int keyboard;

int ret, i;

char c;

fd_set readfd;

struct timeval timeout;

// 打开键盘文件返回键盘文件描述符

keyboard = open("/dev/tty", O_RDONLY | O_NONBLOCK);

assert(keyboard > 0);

while(1) {

// 设置超时信息

timeout.tv_sec = 5;

timeout.tv_usec = 0;

// 对readdf清零

FD_ZERO(&readfd);

// 对resdfd标记keyboard的位置为1

FD_SET(keyboard, &readfd);

// 设置select函数参数并调用

ret = select(keyboard + 1, &readfd, NULL, NULL, &timeout);

if(ret == -1)

perror("select error");

else if(ret) {

// 判断fd是否在readfd集合中

if(FD_ISSET(keyboard, &readfd)) {

// 开始读取键盘输入

i = read(keyboard, &c, 1);

if('\n' == c)

continue;

printf("The time is %c\n", c);

if('q' == c)

break;

}

// 超过5秒没有输入显示超时

else if(ret == 0)

printf("time out\n");

}

}

return 0;