title: How to print out status bar and percentage?
body: <p>To implement a status bar like below:</p>
  
  <pre><code>[==========                ]  45%
  [================          ]  60%
  [==========================] 100%
  </code></pre>
  
  <p>I want to this to be printed out to stdout, and keep refreshing it, not print to another line. How to do this?</p>