spax(1)

NAME

pax - portable archive interchange

SYNOPSIS

spax        [other options] [-cdnv] [-H|-L]  [-f  archive]
[-o options]...  [-s replstr]...  [pattern...]
spax     -r     [other  options]  [-cdiknuv]  [-H|-L]  [-f
archive]  [-o  options]...   [-p  string]...    [-s   replstr]...
[pattern...]
spax     -w     [other   options]  [-dituvX]  [-H|-L]  [-b
blocksize] [-a] [-f archive]  [-o  options]...   [-s  replstr]...
[-x format] [file...]
spax    -r  -w[other  options]  [-diklntuvX]  [-H|-L]  [-o
options]...  [-p string]...  [-s replstr]...  [file...] directory

DESCRIPTION

The pax utility shall read, write, and write lists of the
members of archive files and copy directory hierarchies. A vari
ety of archive formats shall be supported; see the -x format op
tion.
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 speci
fied), 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 direc
tory.: If an attempt is made to extract a directory when; the directory already exists, this shall not be considered an er; ror. If an attempt is made to extract a FIFO when the FIFO al; ready 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 op; tion.
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. 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 an archive file and then subsequently ex; tracted, except that there may be hard links between the original; and the copied files. If the destination directory is a subdirec; tory of one of the files to be copied, the results are unspeci; fied. If the destination directory is a file of a type not de; fined by the System Interfaces volume of IEEE Std 1003.1-2001,; 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 Inter
faces volume of IEEE Std 1003.1-2001, called with the following
arguments:
� The intermediate directory used as the path argu
ment.
� The value of the bitwise-inclusive OR of S_IRWXU,

S_IRWXG

If any specified pattern or file operands are not matched
by at least one file or archive member, pax shall write a diag
nostic 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.
The spax implementation defaults to -x ustar.
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, except that if the files to
be linked are symbolic links and the system is not capable of
making hard links to symbolic links, then separate copies of the
symbolic link shall be created instead. 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 ter
minate.

OPTIONS

The pax utility shall conform to the Base Definitions vol
ume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guide
lines, 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 im
plementation-defined which devices on the system support append
ing. Additional file formats unspecified by this volume of IEEE
Std 1003.1-2001 may impose restrictions on appending.
-b blocksize: Block the output at a positive decimal integer num; ber 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 block; ing 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 di
rectory 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. Other
wise, 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, us
ing the name of the link. The default behavior 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 peri
od, the file or archive member shall be processed with no modifi
cation 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 sym
bolic link is encountered, the hard link created in the destina
tion file hierarchy shall be to the file referenced by the sym
bolic 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 hier
archy or copy the symbolic link to the destination.
-L If a symbolic link referencing a file of type di
rectory is specified on the command line or encountered during
the traversal of a file hierarchy, pax shall archive the file hi
erarchy 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 encoun
tered 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 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 op; tions 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 in; applicable 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 IEEE Std 1003.1-2001, Section 3.276,; 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 val; ue 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 ear; lier 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 pat

tern. When used in read or list mode, pax shall ignore any key

words matching the string pattern in the extended header records.

In both cases, matching shall be performed using the pattern

matching notation described in Patterns Matching a Single Charac

ter and 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 -o delete=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 substi

tutions have been made:

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 fol; lowing character substitutions have been made:; Any other '%' characters in string produce; undefined results.; If no -o globexthdr.name=string is speci; fied, pax shall use the following default value:; $TMPDIR/GlobalHead.%p.%n; where $TMPDIR represents the value of the

TMPDIR

/tmp.
invalid=action: (Applicable only to the -x pax format.) This; keyword allows user control over the action pax takes upon en; countering 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 desti

nation 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 destina

tion 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:

bypass In read or copy mode, pax shall by

pass 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 re

placement 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 implemen

tation, pax shall use the actual UTF-8 encoding for the name.

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 -o invalid= bypass were specified. Any overwrit; ing of existing files that may be allowed by the -o invalid= ac; tions 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 con; tents 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 ambigui; ty, 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 -o listopt= 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 ex
tended 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

in -o option-arguments, in either of two modes: keyword=value: When used in write or copy mode, these key; word/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 glob; al extended header records.
keyword:=value: When used in write or copy mode, these key; word/value pairs shall be included as records at the beginning of; a typeflag x extended header for each file. (This shall be equiv; alent to the equal-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 key; words 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 spec; ifying file characteristics to be retained or discarded on ex; traction. The string shall consist of the specification charac; ters 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 IEEE Std 1003.1-2001,; Section 3.168, 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 implemen; tation-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 ac; cess 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 deter; mined as part of the normal file creation action (see 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 er; ror. 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 pat; tern or file operands according to the substitution expression; replstr, using the syntax of the ed utility. The concepts of "ad; dress" and "line" are meaningless in the context of the pax util; ity, 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, '0 (where n is a digit) back; references, or subexpression matching. The old string shall also; be permitted to contain <newline>s.; 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 be
fore being read by pax.
-u Ignore files that are older (having a less recent
file modification time) than a pre-existing file or archive mem
ber 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 accom
plished 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 path
names 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 EXTEND; ED 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

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 de
fault 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 for
mat different from the existing archive format shall cause pax to
exit immediately with a non-zero exit status.
In copy mode, if no -x format is specified, pax
shall behave as if -x pax were specified.
-X When traversing the file hierarchy specified by a
pathname, pax shall not descend into directories that have a dif
ferent device ID ( st_dev; see the System Interfaces volume of
IEEE Std 1003.1-2001, 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)shallinteractasfollows.Inread
mode, the archive members shall be selected based on the user
specified pattern operands as modified by the -c, -n, and -u op
tions. 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: The manual page for spax is not yet ready. The following; text is a quotation from the POSIX.1-2001 standard.; 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 de; scribed in the Base Definitions volume of IEEE Std 1003.1-2001,; Chapter 5, File Format Notation, with the exceptions 1. through; 5. defined in the EXTENDED DESCRIPTION section of printf(3),; plus the following exceptions:; 6. 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 ustar Head

er Block and Octet-Oriented cpio Archive Entry. The implementa

tion may support the cpio keywords without the leading c_ in ad

dition to the form required by Values for cpio c_mode Field.

� 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 to the character set
appropriate for the local file system, user database, and so on,
as applicable.
7. 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
8. An additional conversion specifier character, M,
shall be used to specify the file mode string as defined in ls(1)
Standard Output. If (keyword) is omitted, the mode keyword shall
be used. For example, %.1M writes the single character corre
sponding to the <entry type> field of the ls -l command.
9. 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 appli
cable, 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>.
10. 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 de
fault shall be (path) if the keyword path is defined; otherwise,
the default shall be (prefix, name).
11. An additional conversion specifier character, L,
shall be used to specify a symbolic line expansion. If the cur
rent 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

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 Pattern Matching Notation ,; including the filename expansion rules in Patterns Used for File; name Expansion. The default, if no pattern is specified, is to; select all members in the archive.

STDIN

In write mode, the standard input shall be used only if no
file operands are specified. It shall be a text file containing a
list of pathnames, one per line, without leading or trailing
<blank>s.
In list and read modes, if -f is not specified, the stan
dard input shall be an archive file.
Otherwise, the standard input shall not be used.

INPUT FILES

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 EX
TENDED DESCRIPTION section or some other implementation-defined
format.
The file /dev/tty shall be used to write prompts and read
responses.

ENVIRONMENT VARIABLES

The following environment variables shall affect the exe
cution of pax:
LANG Provide a default value for the internationaliza
tion variables that are unset or null. (See the Base Definitions
volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for 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 reg; ular expression defined for the yesexpr locale keyword in the; LC_MESSAGES category.
LC_CTYPE: Determine the locale for the interpretation of se; quences 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 for the processing of affirma; tive responses that should be used to affect the format and con; tents of diagnostic messages written to standard error.
LC_TIME: Determine the format and contents of date and time; strings when the -v option is specified.
NLSPATH: [XSI] [Option Start] Determine the location of mes; sage catalogs for the processing of LC_MESSAGES . [Option End]
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

Default.

STDOUT

In write mode, if -f is not specified, the standard output
shall be the archive formatted according to one of the specifica
tions in the EXTENDED DESCRIPTION section, or some other imple
mentation-defined format (see -x format).
In list mode, when the -o listopt= format has been speci
fied, the selected archive members shall be written to standard
output using the format described under List Mode Format Specifi
cations. In list mode without the -o listopt= format option, the
table of contents of the selected archive members shall be writ
ten to standard output using the following format:: "%s0, <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 == %s0, <ls -l listing>, <linkname>
For all other pathnames:: "%s0, <ls -l listing>
where <ls -l listing> shall be the format specified by the
ls(1) 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 informa
tion, although the correct number of <blank>-separated fields
shall be written.
In list mode, standard output shall not be buffered more
than a line at a time.

STDERR

If -v is specified in read, write, or copy modes, pax
shall write the pathnames it processes to the standard error out
put using the following format:: "%s0, <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 >> %s0, <original pathname>, <new pathname>
In all operating modes of pax, optional messages of un
specified 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 er
ror.
In all formats, for both standard output and standard er
ror, it is unspecified how non-printable characters in pathnames
or link names are written.
When pax is in read mode or list mode, using the -x pax
archive format, 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 lo
cale of the implementation, pax shall write a diagnostic message
to standard error, shall process the file as described for the -o
invalid= option, and then shall process the next file in the
archive.

OUTPUT FILES

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
(-o invalid=) tests allow it.
In write mode, the output file named by the -f option-ar
gument shall be a file formatted according to one of the specifi
cations in the EXTENDED DESCRIPTION section, or some other imple
mentation-defined format.

EXTENDED DESCRIPTION

pax Interchange Format: A pax archive tape or file produced in the -x pax 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 head

er records. This header block is of the form described in pax

Header Block

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 con
tents 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 pax Format

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 UTF-8 encoding 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 charac; ter 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 dec
imal 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 deci
mal 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 UTF-8 encoding in the
header record to the character set appropriate for the user
database on the receiving system. If any of the UTF-8 characters
cannot be translated, and if the -o invalid=UTF-8 option is not
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 en
tirely 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 op
tion-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 de
limit <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 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 -o delete=keyword-prefix is used, the af; fected attributes shall be determined from step 7., if applica
ble, or ignored otherwise.
2. If -o keyword:= is used, the affected at
tributes shall be ignored.
3. If -o keyword:=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 -o keyword=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 implemen
tation 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 deci
mal 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 logi
cal 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 indi
cator.
The logical records may be grouped for physical I/O opera
tions, as described under the -b blocksize and -x ustar options.
Each group of logical records may be written with a single opera
tion equivalent to the write(2) 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.
All characters in the header logical record shall be rep
resented in the coded character set of the ISO/IEC 646:1991 stan
dard. 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 en
codings 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 de
scribed in IEEE Std 1003.1-2001. If a filename is found on the
medium that would create an invalid filename, it is implementa
tion-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 in
dicating 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 char
acter. All other fields are leading zero-filled octal numbers us
ing 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 ter
minated 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:
When appropriate privilege is required to set one of these
mode bits, and the user restoring the files from the archive does
not have the appropriate privilege, the mode bits for which the
user does not have appropriate privilege shall be ignored. Some
of the mode bits in the archive format are not mentioned else
where in this volume of IEEE Std 1003.1-2001. If the implementa
tion 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 ze
ro. If the typeflag field is set to specify a file of type 5 (di
rectory), 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
IEEE Std 1003.1-2001, 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 ob
tained from the stat(2) 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 spaces.
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 privilege 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-compati
bility, a typeflag value of binary zero (' ') should be recog
nized 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 typefla 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 IEEE Std 1003.1-2001. Im
plementations may map the device specifications to their own lo
cal 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 di
rectory may hold. A size field of zero indicates no such limit
ing. 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 implemen
tation has associated some high-performance attribute. Implemen
tations without such extensions should treat this file as a regu
lar 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 IEEE Std 1003.1-2001.
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 ap
pend.
Attempts to archive a socket using ustar interchange for
mat 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 fol
lowed 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 con
tained 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 physi
cal 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.
cpio HeaderFor each file in the archive, a header as defined previ
ously 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 stan
dard 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.: Directories, FIFOs, symbolic links, and regular
files shall be supported on a system conforming to this volume of
IEEE Std 1003.1-2001; 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_nlinkContains a number greater than or equal to the num
ber of links in the archive referencing the file. If the -a op
tion 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 ex
isting 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 of the file in octets. This
shall be the length 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 implemen
tations, names should be selected from characters represented by
the portable filename character set as octets with the most sig
nificant bit zero. If an implementation supports the use of char
acters outside the portable filename character set in names for
files, users, and groups, one or more implementation-defined en
codings 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 IEEE Std 1003.1-2001. 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 ig
nored.
cpio File DataFollowing c_name, there shall be c_filesize octets of da
ta. Interpretation of such data occurs in a manner dependent on
the file. If c_filesize is zero, no data shall be contained in
c_filedata.
When restoring from an archive:
� If the user does not have the appropriate privilege
to create a file of the specified type, pax shall ignore the en
try and write an error message to standard error.
� Only regular files have data to be restored. Pre
suming 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 privilege 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 IEEE Std 1003.1-2001. 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. For other special files,
c_filesize is unspecified by this volume of IEEE Std 1003.1-2001.
The header for the next file entry in the archive shall be writ
ten 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

The following exit values shall be returned:: 0 All files were processed successfully.
>0 An error occurred.

CONSEQUENCES OF ERRORS

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 process
ing 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 ex
tracted 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

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 exist
ing 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 origi
nal archive was created on, and with the same pax utility, and in
the knowledge that there has been little or no file system activ
ity 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 dif
ferences between historical tar and cpio implementations. In par
ticular, 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 the appropriate privi
leges, 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 im
plementation-defined attributes.
-p p ``Preserve" the file mode bits. This would be used
by the user with regular privileges who wished to preserve as
pects 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 pre
cludes pathnames containing <newline>s. 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 com
mand line instead of on standard input.
It is almost certain that appropriate privileges are re
quired for pax to accomplish parts of this volume of IEEE Std
1003.1-2001. 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 ap
propriate 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.

EXAMPLES

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 newdirpax -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 Out
put and instead writes:: -rw-rw--- Jan 12 15:53 1492 /usr/foo/bar
Using the options:: -o listopt='%L%(size)D11.7' .br -o listopt='(name)s11(atime)T11T'
overrides the default output description in Standard Out
put and instead writes:
/usr/foo/bar -> /tmp 1492 /usr/fo
Jan 12 1991
Jan 31 15:53

RATIONALE

The pax utility was new for the ISO POSIX-2:1993 standard.
It represents a peaceful compromise between advocates of the his
torical tar and cpio utilities.
A fundamental difference between cpio and tar was in the
way directories were treated. The cpio utility did not treat di
rectories differently from other files, and to select a directory
and its contents required that each file in the hierarchy be ex
plicitly specified. For tar, a directory matched every file in
the file hierarchy it rooted.
The pax utility offers both interfaces; by default, direc
tories map into the file hierarchy they root. The -d option caus
es pax to skip any file not explicitly referenced, as cpio his
torically did. The tar - style behavior was chosen as the de
fault 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 implementa
tions.
The data interchange format specification in this volume
of IEEE Std 1003.1-2001 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 can
not extract files and own them as superuser unless the archive
was created by the superuser. (It should be noted that restora
tion of ownerships and permissions for the superuser, by default,
is historical practice in cpio, but not in tar.) 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 the "appropriate privilege" to re
store full ownership and permission information.
Note also that this volume of IEEE Std 1003.1-2001 re
quires that the file ownership and access permissions shall be
set, on extraction, in the same fashion as the creat(2) 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 ex
tracting 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 path
names. 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. IEEE Std 1003.1-2001 does not
specify any way to create a hard link to a symbolic link, but
many implementations provide this capability as an extension. If
there are hard links to symbolic links when an archive is creat
ed, 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 stan
dard 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 -x pax format overcomes these restric
tions.
The default blocksize value of 5120 bytes for cpio was se
lected 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 (2^15-512 bytes)
is the largest multiple of 512 bytes that fits into a signed
16-bit tape controller transfer register. There are known limita
tions in some historical systems that would prevent larger blocks
from being accepted. Historical values were chosen to improve
compatibility with historical scripts using dd(1) 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 IEEE Std 1003.1-2001 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 en
tire archive. This was viewed by the standard developers as of
fering significant performance advantages over historical imple
mentations. 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 IEEE Std 1003.1-2001, for many rea
sons. 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 con
trol over the special characters is useful because users may wish
to normalize only a single special character in a single file
name. Fourth, given a more general escape mechanism, the previous
behavior of the -n option can be easily obtained using the -s op
tion or a sed script. Finally, writing a diagnostic message when
a pattern specified by the user is unmatched by any file is use
ful 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
IEEE Std 1003.1-2001 described as part of the cp(1) utility. Both
methods are historical practice: cp(1) provides a simpler, more
intuitive interface, while pax offers a finer granularity of con
trol. Each provides additional functionality to the other; in
particular, pax maintains the hard-link structure of the hierar
chy while cp(1) does not. It is the intention of the standard de
velopers 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 sug
gested 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 compati
ble with the current ed specification. Since the delimiter can be
any non-null character, the following usage with single spaces 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 modifica
tion 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 -e charmap option was included to in
crease 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 -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 inadver
tently 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 prob
lem by introducing the -o invalid=option -specifically the UTF-8
action. (Note that an existing file that is named with a UTF-8
encoding is still subject to overwriting in this case. The -k op
tion closes that loophole.)
Some of the file characteristics referenced in this volume
of IEEE Std 1003.1-2001 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 char
acter has been provided, intended to cause all file characteris
tics 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 cre
ation. 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(1) 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 argu
ment as part of the conversion specification.
The T conversion specifier allows time fields to be dis
played in any of the date formats. Unlike the ls(1) 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(1), by using %-8(size)D.
The L conversion specifier handles the ls display for sym
bolic links.
Conversion specifiers were added to generate existing
known types used for ls(1).
pax Interchange FormatThe new POSIX data interchange format was developed pri
marily 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 inter
change format should be very extensible because there were other
requirements they foresaw in the near future:
� Support international character encodings and lo
cale information
� Support security information (ACLs, and so on)
� Support future file types, such as realtime or con
tiguous 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 possess
ing a more flexible file naming methodology, could not be extend
ed 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 hap
pened to read an archive. Since the POSIX.1-1990 standard mandat
ed that a "format-reading utility" had to treat unrecognized
typeflag values as regular files, this allowed the format to in
clude 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 delet
ing would not be reasonable. File permissions of 600 or 700 are
suggested.
The ustar typeflag field was used to accommodate the addi
tional 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 of the first revision to IEEE Std
1003.1-2001 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 minicom
puters). 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 re
placed by the single path extended header record for simplicity.
The concept of a global extended header (typeflag g) 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. Howev
er, if the archive were on a reliable medium, such as a CD-ROM,
the global extended header offers considerable potential size re
ductions 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 ex
tended 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 consid
ered 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 IEEE Std 1003.1-2001 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 -o charset=string command
line option. This assumes that all of the files in the archive
use the same encoding. The "implementation-defined" text is in
cluded 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 in
terchange. 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 stan
dard keywords so that it could be used for future standardiza
tion, if appropriate, by omitting the VENDOR prefix.
The <length> field in the extended header record was in
cluded to make it simpler to step through the records, even if a
record contains an unknown format (to a particular pax) with com
plex interactions of special characters. It also provides a minor
integrity checkpoint within the records to aid a program attempt
ing 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-monolith
ic 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(2) might be
much more restricted. There is no implication in IEEE Std
1003.1-2001 that the security information be honored after it is
restored to the file hierarchy, in spite of what might be improp
erly 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 struc
tured 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 dig
its 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 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 privi
lege" 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 implementa
tion of pax from restoring the value.
The gid, size, and uid extended header records were in
cluded to allow expansion beyond the sizes specified in the regu
lar 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, allow
ing 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 subsequent
ly 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/DecodingThere is a need to exchange archives of files between sys
tems 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-ex
isting files on the system.
For these reasons, the codeset used to represent charac
ters 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, file
names, user names, group names, and link pathnames. Implementa
tions 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 code
set name and perform the appropriate translations to the destina
tion codeset.
� The archive creator includes within the archive the
character mapping table for the source codeset used to encode ex
tended 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 be
tween 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 char
acter 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 repre
sentation 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 state
less 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 informa
tion 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 us
ing UCS2 (16-bit Unicode) as the internal representation. This
repertoire of characters provides a sufficiently rich set to rep
resent 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 en
codes 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 re
alized 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 FormatThe description of the ustar format reflects numerous en
hancements 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 path
name be stored there without the use of the prefix field. Al
though 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 imple
mentation 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 (A-Z) be used, and that the addi
tional 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 file
name, 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 spe
cial 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 protec
tion system as required.
The value 7 in the typeflag field is intended to define
how contiguous files can be stored in a ustar archive. IEEE Std
1003.1-2001 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(1) 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 privilege 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 IEEE
Std 1003.1-2001, yet is extensible to transfer data types specif
ic to extensions beyond IEEE Std 1003.1-2001 (for example, con
tiguous 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 num
ber of the file in the location from which that file is extract
ed.
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 implementa
tion 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 un
known type may be read as "regular files" on some implementa
tions. 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

None.
End of informative sections.

CHANGE HISTORY

First released in Issue 4.
Issue 5
A note is added to the APPLICATION USAGE indicating that
the cpio and tar formats can only support files up to 8 gigabytes
in size.
Issue 6
The pax utility is aligned with the IEEE P1003.2b draft
standard:
� Support has been added for symbolic links in the
options and interchange formats.
� A new format has been devised, based on extensions
to ustar.
� References to the "extended" tar and cpio formats
derived from the POSIX.1-1990 standard have been changed to re
move the "extended" adjective because this could cause confusion
with the extended tar header added in this revision. (All refer
ences to tar are actually to ustar.)
The TZ entry is added to the ENVIRONMENT VARIABLES sec
tion.
IEEE PASC Interpretation 1003.2 #168 is applied, clarify
ing that mkdir(2) and mkfifo(2) calls can ignore an [EEXIST] er
ror when extracting an archive.
IEEE PASC Interpretation 1003.2 #180 is applied, clarify
ing how extracted files are created when in read mode.
IEEE PASC Interpretation 1003.2 #181 is applied, clarify
ing the description of the -t option.
IEEE PASC Interpretation 1003.2 #195 is applied.
IEEE PASC Interpretation 1003.2 #206 is applied, clarify
ing the handling of links for the -H, -L, and -l options.
IEEE Std 1003.1-2001/Cor 1-2002, item XCU/TC1/D6/35 is ap
plied, adding the process ID of the pax process into certain
fields. This change provides a method for the implementation to
ensure that different instances of pax extracting a file named
/a/b/foo will not collide when processing the extended header in
formation associated with foo.
IEEE Std 1003.1-2001/Cor 1-2002, item XCU/TC1/D6/36 is ap
plied, changing -x B to -x pax in the OPTIONS section.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/20 is ap
plied, updating the SYNOPSIS to be consistent with the normative
text.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/21 is ap
plied, updating the DESCRIPTION to describe the behavior when
files to be linked are symbolic links and the system is not capa
ble of making hard links to symbolic links.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/22 is ap
plied, updating the OPTIONS section to describe the behavior for
how multiple options are to be handled.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/23 is ap
plied, updating the write option within the OPTIONS section.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/24 is ap
plied, adding a paragraph into the OPTIONS section that states
that specifying more than one of the mutually-exclusive options
(-H and -L) is not considered an error and that the last option
specified will determine the behavior of the utility.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/25 is ap
plied, removing the ctime paragraph within the EXTENDED DESCRIP
TION. There is a contradiction in the definition of the ctime
keyword for the pax extended header, in that the st_ctime member
of the stat structure does not refer to a file creation time. No
field in the standard stat structure from <sys/stat.h> includes a
file creation time.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/26 is ap
plied, making it clear that typeflag 1 RB ( ustar Interchange
Format) applies not only to files that are hard-linked, but also
to files that are aliased via symlinks.
IEEE Std 1003.1-2001/Cor 2-2004, item XCU/TC2/D6/27 is ap
plied, clarifying the cpio c_nlink field.
End of quoted text from the POSIX.1-2001 standard.

OPTIONS

The following other options are implemented as extension
to the POSIX standard:
-help Prints a summary of the most important options for
spax(1) and exits.
-xhelp Prints a summary of the less important options for
spax(1) and exits.
-version
Prints the spax version number string and exists.

EXAMPLES ENVIRONMENT FILES SEE ALSO DIAGNOSTICS NOTES

The Institute of Electrical and Electronics Engineers and
The Open Group, have given us permission to reprint portions of
their documentation. In the following statement, the phrase
``this text'' refers to portions of the system documentation.
Portions of this text are reprinted and reproduced in
electronic form in the sfind manual, from IEEE Std 1003.1, 2004
Edition, Standard for Information Technology -- Portable Operat
ing System Interface (POSIX), The Open Group Base Specifications
and Electronics Engineers, Inc and The Open Group. In the event
of any discrepancy between these versions 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.opengroup.org/unix/online.html.

BUGS AUTHOR

Joerg Schilling
Seestr. 110
D-13353 Berlin
Germany

Mail bugs and suggestions to:

schilling@fokus.fraunhofer.de or js@cs.tu-berlin.de or
joerg@schily.isdn.cs.tu-berlin.de
Joerg Schilling 05/01/17

docs.sk

comprehensive documentation repository

See also

spax(1)

NAME

SYNOPSIS

DESCRIPTION

S_IRWXG

OPTIONS

TMPDIR

Times

Extended Header

Precedence

DESCRIPTION

Extended Header

OPERANDS

STDIN

INPUT FILES

ENVIRONMENT VARIABLES

ASYNCHRONOUS EVENTS

STDOUT

STDERR

OUTPUT FILES

EXTENDED DESCRIPTION

Header Block

Archive

Times

EXIT STATUS

CONSEQUENCES OF ERRORS

APPLICATION USAGE

EXAMPLES

RATIONALE

FUTURE DIRECTIONS

SEE ALSO

CHANGE HISTORY

OPTIONS

EXAMPLES ENVIRONMENT FILES SEE ALSO DIAGNOSTICS NOTES

BUGS AUTHOR