Signal.h

int sigemptyset(sigset_t *set)

The sigemptyset() function initialises the signal set pointed to by set, such that all signals defined in this document are excluded.

struct sigaction 
{
   void (*sa_handler)(int);
   void (*sa_sigaction)(int, siginfo_t *, void *);
   sigset_t sa_mask;
   int sa_flags;
   void (*sa_restorer)(void);
}