how to use grep, sed, and awk to parse tags?

Question

I want to write a script that finds a open/close tag pair in a text file and prepends a fixed string to each line between the pair. I figure I use grep to find the tag line numbers and either awk or sed to place the tags, however, I'm not sure how exactly to do it.

Can someone help?

Answer 1

In awk:

START                  {noprefix="true"}
/<close tag regex>/    {noprefix="true"}
noprefix=="false"      {print "prefix", $0}
noprefix=="true"       {print $0}
/<open tag regex>/     {noprefix="false"}

Answer 2

It should be done by one of the traditionally syntax aware languages (yacc etc). Doing it with grep and the like may be okay for specific cases but regexp simply is not powerful enough to catch the subtleties of HTML

Answer 3

You should consider using yacc for it. It is NOT possible to do this with sed, awk or grep without a considerable amount of effort. As for learning yacc, it wouldn't take more time than it did for learning sed/awk/grep. And it will be really easy that way.