AR(1P) POSIX Programmer's Manual AR(1P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEar — create and maintain library archives
SYNOPSISar −d [−v] archive file...
ar −m [−v] archive file...
ar −m −a [−v] posname archive file...
ar −m −b [−v] posname archive file...
ar −m −i [−v] posname archive file...
ar −p [−v] [−s] archive [file...]
ar −q [−cv] archive file...
ar −r [−cuv] archive file...
ar −r −a [−cuv] posname archive file...
ar −r −b [−cuv] posname archive file...
ar −r −i [−cuv] posname archive file...
ar −t [−v] [−s] archive [file...]
ar −x [−v] [−sCT] archive [file...]
DESCRIPTION
The ar utility is part of the Software Development Utilities option.
The ar utility can be used to create and maintain groups of files com‐
bined into an archive. Once an archive has been created, new files can
be added, and existing files in an archive can be extracted, deleted,
or replaced. When an archive consists entirely of valid object files,
the implementation shall format the archive so that it is usable as a
library for link editing (see c99 and fort77). When some of the
archived files are not valid object files, the suitability of the ar‐
chive for library use is undefined. If an archive consists entirely of
printable files, the entire archive shall be printable.
When ar creates an archive, it creates administrative information indi‐
cating whether a symbol table is present in the archive. When there is
at least one object file that ar recognizes as such in the archive, an
archive symbol table shall be created in the archive and maintained by
ar; it is used by the link editor to search the archive. Whenever the
ar utility is used to create or update the contents of such an archive,
the symbol table shall be rebuilt. The −s option shall force the symbol
table to be rebuilt.
All file operands can be pathnames. However, files within archives
shall be named by a filename, which is the last component of the path‐
name used when the file was entered into the archive. The comparison of
file operands to the names of files in archives shall be performed by
comparing the last component of the operand to the name of the file in
the archive.
It is unspecified whether multiple files in the archive may be identi‐
cally named. In the case of such files, however, each file and posname
operand shall match only the first file in the archive having a name
that is the same as the last component of the operand.
OPTIONS
The ar utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except for
Guideline 9.
The following options shall be supported:
−a Position new files in the archive after the file named by the
posname operand.
−b Position new files in the archive before the file named by
the posname operand.
−c Suppress the diagnostic message that is written to standard
error by default when the archive archive is created.
−C Prevent extracted files from replacing like-named files in
the file system. This option is useful when −T is also used,
to prevent truncated filenames from replacing files with the
same prefix.
−d Delete one or more files from archive.
−i Position new files in the archive before the file in the ar‐
chive named by the posname operand (equivalent to −b).
−m Move the named files in the archive. The −a, −b, or −i
options with the posname operand indicate the position; oth‐
erwise, move the names files in the archive to the end of the
archive.
−p Write the contents of the files in the archive named by file
operands from archive to the standard output. If no file op‐
erands are specified, the contents of all files in the ar‐
chive shall be written in the order of the archive.
−q Append the named files to the end of the archive. In this
case ar does not check whether the added files are already in
the archive. This is useful to bypass the searching other‐
wise done when creating a large archive piece by piece.
−r Replace or add files to archive. If the archive named by ar‐
chive does not exist, a new archive shall be created and a
diagnostic message shall be written to standard error (unless
the −c option is specified). If no files are specified and
the archive exists, the results are undefined. Files that
replace existing files in the archive shall not change the
order of the archive. Files that do not replace existing
files in the archive shall be appended to the archive unless
a −a, −b, or −i option specifies another position.
−s Force the regeneration of the archive symbol table even if ar
is not invoked with an option that modifies the archive con‐
tents. This option is useful to restore the archive symbol
table after it has been stripped; see strip.
−t Write a table of contents of archive to the standard output.
Only the files specified by the file operands shall be
included in the written list. If no file operands are speci‐
fied, all files in archive shall be included in the order of
the archive.
−T Allow filename truncation of extracted files whose archive
names are longer than the file system can support. By
default, extracting a file with a name that is too long shall
be an error; a diagnostic message shall be written and the
file shall not be extracted.
−u Update older files in the archive. When used with the −r
option, files in the archive shall be replaced only if the
corresponding file has a modification time that is at least
as new as the modification time of the file in the archive.
−v Give verbose output. When used with the option characters −d,
−r, or −x, write a detailed file-by-file description of the
archive creation and maintenance activity, as described in
the STDOUT section.
When used with −p, write the name of the file in the archive
to the standard output before writing the file in the archive
itself to the standard output, as described in the STDOUT
section.
When used with −t, include a long listing of information
about the files in the archive, as described in the STDOUT
section.
−x Extract the files in the archive named by the file operands
from archive. The contents of the archive shall not be
changed. If no file operands are given, all files in the ar‐
chive shall be extracted. The modification time of each file
extracted shall be set to the time the file is extracted from
the archive.
OPERANDS
The following operands shall be supported:
archive A pathname of the archive.
file A pathname. Only the last component shall be used when com‐
paring against the names of files in the archive. If two or
more file operands have the same last pathname component
(basename), the results are unspecified. The implementation's
archive format shall not truncate valid filenames of files
added to or replaced in the archive.
posname The name of a file in the archive, used for relative posi‐
tioning; see options −m and −r.
STDIN
Not used.
INPUT FILES
The archive named by archive shall be a file in the format created by
ar −r.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of ar:
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input
files).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard
error.
LC_TIME Determine the format and content for date and time strings
written by ar −tv.
NLSPATH Determine the location of message catalogs for the processing
of LC_MESSAGES.
TMPDIR Determine the pathname that overrides the default directory
for temporary files, if any.
TZ Determine the timezone used to calculate date and time
strings written by ar −tv. If TZ is unset or null, an
unspecified default timezone shall be used.
ASYNCHRONOUS EVENTS
Default.
STDOUT
If the −d option is used with the −v option, the standard output format
shall be:
"d − %s\n", <file>
where file is the operand specified on the command line.
If the −p option is used with the −v option, ar shall precede the con‐
tents of each file with:
"\n<%s>\n\n", <file>
where file is the operand specified on the command line, if file oper‐
ands were specified, and the name of the file in the archive if they
were not.
If the −r option is used with the −v option:
* If file is already in the archive, the standard output format shall
be:
"r − %s\n", <file>
where <file> is the operand specified on the command line.
* If file is not already in the archive, the standard output format
shall be:
"a − %s\n", <file>
where <file> is the operand specified on the command line.
If the −t option is used, ar shall write the names of the files in the
archive to the standard output in the format:
"%s\n", <file>
where file is the operand specified on the command line, if file oper‐
ands were specified, or the name of the file in the archive if they
were not.
If the −t option is used with the −v option, the standard output format
shall be:
"%s %u/%u %u %s %d %d:%d %d %s\n", <member mode>, <user ID>,
<group ID>, <number of bytes in member>,
<abbreviated month>, <day-of-month>, <hour>,
<minute>, <year>, <file>
where:
<file> Shall be the operand specified on the command line, if file
operands were specified, or the name of the file in the ar‐
chive if they were not.
<member mode>
Shall be formatted the same as the <file mode> string defined
in the STDOUT section of ls, except that the first character,
the <entry type>, is not used; the string represents the file
mode of the file in the archive at the time it was added to
or replaced in the archive.
The following represent the last-modification time of a file when it
was most recently added to or replaced in the archive:
<abbreviated month>
Equivalent to the format of the %b conversion specification
format in date.
<day-of-month>
Equivalent to the format of the %e conversion specification
format in date.
<hour> Equivalent to the format of the %H conversion specification
format in date.
<minute> Equivalent to the format of the %M conversion specification
format in date.
<year> Equivalent to the format of the %Y conversion specification
format in date.
When LC_TIME does not specify the POSIX locale, a different format and
order of presentation of these fields relative to each other may be
used in a format appropriate in the specified locale.
If the −x option is used with the −v option, the standard output format
shall be:
"x − %s\n", <file>
where file is the operand specified on the command line, if file oper‐
ands were specified, or the name of the file in the archive if they
were not.
STDERR
The standard error shall be used only for diagnostic messages. The
diagnostic message about creating a new archive when −c is not speci‐
fied shall not modify the exit status.
OUTPUT FILES
Archives are files with unspecified formats.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
None.
EXAMPLES
None.
RATIONALE
The archive format is not described. It is recognized that there are
several known ar formats, which are not compatible. The ar utility is
included, however, to allow creation of archives that are intended for
use only on one machine. The archive is specified as a file, and it can
be moved as a file. This does allow an archive to be moved from one
machine to another machine that uses the same implementation of ar.
Utilities such as pax (and its forebears tar and cpio) also provide
portable ``archives''. This is a not a duplication; the ar utility is
included to provide an interface primarily for make and the compilers,
based on a historical model.
In historical implementations, the −q option (available on XSI-conform‐
ing systems) is known to execute quickly because ar does not check on
whether the added members are already in the archive. This is useful to
bypass the searching otherwise done when creating a large archive
piece-by-piece. These remarks may but need not remain true for a brand
new implementation of this utility; hence, these remarks have been
moved into the RATIONALE.
BSD implementations historically required applications to provide the
−s option whenever the archive was supposed to contain a symbol table.
As in this volume of POSIX.1‐2008, System V historically creates or
updates an archive symbol table whenever an object file is removed
from, added to, or updated in the archive.
The OPERANDS section requires what might seem to be true without speci‐
fying it: the archive cannot truncate the filenames below {NAME_MAX}.
Some historical implementations do so, however, causing unexpected
results for the application. Therefore, this volume of POSIX.1‐2008
makes the requirement explicit to avoid misunderstandings.
According to the System V documentation, the options −dmpqrtx are not
required to begin with a <hyphen> ('−'). This volume of POSIX.1‐2008
requires that a conforming application use the leading <hyphen>.
The archive format used by the 4.4 BSD implementation is documented in
this RATIONALE as an example:
A file created by ar begins with the ``magic'' string
"!<arch>\n". The rest of the archive is made up of objects,
each of which is composed of a header for a file, a possible
filename, and the file contents. The header is portable between
machine architectures, and, if the file contents are printable,
the archive is itself printable.
The header is made up of six ASCII fields, followed by a two-
character trailer. The fields are the object name (16 charac‐
ters), the file last modification time (12 characters), the user
and group IDs (each 6 characters), the file mode (8 characters),
and the file size (10 characters). All numeric fields are in
decimal, except for the file mode, which is in octal.
The modification time is the file st_mtime field. The user and
group IDs are the file st_uid and st_gid fields. The file mode
is the file st_mode field. The file size is the file st_size
field. The two-byte trailer is the string "`<newline>".
Only the name field has any provision for overflow. If any file‐
name is more than 16 characters in length or contains an embed‐
ded space, the string "#1/" followed by the ASCII length of the
name is written in the name field. The file size (stored in the
archive header) is incremented by the length of the name. The
name is then written immediately following the archive header.
Any unused characters in any of these fields are written as
<space> characters. If any fields are their particular maximum
number of characters in length, there is no separation between
the fields.
Objects in the archive are always an even number of bytes long;
files that are an odd number of bytes long are padded with a
<newline>, although the size in the header does not reflect
this.
The ar utility description requires that (when all its members are
valid object files) ar produce an object code library, which the link‐
age editor can use to extract object modules. If the linkage editor
needs a symbol table to permit random access to the archive, ar must
provide it; however, ar does not require a symbol table.
The BSD −o option was omitted. It is a rare conforming application that
uses ar to extract object code from a library with concern for its mod‐
ification time, since this can only be of importance to make. Hence,
since this functionality is not deemed important for applications
portability, the modification time of the extracted files is set to the
current time.
There is at least one known implementation (for a small computer) that
can accommodate only object files for that system, disallowing mixed
object and other files. The ability to handle any type of file is not
only historical practice for most implementations, but is also a rea‐
sonable expectation.
Consideration was given to changing the output format of ar −tv to the
same format as the output of ls −l. This would have made parsing the
output of ar the same as that of ls. This was rejected in part because
the current ar format is commonly used and changes would break histori‐
cal usage. Second, ar gives the user ID and group ID in numeric format
separated by a <slash>. Changing this to be the user name and group
name would not be correct if the archive were moved to a machine that
contained a different user database. Since ar cannot know whether the
archive was generated on the same machine, it cannot tell what to
report.
The text on the −ur option combination is historical practice—since one
filename can easily represent two different files (for example, /a/foo
and /b/foo), it is reasonable to replace the file in the archive even
when the modification time in the archive is identical to that in the
file system.
FUTURE DIRECTIONS
None.
SEE ALSO
c99, date, fort77, pax, strip
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines, <unistd.h>,
description of {POSIX_NO_TRUNC}
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 AR(1P)
