sigalrm
struct sigaction sa = { .sa_handler = sigalrm };
(void) signal(SIGALRM, sigalrm);
extern void sigalrm();
signal(SIGALRM, sigalrm);
static void sigalrm(int s UNUSED);
SIGTYPE sigalrm(int signo);
signal(SIGALRM, sigalrm); /* that can cause hanging in read() */
signal(SIGALRM, sigalrm);