sigaddset example

#include <signal.h>
#include <errno.h>

/* 

 * <signal.h> usually defines NSIG to include signal number 0 

 */
#define SIGBAD(signo) ((signo) <= 0 || (signo) >= NSIG)
 
int sigaddset(sigset_t *set, int signo)v{
    if (SIGBAD(signo)) {
        errno = EINVAL;
        return(-1);
    }
    *set |= 1 << (signo - 1); /* turn bit on */
    return(0);
}

See Also:

1. sigdelset
2. sigismember