Comparing text files on Emacs

diff()emacs

I have a couple of questions about comparing text files on Emacs

I have been playing with M-x compare-windows and I read in the documentation that, if I pass it a numeric argument, Emacs ignores whitespaces on the comparison, but how do I pass a numeric argument to this command? (e.g.. if I type M-x compare-windows and then I press space, it will try to autocomplete with a -)
Are there any other more powerful tools or plugins for Emacs (maybe third-party?) for comparing text files?

For example, on WinMerge for Windows, you can compare two documents side-by-side and the program automatically highlights the differences. On WinMerge I can also simultaneously scroll both windows, and it aligns regions with identical text on both windows for easy comparison. See a snapshot here.

Is there anything like this for Emacs?

Best Answer

To pass a numeric argument to a command, enter the argument first. For example, Escape 3 Left moves 3 characters left. So type ESC 3 ESC x compare-windows RET or M-3 M-x compare-windows RET.

The most frequently used commands to compare two files are those of ediff. You can invoke them from the “Tools > Compare (Ediff)” menu. There is a command called ediff-windows-linewise, though usually you would compare two buffers (ediff-buffers) or two files (ediff-files) or two revisions under a version control system (ediff-revision). Press n and p to navigate between diff regions; press ? to see more available commands.

Related Solutions

Vim – How to Compare Two Files

Open the side by side view:

Ctrl+w v

Change between them:

Ctrl+w h or l

Checkout the vimdiff command, part of the vim package, if you want a diff-like view:

vimdiff file1.txt file2.txt

Emacs Text Colorization – How to Guide

I think the piece you're missing is the interactive form. It's how Emacs distinguishes between a function designed to be called by other functions, and a function designed to be called directly by the user. See the Emacs Lisp Intro node

Now if you read the definition of ansi-color-apply-on-region, you'll see that it's not designed for interactive use. "ansi-color" is designed to filter comint output. However it's easy to make an interactive wrapper for it.

(defun ansi-color-apply-on-region-int (beg end)
  "interactive version of func"
  (interactive "r")
  (ansi-color-apply-on-region beg end))

The next bit is you want to turn on ansi colors for the .col extension. You can add a hook function to whatever major-mode you want use to edit those files. The function would be run whenever you turn on the major-mode, so you will have to add a check for the proper file suffix.

Alternatively you can hack a quick derived mode based on "fundamental" mode.

(define-derived-mode fundamental-ansi-mode fundamental-mode "fundamental ansi"
  "Fundamental mode that understands ansi colors."
  (require 'ansi-color)
  (ansi-color-apply-on-region (point-min) (point-max)))

and associate it with that extension.

(setq auto-mode-alist
      (cons '("\\.col\\'" . fundamental-ansi-mode) auto-mode-alist))

Best Answer

Related Solutions

Vim – How to Compare Two Files

Emacs Text Colorization – How to Guide

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