title: Update text in place for Mac OS command line app
body: <p>I'm writing a simple mac os (10.11) command line app in Swift to download a file from a valid remote URL and I'd like to show the % of file downloaded in place on the console. </p>
  
  <p>It would start with:</p>
  
  <pre><code>0% of 10Mb file downloaded
  </code></pre>
  
  <p>Then when I have some percentage of the file downloaded, the above line would get replaced with:</p>
  
  <pre><code>18% of 10Mb file downloaded
  </code></pre>
  
  <p>Finally, when it finishes, the string gets replaced in line with:</p>
  
  <pre><code>100% of 10Mb file downloaded
  </code></pre>
  
  <p><code>print(..)</code> will keep append to existing text - is there another function that will do what I need?</p>