title: Check for number of files starting with some string
body: <p>I want to check in my SD card root for files starting with "thisfile" and return the number of files in an int or a string. </p>
  
  <p>For example i have 10 files on my SD card with the following names:</p>
  
  <pre><code>thisfile1.txt
  thisfile444.txt
  thisfileffvdfv.txt
  thisfilefdfvdfv.txt
  thisfile4fvdfv.txt
  thisfilefvdfvdf.txt
  thisfiledfvdfvdfv.txt
  thisfilefdvdfvdf.txt
  thisfilewedwed.txt
  thisfilewedwedfff.txt
  </code></pre>
  
  <p>For this example, I want my code to return 10 for this. </p>
  
  <p>Can somebody help ?</p>