|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
|
|
|
AR(1P) POSIX Programmer's Manual AR(1P)
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.
ar — create and maintain library archives
ar -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...]
The ar utility is part of the Software Development Utilities
option.
The ar utility can be used to create and maintain groups of files
combined 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 archive 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
indicating 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
pathname 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
identically 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.
The ar utility shall conform to the Base Definitions volume of
POSIX.1‐2017, 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
archive 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;
otherwise, 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 operands are specified, the contents of all files
in the archive 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 otherwise done when creating a large archive
piece by piece.
-r Replace or add files to archive. If the archive named
by archive 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 contents. 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 specified, 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 archive shall be extracted. The
modification time of each file extracted shall be set to
the time the file is extracted from the archive.
The following operands shall be supported:
archive A pathname of the archive.
file A pathname. Only the last component shall be used when
comparing 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
positioning; see options -m and -r.
Not used.
The archive named by archive shall be a file in the format created
by ar -r.
The following environment variables shall affect the execution of
ar:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, 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_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.
Default.
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
contents of each file with:
"\n<%s>\n\n", <file>
where file is the operand specified on the command line, if file
operands 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
operands 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 archive 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
operands were specified, or the name of the file in the archive if
they were not.
The standard error shall be used only for diagnostic messages.
The diagnostic message about creating a new archive when -c is not
specified shall not modify the exit status.
Archives are files with unspecified formats.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
None.
None.
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-
conforming 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.1‐2017, 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
specifying 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.1‐2017 makes the requirement explicit to avoid
misunderstandings.
According to the System V documentation, the options -dmpqrtx are
not required to begin with a <hyphen-minus> ('-'). This volume of
POSIX.1‐2017 requires that a conforming application use the
leading <hyphen-minus>.
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
characters), 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
filename is more than 16 characters in length or contains
an embedded 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
linkage 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 modification 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 reasonable 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 historical 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.
None.
c99(1p), date(1p), fort77(1p), pax(1p), strip(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines,
unistd.h(0p), description of {POSIX_NO_TRUNC}
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. 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.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 AR(1P)
Pages that refer to this page: c99(1p), file(1p), fort77(1p), make(1p), nm(1p), strip(1p)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|