select.c

#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

#define TIMEOUT 5
#define BUF_LEN 1024
int main(void)
{
	struct timeval tv;
	fd_set readfds;
	int ret;

	FD_ZERO(&readfds);
	FD_SET(STDIN_FILENO,&readfds);

	tv.tv_sec = TIMEOUT;
	tv.tv_usec = 0;

	ret = select(STDIN_FILENO+1,
				&readfds,
				NULL,
				NULL,
				&tv);
	if(ret == -1){
		perror("select");
		return 1;
	}else if(!ret){
		printf("%d seconds elapsed.\n",TIMEOUT);
		return 0;
	}

	if(FD_ISSET(STDIN_FILENO,&readfds)){
		char buf[BUF_LEN+1];
		int len;
		len = read(STDIN_FILENO,buf,BUF_LEN);
		if(len == -1){
			perror("read");
		}
		if(len){
			buf[len] = '\0';
			printf("read: %s\n",buf);
		}
		return 0;
	}
	fprintf(stderr,"This is should not happen!\n");
	return 1;
}