title: How to add column indices in bash
body: <p>I have a text file with a number of rows and columns like this:</p>
  
  <pre><code>a b c d ...  
  e f g h ...  
  i j k l ...  
  ...  
  </code></pre>
  
  <p>I want to add column indices for each entry with the output look like this</p>
  
  <pre><code>1:a 2:b 3:c 4:d ...  
  1:e 2:f 3:g 4:h ...  
  1:i 2:j 3:k 4:l ...  
  ... 
  </code></pre>
  
  <p>I am wondering if there is a simple way to realize this in bash. Thanks!</p>