title: Delete every other row in CSV file using AWK or grep
body: <p>I have a file like this:</p>
  
  <pre><code>1000_Tv178.tif,34.88552709  
  1000_Tv178.tif,  
  1000_Tv178.tif,34.66987165  
  1000_Tv178.tif,  
  1001_Tv180.tif,65.51335742  
  1001_Tv180.tif,  
  1002_Tv184.tif,33.83784863  
  1002_Tv184.tif,  
  1002_Tv184.tif,22.82542442  
  1002_Tv184.tif,  
  </code></pre>
  
  <p>How can I make it like this using a simple Bash command? :</p>
  
  <pre><code>1000_Tv178.tif,34.88552709    
  1000_Tv178.tif,34.66987165    
  1001_Tv180.tif,65.51335742  
  1002_Tv184.tif,33.83784863   
  1002_Tv184.tif,22.82542442
  </code></pre>
  
  <p>Im other words, I need to delete every other row, starting with the second.</p>
  
  <p>Thanks!  </p>