M-x call with optional arg; call from Elisp

[Emanuel Berg <embe8573@student.uu.se>]

Take a look at the below code, and you'll understand immediately what
I ask.

1. How can I call a function with M-x and provide an optional string
arg?

2. Why do I get 0 when I call from Elisp? (Is it the return code - $?
- and not the output?) I tried with eval and funcall as well:
same. How do I call from Elisp?

;;; word count
(defun words (&optional opts)
  "Count buffer words with wc OPTS, or wc -w if not OPTS is given."
  (interactive)
  (defvar count-cmd)
  (setq count-cmd (format "wc %s" (if (stringp opts) opts "-w")))
  (if mark-active
    (shell-command-on-region (region-beginning) (region-end) count-cmd)
    (shell-command-on-region (point-min) (point-max) count-cmd) ))
(words "-l") ; doesn't work (0) - can I call this with M-x and an arg?
(words)      ; same, but `M-x words' works

(defun count-buffer-wc-option (option)
  (interactive "s wc options: ")
  "Count buffer according to wc OPTION."
  (shell-command-on-region (point-min) (point-max)
                           (format "wc %s" option)) )
(count-buffer-wc-option "-l") ; same, but
                              ; `M-x count-... RET -l' works

-- 
Emanuel Berg - programmer (hire me! CV below)
computer projects: http://user.it.uu.se/~embe8573
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