AR

File Format
Name	AR
Ontology	Electronic File Formats Archiving AR
Extension(s)	.a, .lib

ar is a non-compressed archive format for Unix-style operating systems. It was mostly superseded by tar for general archiving use, but persists in use for specialized applications involving linkable libraries for development.

Overview

There are at least 5 different variants of the ar file format since it has never been formally standardized: AIX(big), AIX(small), Coherent, BSD, and GNU.

References

• Wikipedia page for the ar archiver
• IBM AIX documentation on scribd here (page 386+; someone might find a better accessible version)
• Also from IBM is this description (and this for the "small" variant)
• The Microsoft PE/COFF documentation also has a section on .lib files which use the same format