ar [-]p[mod [relpos]] archive [member ...]
ar -M [ <mri-script ]

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 only the table.

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.

Controlling ar on the command line

ar [-]p[mod [relpos]] archive [member ...]

When you use ar in the Unix style, ar insists on at least two arguments to execute: one keyletter specifying the operation (optionally accompanied by other keyletters specifying modifiers), and the archive name to act on.

Most operations can also accept further member arguments, specifying particular files to operate on.

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
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; 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.
r
Replacement; inserts the files member... into archive. 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.
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 (for instance, ‘fie’) in an archive (for instance, ‘b.a’), ‘ar t b.a fie’ lists only the first instance; to see them all, you must ask for a complete listing—in the earlier 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.
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.
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.
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.
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.
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’.
v
This modifier requests the verbose version of an operation. Many operations display additional information, such as file names processed, when the modifier ‘v’ is appended.
V
This modifier shows the version number of ar.

ar -M [ < script ]

If you use the single command-line option ‘-M’ with ar, you can control its operation with a rudimentary command language. This form of ar operates interactively if standard input is coming directly from a terminal. During interactive use, ar prompts for input (the prompt is ‘AR >’), and continues executing even after errors. If you redirect standard input to a script file, no prompts are issued, and ar abandons execution (with a nonzero exit code) on any error.

The ar command language is not designed to be equivalent to the command-line options; in fact, it provides somewhat less control over archives. The only purpose of the command language is to ease the transition to GNU ar for developers who already have scripts written for the MRI librarian program.

The syntax for the ar command language is straightforward:

• Commands are recognized in upper or lower case; for example, LIST is the same as list. In the following descriptions, commands are shown in upper case for clarity.
• A single command may appear on each line; it is the first word on the line.
• Empty lines are allowed, and have no effect.
• Comments are allowed; text after either of the characters ‘*’ or ‘;’ is ignored.
• Whenever you use a list of names as part of the argument to an ar command, you can separate the individual names with either commas or blanks. Commas are shown in the explanations below, for clarity.
• ‘+’ is used as a line continuation character; if ‘+’ appears at the end of a line, the text on the following line is considered part of the current command.
The following are the commands you can use in ar scripts, or when using ar interactively. Three of them have special significance. OPEN or CREATE specify a current archive, which is a temporary file required for most of the other commands. SAVE commits the changes so far specified by the script. Prior to SAVE, commands affect only the temporary copy of the current archive.
 
ADDLIB archive

ADDLIB archive(module, module, ...module)
Add all the contents of archive(or, if specified, each named modulefrom archive) to the current archive.
Requires prior use of OPEN or CREATE.
ADDMOD member, member, ...member
Add each named member as a module in the current archive.
Requires prior use of OPEN or CREATE.
CLEAR
Discard the contents of the current archive, canceling the effect of any operations since the last SAVE. May be executed (with no effect) even if no current archive is specified.
CREATE archive
Creates an archive, and makes it the current archive (required for many other commands). The new archive is created with a temporary name; it is not actually saved as archive until you use SAVE. You can overwrite existing archives; similarly, the contents of any existing file named archive will not be destroyed until SAVE.
DELETE module, module, ...module
Delete each listed module from the current archive.
Equivalent to ‘ar -d archive module ...module’.
Requires prior use of OPEN or CREATE.
DIRECTORY archive(module, ...module)

DIRECTORY archive( module, ...module) outputfile
List each named module present in archive. The separate command, VERBOSE, specifies the form of the output: when verbose output is off, output is like that of ‘ar -t archive module ...’. When verbose output is on, the listing is like ‘ar -tv archive module ...’.
Output normally goes to the standard output stream; however, if you specify outputfile as a final argument, ar directs the output to that file.
END
Exit from ar, with a 0 exit code to indicate successful completion. This command does not save the output file; if you have changed the current archive since the last SAVE command, those changes are lost.
EXTRACT module, module, ...module
Extract each named module from the current archive, writing them into the current directory as separate files.
Equivalent to ‘ar -x archive module ...’.
Requires prior use of OPEN or CREATE.
LIST
Display full contents of the current archive, in verbose style regardless of the state of VERBOSE. The effect is like ‘ar tv archive’). (This single command is a GNU ld enhancement, rather than present for MRI compatibility.)
Requires prior use of OPEN or CREATE.
OPEN archive
Opens an existing archive for use as the current archive (required for many other commands). Any changes as the result of subsequent commands will not actually affect archive until you next use SAVE.
REPLACE module, module, ...module
In the current archive, replace each existing module (named in the REPLACE arguments) from files in the current working directory. To execute this command without errors, both the file, and the module in the current archive, must exist. Requires prior use of OPEN or CREATE.
VERBOSE
Toggle an internal flag governing the output from DIRECTORY. When the flag is on, DIRECTORY output matches output from ‘ar -tv ’.
SAVE
Commit your changes to the current archive, and actually save it as a file with the name specified in the last CREATE or OPEN command.
Requires prior use of OPEN or CREATE.