It might be worth noting,

While most Unixes (all the ones i know of offhand) include useradd, when adding multiple users it becomes very nice (nay, necessary!) to have something a little more robust. However, such a topic is far too broad to include all the details here. A good place to start is Perl for System Administration. It covers pretty much everything you'll need to think about carefully when designing adduser,deleteuser, et al scripts.

Hope This Helps,
jynx