listen_int_handler
nsig.sa_handler = listen_int_handler;
sig_int = signal(SIGINT, listen_int_handler);
nsig.sa_handler = listen_int_handler; /* fgets is not signal-safe */
if ((void (*)(int))csig.sa_handler==(void (*)(int))listen_int_handler)
sig_cont = signal(SIGCONT, listen_int_handler);
if (sig_cont == listen_int_handler)