title: Cut the first and the last part of a string in bash
body: <p>I have a string having this formats:</p>
  
  <pre><code>aa_bb_cc_dd
  aa_bb_cc_dd_ee_ff
  </code></pre>
  
  <p>I want to obtain:</p>
  
  <pre><code>bb_cc
  bb_cc_dd_ee
  </code></pre>
  
  <p>I've tried 'cut', but I didn't manage to obtain what I wanted.</p>