gistfile1.clj

#!/usr/bin/env clojure
; vim:ft=clojure

(defn fact [n]
  (loop [n n f 1]
    (if (= n 1)
      f
      (recur (dec n) (* f n)))))

(if (not= (count *command-line-args*) 1)
  (println "usage: fact.clj NUMBER")
  (let [n (Integer/parseInt (first *command-line-args*))]
    (println (fact n))))