Where can I find the GNU ar file format specification?

Question

I need to access an ar created file, but I cannot find a specification document defining the format. Can someone point me in the right direction?

Answer 1

From Wikipedia:

The ar format has never been standardized; modern archives are based on a common format with two known variants, BSD and GNU.

More information is there, too.

Answer 2

Some information on IBM website: http://pic.dhe.ibm.com/infocenter/aix/v7r1/index.jsp?topic=%2Fcom.ibm.aix.files%2Fdoc%2Faixfiles%2Far_big.htm