title: awk/grep certain parts of a specific column
body: <p>I have a question that I am at a loss to solve.
  I have 3 column tab-separated data, such as:</p>
  
  <pre><code>abs nmod+n+n-commitment-n   349.200023
  abs nmod+n+n-a-commitment-n 333.306429
  abs into+ns-j+vn-pass-rb-divide-v   295.57316
  abs nmod+n+ns-commitment-n  182.085018
  abs nmod+n+n-pledge-n   149.927391
  abs nmod+n+ns-reagent-n 142.347358
  </code></pre>
  
  <p>I need to isolate the last two "elements" of the third column, in which my desired result would be a 4-column output that only contains those elements that end with "-n".</p>
  
  <p>such as: </p>
  
  <pre><code>abs nmod+n+n   commitment-n   349.200023
  abs nmod+n+n-a   commitment-n 333.306429
  abs nmod+n+ns   commitment-n  182.085018
  abs nmod+n+n   pledge-n   149.927391
  abs nmod+n+ns   reagent-n 142.347358
  </code></pre>
  
  <p>In this case, is there an <code>awk</code>, <code>grep</code> anything that can help? The files are approx. 500 MB, so they are not huge, but not small either.
  Thanks for any insight.</p>