I've searched the archives and (re)read the man page of useradd, but I can't understand why the -p option exists. To me, I can see no way of using it safely (securely) as it can display on the process listing.
Admittedly, there might be some use for it that I haven't thought of - but in it's current form it seems far to easy to reveal a passwd hash; the only application I can think of is when no one other than trusted users have access to the process listing. Despite that, I think it would be better - although less clean - to have the pasword passwed on stdin. So, my question is: why is it like it currently is? Thanks