title: Add an extra column after grep content
body: <p>I understand that grep can extract the specific content from a file line by line. 
  Just wondering how can add another column before or after each line as an index. 
  For example: </p>
  
  <pre><code>grep "aaa"  text.txt &gt; tmp.txt
  </code></pre>
  
  <p>In the tmp.txt file, we can see the content as follows, </p>
  
  <pre><code>aaawekjre
  qejrteraaa
  wrgeaaaere
  </code></pre>
  
  <p>However, I would like to add a specific index as an extra column. 
  Therefore, the tmp.txt might look like this:</p>
  
  <pre><code>John aaawekjre
  John qejrteraaa
  John wrgeaaaere
  </code></pre>