recursively find/replace text in files

[bruce]

hi..

can't find my old solution to this!! need to know how to find/replace 'text'
in files in a directory tree. i'd like to be able to either do all files, or
all files of a specific extension

 replace "foo" with "bar" in all files in the dir tree
 replace "foo" with "bar" in all (*.cpp) files in the dir tree

thanks

-bruce
bedouglas at earthlink.net