comint-ctrl-m: handle ^M intelligently in subprocess output

[bobg]

Tired of seeing your shell buffers full of garbage like this?

0% done, 1:40 remaining...^M2% done, 1:38 remaining...^M4% done, 1:36 
remaining...^M6% done, 1:34 remaining...^M8% done, 1:32 remaining...^M10% done, 
1:30 remaining...^M12% done, 1:28 remaining...^M14% done, 1:26 
remaining...^M16% done, 1:24 remaining...^M18% done, 1:22 remaining...^M20% 
done, 1:20 remaining...^M22% done, 1:18 remaining...^M24% done, 1:16 
remaining...^M26% done, 1:14 remaining...^M28% done, 1:12 remaining...^M30% 
done, 1:10 remaining...^M32% done, 1:08 remaining...^M34% done, 1:06 
remaining...^M36% done, 1:04 remaining...^M38% done, 1:02 remaining...^M40% 
done, 1:00 remaining...^M42% done, 0:58 remaining...^M44% done, 0:56 
remaining...^M46% done, 0:54 remaining...^M48% done, 0:52 remaining...^M50% 
done, 0:50 remaining...^M52% done, 0:48 remaining...^M54% done, 0:46 
remaining...^M56% done, 0:44 remaining...^M58% done, 0:42 remaining...^M60% 
done, 0:40 remaining...^M62% done, 0:38 remaining...^M64% done, 0:36 
remaining...^M66% done, 0:34 remaining...^M68% done, 0:32 remaining...^M70% 
done, 0:30 remaining...^M72% done, 0:28 remaining...^M74% done, 0:26 
remaining...^M76% done, 0:24 remaining...^M78% done, 0:22 remaining...^M80% 
done, 0:20 remaining...^M82% done, 0:18 remaining...^M84% done, 0:16 
remaining...^M86% done, 0:14 remaining...^M88% done, 0:12 remaining...^M90% 
done, 0:10 remaining...^M92% done, 0:08 remaining...^M94% done, 0:06 
remaining...^M96% done, 0:04 remaining...^M98% done, 0:02 remaining...^M100% 
done, 0:00 remaining...

Just switch on comint-ctrl-m-mode and stop giving your xterm-using
friends a reason to feel superior.

You can

  (add-hook 'shell-mode-hook 'turn-on-comint-ctrl-m-mode)

in your .emacs if you like.

(Sorry I haven't packaged this up as a proper .el file with comments
and documentation and everything, but hey, it's tiny, and it's free.)

  (defun crlf-to-lf (str)
    (save-match-data
      (while (string-match "\r\n" str)
        (setq str (replace-match "\n" nil t str))))
    str)

  (defun comint-ctrl-m-magic (str)
    (setq str (crlf-to-lf str))
    (save-match-data
      (when (string-match ".*\r" str)
        (setq str (replace-match "" nil t str))
        (save-excursion
          (goto-char (point-max))
          (forward-line 0)
          (delete-region (point) (point-max)))))
    str)

  (defvar comint-ctrl-m-mode nil)
  (make-variable-buffer-local 'comint-ctrl-m-mode)

  (defun comint-ctrl-m-mode (&optional arg)
    (interactive "P")
    (setq comint-ctrl-m-mode
          (if (null arg)
              (not comint-ctrl-m-mode)
            (> (prefix-numeric-value arg) 0)))
    (funcall (if comint-ctrl-m-mode
                 'add-hook
               'remove-hook)
             'comint-preoutput-filter-functions
             'comint-ctrl-m-magic))

  (defun turn-on-comint-ctrl-m-mode () (comint-ctrl-m-mode 1))

  (if (not (assq 'comint-ctrl-m-mode minor-mode-alist))
      (setq minor-mode-alist
            (cons '(comint-ctrl-m-mode " ^M")
                  minor-mode-alist)))