select 实例程序

/*
 * select.c
 *
 *  Created on: 2011-11-7
 *      Author: lc
 */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <time.h>

int main() {
 int count, maxfd;
 char buf[7];
 int fds[2];
 fd_set setr, setw;
 struct timeval tv;

 if ((fds[0] = open("file1", O_CREAT | O_RDWR, 0666)) < 0) {
  perror("open file1");
 }
 if ((fds[1] = open("file2", O_CREAT | O_RDWR, 0666)) < 0) {
  perror("open file2");
 }

 if ((count = write(fds[0], "hello!\n", 7))) {
  printf("count=%d\n", count);
 }

 lseek(fds[0], 0, SEEK_SET);

 tv.tv_sec = 2;
 tv.tv_usec = 0;

 maxfd = fds[0] > fds[1] ? fds[0] : fds[1];

 FD_ZERO(&setr);
 FD_ZERO(&setw);
 FD_SET(fds[0],&setr);
 FD_SET(fds[1],&setw);

 while (FD_ISSET(fds[0],&setr) || FD_ISSET(fds[1],&setw)) {
  if ((select(maxfd + 1, &setr, &setw, NULL, &tv)) < 0) {
   perror("select");
  } else {
   //阻塞时，读取的count值为0
   if (FD_ISSET(fds[0],&setr)) {
    count = read(fds[0],buf,7);
    if(count > 0) {
     buf[count] = '\0';
     printf("count = %d,read : %s\n",count,buf);
    } else {
     perror("read file1");
    }
   }

   if (FD_ISSET(fds[1],&setw)) {
    count = write(fds[1],buf,7);

    if(count > 0) {
     buf[count] = '\0';
     printf("count=%d,write : %s\n",count,buf);
    } else {
     perror("write file2");
    }

 

 

 

    sleep(5);

   }
  }
 }

 return 0;
}