If you enable CUA selection mode:
M-x cua-selection-mode RET
or permanently in your init file:
(cua-selection-mode 1)
You can then use its advanced rectangle editing facilities.
(or if you’re a cua-mode user, then you don’t need to do that.)
- C-RET to mark a corner.
- Move point to opposite corner.
- M-r to do a regexp replace within the marked rectangle.
- C-RET to unmark/exit rectangle editing.
For documentation, look for the “CUA rectangle support” heading in the commentary in M-x find-library RET cua-base RET
If you don’t want to use the cua rectangle facilities for some reason (perhaps if you really need replace-string specifically), a custom function using apply-on-rectangle would be pretty simply to put together.
Edit: Actually, slightly more complex than I had expected, but most of the code is the interactive spec and the support for the ‘delimited’ prefix argument behaviour (both based on replace-string).
Edit 2: I decided this was worth doing in a more fully-featured manner:
The following provides C-xrM-% and C-xrC-M-%, which (hopefully) act the way you would expect.
(require 'rect)
(defun my-search-replace-in-rectangle
(start end search-pattern replacement search-function literal)
"Replace all instances of SEARCH-PATTERN (as found by SEARCH-FUNCTION)
with REPLACEMENT, in each line of the rectangle established by the START
and END buffer positions.
SEARCH-FUNCTION should take the same BOUND and NOERROR arguments as
`search-forward' and `re-search-forward'.
The LITERAL argument is passed to `replace-match' during replacement.
If `case-replace' is nil, do not alter case of replacement text."
(apply-on-rectangle
(lambda (start-col end-col search-function search-pattern replacement)
(move-to-column start-col)
(let ((bound (min (+ (point) (- end-col start-col))
(line-end-position)))
(fixedcase (not case-replace)))
(while (funcall search-function search-pattern bound t)
(replace-match replacement fixedcase literal))))
start end search-function search-pattern replacement))
(defun my-replace-regexp-rectangle-read-args (regexp-flag)
"Interactively read arguments for `my-replace-regexp-rectangle'
or `my-replace-string-rectangle' (depending upon REGEXP-FLAG)."
(let ((args (query-replace-read-args
(concat "Replace"
(if current-prefix-arg " word" "")
(if regexp-flag " regexp" " string"))
regexp-flag)))
(list (region-beginning) (region-end)
(nth 0 args) (nth 1 args) (nth 2 args))))
(defun my-replace-regexp-rectangle
(start end regexp to-string &optional delimited)
"Perform a regexp search and replace on each line of a rectangle
established by START and END (interactively, the marked region),
similar to `replace-regexp'.
Optional arg DELIMITED (prefix arg if interactive), if non-nil, means
replace only matches surrounded by word boundaries.
If `case-replace' is nil, do not alter case of replacement text."
(interactive (my-replace-regexp-rectangle-read-args t))
(when delimited
(setq regexp (concat "\\b" regexp "\\b")))
(my-search-replace-in-rectangle
start end regexp to-string 're-search-forward nil))
(defun my-replace-string-rectangle
(start end from-string to-string &optional delimited)
"Perform a string search and replace on each line of a rectangle
established by START and END (interactively, the marked region),
similar to `replace-string'.
Optional arg DELIMITED (prefix arg if interactive), if non-nil, means
replace only matches surrounded by word boundaries.
If `case-replace' is nil, do not alter case of replacement text."
(interactive (my-replace-regexp-rectangle-read-args nil))
(let ((search-function 'search-forward))
(when delimited
(setq search-function 're-search-forward
from-string (concat "\\b" (regexp-quote from-string) "\\b")))
(my-search-replace-in-rectangle
start end from-string to-string search-function t)))
(global-set-key (kbd "C-x r M-%") 'my-replace-string-rectangle)
(global-set-key (kbd "C-x r C-M-%") 'my-replace-regexp-rectangle)