The actual value to be set for sigset_t (correct?)
sigset_addr
The address of the signal set (sigset_t) to be
implemented
oldsigset_addr
The old address of the signal set (sigset_t)
how
Indicates how to change the blocked signals; possible
values are SIG_BLOCK=0 (for blocking signals), SIG_UNBLOCK=1 (for unblocking
signals), and SIG_SETMASK=2 for setting the signal mask.