title: What does this operator do?
body: <p>I am writing a Linux driver for my chinese arduino. At one moment I need to change the baud rate. I looked for examples and found that listing:</p>
  
  <pre><code>Listing 2 - Setting the baud rate.
  
  struct termios options;
  
  /*
   * Get the current options for the port...
   */
  
  tcgetattr(fd, &amp;options);
  
  /*
   * Set the baud rates to 19200...
   */
  
  cfsetispeed(&amp;options, B19200);
  cfsetospeed(&amp;options, B19200);
  
  /*
   * Enable the receiver and set local mode...
   */
  
  options.c_cflag |= (CLOCAL | CREAD);
  
  /*
   * Set the new options for the port...
   */
  
  tcsetattr(fd, TCSANOW, &amp;options);
  </code></pre>
  
  <p>The next to last line of code has the <code>|=</code> operator. What does it do? I've never seen it before. </p>