title: get 1 line with the same field in a file using shell script
body: <p>I have a file, with contents like:</p>
  
  <pre><code>onelab2.warsaw.rd.tp.pl    5
  onelab3.warsaw.rd.tp.pl    5
  lefthand.eecs.harvard.edu  7
  righthand.eecs.harvard.edu 7
  planetlab2.netlab.uky.edu  8
  planet1.scs.cs.nyu.edu     9
  planetx.scs.cs.nyu.edu     9
  </code></pre>
  
  <p>so for each line, there is a number I want the 1st line for each number so for
  the content above, I want to get:</p>
  
  <pre><code>onelab2.warsaw.rd.tp.pl    5
  lefthand.eecs.harvard.edu  7
  planetlab2.netlab.uky.edu  8
  planet1.scs.cs.nyu.edu     9
  </code></pre>
  
  <p>How can I achieve this? I hope for shell scripts, with awk, sed, etc.</p>