Tcl / regsub - changing a string and using interesting bits

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Tcl / regsub - changing a string and using interesting bits

Archive - Originally posted on "The Horse's Mouth" - 2007-10-27 07:05:28 - Graham Ellis
Regexp matches a string to a regular expression, and regsub goes one further in that it replaces the found string with something else, saving the transformed output into a new variable. But what if I want the output pattern to include part of the string that was matched? I can refer to the "interesting bits" using , , etc, if I wish.

Example:

# In Tcl, 

#       regub needle haystack newneedle saveithere

#

# Refer to matches in the newneedle via 

# Example - to surround dogs, cats and rabbits with !s

#

regsub -all (cat|dog|rabbit) "The cat and dog and budgie" \

  {!!} result

puts $result

Results:

earth-wind-and-fire:~/oct07/camb grahamellis$ tclsh rsd

The !cat! and !dog! and budgie

earth-wind-and-fire:~/oct07/camb grahamellis$