Passphrase in babashka using /dev/urandom and /usr/share/dict/words

passphrase.clj

#!/usr/bin/env bb

(defn random-bytes
  [n]
  (with-open [in (io/input-stream (io/file "/dev/urandom"))]
    (let [buf (byte-array n)]
      (.read in buf)
      buf)))

(defn random-number
  [n]
  (let [factor (/ n (+ Integer/MAX_VALUE 1))]
    (-> (random-bytes 4)
        byte-array
        java.math.BigInteger.
        (as-> rand-int
              (+ (* factor rand-int) 0))
        int
        (as-> num
              (max num (- num))))))

(def word-list (->> "/usr/share/dict/words"
                    io/reader
                    line-seq
                    (filter #(> 10 (count %) 4))
                    (map str/lower-case)))

(def word-count (count word-list))

(defn passphrase!
  []
  (->> (fn [] (nth word-list (random-number word-count)))
       (repeatedly 5)
       (str/join " ")))

(println (passphrase!))

Updated to use a single filter expression for the word length. Thanks @kthu.

Don't bind the read operation of the input stream in read-bytes to the _ symbol. Simply evaluate this side-effecting thing inside the let-expression's body.