apropos permissions

[Jack Coates <jack nemo index berkeley edu>]

Hi all,

where should I look for a quick and dirty explanation of permissions?
I've figured out what commands like chmod 766 foo.bar or chmod u+x
foo.bar do, sort of, but I don't see how to do something like:

log in as root
create shared directory structure
Assign group A read-only rights, group B read-write, and group C
no-access.

man chmod gives nothing but command-line switches. Midnight Commander's
interface made things a lot clearer, but I still don't really grasp
what's going on.


Jack