RE: coreutils uniq -d -u does not conform to POSIX

[P]

Paul Eggert wrote:
> I asked my students to clone Debian GNU/Linux uniq in Python, giving
> them a POSIX-compatible uniq to start with.  Josh Hyman, one of my
> students, pointed out a disagreement between the two programs which
> turns out to be a POSIX-compatibility bug in coreutils.  POSIX says
> that "uniq -d -u" should output nothing, but with coreutils uniq, -d
> overrides -u and vice versa.
>
> Here is a proposed patch.  While I was at it I noticed a few related
> infelicities in the documentation, so this patch fixes them too.

There are other invalid combinations not handled either:
See the last 6 lines of this patch for a summary:
http://www.pixelbeat.org/patches/textutils-2.0.21-uniq-group.diff

regards,
Pádraig.