title: How to convert CSV file in bash?
body: <p>I have a file, each line of which is a list of comma separated values. For example,</p>
  
  <pre>1, a, b, c, d, e
  2, x, y, z</pre>
  
  <p>Now I would like to convert it in <code>bash</code> as follows:</p>
  
  <pre>1 a
  1 b
  1 c
  1 d
  1 e
  2 x
  2 y
  2 z</pre>
  
  <p>How to do it with a <code>shell (bash)</code> script?</p>