NAME
ar - create and maintain library archives
SYNOPSIS
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 ...]
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
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.
OPTIONS
The ar utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
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.
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.
OPERANDS
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.
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 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_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
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.
STDERR
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.
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-
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 IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001 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
IEEE Std 1003.1-2001 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 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>s.
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.
FUTURE DIRECTIONS
None.
SEE ALSO
c99 , date , fort77 , pax , strip the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 13, Headers, <unistd.h> description of
{POSIX_NO_TRUNC}
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .