Adds a signal to a signal set.
#include <signal.h>
int sigaddset (
sigset_t *set,
const int sig);
(IN) Points to the signal set.
(IN) Specifies the signal to add to the signal set. For a list of signals, see Section 5.1, Standard Signals.
If successful, returns 0. Otherwise, returns -1 and sets errno to the following:
You must call either sigemptyset or sigfillset at least once to initialized each object of type sigset_t before calling sigaddset or any of the other functions which manage the signal set.