ar — Create, modify, and extract from archives
ar [ - ] dmpqrtx[abcilosuvV] [ membername ] archive files ...
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 may be reconstituted 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 will create 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.
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 files 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-lineargument.
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 files ; the archive is untouched if you specify no files to delete.
If you specify the v modifier, ar will list 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 files 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 membername before copying its contents to standard output.
If you specify no files, all the files in the archive are printed.
q – Quick append; add files 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 – Insert files 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 files 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, and 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 files that are present in the archive. Normally, only the membername 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 any files, 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 will
list 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 files) 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 any files, 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, as
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 membername 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 membername argument, before the archive specification (same as i).
c – 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 that you expect to create it by using this modifier.
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 membername 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 will be 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 filenames processed, when the modifier v is appended.
V – This modifier shows the version number of ar.