Compare files in dired mode: Cannot operate on ‘.’ or ‘..’

Question

windows 10 (64 bit)

Emacs 26.1, Dired+

I need tool that can compare files by content with highlight different symbols.

Example:

As you can see I mark two files. Is it possible to compare this files in dired mode? Smt like press C-c and compare only mark files.

M-x dired-diff

Error:

dired-get-filename: Cannot operate on ‘.’ or ‘..’

To avoid this error I need to set cursor over file.

Is it possible Emacs ,by default, compare marks files? Without asking me about files.

Answer 1

That's not how dired-diff works - it does not operate on the marked files. Same thing for diredp-ediff.

These commands operate on the current-line's file and another file whose name you enter.

C-h f diredp-ediff tells you, about the file name you enter:

Try to guess a useful default value for FILE2, as follows:

• If the mark is active, use the file at mark.

• Else if the file at cursor is a autosave file or a backup file, use the corresponding base file.

• Else if there is any backup file for the file at point, use the newest backup file for it.

• Else use the file at point.

This will do more or less what you want:

(defun diredp-ediff-marked-files ()
  "..."
  (interactive)
  (let ((files  (dired-get-marked-files)))
    (unless (and (listp files)  (= 2 (length files)))
      (error "There are not (only) 2 marked files"))
    (ediff-files (car files) (cadr files))))