sighup_handler
ssh_signal(SIGHUP, sighup_handler);
act.sa_handler = sighup_handler;
if (signal(SIGHUP,sighup_handler) == SIG_ERR)
sighup_handler(0);
if (signal(SIGHUP,sighup_handler) == SIG_ERR) /* Re-enable HUP signal */
static void sighup_handler(int); /* SIGHUP handler */
sighup_handler(int),
signal(SIGHUP, sighup_handler);