Clojure function to tokenize shell commands.

shell.clj

;; Clojure translation of https://sourceforge.net/p/drjava/git_repo/ci/master/tree/drjava/src/edu/rice/cs/util/ArgumentTokenizer.java
;; Input:  "sh -c \"while sleep 1; do echo \\\"${RANDOM}\\\"; done\""
;; Output: ["sh", "-c", "while sleep 1; do echo \"${RANDOM}\"; done"]

(defn shell-tokenize!
  [^String command]
  (let [[escaped?
         current-arg
         args
         state] (loop [cmd         command
                       escaped?    false
                       state       :no-token
                       current-arg ""
                       args        []]
                  (if (or (nil? cmd)
                          (zero? (count cmd)))
                    [escaped? current-arg args state]
                    (let [char ^Character (first cmd)]
                      (if escaped?
                        (recur (rest cmd) false state (str current-arg char) args)
                        (case state
                          :single-quote (if (= char \')
                                          (recur (rest cmd) escaped? :normal current-arg args)
                                          (recur (rest cmd) escaped? state (str current-arg char) args))
                          :double-quote (case char
                                          \" (recur cmd escaped? :normal current-arg args)
                                          \\ (let [next (second cmd)]
                                               (if (or (= next \")
                                                       (= next \\))
                                                 (recur (drop 2 cmd) escaped? state (str current-arg next) args)
                                                 (recur (drop 2 cmd) escaped? state (str current-arg char next) args)))
                                          (recur (rest cmd) escaped? state (str current-arg char) args))
                          (:no-token :normal) (case char
                                                \\ (recur (rest cmd) true :normal current-arg args)
                                                \' (recur (rest cmd) escaped? :single-quote current-arg args)
                                                \" (recur (rest cmd) escaped? :double-quote current-arg args)
                                                (if-not (Character/isWhitespace char)
                                                  (recur (rest cmd) escaped? :normal (str current-arg char) args)
                                                  (if (= state :normal)
                                                    (recur (rest cmd) escaped? :no-token "" (conj args current-arg))
                                                    (recur (rest cmd) escaped? state current-arg args))))
                          (throw (IllegalStateException.
                                   (format "Invalid shell command: %s, unexpected token %s found." command state))))))))]
    (if escaped?
      (conj args (str current-arg \\))
      (if (not= state :no-token)
        (conj args current-arg)
        args))))