设置读取标准输入的超时时间

Question

有没有办法超时stdin读取,以免程序挂起太长时间？

read(0, var, numberofbytes);

Answer 1

您可以使用ncurses,或者如果您不想,可以使用此博客文章中所述的select .基本上,您可以使用select并指定超时.如果设置了stdin FD,那么您可以安全地读取它并且不会阻塞.如果您想选择更多信息,请查看该出,当然维基百科.知道这是一个方便的电话.

编辑:我觉得有必要提供代码,所以在这里,直接从博客文章中提供一些评论.

// if != 0, then there is data to be read on stdin
int kbhit()
{
    // timeout structure passed into select
    struct timeval tv;
    // fd_set passed into select
    fd_set fds;
    // Set up the timeout.  here we can wait for 1 second
    tv.tv_sec = 1;
    tv.tv_usec = 0;

    // Zero out the fd_set - make sure it's pristine
    FD_ZERO(&fds);
    // Set the FD that we want to read
    FD_SET(STDIN_FILENO, &fds); //STDIN_FILENO is 0
    // select takes the last file descriptor value + 1 in the fdset to check,
    // the fdset for reads, writes, and errors.  We are only passing in reads.
    // the last parameter is the timeout.  select will return if an FD is ready or 
    // the timeout has occurred
    select(STDIN_FILENO+1, &fds, NULL, NULL, &tv);
    // return 0 if STDIN is not ready to be read.
    return FD_ISSET(STDIN_FILENO, &fds);
}

Answer 2

使用select,poll或任何其他IO多路复用工具.他们都采取超时论证.请注意,如果stdin是常规文件,这将不起作用,但如果stdin是终端/ tty,套接字,管道,则它将起作用.

例如

fd_set selectset;
struct timeval timeout = {10,0}; //timeout of 10 secs.
int ret;
FD_ZERO(&selectset);
FD_SET(0,&selectset);
ret =  select(1,&selectset,NULL,NULL,&timeout);
if(ret == 0)
  //timeout
else if(ret == -1)
  //error
else 
   // stdin has data, read it
   // (we know stdin is readable, since we only asked for read events
   //and stdin is the only fd in our select set.