title: Getting unique values from column in a csv file
body: <p>I have the following input:</p>
  
  <pre><code>no,zadrar,MENTOR,rossana@xt.com,AGRATE
  no,mittalsu,MENTOR,rossana@xt.com,GREATER NOIDA
  no,abousamr,CADENCE,selim@xt.com,CROLLES
  no,lokinsks,MENTOR,sergey@xt.com,CROLLES
  no,billys,MENTOR,billy@xt.com,CROLLES
  no,basiles1,CADENCE,stephane@xt.com,CASTELLETTO
  no,cesaris1,CADENCE,stephane@xt.com,CROLLES
  </code></pre>
  
  <p>I want to get only the lines where column 4 is unique:</p>
  
  <pre><code>no,abousamr,CADENCE,selim@xt.com,CROLLES
  no,lokinsks,MENTOR,sergey@xt.com,CROLLES
  no,billys,MENTOR,billy@xt.com,CROLLES
  </code></pre>
  
  <p>I tried with:</p>
  
  <pre><code>awk -F"," '{print $4}' $vendor.csv | sort | uniq -u
  </code></pre>
  
  <p>But I get:</p>
  
  <pre><code>    selim@xt.com
      sergey@xt.com
      billy@xt.com
  </code></pre>