Custom command like execute-extended-command

Question

I want to implement a custom M-x (execute-extended-command). This time real skeleton-coding (crying)

(defun gbq-extended-command (inst) 
  (interactive "sgbq-X ")
  (cond ((equal inst "eob") (end-of-buffer)))
  ;; BODY of function
  )

in this function, I want completion instruction. for example, if call the function, like M-x, when I type eo, Completion from eo to eob. but I have no idea how.

Answer 1

Have you looked at the definition of execute-extended-command for inspiration (in simple.el, reachable via the link in C-h o execute-extended-command)?

In any case, to prompt the user in the minibuffer with completion, you want to use the completing-read function (about which you can read in the Elisp manual).