Even easier (if you are on a secure system and don't mind having encrypted
passwords show up in a process listing for a split second) you could use
htpasswd which, given the command line args:

htpasswd -nb test test
test:sVa6SX4wKM2t.

write a script around that, and have it call 'user' or 'usermod'

usermod -p sVa6SX4wKM2t. test

test $? for errors

Good luck!