I have installed the matlab-mode-20160902.459 package from MELPA and whenever I open an m file (i.e., a file with the file extension .m which is the file extension of most MATLAB/GNU Octave scripts) I get an error message shown in the below screenshot:

enter image description here

Here is my present ~/.emacs file. As you can see on line 129 I have added the line:

(add-to-list 'auto-mode-alist '("\\.m$" . matlab-mode))

to hopefully autoload matlab-mode whenever I open an m file. I really have no idea how to fix this error as I haven't pressed C-x when I opened this file... If relevant I opened my m files using the Emacs directory browser shown in the screenshot.

Is it perhaps that this ~/.emacs line that sets .m files to be handled by matlab-mode conflicts with the default handling of .m files as Objective C files? Regardless of the cause a solution would be wonderful. I don't ever code in objective C (I am a loyal Linux user with no interest in iOS or macOS development), but I do code in GNU Octave / MATLAB, so setting m files as being associated with matlab-mode would be ideal.


I have tried using octave-mod instead by adding:

(setq auto-mode-alist
      (cons '("\\.m$" . octave-mode) auto-mode-alist))
(add-hook 'octave-mode-hook
          (lambda ()
            (abbrev-mode 1)
            (auto-fill-mode 1)
            (if (eq window-system 'x)
                (font-lock-mode 1))))

to my ~/.emacs file (in accordance with this guide). That gave the same error when opening an ~/.emacs file (and yes I did remove the matlab-mode line before I added these lines to make it a fair test of whether it works).

I have seen this question at StackOverflow but neither upvoted answer (which presently are this and this) worked for me: they both returned the same error whenever I opened an m file and neither caused syntax-highlighting of the m file to occur.

The backtrace generated by going to Options→Enter Debugger on Error was, when I opened the m file /home/fusion809/GitHub/mine/scripts/GNU_Octave/first.m:

Debugger entered--Lisp error: (file-error "Cannot open load file" "No such file or directory" "octave-mode")
  set-auto-mode-0(octave-mode nil)
  after-find-file(nil t)
  find-file-noselect-1(#<buffer first.m> "~/GitHub/mine/scripts/GNU_Octave/first.m" nil nil "~/GitHub/mine/scripts/GNU_Octave/first.m" (21370145 2052))
  find-file-noselect("/home/fusion809/GitHub/mine/scripts/GNU_Octave/first.m" nil nil nil)
  dired-mouse-find-file-other-window((mouse-2 (#<window 3 on GNU_Octave> 419 (546 . 123) 39532480 nil 419 (60 . 6) nil (6 . 15) (9 . 18))))
  funcall-interactively(dired-mouse-find-file-other-window (mouse-2 (#<window 3 on GNU_Octave> 419 (546 . 123) 39532480 nil 419 (60 . 6) nil (6 . 15) (9 . 18))))
  call-interactively(dired-mouse-find-file-other-window nil nil)

With MATLAB mode (instead of Octave mode as in the last backtrace) I get the backtrace http://paste2.org/wDE8VcbV (too long to paste here).

  • Please, activate Options->Enter Debugger On Error and paste the backtrace here when you get it on the file mode specification error.
    – Tobias
    Commented Dec 9, 2016 at 16:44
  • Done, refer to the last paragraph of the question. I thought octave-mode came pre-installed with Emacs. I have Emacs 25.1.90 (the latest experimental release). I searched ELPA for the package octave-mode but I couldn't find it...
    – Josh Pinto
    Commented Dec 9, 2016 at 16:50
  • That's an easy one. You do not have octave-mode installed. Install it if you want to use it.
    – Tobias
    Commented Dec 9, 2016 at 16:54
  • Didn't you read my last comment? I don't know how to install it so it isn't so easy. I've searched MELPA for it. I've also got other package archives enabled (see github.com/fusion809/emacs/blob/master/.emacs for details) and still I can't find it in the package list generated by M-x package-list.
    – Josh Pinto
    Commented Dec 9, 2016 at 16:57
  • Should be in lisp/progmodes that comes with emacs. Hm.
    – Tobias
    Commented Dec 9, 2016 at 16:59

1 Answer 1


This part of your config is causing the problem. You should use something like cua-mode instead of binding keys like C-c and C-x, which conflict with commonly used prefixes in emacs. cua-mode should make some of key combinations you use work as expected, and give you a way to use proper keybindings that begin with C-c and C-x.


  • Wrong question. This question isn't about my keybindings it's about MATLAB/Octave mode!
    – Josh Pinto
    Commented Dec 9, 2016 at 16:51
  • @BrentonHorne Note, that DoMiNeLa10 is right. You can try to comment out the lines (global-set-key (kbd "C-c") 'kill-ring-save) and (global-set-key (kbd "C-x") 'kill-region) in your config and restart emacs. You will see that the file mode specification error goes away.
    – Tobias
    Commented Dec 9, 2016 at 17:03
  • I'll be ****ed, it worked for MATLAB. But not Octave. Octave is giving: File error: Cannot open load file, No such file or directory, octave-mode. This question is about MATLAB, should I accept his answer and create a new question specific to Octave mode?
    – Josh Pinto
    Commented Dec 9, 2016 at 17:06
  • @BrentonHorne This is not so much about octave-mode but more about something wired going on with your installation or your setup of load-path. I've invited you to a discussion at chat.stackexchange.com/rooms/49851/…. Please, join now. I do not have too much time.
    – Tobias
    Commented Dec 9, 2016 at 17:11

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