Description

   Signal i is blocked if the i - 1 bit in mask is a 1. For example,
   to add the protection-violation signal to the set of blocked
   signals, use the following line:

   sigblock(1 << (SIGBUS - 1));

   You can express signals in mnemonics (such as SIGBUS for a
   protection violation) or numbers as defined in the <signal.h>
   header file, and you can express combinations of signals by using
   the bitwise OR operator (|).