#include <signal.h>
#include <stdio.h>
#include <unistd.h>

extern char *environ[];

void
handler(int sig, siginfo_t *si, void *ctx __attribute__((unused)))
{
	char buf[1024];
	snprintf(buf, 1024, "signal %d process %d", sig, si->si_pid);
	puts(buf);
}

int
main(void)
{
	char *args[] = {"/bin/sleep", "2", NULL};
	struct sigaction sa;
	sa.sa_sigaction = handler;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_SIGINFO | SA_NODEFER;
	sigaction(SIGCHLD, &sa, NULL);
	if (fork() == 0) {
		execve(args[0], args, environ);
	}
	if (fork() == 0) {
		execve(args[0], args, environ);
	}
	if (vfork() == 0) {
		struct timespec ts = {4, 0};
		nanosleep(&ts, NULL);
		_exit(0);
	}
	while (1)
		pause();
}