sed

[michael <cs@networkingnewsletter.org.uk>]

I've been struggling to get this to work but I think 'sed' should be
able to do it if I could just get some help with the correct
incantation...


given a file with many strings, include many of the form
  <a href="some url or other">www</a>

I wish each to be transformed to
  <a href="some url or other">some url or other</a>

ie so literal 'www' is replaced with the actual URL for each
occurance... 

any ideas? ta, M