binutils: ar
1 ar
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ar [-]P[MOD] [--plugin NAME] [--target BFDNAME] [RELPOS] [COUNT] 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 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 archive. This is useful for building libraries for use within a
local build tree, where the relocatable objects are expected to remain
available, and copying the contents of each object would only waste time
and space.
An archive can either be _thin_ or it can be normal. It cannot be
both at the same time. Once an archive is created its format cannot be
changed without first deleting it and then creating a new archive in its
place.
Thin archives are also _flattened_, so that adding one thin archive
to another thin archive does not nest it, as would happen with a normal
archive. Instead the elements of the first archive are added
individually to the second archive.
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.
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