struct sigaction sa = { .sa_handler = signal_handler };
sigaction(SIGUSR1, &sa, 0);
sigaction(SIGINT, &sa, 0);
sigaction(SIGTERM, &sa, 0);
sigaction(SIGHUP, &sa, 0);
struct sigaction sa = { .sa_handler = signal_handler };
sigaction(SIGUSR1, &sa, 0);
sigaction(SIGINT, &sa, 0);
sigaction(SIGTERM, &sa, 0);
sigaction(SIGHUP, &sa, 0);