Emacs buffer filtering

filter-buffer.el

(defun my-filter-current-buffer (program &rest args)
  (let* ((stdout-buffer (generate-new-buffer " stdout"))
         (ret (apply 'call-process-region (point-min) (point-max) program
                     nil (list stdout-buffer) nil args)))
    (when (zerop ret)
      (let ((output (with-current-buffer stdout-buffer
                      (buffer-string))))
        (erase-buffer)
        (insert output)))
    (kill-buffer stdout-buffer)))