title: What does the FD_CLOEXEC fcntl() flag do?
body: <p>Like so:</p>
  
  <pre><code>if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) {
  ...
  </code></pre>
  
  <p>Though I've read <code>man fcntl</code>, I can't figure out what it does.</p>