从 fd_set c++ linux 获取 x 处的文件描述符

Question

I know on windows you can get a file descriptor by doing myfd_set.fd_array[x] but when I try and do that on Linux it does not work. What do I have to do to get a file descriptor?

Answer 1

There's no macro defined by POSIX to do what you're asking.

The technique you've used on Windows is viable because the structure of a descriptor set is documented on that platform, so you have reliable access to its innards.

Generally, you wouldn't need this functionality. I don't think I've ever seen a poll loop that needed to obtain the n ^th descriptor in an FD_SET . Usually, you add your FDs to a set, pass it to select , then — looping back over your descriptors — use FD_ISSET to see whether there is any activity on that file. Or, better yet, use poll or epoll for a much more efficient and scalable approach.

I recommend you try to re-structure your code into a more common pattern, in order to obviate your requirement.