emacs lisp call function with prefix argument programmatically

Question

I want to call a function from some elisp code as if I had called it interactively with a prefix argument. Specifically, I want to call grep with a prefix.

The closest I've gotten to making it work is using execute-extended-command, but that still requires that I type in the command I want to call with a prefix...

;; calls command with a prefix, but I have to type the command to be called...
(global-set-key (kbd "C-c m g")
 (lambda () (interactive)
 (execute-extended-command t)))

The documentation says that execute-extended-command uses command-execute to execute the command read from the minibuffer, but I haven't been able to make it work:

;; doesn't call with prefix...
(global-set-key (kbd "C-c m g")
 (lambda () (interactive)
 (command-execute 'grep t [t] t)))

Is there any way to call a function with a prefix yet non-interactively?

Answer 1

If I'm understanding you right, you're trying to make a keybinding that will act like you typed C-u M-x grep <ENTER>. Try this:

(global-set-key (kbd "C-c m g")
 (lambda () (interactive)
 (setq current-prefix-arg '(4)) ; C-u
 (call-interactively 'grep)))

Although I would probably make a named function for this:

(defun grep-with-prefix-arg ()
 (interactive)
 (setq current-prefix-arg '(4)) ; C-u
 (call-interactively 'grep))
(global-set-key (kbd "C-c m g") 'grep-with-prefix-arg)

• Gilles 'SO- stop being evil': It doesn't matter in this particular case, but in general, I'd use (let ((current-prefix-arg '(4))) (call-interactively 'grep)) so that the behavior of subsequent functions called in the commands is not affected.
• eugene: @cjm why 4? C-u is 4?

Answer 2

Or you could just use a keyboard macro

(global-set-key (kbd "s-l") (kbd "C-u C-SPC"))

In this example, the key combination "s-l" (s ("super") is the "windows logo" key on a PC keyboard) will go up the mark ring, just like you if typed "C-u C-SPC".