How to detect the key binding for a function in elisp?

Question

How would I go about getting the key binding for a function in elisp?

I'd like to know which key is used to quit. e.g. keyboard-quit.

I tried using the function used by help functionality but it's not working.

(require 'help-fns)
(message "%S" (help-fns--key-bindings (quote keyboard-quit)))

However I get the error Symbol’s value as variable is void: keyboard-quit

Answer 1

Try this:

(defun foo (function &optional descriptionp)
  (unless (commandp function) (error "Not a command: %s" function))
  (let* ((key   (car (where-is-internal
                      (or (command-remapping function) function)
                      overriding-local-map nil nil)))
         (desc  (and descriptionp  (key-description key))))
    (or desc  key)))

(foo 'keyboard-quit)   ; [7]
(foo 'keyboard-quit t) ; "C-g"

Function help-fns--key-bindings is intended to be used in a particular context, which is not available or relevant here.

Answer 2

You can use substitute-command-keys, e.g.,

(substitute-command-keys "\\[keyboard-quit]")
;; => "C-g"

though if there are multiple key bindings, it returns only one of them (the "first" one), for example,

(substitute-command-keys "\\[kmacro-start-macro]")
;; => "C-x ("

see also it's docstring and (elisp) Keys in Documentation.