On 03/13/2011 07:30 AM, Reuben Thomas wrote: > They're specified in POSIX
They're marked as an obsolescent XSI extension in POSIX.1-2008. That is, they're not required by POSIX, and even as an optional extension they may go away in future versions. The rationale explains why -a and -o are deprecated. One thing that the rationale doesn't fully go into, though, is that -a and -o are syntactically ambiguous in some cases.
