epoll simple demonstration

main_epoll.c

// compile: gcc main_epoll.c -o main_epoll -std=c99
// run: ./main_epoll
// environment: Linux

#define MAX_EVENTS 5
#define READ_SIZE 5

#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/epoll.h>

static int exit=0;

// signal callback
void sigint_handler(int signum)
{
	if(signum==SIGINT)
	{
		printf("\nSIGINT triggered\n");
		exit=1;
	}
}

int main(int argc, char * argv[])
{
  	// register signal handler
	signal(SIGINT, sigint_handler);
  
  	// init epoll structs
	struct epoll_event config;
	struct epoll_event events[MAX_EVENTS];
  
  	// create buffer
	char buffer[READ_SIZE+1];
  
  	// init epoll
	int efd=epoll_create1(0);
  
  	// check epoll creation status
	if(efd==-1)
	{
		perror("epoll_create1");
		return 1;
	}

  	// setup epoll configurations: level-triggered, fd is stdin
	config.events=EPOLLIN;
	config.data.fd=0;
	int err=epoll_ctl(efd, EPOLL_CTL_ADD, 0, &config);
	if(err!=0)
	{
		perror("epoll_ctl");
		close(efd);
		return 2;		
	}

  	// start the loop
	while(exit==0)
	{
   		// poll events, timeout is 30000 millisec
		int count=epoll_wait(efd, events, MAX_EVENTS, 30000);
		printf("\nEvent count: %d\n", count);
		for(int i=0; i<count; i++)
		{
      			// read the buffer
			int bytes_read=read(events[i].data.fd, buffer, READ_SIZE);
			printf("\nBytes read: %d...\n", bytes_read);
      			// set null-terminator for display purpose
			buffer[bytes_read]='\0';
			printf("\nBuffer content: %s\n", buffer);
		}

    		// prepare if sigint is raised at this point
		if(exit==1) { break; }
	}	

  	// cleanup epoll's fd
	close(efd);
	return 0;
}