/* gcc -opolltest polltest.c */ 

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

void callback_alarm(int sig) { return; } 

int main() 
{ 
	struct pollfd p[3]; 

	memset(p, 0, sizeof(struct pollfd) * 3); 

	p[0].fd = -1; 
	p[1].fd = -1; 
	p[2].fd = -1; 

	printf("no descriptor is valid - poll() must wait for 2 seconds\n"); 
	poll(p, 3, 2000); 
	printf("no descriptor is valid - revents for any descriptor must be 0: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 

	p[2].fd = 0; 
	printf("no descriptor is ready - poll() must return 0: %d\n", poll(p, 3, 500)); 
	printf("no descriptor is ready - revents for any descriptor must be 0: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 

	signal(SIGALRM, callback_alarm); 

	alarm(1); 

	printf("SIGALRM - poll() must return -1: %d\n", poll(p, 3, 1500)); 
	printf("SIGALRM - revents for any descriptor must be 0: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 
}