title: Replace column values in a CSV file with awk
body: <p>I have this file </p>
  
  <p>error.log</p>
  
  <blockquote>
    <p>[00:00:00.284],501,</p>
    
    <p>[00:00:00.417],5,5294100071980</p>
    
    <p>[00:00:02.463],501,</p>
    
    <p>[00:00:05.169],501,</p>
    
    <p>[00:00:05.529],501,</p>
    
    <p>[00:00:05.730],501,</p>
  </blockquote>
  
  <p>so, if the field $3 its empty i want to print "No value"</p>
  
  <p>Im trying this code</p>
  
  <pre><code>awk '{{FS=","} if($3=="") {print $1,$2,"No value"}}'
  </code></pre>
  
  <p>But it prints </p>
  
  <pre><code>&gt;[00:00:00.284] 501 No value
  &gt;[00:00:02.463] 501 No value
  &gt;[00:00:05.169] 501 No value
  &gt;[00:00:05.529] 501 No value
  &gt;[00:00:05.730] 501 No value
  &gt;[00:00:07.193] 501 No value
  &gt;[00:00:09.899] 501 No value
  &gt;[00:00:31.312] 501 No value
  </code></pre>