ultrix man page for sigblock

sigblock(2)							System Calls Manual						       sigblock(2)

Name
       sigblock - block signals

Syntax
       sigblock(mask)
       int mask;

Description
       The  system call causes the signals specified in mask to be added to the set of signals currently being blocked from delivery.  Signal i is
       blocked if the ith bit in mask is a 1.

       It is not possible to block SIGKILL or SIGSTOP.	This restriction is silently imposed by the system.

       The previous set of masked signals is returned.

See Also
       kill(2), sigsetmask(2), sigvec(2)

																       sigblock(2)