title: Add index column to CSV file
body: <p>I have a large Comma-Separated File (6GB) and would like to add an index column to it. I'm looking at Unix type solutions for efficiency. I'm using a Mac.</p>
  
  <p>I have this:</p>
  
  <pre><code>V1  V2  V3
  0.4625  0.9179  0.8384
  0.9324  0.2486  0.1114 
  0.6691  0.7813  0.6705
  0.1935  0.3303  0.4336
  </code></pre>
  
  <p>Would like to get this:</p>
  
  <pre><code>ID  V1  V2  V3
  1   0.4625  0.9179  0.8384
  2   0.9324  0.2486  0.1114
  3   0.6691  0.7813  0.6705
  4   0.1935  0.3303  0.4336
  </code></pre>