Changing the group to nogroup in Mac OS X

Question

I'm trying to change the group of several files in Mac OS X using the group nogroup:

chown my_user:nogroup file.txt

Problem is that it does not change at all, although the nogroup is currently listed in /etc/group and Directory Service (I checked it with dscl . list /groups).

What can be happening?

EDIT: I wanted to do this because XAMMP user and group is nobody:nogroup, and I needed XAMMP's httpd server to be able to write in some directories. I ended up changing the group to _www, but curiosity made ask this question.

Thanks!

Answer 1

Because the GID of nogroup is (intentionally) -1, which is an illegal GID for chown.

Why do you want to do that?