Has anyone ever seen this situation in HP-UX:

/etc/group:
lp::7:root,lp,trnadm

trnadm# groups
bin users

As user trnadm, I'm in the groups file under the group lp, however when I run the groups command on the command line, I don't show up in that group. When I try to use the priviledges of that group I get denied. However, when I use the newgrp command, I'm suddenly in that group. I thought that if I was in the groups file in a specific group, I'm always a part of that group. I've never used the newgrp command before. Does anyone here have experience with it? How does it work? Is it something to configure on install?