ar Cheatsheet

ar is the classic Unix/Linux tool used to work with archive files. An archive file is typically used for a static library, holding a collection of .o object files and typically has the file extension .a. The files inside an archive are called its members.

On Linux, it ships as part of the GNU Binutils.

• To create an empty archive:

$ ar -cr foobar.a

Note that providing just -c does not work: it has to be used along with a member operation like -r.

• To add members to an archive, replacing members if they already exist in the archive:

$ ar -cr foobar.a member1.o member2.o member3.o

The comparison for replacement is done based on member filename only, not on the size or contents of the members. The archive will store the members in the order they are inserted.

• To extract all the members inside an archive:

$ ar -x foobar.a

• By default, extracting does not print the names of members extracted. To extract all the members inside an archive and also print their names:

$ ar -xv foobar.a

• To extract specific members from inside an archive:

$ ar -x foobar.a member1.o member2.o member3.o

• To list the members of an archive:

$ ar -t foobar.a

This option is confusingly named -t instead of -l (for list). An easy way to remember this option is to think about it as printing a table of members.

• To list the members of an archive, along with their permissions, size and date:

$ ar -tv foobar.a

• Note that a .deb file is also actually an archive file. So all the actions above can be used on these files too.

Tried with: Binutils 2.30 and Ubuntu 18.04