How to check if emacs shell buffer busy or not?

Question

If I start a long-running process in an emacs shell create by (shell), the shell will be busy for a while. How can I detect that programmatically (i.e., using elisp)?

I tried: get the process by (get-process "shell") and test (process-live-p proc), but it always return t.

Answer 1

(defun shell-process-running-child-p (process-name)
  (interactive)
  (if (process-running-child-p process-name)
      (print t)
    (print nil)))