How do I perform a replace operation across more than one file?

The "tags" feature of Emacs includes the command tags-query-replace which performs a query-replace across all the files mentioned in the TAGS file. See `Tags:Tags Search' in the online manual.

In addition, Martin Boyer has written a package named global-replace which will perform a query-replace across all the files mentioned in the

• compilation* buffer (usually done after a `grep'), which is available via

anonymous FTP:

  /ireq-robot.hydro.qc.ca:pub/emacs/lisp/compile.el.Z
  /ireq-robot.hydro.qc.ca:pub/emacs/lisp/global-replace.el.Z
  /ireq-robot.hydro.qc.ca:pub/emacs/lisp/query.el.Z