Question

Given the following sentence:

This is one two three.

When I move the cursor to the space between one and two, I would like to replace two with XXX.
I know there is a way in vi so that I can mark two as the modified string so that when I finish entering the new string and the new string replaces the two in-place.

// Update-1 //

The corresponding command in vi is ‘cw’

Answer 1

I would probably just use M-d SPC X X X (if the SPC is necessary depends on wether the cursor is placed directly after “one” or before “two”) or M-f M-DEL X X X, but maybe that’s not what you’re looking for.

Ok, you didn’t answer my comment, and didn’t vote up an answer, so I guessed what you might like and here is a little hack:

(defun change-word (n)
  (interactive "p")
  (lexical-let ((old-window-configuration (current-window-configuration)))
    (clone-indirect-buffer "*edit-word*" t)
    (narrow-to-region (point) (save-excursion
                                (forward-word n)
                                (point)))
    (overwrite-mode 1)
    (local-set-key (kbd "C-c C-c")
                   (lambda ()
                     (interactive)
                     (widen)
                     (let ((end-of-edit (point)))
                       (kill-buffer)
                       (set-window-configuration old-window-configuration)
                       (goto-char end-of-edit))))))

Invoke M-x change-word (or bind it to a key you like), edit the word, and type C-c C-c when you’re done. If you want to edit the next n words, give it a prefix argument (e.g. M-3 M-x change-word to change the next three words). It’s not exactly the same — You’ll edit in another buffer — but it comes close. Try and see if you like it. It is not a very elaborate solution. Maybe the best, and most emacs-style approach, would be to have something akin to isearch-mode, that highlights the changed region and so on. Note that you’ll have to (require 'cl) because of lexical-let.

Another possibility would be something like this:

(defun change-word ()
  (interactive)
  (dotimes (i (- (save-excursion (end-of-thing 'word)) (point)))
    (insert (read-char))
    (delete-char 1)))

But this example is just a very crude hack — You won’t even be able to navigate while editing your word. Maybe one could write something modifying the command-loop behavior, but I didn’t look into that.

I don’t know about any built-in functionality that does exactly what you seem to want, but of course there are Viper and other Vi emulation modes built in.