title: How to change date format ONLY in first column in .csv file using sed in shell
body: <p>Hello I am trying to change the date format only in first column of .csv file 
  from:  </p>
  
  <blockquote>
    <p>2015-03-31|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    2015-03-31|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31    </p>
  </blockquote>
  
  <p>TO:</p>
  
  <blockquote>
    <p>03/31/2015|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.225|3.225|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31<br>
    03/31/2015|base|2015-03-31|100|0|3.475|3.475|0|0|0|2015-03-31 </p>
  </blockquote>
  
  <p>I have tried using sed :</p>
  
  <pre><code>sed 's/^\(....\-\)\(..\-\)(..|\)/\2\1\3/'
  </code></pre>
  
  <p>and</p>
  
  <pre><code>sed -re 's/^([0-9][0-9])\-([0-9][0-9])\-[0-9][0-9][0-9][0-9](.*)$/\2\/\1\/\3\4/'
  </code></pre>
  
  <p>but it's throwing an error.</p>