linux poll

poll的作用

• it waits for one of a set of file descriptors to become ready to perform I/O. 也就是poll的作用是等待一组文件描述符变得可执行；
• 假若刚进行监测时不可执行怎么处理呢？会根据timeout参数阻塞；
  The timeout argument specifies the number of milliseconds that poll() should block waiting for a file descriptor to become ready.

总结

The call will block until either:

• a file descriptor becomes ready;
• the call is interrupted by a signal handler; or
• the timeout expires.

用户层使用

poll (struct pollfd *__fds, nfds_t __nfds, int __timeout)

• struct pollfd *__fds：是一个数组的指针，可以有多个struct pollfd;
• nfds:既然上面的指针是一个数组，那有多少个成员呢，通过该nfds指示；
• timeout：指示当描述符不可用时，应该等待多长；

流程