title: How to return the line number of the first occurrence of a text in a file in linux
body: <p>How to return the line number of the first occurrence of a text in a file in linux? For instance, a file as follows.</p>
  
  <pre><code>12:04:56 xxxx
  12:06:23 xxxx
  12:09:11 xxxx
  12:09:13 xxxx
  12:10:12 xxxx
  </code></pre>
  
  <p>Can anyone provide a line command which returns 3 if the desire text is "12:09:"?</p>