title: Get duplicate ids with bash
body: <p>I have a log file with format</p>
  <blockquote>
  <p>id operation</p>
  <p>id success message</p>
  </blockquote>
  <p>The second id is same as the first, but if only the the operation is successful. How can I get these two lines from the log to a new file?</p>