osx snow leopard - Is there a usermod equivalent in terminal for OS X 10.6.1

Can anyone tell me how to modify a user and add them to a group in terminal on SL (10.6.1)?

It seems that usermod is not used by Mac.

Answer

dscl is the usual way to modify any stuff from Directory Services (whether local or remote) from the command line. See the dscl manpage for all the info (or the local one if you are not running 10.6). Google turns up many examples of how to use it (including many from macosxhints.com).