signalfd SFD_NONBLOCK test

gistfile1.c

#include <stdio.h>
#include <sys/signalfd.h>
#include <signal.h>
#include <errno.h>
#include <stdlib.h>

int sigfd_read(int fd) {
	ssize_t n;
	struct signalfd_siginfo buf;
	
	n = read(fd, &buf, sizeof buf);
	return (n <= 0) ? n : buf.ssi_signo ;
}

int sigfd_make(void) {
	sigset_t mask;
	sigemptyset(&mask);
	sigaddset(&mask, SIGUSR1);
	sigaddset(&mask, SIGUSR2);
	if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0) {
		perror("sigprocmask");
		return -1;
	}
	return signalfd(-1, &mask, SFD_NONBLOCK);
}

int main(int argc, char **argv) {
	int fd;
	int sig;
	
	if ((fd = sigfd_make()) < 0) {
		perror("sigfd");
		exit(1);
	}

	for(;;) {
		printf("Listen for signal...\n\t");
		sig = sigfd_read(fd);
		switch(sig) {
		case SIGUSR1:
			puts(" User signal 1");
			break;
		case SIGUSR2:
			puts(" User signal 2");
			break;
		case -1:
			if (errno == EAGAIN) {
				printf(" nothing\n");
			} else {
				perror("read signal");
				exit(1);
			}
			break;
		default:
			break;
		}
		sleep(1);
	}
}