archive(5) - Unix First Edition Manual Page
11/3/71ARCHIVE (V)

NAME archive (library) file format
DESCRIPTION The archive command ar is used to combine several filesinto one. Its use has three benefits: when files are

combined, the file space consumed by the breakage at theend of each file (256 bytes on the average) is saved; directories are smaller and less confusing; archive filesof object programs may be searched as libraries by the loader ld. A file produced by ar has a "magic number" at the start,followed by the constituent files, each preceded by a file header. The magic number is --147(10), or 177555(8) (it waschosen to be unlikely to occur anywhere else). The header of each file is 16 bytes long:

0--7file name, null padded on the right

8--IlModification time of the file

12User ID of file owner 13file mode 14--15file size If the file is an odd number of bytes long, it is paddedwith a null byte, but the size in the header is correct. Notice there is no provision for empty areas in an archivefile.
OWNER ken, dmr