Idiomatic clojure to parse command line switches and args from string

Question

I'd like to parse a command line string, and group any command switches with their subsequent arguments. So, for example:

(parse "git branch -d f1 f2 -a -m message") => 
[["-d" "f1" "f2"]["-a"]["-m" "message"]]

I ignore args not immediately following a switch.

The code I wrote to do this is as follows:

(defn switch? [s] (re-find #"\-+" s))
(defn tokenify [s] (clojure.string/split s #" "))
(defn parse [cmd-str]
  (loop [lst (tokenify cmd-str), acc [], _acc []]
    (let [fs (first lst), rs (rest lst), new? (empty? _acc)]
      (cond (empty? lst) (if new? acc (conj acc _acc))
            (switch? fs) (if new?
                           (recur rs acc (conj _acc fs))
                           (recur rs (conj acc _acc) (conj [] fs)))
            :else (if new?
                    (recur rs acc _acc)
                    (recur rs acc (conj _acc fs)))))))

That works, but it's pretty low level and horrible. Is there a simple way using reduce or partition or group-by that would make the same functionality a lot cleaner and more idiomatic?

Use tools.cli and then manipulate the parameters as data. github.com/clojure/tools.cli — noahlz
– noahlz, Commented May 27, 2015 at 19:19

Mars · Accepted Answer · 2015-05-27 23:31:44Z

here's a basic outline of using clojure.tools.cli

(def command-line-spec
  [["-m" "--mode 0|1" "description of option that takes 1 or 0"
    :parse-fn #(case (s/lower-case %)
                 ("1" "true" "create") :one
                 ("0" "false" "destroy") :zero
                 :invalid)
    :default :one
    :validate [#{:one :zero} "Unsupported mode"]]
   ["-c" "--config type1|type2|..."
    :desc "config specifies what to do"
    :default :dostuff
    :parse-fn #(if (keyword? %)
                 %
                 (-> % s/lower-case keyword))
    :validate-fn #(contains? configurations %)]
    ["-n" "--name service Name"
     :default (getenv "NAME")]
   [nil "--min number"
    :default 7 :parse-fn #(Integer/parseInt %)]
   [nil "--max number"
    :default 7 :parse-fn #(Integer/parseInt %)]
   [nil "--public true|false" "true or false"
    :default false
    :parse-fn #(Boolean/parseBoolean %)]
   ["-h" "--help"]])

(defn -main [& args]
  (let [{:keys [options arguments errors summary]}
         (parse-opts args
                     command-line-spec)
 ... )

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