title: Repeat-replace fields in single lines within text files
body: <p>I'm trying to batch replace a delimited field in every line of many text files (actually *.dlf) in the following way:</p>
  
  <p>xxx|xxx|a|xxx|DD|..</p>
  
  <p>with </p>
  
  <p>xxx|xxx|a|xxx|a|..., etc.</p>
  
  <p>Is there a syntax in cygwin or other DOS shell that I can used to do this, or even an app which will serve?  Processing indirectly with Excel and Word is tiresome.</p>