I have the
groups command on my list of applications to share, and I was sorely tempted to leave it out, except I couldn’t think of a good reason. So here goes.
Best I can tell — and please, as always, let me know if there’s some sort of kung-fu master way to use this —
groups only returns the groups a user account belongs to.
And I think that’s it. The man page is like four lines long, and I swear, there’s nothing there except
groups [user], end of page.
Now if you want to know what groups are available on a machine, I usually
cat /etc/group, which in Arch spits out a list.