title: awk linux take difference and add tab delimited columns file
body: <p>I have a tab delimited file (no header) and I'd like to take the difference of column 3 and 2, and then add them all together.</p>
  
  <p>Ie,</p>
  
  <pre><code>col1\tcol2\tcol3\tcol4
  hi\t10\t100\t0.4
  bye\t150\t400\t5.6
  </code></pre>
  
  <p>The result would be: (100-10)+(400-150)=340</p>
  
  <p>How would I do such operation one-line using awk?</p>
  
  <p>Thanks.</p>