ar is deprecated from the LSB and is expected to disappear from a future version of the LSB. [1]
ar is as specified in the Single UNIX Specification but with differences as listed below.
need not be accepted.
has unspecified behavior.
has unspecified behavior; using -r is suggested.
| [1] | The LSB generally does not include software development utilities nor does it specify .o and .a file formats. |