一个select函数的例子

一个select函数的例子
#include
#include
#include
#include
#include
int main()
{
    struct timeval tv;
    char buf[100] = "pig";
    fd_set readfds;
    tv.tv_sec = 4;
    tv.tv_usec = 500000;
    FD_ZERO(&readfds);
    FD_SET(0, &readfds);
    //scanf("%s", buf);
    int flags = fcntl(1,F_GETFL,0);
    flags |= O_NONBLOCK;
    fcntl(1,F_SETFL,flags);//将标准输入设问非阻塞
    printf("before select\n");
    select(1, &readfds, NULL, NULL, &tv);//等待4.5秒，如果4.5秒内没有输入。则time out
    printf("after select\n");
    scanf("%s", buf);
    if(FD_ISSET(0, &readfds))
{
        printf("A key was pressed!\n");
    }
    else
    {
        printf("Time out.\n");
    }
    printf("buf:%s\n", buf);
    return 0;
}