#!/usr/bin/sbcl --script

(defun stream-to-lines (stream)
  (let ((line (read-line stream nil)))
    (and line
         (cons line (stream-to-lines stream)))))

(defun print-stream-reversed-order (stream &key (printer 'write-line))
  (mapcar printer (reverse (stream-to-lines stream))))

(defun tac (filepath)
  (let ((stream (or (and filepath (open filepath))
                    *standard-input*)))
    (print-stream-reversed-order stream)
    (close stream)))

(tac (cadr *posix-argv*))