title: Does a file descriptor used with POSIX AIO need to be opened with `O_NONBLOCK` in `open()`?
body: <p>When using POSIX AIO with a file descriptor, did the file descriptor need to be opened with <code>O_NONBLOCK</code> in <code>open()</code>?</p>
  
  <p>In APUE, I don't find it explicitly say yes or no, but I don't find such a file descriptor is opened with <code>O_NONBLOCK</code> in <code>open()</code> in one example.</p>
  
  <p>Thank.</p>