elisp - Emacs custom command line argument

Question

From the documentation I can see I can access command line arguments (command-line-args). I'd like to add my own arguments but Emacs complains at start up that it doesn't recognize them.

E.g.

emacs -my_argument

I get:

command-line-1: Unknown option `-my_argument'

What's a proper way to define my custom arguments and provide information to my Emacs session? Is there a way to pop an argument from a command line?

Answer 1

Add something like this to your ~/.emacs, ~/.emacs.el, or ~/.emacs.d/init.el file:

(defun my-argument-fn (switch)
  (message "i was passed -my_argument"))

(add-to-list 'command-switch-alist '("-my_argument" . my-argument-fn))

Then you can execute emacs -my_argument and it should print i was passed -my_argument to the minibuffer. You can find more information in the GNU elisp reference.