log user off from c prog

ok, heres what i want i need....well want, hehe...

in a program, its a simple menu, i need to log the user running the program off...back to the login prompt. this is not a super user, just a normal account.

i know i could just set the program to be the users login shell..but i'd rather do it this way. im not sure if this is possible. and i know it may not be that secure. but is there a way to do this?

if its not possible from within a c prog, what about from a shell script?

any one?

The program would have to run as either root, or the user you're killing. Simply kill the shell, and the rest should die (unless they've been told not to - in which case you have to kill each one).