title: How to set the timer in shell
body: <p>Can we set the timer in shell script?
  means if I set the timer for 20 secs my shell scripts should be execute like this :</p>
  
  <pre><code>20..19..18..17..
  </code></pre>
  
  <p>after completing the I should get the result. Is it possible ? Please assist me.</p>