title: C - subtracting a string from another
body: <p>Using <code>ftw()</code> function, I have a list of paths I want to write on a file. 
  I need only paths starting from a specified folder, like: </p>
  
  <pre><code>source folder: /Users/me
  subfolder1:    /Users/me/school
  subfolder2:    /Users/me/school/english
  
  result I need: /school  
                 /school/english
  </code></pre>
  
  <p>Is there a way to "subtract" one string from another, in the way i explained above? I know there is <code>strtok()</code>function, but i don't know if it works with more than one char at a time.</p>
  
  <p>Thanks.</p>