ultrix man page for sigsetmask

sigsetmask(2)							System Calls Manual						     sigsetmask(2)

Name
       sigsetmask - set current signal mask

Syntax
       sigsetmask(mask)
       int mask;

Description
       The system call sets the current signal mask (those signals that are blocked from delivery).  Signal i is blocked if the ith bit in mask is
       a 1.

       The system quietly disallows SIGKILL or SIGSTOP to be blocked.

       The previous set of masked signals is returned.

See Also
       kill(2), sigblock(2), sigpause(2), sigvec(2)

																     sigsetmask(2)