ar
create, modify, and extract from archives
see also :
nm - ranlib
Synopsis
ar
[--plugin name]
[-X32_64] [-]p[mod
[relpos] [count]] [--target
bfdname] archive [member...]
add an example, a script, a trick and tips
examples
description
The
GNU ar program creates, modifies, and
extracts from archives. An archive is a single file
holding a collection of other files in a structure that
makes it possible to retrieve the original individual files
(called members of the archive).
The original
files’ contents, mode (permissions), timestamp, owner,
and group are preserved in the archive, and can be restored
on extraction.
GNU
ar can maintain archives whose members have names of
any length; however, depending on how ar is
configured on your system, a limit on member-name length may
be imposed for compatibility with archive formats maintained
with other tools. If it exists, the limit is often 15
characters (typical of formats related to a.out) or 16
characters (typical of formats related to coff).
ar is
considered a binary utility because archives of this sort
are most often used as libraries holding commonly
needed subroutines.
ar
creates an index to the symbols defined in relocatable
object modules in the archive when you specify the modifier
s. Once created, this index is updated in the archive
whenever ar makes a change to its contents (save for
the q update operation). An archive with such an
index speeds up linking to the library, and allows routines
in the library to call each other without regard to their
placement in the archive.
You may use
nm -s or nm
--print-armap to list this index
table. If an archive lacks the table, another form of
ar called ranlib can be used to add just the
table.
GNU
ar can optionally create a thin archive, which
contains a symbol index and references to the original
copies of the member files of the archives. Such an archive
is useful for building libraries for use within a local
build, where the relocatable objects are expected to remain
available, and copying the contents of each object would
only waste time and space. Thin archives are also
flattened, so that adding one or more archives to a
thin archive will add the elements of the nested archive
individually. The paths to the elements of the archive are
stored relative to the archive itself.
GNU
ar is designed to be compatible with two different
facilities. You can control its activity using command-line
options, like the different varieties of ar on Unix
systems; or, if you specify the single command-line option
-M, you can control it with a script supplied
via standard input, like the MRI
"librarian" program.
options
GNU
ar allows you to mix the operation code p and
modifier flags mod in any order, within the first
command-line argument.
If you wish,
you may begin the first command-line argument with a
dash.
The p
keyletter specifies what operation to execute; it may be any
of the following, but you must specify only one of them:
d
Delete modules from the archive. Specify the
names of modules to be deleted as member...; the
archive is untouched if you specify no files to delete.
If you specify
the v modifier, ar lists each module as it is
deleted.
m
Use this operation to
move members in an archive.
The ordering of
members in an archive can make a difference in how programs
are linked using the library, if a symbol is defined in more
than one member.
If no modifiers
are used with "m", any members you name
in the member arguments are moved to the end
of the archive; you can use the a, b, or
i modifiers to move them to a specified place
instead.
p
Print the specified
members of the archive, to the standard output file. If the
v modifier is specified, show the member name before
copying its contents to standard output.
If you specify
no member arguments, all the files in the archive are
printed.
q
Quick append;
Historically, add the files member... to the end of
archive, without checking for replacement.
The modifiers
a, b, and i do not affect this
operation; new members are always placed at the end of the
archive.
The modifier
v makes ar list each file as it is
appended.
Since the point
of this operation is speed, the archive’s symbol table
index is not updated, even if it already existed; you can
use ar s or ranlib explicitly to update the
symbol table index.
However, too
many different systems assume quick append rebuilds the
index, so GNU ar implements q
as a synonym for r.
r
Insert the files
member... into archive (with
replacement). This operation differs from q in
that any previously existing members are deleted if their
names match those being added.
If one of the
files named in member... does not exist, ar
displays an error message, and leaves undisturbed any
existing members of the archive matching that name.
By default, new
members are added at the end of the file; but you may use
one of the modifiers a, b, or i to
request placement relative to some existing member.
The modifier
v used with this operation elicits a line of output
for each file inserted, along with one of the letters
a or r to indicate whether the file was
appended (no old member deleted) or replaced.
s
Add an index to the archive, or
update it if it already exists. Note this command is an
exception to the rule that there can only be one command
letter, as it is possible to use it as either a command or a
modifier. In either case it does the same thing.
t
Display a table listing the contents of
archive, or those of the files listed in
member... that are present in the archive. Normally
only the member name is shown; if you also want to see the
modes (permissions), timestamp, owner, group, and size, you
can request that by also specifying the v
modifier.
If you do not
specify a member, all files in the archive are
listed.
If there is
more than one file with the same name (say, fie) in
an archive (say b.a), ar t b.a fie lists only
the first instance; to see them all, you must ask for a
complete listing---in our example, ar t
b.a.
x
Extract members (named
member) from the archive. You can use the v
modifier with this operation, to request that ar list
each name as it extracts it.
If you do not
specify a member, all files in the archive are
extracted.
Files cannot be
extracted from a thin archive.
--help
Displays the list of command
line options supported by ar and then exits.
--version
Displays the version
information of ar and then exits.
A number of
modifiers (mod) may immediately follow the p
keyletter, to specify variations on an operation’s
behavior:
a
Add new files after an existing member of the
archive. If you use the modifier a, the name of an
existing archive member must be present as the relpos
argument, before the archive specification.
b
Add new files before an existing member of the
archive. If you use the modifier b, the name of an
existing archive member must be present as the relpos
argument, before the archive specification. (same as
i).
c
Create the archive. The specified archive
is always created if it did not exist, when you request an
update. But a warning is issued unless you specify in
advance that you expect to create it, by using this
modifier.
D
Operate in deterministic mode. When adding files
and the archive index use zero for UIDs, GIDs, timestamps,
and use consistent file modes for all files. When this
option is used, if ar is used with identical options
and identical input files, multiple runs will create
identical output files regardless of the input files’
owners, groups, file modes, or modification times.
If
binutils was configured with
--enable-deterministic-archives,
then this mode is on by default. It can be disabled with the
U modifier, below.
f
Truncate names in the archive.
GNU ar will normally permit file names
of any length. This will cause it to create archives which
are not compatible with the native ar program on some
systems. If this is a concern, the f modifier may be
used to truncate file names when putting them in the
archive.
i
Insert new files before an existing member of the
archive. If you use the modifier i, the name of an
existing archive member must be present as the relpos
argument, before the archive specification. (same as
b).
l
This modifier is accepted but not used.
N
Uses the count parameter. This is used if there
are multiple entries in the archive with the same name.
Extract or delete instance count of the given name
from the archive.
o
Preserve the original dates of members when
extracting them. If you do not specify this modifier, files
extracted from the archive are stamped with the time of
extraction.
P
Use the full path name when matching names in the
archive. GNU ar can not create an
archive with a full path name (such archives are not
POSIX complaint), but other archive creators
can. This option will cause GNU ar to
match file names using a complete path name, which can be
convenient when extracting a single file from an archive
created by another tool.
s
Write an object-file index into the archive, or update
an existing one, even if no other change is made to the
archive. You may use this modifier flag either with any
operation, or alone. Running ar s on an archive is
equivalent to running ranlib on it.
S
Do not generate an archive symbol table. This can speed
up building a large library in several steps. The resulting
archive can not be used with the linker. In order to build a
symbol table, you must omit the S modifier on the
last execution of ar, or you must run ranlib
on the archive.
T
Make the specified archive a thin archive.
If it already exists and is a regular archive, the existing
members must be present in the same directory as
archive.
u
Normally, ar r... inserts all files listed into
the archive. If you would like to insert only those
of the files you list that are newer than existing members
of the same names, use this modifier. The u modifier
is allowed only for the operation r (replace). In
particular, the combination qu is not allowed, since
checking the timestamps would lose any speed advantage from
the operation q.
U
Do not operate in deterministic mode. This
is the inverse of the D modifier, above: added files
and the archive index will get their actual
UID , GID , timestamp, and
file mode values.
This is the
default unless binutils was configured with
--enable-deterministic-archives.
v
This modifier requests the
verbose version of an operation. Many operations
display additional information, such as filenames processed,
when the modifier v is appended.
V
This modifier shows the version number of ar.
ar
ignores an initial option spelt -X32_64, for
compatibility with AIX . The behaviour
produced by this option is the default for
GNU ar. ar does not support any
of the other -X options; in particular, it does
not support -X32 which is the default for
AIX ar.
The optional
command line switch --plugin name
causes ar to load the plugin called name which
adds support for more file formats. This option is only
available if the toolchain has been built with plugin
support enabled.
The optional
command line switch --target
bfdname specifies that the archive members are in an
object code format different from your system’s
default format. See
@file
Read command-line options from
file. The options read are inserted in place of the
original @file option. If file does not exist,
or cannot be read, then the option will be treated
literally, and not removed.
Options in
file are separated by whitespace. A whitespace
character may be included in an option by surrounding the
entire option in either single or double quotes. Any
character (including a backslash) may be included by
prefixing the character to be included with a backslash. The
file may itself contain additional @file
options; any such options will be processed recursively.
copyright
Copyright (c) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
2010, 2011, 2012, 2013 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free
Documentation License, Version 1.3 or any later version published
by the Free Software Foundation; with no Invariant Sections, with
no Front-Cover Texts, and with no Back-Cover Texts. A copy of the
license is included in the section entitled " GNU
Free Documentation License".
see also
nm ,
ranlib , and the Info entries for
binutils.