autocompletion for usernames (passwd, chown, chgrp)

I'm sorry if this is not a new ideea to you.

I have noticed that the "su" command has autocompletion [Tab] for 
usernames, and I thought that it would be nice to have that feature too, 
for passwd, chown, chgrp etc.

Thanks, and again, sorry if it's not something new.

-- 
Linux/Unix Systems Engineer http://www.genesys.ro
Phone +40723-267961