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Create and maintain library archives (POSIX)


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


See below.


The ar program creates and modifies archives, and extracts members from them. 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; you can restore them on extraction. The ar utility can maintain archives whose members have names of any length.

The ar utility creates an index to the symbols defined in relocatable object modules in the archive when you specify the modifier s. This index is created automatically for object modules. It's updated in the archive whenever ar makes a change to its contents (except for the -q update operation). An archive with such an index speeds up linking to the library, and lets routines in the library call each other without regard to their placement in the archive. You can use nm -s to list this index table.

The ar utility insists on at least two arguments to execute:

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

The ar utility lets you mix the operation code key_letter and modifier flags mod in any order, within the first command-line argument.

Key letters

The key_letter specifies what operation to execute; it may be any of the following, but you must specify only one of them:

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's deleted.

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 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.

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.

Quick append; historically, add the files member... to the end of archive, without checking for replacement.

The modifiers a, b, and i don't affect this operation; new members are always placed at the end of the archive.

The modifier v makes ar list each file as it's appended.

Since the point of this operation is speed, the archive's symbol table index isn't updated, even if it already exists; you can use ar -s explicitly to update the symbol table index.

However, too many different systems assume quick append rebuilds the index, so ar implements -q as a synonym for -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... doesn't 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.

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 don't specify a member, all files in the archive are listed.

If there's more than one file with the same name (say, foo) in an archive (say b.a), ar t b.a foo lists only the first instance; to see them all, you must ask for a complete listing -- in our example, ar t b.a.

Extract members (named member) from the archive. You can use the v modifier with this operation to ask ar to list each name as it extracts it.

If you don't specify a member, all files in the archive are extracted.


Some modifiers (mod) may immediately follow key_letter to specify variations on an operation's behavior:

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.
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).
Create the archive. The specified archive is always created (if it didn't exist) when you request an update. But a warning is issued unless you specify in advance -- by using this modifier -- that you expect to create it.
Truncate names in the archive. The ar utility normally permits file names of any length. This causes it to create archives that aren't compatible with the native ar program on some non-QNX systems. If this is a concern, the f modifier may be used to truncate file names when putting them in the archive.
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).
This modifier is accepted but not used.
Preserve the original dates of members when extracting them. If you don't specify this modifier, files extracted from the archive are stamped with the time of extraction.
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.
Don't generate an archive symbol table. This can speed up building a large library in several steps. The resulting archive can't be used with the linker. In order to build a symbol table, you must omit the S modifier on the last execution of ar.
Normally, ar -r... inserts all files listed into the archive. If you want 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 isn't allowed, since checking the timestamps loses any speed advantage from the operation -q.
This modifier requests the verbose version of an operation. Many operations display additional information, such as filenames processed, when the modifier v is appended.
This modifier shows the version number of ar. The V modifier isn't POSIX or common Unix.

Controlling ar with a script

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 isn't 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 ar for developers who already have scripts written for the MRI "librarian" program.

The syntax for the ar command language is straightforward:

Here are the commands you can use in ar scripts, or when using ar interactively. Three of them have special significance:

ADDLIB archive
ADDLIB archive (module, module, ... module)
Add all the contents of archive (or, if specified, each named module from 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.
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 isn't actually saved as archive until you use SAVE. You can overwrite existing archives; similarly, the contents of any existing file named archive aren't 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.

Exit from ar, with a 0 exit code to indicate successful completion. This command doesn't 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.
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 an 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 don't 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.
Toggle an internal flag governing the output from DIRECTORY. When the flag is on, DIRECTORY output matches output from ar -tv ....
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.



See also:


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