sighup
SIGTYPE sighup(int signo);
signal(SIGHUP, sighup);
signal(SIGHUP, sighup);
sig_t sighup, sigint, sigquit, sigchld;
sighup = signal(SIGHUP, SIG_IGN);
(void)signal(SIGHUP, sighup);
(void)signal(SIGHUP, sighup);
sa.sa_handler = sighup;
static void sighup