Emacs Lisp: How to Write a Command

• A command is a function that emacs user can call by execute-extended-command 【Alt+x】.
• To make a function a command, add (interactive) right after the doc string. [see Emacs Lisp: Interactive Form]
• When a function is also a command, we say that the function is available for interactive use.

Evaluate the following code. Then, you can call it by execute-extended-command 【Alt+x】

(defun yay ()
  "Insert YES at cursor position."
  (interactive)
  (insert "YES"))

Defining Commands (ELISP Manual)

Command Template

Here is a function definition template that majority of elisp commands follow:

(defun my-command ()
  "One sentence summary of what this command do. Less than 70 chars, try.

More details here.
Be sure to document the parameters.
Be sure to mention the return value, if any.

Lines here should not be indented."
  (interactive)
  (let (var1 var2 etc)
    ;; do something here
    ;; last expression is returned
    ))