/*======================================================================    A test program in userspace       This example is to introduce the ways to use "select"     and driver poll                           The initial developer of the original code is Baohua Song    <author@linuxdriver.cn>. All Rights Reserved.======================================================================*/#include <sys/types.h>#include <sys/stat.h>#include <stdio.h>#include <fcntl.h>#include <unistd.h>#include <sys/time.h>#define FIFO_CLEAR 0x1#define BUFFER_LEN 20main(){  int fd, num;  char rd_ch[BUFFER_LEN];  fd_set rfds,wfds;    /*以非阻塞方式打開/dev/globalmem設(shè)備文件*/  fd = open("/dev/globalfifo", O_RDONLY | O_NONBLOCK);  if (fd !=  - 1)  {    /*FIFO清0*/    if (ioctl(fd, FIFO_CLEAR, 0) < 0)    {      printf("ioctl command failed\n");    }    while (1)    {      FD_ZERO(&rfds);      FD_ZERO(&wfds);      FD_SET(fd, &rfds);      FD_SET(fd, &wfds);      select(fd + 1, &rfds, &wfds, NULL, NULL);      /*數(shù)據(jù)可獲得*/      if (FD_ISSET(fd, &rfds))      {      	printf("Poll monitor:can be read\n");      }      /*數(shù)據(jù)可寫入*/      if (FD_ISSET(fd, &wfds))      {      	printf("Poll monitor:can be written\n");      }          }  }  else  {    printf("Device open failure\n");  }}