Emacs shell command on buffer

This works for me:

(defun shell-command-on-buffer (command)
  (interactive "sShell command on buffer: ")
  (shell-command-on-region (point-min) (point-max) command t))

This one has the advantage of using the "shell command" minibuffer history instead of the general minibuffer history.

(defun shell-command-on-buffer ()
  (interactive)
  (shell-command-on-region (point-min) (point-max) (read-shell-command "Shell command on buffer: ") t))