they may be ignored.

   cpio Special Entries
       FIFO special files, directories, and the trailer shall be recorded
       with c_filesize equal to zero. Symbolic links shall be recorded with
       c_filesize equal to the length of the contents of the symbolic link.
       For other special files, c_filesize is unspecified by this volume of
       POSIX.1‐2008. The header for the next file entry in the archive shall
       be written directly after the last octet of the file entry preceding
       it. A header denoting the filename TRAILER!!!  shall indicate the end
       of the archive; the contents of octets in the last block of the
       archive following such a header are undefined.

EXIT STATUS         top

       The following exit values shall be returned:

        0    All files were processed successfully.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       If pax cannot create a file or a link when reading an archive or
       cannot find a file when writing an archive, or cannot preserve the
       user ID, group ID, or file mode when the −p option is specified, a
       diagnostic message shall be written to standard error and a non-zero
       exit status shall be returned, but processing shall continue. In the
       case where pax cannot create a link to a file, pax shall not, by
       default, create a second copy of the file.

       If the extraction of a file from an archive is prematurely terminated
       by a signal or error, pax may have only partially extracted the file
       or (if the −n option was not specified) may have extracted a file of
       the same name as that specified by the user, but which is not the
       file the user wanted.  Additionally, the file modes of extracted
       directories may have additional bits from the S_IRWXU mask set as
       well as incorrect modification and access times.

       The following sections are informative.

APPLICATION USAGE         top

       Caution is advised when using the −a option to append to a cpio
       format archive. If any of the files being appended happen to be given
       the same c_dev and c_ino values as a file in the existing part of the
       archive, then they may be treated as links to that file on
       extraction. Thus, it is risky to use −a with cpio format except when
       it is done on the same system that the original archive was created
       on, and with the same pax utility, and in the knowledge that there
       has been little or no file system activity since the original archive
       was created that could lead to any of the files appended being given
       the same c_dev and c_ino values as an unrelated file in the existing
       part of the archive. Also, when (intentionally) appending additional
       links to a file in the existing part of the archive, the c_nlink
       values in the modified archive can be smaller than the number of
       links to the file in the archive, which may mean that the links are
       not preserved on extraction.

       The −p (privileges) option was invented to reconcile differences
       between historical tar and cpio implementations. In particular, the
       two utilities use −m in diametrically opposed ways. The −p option
       also provides a consistent means of extending the ways in which
       future file attributes can be addressed, such as for enhanced
       security systems or high-performance files. Although it may seem
       complex, there are really two modes that are most commonly used:

       −p e    ``Preserve everything''. This would be used by the historical
               superuser, someone with all appropriate privileges, to
               preserve all aspects of the files as they are recorded in the
               archive. The e flag is the sum of o and p, and other
               implementation-defined attributes.

       −p p    ``Preserve'' the file mode bits. This would be used by the
               user with regular privileges who wished to preserve aspects
               of the file other than the ownership. The file times are
               preserved by default, but two other flags are offered to
               disable these and use the time of extraction.

       The one pathname per line format of standard input precludes
       pathnames containing <newline> characters. Although such pathnames
       violate the portable filename guidelines, they may exist and their
       presence may inhibit usage of pax within shell scripts. This problem
       is inherited from historical archive programs. The problem can be
       avoided by listing filename arguments on the command line instead of
       on standard input.

       It is almost certain that appropriate privileges are required for pax
       to accomplish parts of this volume of POSIX.1‐2008. Specifically,
       creating files of type block special or character special, restoring
       file access times unless the files are owned by the user (the −t
       option), or preserving file owner, group, and mode (the −p option)
       all probably require appropriate privileges.

       In read mode, implementations are permitted to overwrite files when
       the archive has multiple members with the same name. This may fail if
       permissions on the first version of the file do not permit it to be
       overwritten.

       The cpio and ustar formats can only support files up to 8589934592
       bytes (8 ∗ 2^30) in size.

       When archives containing binary header information are listed , the
       filenames printed may cause strange behavior on some terminals.

       When all of the following are true:

        1. A file of type directory is being placed into an archive.

        2. The ustar archive format is being used.

        3. The pathname of the directory is less than or equal to 155 bytes
           long (it will fit in the prefix field in the ustar header block).

        4. The last component of the pathname of the directory is longer
           than 100 bytes long (it will not fit in the name field in the
           ustar header block).

       some implementations of the pax utility will place the entire
       directory pathname in the prefix field, set the name field to an
       empty string, and place the directory in the archive.  Other
       implementations of the pax utility will give an error under these
       conditions because the name field is not large enough to hold the
       last component of the directory name.  This standard allows either
       behavior. However, when extracting a directory from a ustar format
       archive, this standard requires that all implementations be able to
       extract a directory even if the name field contains an empty string
       as long as the prefix field does not also contain an empty string.

EXAMPLES         top

       The following command:

           pax −w −f /dev/rmt/1m .

       copies the contents of the current directory to tape drive 1, medium
       density (assuming historical System V device naming procedures—the
       historical BSD device name would be /dev/rmt9).

       The following commands:

           mkdir newdir
           pax −rw olddir newdir

       copy the olddir directory hierarchy to newdir.

           pax −r −s ',^//*usr//*,,' −f a.pax

       reads the archive a.pax, with all files rooted in /usr in the archive
       extracted relative to the current directory.

       Using the option:

           −o listopt="%M %(atime)T %(size)D %(name)s"

       overrides the default output description in Standard Output and
       instead writes:

           −rw−rw−−− Jan 12 15:53 2003 1492 /usr/foo/bar

       Using the options:

           −o listopt='%L\t%(size)D\n%.7' \
           −o listopt='(name)s\n%(atime)T\n%T'

       overrides the default output description in Standard Output and
       instead writes:

           /usr/foo/bar −> /tmp   1492
           /usr/fo
           Jan 12 15:53 1991
           Jan 31 15:53 2003

RATIONALE         top

       The pax utility was new for the ISO POSIX‐2:1993 standard. It
       represents a peaceful compromise between advocates of the historical
       tar and cpio utilities.

       A fundamental difference between cpio and tar was in the way
       directories were treated. The cpio utility did not treat directories
       differently from other files, and to select a directory and its
       contents required that each file in the hierarchy be explicitly
       specified. For tar, a directory matched every file in the file
       hierarchy it rooted.

       The pax utility offers both interfaces; by default, directories map
       into the file hierarchy they root. The −d option causes pax to skip
       any file not explicitly referenced, as cpio historically did. The tar
       style behavior was chosen as the default because it was believed
       that this was the more common usage and because tar is the more
       commonly available interface, as it was historically provided on both
       System V and BSD implementations.

       The data interchange format specification in this volume of
       POSIX.1‐2008 requires that processes with ``appropriate privileges''
       shall always restore the ownership and permissions of extracted files
       exactly as archived. If viewed from the historic equivalence between
       superuser and ``appropriate privileges'', there are two problems with
       this requirement. First, users running as superusers may unknowingly
       set dangerous permissions on extracted files. Second, it is
       needlessly limiting, in that superusers cannot extract files and own
       them as superuser unless the archive was created by the superuser.
       (It should be noted that restoration of ownerships and permissions
       for the superuser, by default, is historical practice in cpio, but
       not in In order to avoid these two problems, the pax specification
       has an additional ``privilege'' mechanism, the −p option. Only a pax
       invocation with the privileges needed, and which has the −p option
       set using the e specification character, has appropriate privileges
       to restore full ownership and permission information.

       Note also that this volume of POSIX.1‐2008 requires that the file
       ownership and access permissions shall be set, on extraction, in the
       same fashion as the creat() function when provided with the mode
       stored in the archive. This means that the file creation mask of the
       user is applied to the file permissions.

       Users should note that directories may be created by pax while
       extracting files with permissions that are different from those that
       existed at the time the archive was created. When extracting
       sensitive information into a directory hierarchy that no longer
       exists, users are encouraged to set their file creation mask
       appropriately to protect these files during extraction.

       The table of contents output is written to standard output to
       facilitate pipeline processing.

       An early proposal had hard links displaying for all pathnames. This
       was removed because it complicates the output of the case where −v is
       not specified and does not match historical cpio usage. The hard-link
       information is available in the −v display.

       The description of the −l option allows implementations to make hard
       links to symbolic links.  Earlier versions of this standard did not
       specify any way to create a hard link to a symbolic link, but many
       implementations provided this capability as an extension. If there
       are hard links to symbolic links when an archive is created, the
       implementation is required to archive the hard link in the archive
       (unless −H or −L is specified). When in read mode and in copy mode,
       implementations supporting hard links to symbolic links should use
       them when appropriate.

       The archive formats inherited from the POSIX.1‐1990 standard have
       certain restrictions that have been brought along from historical
       usage. For example, there are restrictions on the length of pathnames
       stored in the archive.  When pax is used in copy(−rw) mode (copying
       directory hierarchies), the ability to use extensions from the −xpax
       format overcomes these restrictions.

       The default blocksize value of 5120 bytes for cpio was selected
       because it is one of the standard block-size values for cpio, set
       when the −B option is specified. (The other default block-size value
       for cpio is 512 bytes, and this was considered to be too small.) The
       default block value of 10240 bytes for tar was selected because that
       is the standard block-size value for BSD tar.  The maximum block size
       of 32256 bytes (215−512 bytes) is the largest multiple of 512 bytes
       that fits into a signed 16-bit tape controller transfer register.
       There are known limitations in some historical systems that would
       prevent larger blocks from being accepted. Historical values were
       chosen to improve compatibility with historical scripts using dd or
       similar utilities to manipulate archives. Also, default block sizes
       for any file type other than character special file has been deleted
       from this volume of POSIX.1‐2008 as unimportant and not likely to
       affect the structure of the resulting archive.

       Implementations are permitted to modify the block-size value based on
       the archive format or the device to which the archive is being
       written. This is to provide implementations with the opportunity to
       take advantage of special types of devices, and it should not be used
       without a great deal of consideration as it almost certainly
       decreases archive portability.

       The intended use of the −n option was to permit extraction of one or
       more files from the archive without processing the entire archive.
       This was viewed by the standard developers as offering significant
       performance advantages over historical implementations. The −n option
       in early proposals had three effects; the first was to cause special
       characters in patterns to not be treated specially. The second was to
       cause only the first file that matched a pattern to be extracted. The
       third was to cause pax to write a diagnostic message to standard
       error when no file was found matching a specified pattern. Only the
       second behavior is retained by this volume of POSIX.1‐2008, for many
       reasons. First, it is in general not acceptable for a single option
       to have multiple effects. Second, the ability to make pattern
       matching characters act as normal characters is useful for parts of
       pax other than file extraction. Third, a finer degree of control over
       the special characters is useful because users may wish to normalize
       only a single special character in a single filename. Fourth, given a
       more general escape mechanism, the previous behavior of the −n option
       can be easily obtained using the −s option or a sed script. Finally,
       writing a diagnostic message when a pattern specified by the user is
       unmatched by any file is useful behavior in all cases.

       In this version, the −n was removed from the copy mode synopsis of
       pax; it is inapplicable because there are no pattern operands
       specified in this mode.

       There is another method than pax for copying subtrees in POSIX.1‐2008
       described as part of the cp utility. Both methods are historical
       practice: cp provides a simpler, more intuitive interface, while pax
       offers a finer granularity of control. Each provides additional
       functionality to the other; in particular, pax maintains the hard-
       link structure of the hierarchy while cp does not. It is the
       intention of the standard developers that the results be similar
       (using appropriate option combinations in both utilities). The
       results are not required to be identical; there seemed insufficient
       gain to applications to balance the difficulty of implementations
       having to guarantee that the results would be exactly identical.

       A single archive may span more than one file. It is suggested that
       implementations provide informative messages to the user on standard
       error whenever the archive file is changed.

       The −d option (do not create intermediate directories not listed in
       the archive) found in early proposals was originally provided as a
       complement to the historic −d option of cpio.  It has been deleted.

       The −s option in early proposals specified a subset of the
       substitution command from the ed utility. As there was no reason for
       only a subset to be supported, the −s option is now compatible with
       the current ed specification. Since the delimiter can be any non-null
       character, the following usage with single <space> characters is
       valid:

           pax −s " foo bar " ...

       The −t description is worded so as to note that this may cause the
       access time update caused by some other activity (which occurs while
       the file is being read) to be overwritten.

       The default behavior of pax with regard to file modification times is
       the same as historical implementations of tar.  It is not the
       historical behavior of cpio.

       Because the −i option uses /dev/tty, utilities without a controlling
       terminal are not able to use this option.

       The −y option, found in early proposals, has been deleted because a
       line containing a single <period> for the −i option has equivalent
       functionality. The special lines for the −i option (a single <period>
       and the empty line) are historical practice in cpio.

       In early drafts, a −echarmap option was included to increase
       portability of files between systems using different coded character
       sets. This option was omitted because it was apparent that consensus
       could not be formed for it. In this version, the use of UTF‐8 should
       be an adequate substitute.

       The ISO POSIX‐2:1993 standard and ISO POSIX‐1 standard requirements
       for pax, however, made it very difficult to create a single archive
       containing files created using extended characters provided by
       different locales.  This version adds the hdrcharset keyword to make
       it possible to archive files in these cases without dropping files
       due to translation errors.

       Translating filenames and other attributes from a locale's encoding
       to UTF‐8 and then back again can lose information, as the resulting
       filename might not be byte-for-byte equivalent to the original. To
       avoid this problem, users can specify the −o hdrcharset=binary
       option, which will cause the resulting archive to use binary format
       for all names and attributes. Such archives are not portable among
       hosts that use different native encodings (e.g., EBCDIC versus ASCII-
       based encodings), but they will allow interchange among the vast
       majority of POSIX file systems in practical use. Also, the −o
       hdrcharset=binary option will cause pax in copy mode to behave more
       like other standard utilities such as cp.

       If the values specified by the −o exthdr.name=value, −o
       globexthdr.name=value, or by $TMPDIR (if −o globexthdr.name is not
       specified) require a character encoding other than that described in
       the ISO/IEC 646:1991 standard, a path extended header record will
       have to be created for the file. If a hdrcharset extended header
       record is active for such headers, it will determine the codeset used
       for the value field in these extended path header records. These path
       extended header records always need to be created when writing an
       archive even if hdrcharset=binary has been specified and would
       contain the same (binary) data that appears in the ustar header
       record prefix and name fields. (In other words, an extended header
       path record is always required to be generated if the prefix or name
       fields contain non-ASCII characters even when hdrcharset=binary is
       also in effect for that file.)

       The −k option was added to address international concerns about the
       dangers involved in the character set transformations of −e (if the
       target character set were different from the source, the filenames
       might be transformed into names matching existing files) and also was
       made more general to protect files transferred between file systems
       with different {NAME_MAX} values (truncating a filename on a smaller
       system might also inadvertently overwrite existing files). As stated,
       it prevents any overwriting, even if the target file is older than
       the source. This version adds more granularity of options to solve
       this problem by introducing the −oinvalid=option—specifically the
       UTF‐8 and binary actions. (Note that an existing file is still
       subject to overwriting in this case. The −k option closes that
       loophole.)

       Some of the file characteristics referenced in this volume of
       POSIX.1‐2008 might not be supported by some archive formats. For
       example, neither the tar nor cpio formats contain the file access
       time. For this reason, the e specification character has been
       provided, intended to cause all file characteristics specified in the
       archive to be retained.

       It is required that extracted directories, by default, have their
       access and modification times and permissions set to the values
       specified in the archive. This has obvious problems in that the
       directories are almost certainly modified after being extracted and
       that directory permissions may not permit file creation. One possible
       solution is to create directories with the mode specified in the
       archive, as modified by the umask of the user, with sufficient
       permissions to allow file creation. After all files have been
       extracted, pax would then reset the access and modification times and
       permissions as necessary.

       The list-mode formatting description borrows heavily from the one
       defined by the printf utility. However, since there is no separate
       operand list to get conversion arguments, the format was extended to
       allow specifying the name of the conversion argument as part of the
       conversion specification.

       The T conversion specifier allows time fields to be displayed in any
       of the date formats. Unlike the ls utility, pax does not adjust the
       format when the date is less than six months in the past. This makes
       parsing the output more predictable.

       The D conversion specifier handles the ability to display the
       major/minor or file size, as with ls, by using %−8(size)D.

       The L conversion specifier handles the ls display for symbolic links.

       Conversion specifiers were added to generate existing known types
       used for ls.

   pax Interchange Format
       The new POSIX data interchange format was developed primarily to
       satisfy international concerns that the ustar and cpio formats did
       not provide for file, user, and group names encoded in characters
       outside a subset of the ISO/IEC 646:1991 standard. The standard
       developers realized that this new POSIX data interchange format
       should be very extensible because there were other requirements they
       foresaw in the near future:

        *  Support international character encodings and locale information

        *  Support security information (ACLs, and so on)

        *  Support future file types, such as realtime or contiguous files

        *  Include data areas for implementation use

        *  Support systems with words larger than 32 bits and timers with
           subsecond granularity

       The following were not goals for this format because these are better
       handled by separate utilities or are inappropriate for a portable
       format:

        *  Encryption

        *  Compression

        *  Data translation between locales and codesets

        *  inode storage

       The format chosen to support the goals is an extension of the ustar
       format. Of the two formats previously available, only the ustar
       format was selected for extensions because:

        *  It was easier to extend in an upwards-compatible way. It offered
           version flags and header block type fields with room for future
           standardization. The cpio format, while possessing a more
           flexible file naming methodology, could not be extended without
           breaking some theoretical implementation or using a dummy
           filename that could be a legitimate filename.

        *  Industry experience since the original ``tar wars'' fought in
           developing the ISO POSIX‐1 standard has clearly been in favor of
           the ustar format, which is generally the default output format
           selected for pax implementations on new systems.

       The new format was designed with one additional goal in mind:
       reasonable behavior when an older tar or pax utility happened to read
       an archive. Since the POSIX.1‐1990 standard mandated that a ``format-
       reading utility'' had to treat unrecognized typeflag values as
       regular files, this allowed the format to include all the extended
       information in a pseudo-regular file that preceded each real file. An
       option is given that allows the archive creator to set up reasonable
       names for these files on the older systems. Also, the normative text
       suggests that reasonable file access values be used for this ustar
       header block. Making these header files inaccessible for convenient
       reading and deleting would not be reasonable. File permissions of 600
       or 700 are suggested.

       The ustar typeflag field was used to accommodate the additional
       functionality of the new format rather than magic or version because
       the POSIX.1‐1990 standard (and, by reference, the previous version of
       pax), mandated the behavior of the format-reading utility when it
       encountered an unknown typeflag, but was silent about the other two
       fields.

       Early proposals for the first version of this standard contained a
       proposed archive format that was based on compatibility with the
       standard for tape files (ISO 1001, similar to the format used
       historically on many mainframes and minicomputers). This format was
       overly complex and required considerable overhead in volume and
       header records. Furthermore, the standard developers felt that it
       would not be acceptable to the community of POSIX developers, so it
       was later changed to be a format more closely related to historical
       practice on POSIX systems.

       The prefix and name split of pathnames in ustar was replaced by the
       single path extended header record for simplicity.

       The concept of a global extended header (typeflagg) was
       controversial. If this were applied to an archive being recorded on
       magnetic tape, a few unreadable blocks at the beginning of the tape
       could be a serious problem; a utility attempting to extract as many
       files as possible from a damaged archive could lose a large
       percentage of file header information in this case. However, if the
       archive were on a reliable medium, such as a CD‐ROM, the global
       extended header offers considerable potential size reductions by
       eliminating redundant information. Thus, the text warns against using
       the global method for unreliable media and provides a method for
       implanting global information in the extended header for each file,
       rather than in the typeflag g records.

       No facility for data translation or filtering on a per-file basis is
       included because the standard developers could not invent an
       interface that would allow this in an efficient manner. If a filter,
       such as encryption or compression, is to be applied to all the files,
       it is more efficient to apply the filter to the entire archive as a
       single file. The standard developers considered interfaces that would
       invoke a shell script for each file going into or out of the archive,
       but the system overhead in this approach was considered to be too
       high.

       One such approach would be to have filter= records that give a
       pathname for an executable. When the program is invoked, the file and
       archive would be open for standard input/output and all the header
       fields would be available as environment variables or command-line
       arguments. The standard developers did discuss such schemes, but they
       were omitted from POSIX.1‐2008 due to concerns about excessive
       overhead. Also, the program itself would need to be in the archive if
       it were to be used portably.

       There is currently no portable means of identifying the character
       set(s) used for a file in the file system. Therefore, pax has not
       been given a mechanism to generate charset records automatically. The
       only portable means of doing this is for the user to write the
       archive using the −ocharset=string command line option. This assumes
       that all of the files in the archive use the same encoding. The
       ``implementation-defined'' text is included to allow for a system
       that can identify the encodings used for each of its files.

       The table of standards that accompanies the charset record
       description is acknowledged to be very limited. Only a limited number
       of character set standards is reasonable for maximal interchange. Any
       character set is, of course, possible by prior agreement. It was
       suggested that EBCDIC be listed, but it was omitted because it is not
       defined by a formal standard. Formal standards, and then only those
       with reasonably large followings, can be included here, simply as a
       matter of practicality. The <value>s represent names of officially
       registered character sets in the format required by the ISO 2375:1985
       standard.

       The normal <comma> or <blank>-separated list rules are not followed
       in the case of keyword options to allow ease of argument parsing for
       getopts.

       Further information on character encodings is in pax Archive
       Character Set Encoding/Decoding.

       The standard developers have reserved keyword name space for vendor
       extensions. It is suggested that the format to be used is:

           VENDOR.keyword

       where VENDOR is the name of the vendor or organization in all
       uppercase letters. It is further suggested that the keyword following
       the <period> be named differently than any of the standard keywords
       so that it could be used for future standardization, if appropriate,
       by omitting the VENDOR prefix.

       The <length> field in the extended header record was included to make
       it simpler to step through the records, even if a record contains an
       unknown format (to a particular pax) with complex interactions of
       special characters. It also provides a minor integrity checkpoint
       within the records to aid a program attempting to recover files from
       a damaged archive.

       There are no extended header versions of the devmajor and devminor
       fields because the unspecified format ustar header field should be
       sufficient. If they are not, vendor-specific extended keywords (such
       as VENDOR.devmajor) should be used.

       Device and i-number labeling of files was not adopted from cpio;
       files are interchanged strictly on a symbolic name basis, as in
       ustar.

       Just as with the ustar format descriptions, the new format makes no
       special arrangements for multi-volume archives. Each of the pax
       archive types is assumed to be inside a single POSIX file and
       splitting that file over multiple volumes (diskettes, tape
       cartridges, and so on), processing their labels, and mounting each in
       the proper sequence are considered to be implementation details that
       cannot be described portably.

       The pax format is intended for interchange, not only for backup on a
       single (family of) systems. It is not as densely packed as might be
       possible for backup:

        *  It contains information as coded characters that could be coded
           in binary.

        *  It identifies extended records with name fields that could be
           omitted in favor of a fixed-field layout.

        *  It translates names into a portable character set and identifies
           locale-related information, both of which are probably
           unnecessary for backup.

       The requirements on restoring from an archive are slightly different
       from the historical wording, allowing for non-monolithic privilege to
       bring forward as much as possible. In particular, attributes such as
       ``high performance file'' might be broadly but not universally
       granted while set-user-ID or chown() might be much more restricted.
       There is no implication in POSIX.1‐2008 that the security information
       be honored after it is restored to the file hierarchy, in spite of
       what might be improperly inferred by the silence on that topic. That
       is a topic for another standard.

       Links are recorded in the fashion described here because a link can
       be to any file type. It is desirable in general to be able to restore
       part of an archive selectively and restore all of those files
       completely. If the data is not associated with each link, it is not
       possible to do this. However, the data associated with a file can be
       large, and when selective restoration is not needed, this can be a
       significant burden.  The archive is structured so that files that
       have no associated data can always be restored by the name of any
       link name of any link, and the user may choose whether data is
       recorded with each instance of a file that contains data. The format
       permits mixing of both types of links in a single archive; this can
       be done for special needs, and pax is expected to interpret such
       archives on input properly, despite the fact that there is no pax
       option that would force this mixed case on output. (When −o linkdata
       is used, the output must contain the duplicate data, but the
       implementation is free to include it or omit it when −o linkdata is
       not used.)

       The time values are included as extended header records for those
       implementations needing more than the eleven octal digits allowed by
       the ustar format. Portable file timestamps cannot be negative. If pax
       encounters a file with a negative timestamp in copy or write mode, it
       can reject the file, substitute a non-negative timestamp, or generate
       a non-portable timestamp with a leading '−'.  Even though some
       implementations can support finer file-time granularities than
       seconds, the normative text requires support only for seconds since
       the Epoch because the ISO POSIX‐1 standard states them that way. The
       ustar format includes only mtime; the new format adds atime and ctime
       for symmetry. The atime access time restored to the file system will
       be affected by the −p a and −p e options. The ctime creation time
       (actually inode modification time) is described with appropriate
       privileges so that it can be ignored when writing to the file system.
       POSIX does not provide a portable means to change file creation time.
       Nothing is intended to prevent a non-portable implementation of pax
       from restoring the value.

       The gid, size, and uid extended header records were included to allow
       expansion beyond the sizes specified in the regular tar header. New
       file system architectures are emerging that will exhaust the 12-digit
       size field. There are probably not many systems requiring more than 8
       digits for user and group IDs, but the extended header values were
       included for completeness, allowing overrides for all of the decimal
       values in the tar header.

       The standard developers intended to describe the effective results of
       pax with regard to file ownerships and permissions; implementations
       are not restricted in timing or sequencing the restoration of such,
       provided the results are as specified.

       Much of the text describing the extended headers refers to use in
       ``write or copy modes''. The copy mode references are due to the
       normative text: ``The effect of the copy shall be as if the copied
       files were written to an archive file and then subsequently extracted
       ...''. There is certainly no way to test whether pax is actually
       generating the extended headers in copy mode, but the effects must be
       as if it had.

   pax Archive Character Set Encoding/Decoding
       There is a need to exchange archives of files between systems of
       different native codesets. Filenames, group names, and user names
       must be preserved to the fullest extent possible when an archive is
       read on the receiving platform. Translation of the contents of files
       is not within the scope of the pax utility.

       There will also be the need to represent characters that are not
       available on the receiving platform. These unsupported characters
       cannot be automatically folded to the local set of characters due to
       the chance of collisions. This could result in overwriting previous
       extracted files from the archive or pre-existing files on the system.

       For these reasons, the codeset used to represent characters within
       the extended header records of the pax archive must be sufficiently
       rich to handle all commonly used character sets. The fields requiring
       translation include, at a minimum, filenames, user names, group
       names, and link pathnames. Implementations may wish to have localized
       extended keywords that use non-portable characters.

       The standard developers considered the following options:

        *  The archive creator specifies the well-defined name of the source
           codeset. The receiver must then recognize the codeset name and
           perform the appropriate translations to the destination codeset.

        *  The archive creator includes within the archive the character
           mapping table for the source codeset used to encode extended
           header records.  The receiver must then read the character
           mapping table and perform the appropriate translations to the
           destination codeset.

        *  The archive creator translates the extended header records in the
           source codeset into a canonical form. The receiver must then
           perform the appropriate translations to the destination codeset.

       The approach that incorporates the name of the source codeset poses
       the problem of codeset name registration, and makes the archive
       useless to pax archive decoders that do not recognize that codeset.

       Because parts of an archive may be corrupted, the standard developers
       felt that including the character map of the source codeset was too
       fragile. The loss of this one key component could result in making
       the entire archive useless. (The difference between this and the
       global extended header decision was that the latter has a workaround—
       duplicating extended header records on unreliable media—but this
       would be too burdensome for large character set maps.)

       Both of the above approaches also put an undue burden on the pax
       archive receiver to handle the cross-product of all source and
       destination codesets.

       To simplify the translation from the source codeset to the canonical
       form and from the canonical form to the destination codeset, the
       standard developers decided that the internal representation should
       be a stateless encoding. A stateless encoding is one where each
       codepoint has the same meaning, without regard to the decoder being
       in a specific state. An example of a stateful encoding would be the
       Japanese Shift-JIS; an example of a stateless encoding would be the
       ISO/IEC 646:1991 standard (equivalent to 7-bit ASCII).

       For these reasons, the standard developers decided to adopt a
       canonical format for the representation of file information strings.
       The obvious, well-endorsed candidate is the ISO/IEC 10646‐1:2000
       standard (based in part on Unicode), which can be used to represent
       the characters of virtually all standardized character sets. The
       standard developers initially agreed upon using UCS2 (16-bit Unicode)
       as the internal representation. This repertoire of characters
       provides a sufficiently rich set to represent all commonly-used
       codesets.

       However, the standard developers found that the 16-bit Unicode
       representation had some problems. It forced the issue of
       standardizing byte ordering. The 2-byte length of each character made
       the extended header records twice as long for the case of strings
       coded entirely from historical 7-bit ASCII. For these reasons, the
       standard developers chose the UTF‐8 defined in the
       ISO/IEC 10646‐1:2000 standard. This multi-byte representation encodes
       UCS2 or UCS4 characters reliably and deterministically, eliminating
       the need for a canonical byte ordering. In addition, NUL octets and
       other characters possibly confusing to POSIX file systems do not
       appear, except to represent themselves. It was realized that certain
       national codesets take up more space after the encoding, due to their
       placement within the UCS range; it was felt that the usefulness of
       the encoding of the names outweighs the disadvantage of size increase
       for file, user, and group names.

       The encoding of UTF‐8 is as follows:

           UCS4 Hex Encoding  UTF-8 Binary Encoding

           00000000-0000007F  0xxxxxxx
           00000080-000007FF  110xxxxx 10xxxxxx
           00000800-0000FFFF  1110xxxx 10xxxxxx 10xxxxxx
           00010000-001FFFFF  11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
           00200000-03FFFFFF  111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
           04000000-7FFFFFFF  1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx

       where each 'x' represents a bit value from the character being
       translated.

   ustar Interchange Format
       The description of the ustar format reflects numerous enhancements
       over pre-1988 versions of the historical tar utility. The goal of
       these changes was not only to provide the functional enhancements
       desired, but also to retain compatibility between new and old
       versions. This compatibility has been retained.  Archives written
       using the old archive format are compatible with the new format.

       Implementors should be aware that the previous file format did not
       include a mechanism to archive directory type files. For this reason,
       the convention of using a filename ending with <slash> was adopted to
       specify a directory on the archive.

       The total size of the name and prefix fields have been set to meet
       the minimum requirements for {PATH_MAX}.  If a pathname will fit
       within the name field, it is recommended that the pathname be stored
       there without the use of the prefix field. Although the name field is
       known to be too small to contain {PATH_MAX} characters, the value was
       not changed in this version of the archive file format to retain
       backwards-compatibility, and instead the prefix was introduced. Also,
       because of the earlier version of the format, there is no way to
       remove the restriction on the linkname field being limited in size to
       just that of the name field.

       The size field is required to be meaningful in all implementation
       extensions, although it could be zero. This is required so that the
       data blocks can always be properly counted.

       It is suggested that if device special files need to be represented
       that cannot be represented in the standard format, that one of the
       extension types (AZ) be used, and that the additional information
       for the special file be represented as data and be reflected in the
       size field.

       Attempting to restore a special file type, where it is converted to
       ordinary data and conflicts with an existing filename, need not be
       specially detected by the utility. If run as an ordinary user, pax
       should not be able to overwrite the entries in, for example, /dev in
       any case (whether the file is converted to another type or not). If
       run as a privileged user, it should be able to do so, and it would be
       considered a bug if it did not. The same is true of ordinary data
       files and similarly named special files; it is impossible to
       anticipate the needs of the user (who could really intend to
       overwrite the file), so the behavior should be predictable (and thus
       regular) and rely on the protection system as required.

       The value 7 in the typeflag field is intended to define how
       contiguous files can be stored in a ustar archive. POSIX.1‐2008 does
       not require the contiguous file extension, but does define a standard
       way of archiving such files so that all conforming systems can
       interpret these file types in a meaningful and consistent manner. On
       a system that does not support extended file types, the pax utility
       should do the best it can with the file and go on to the next.

       The file protection modes are those conventionally used by the ls
       utility. This is extended beyond the usage in the ISO POSIX‐2
       standard to support the ``shared text'' or ``sticky'' bit. It is
       intended that the conformance document should not document anything
       beyond the existence of and support of such a mode. Further
       extensions are expected to these bits, particularly with overloading
       the set-user-ID and set-group-ID flags.

   cpio Interchange Format
       The reference to appropriate privileges in the cpio format refers to
       an error on standard output; the ustar format does not make
       comparable statements.

       The model for this format was the historical System V cpio−c data
       interchange format. This model documents the portable version of the
       cpio format and not the binary version. It has the flexibility to
       transfer data of any type described within POSIX.1‐2008, yet is
       extensible to transfer data types specific to extensions beyond
       POSIX.1‐2008 (for example, contiguous files). Because it describes
       existing practice, there is no question of maintaining upwards-
       compatibility.

   cpio Header
       There has been some concern that the size of the c_ino field of the
       header is too small to handle those systems that have very large
       inode numbers. However, the c_ino field in the header is used
       strictly as a hard-link resolution mechanism for archives. It is not
       necessarily the same value as the inode number of the file in the
       location from which that file is extracted.

       The name c_magic is based on historical usage.

   cpio Filename
       For most historical implementations of the cpio utility, {PATH_MAX}
       octets can be used to describe the pathname without the addition of
       any other header fields (the NUL character would be included in this
       count).  {PATH_MAX} is the minimum value for pathname size,
       documented as 256 bytes.  However, an implementation may use
       c_namesize to determine the exact length of the pathname. With the
       current description of the <cpio.h> header, this pathname size can be
       as large as a number that is described in six octal digits.

       Two values are documented under the c_mode field values to provide
       for extensibility for known file types:

       0110 000  Reserved for contiguous files. The implementation may treat
                 the rest of the information for this archive like a regular
                 file. If this file type is undefined, the implementation
                 may create the file as a regular file.

       This provides for extensibility of the cpio format while allowing for
       the ability to read old archives. Files of an unknown type may be
       read as ``regular files'' on some implementations.  On a system that
       does not support extended file types, the pax utility should do the
       best it can with the file and go on to the next.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Chapter 2, Shell Command Language, cp(1p), ed(1p), getopts(1p),
       ls(1p), printf(1p)

       The Base Definitions volume of POSIX.1‐2008, Section 3.169, File Mode
       Bits, Chapter 5, File Format Notation, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines, cpio.h(0p)

       The System Interfaces volume of POSIX.1‐2008, chown(3p), creat(3p),
       fstatat(3p), mkdir(3p), mkfifo(3p), utime(3p), write(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                             PAX(1P)