select()

Reference:

1. man7.org > Linux > man-pages: select()
2. 幻滅名為不動： linux下select和poll的用法

int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);

1. nfds: is the highest-numbered file descriptor, plus 1.
2. readfds:
3. writefds:
4. exceptfds:
5. timeout: