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Tools for working with command line arguments.

Stable Releases and Dependency Information

Latest stable release: 0.4.2

clj/deps.edn dependency information: clojure clj -Sdeps '{:deps {org.clojure/tools.cli {:mvn/version "0.4.2"}}}'

Leiningen dependency information: clojure [org.clojure/tools.cli "0.4.2"] Maven dependency information: xml <dependency> <groupId>org.clojure</groupId> <artifactId>tools.cli</artifactId> <version>0.4.2</version> </dependency> The 0.4.x series of tools.cli supports use with clj/deps.edn and brings the legacy API to ClojureScript by switching to .cljc files. This means it requires Clojure(Script) 1.8 or later.

The 0.3.x series of tools.cli features a new flexible API, better adherence to GNU option parsing conventions, and ClojureScript support.

The function has been superseded by, and should not be used in new programs.

The previous function will remain for the foreseeable future. It has also been adapted to use the new tokenizer, so upgrading is still worthwhile even if you are not ready to migrate to parse-opts.

Quick Start

(ns my.program
  (:require [ :refer [parse-opts]])

(def cli-options
  ;; An option with a required argument
  [["-p" "--port PORT" "Port number"
    :default 80
    :parse-fn #(Integer/parseInt %)
    :validate [#(< 0 % 0x10000) "Must be a number between 0 and 65536"]]
   ;; A non-idempotent option (:default is applied first)
   ["-v" nil "Verbosity level"
    :id :verbosity
    :default 0
    :update-fn inc] ; Prior to 0.4.1, you would have to use:
                   ;; :assoc-fn (fn [m k _] (update-in m [k] inc))
   ;; A boolean option defaulting to nil
   ["-h" "--help"]])

(defn -main [& args]
  (parse-opts args cli-options))

Execute the command line:

my-program -vvvp8080 foo --help --invalid-opt

to produce the map:

{:options   {:port 8080
             :verbosity 3
             :help true}

 :arguments ["foo"]

 :summary   "  -p, --port PORT  80  Port number
               -v                   Verbosity level
               -h, --help"

 :errors    ["Unknown option: \"--invalid-opt\""]}

Note that exceptions are not thrown on parse errors, so errors must be handled explicitly after checking the :errors entry for a truthy value.

Please see the example program for a more detailed example and refer to the docstring of parse-opts for comprehensive documentation:

New Features in 0.3.x

Better Option Tokenization

In accordance with the GNU Program Argument Syntax Conventions, two features have been added to the options tokenizer:

For instance, -abc is equivalent to -a -b -c. If the -b option requires an argument, the same -abc is interpreted as -a -b "c".

--long-opt=ARG is equivalent to --long-opt "ARG".

If the argument is omitted, it is interpreted as the empty string. e.g. --long-opt= is equivalent to --long-opt ""

In-order Processing for Subcommands

Large programs are often divided into subcommands with their own sets of options. To aid in designing such programs, accepts an :in-order option that directs it to stop processing arguments at the first unrecognized token.

For instance, the git program has a set of top-level options that are unrecognized by subcommands and vice-versa:

git --git-dir=/other/proj/.git log --oneline --graph

By default, interprets this command line as:

options:   [[--git-dir /other/proj/.git]
arguments: [log]

When :in-order is true however, the arguments are interpreted as:

options:   [[--git-dir /other/proj/.git]]
arguments: [log --oneline --graph]

Note that the options to log are not parsed, but remain in the unprocessed arguments vector. These options could be handled by another call to parse-opts from within the function that handles the log subcommand.

Options Summary

parse-opts returns a minimal options summary string:

  -p, --port NUMBER  8080       Required option with default
      --host HOST    localhost  Short and long options may be omitted
  -d, --detach                  Boolean option
  -h, --help

This may be inserted into a larger usage summary, but it is up to the caller.

If the default formatting of the summary is unsatisfactory, a :summary-fn may be supplied to parse-opts. This function will be passed the sequence of compiled option specification maps and is expected to return an options summary.

The default summary function is public and may be useful within your own :summary-fn for generating the default summary.

Option Argument Validation

There is a new option entry :validate, which takes a tuple of [validation-fn validation-msg]. The validation-fn receives an option's argument after being parsed by :parse-fn if it exists.

["-p" "--port PORT" "A port number"
 :parse-fn #(Integer/parseInt %)
 :validate [#(< 0 % 0x10000) "Must be a number between 0 and 65536"]]

If the validation-fn returns a falsey value, the validation-msg is added to the errors vector.

Error Handling and Return Values

Instead of throwing errors, parse-opts collects error messages into a vector and returns them to the caller. Unknown options, missing required arguments, validation errors, and exceptions thrown during :parse-fn are all added to the errors vector.

Correspondingly, parse-opts returns the following map of values:

{:options     A map of default options merged with parsed values from the command line
 :arguments   A vector of unprocessed arguments
 :summary     An options summary string
 :errors      A vector of error messages, or nil if no errors}

During development, parse-opts asserts the uniqueness of option :id, :short-opt, and :long-opt values and throws an error on failure.

ClojureScript Support

As of 0.4.x, the namespace is for both Clojure and ClojureScript programs. The entire API, including the legacy (pre-0.3.x) functions, is now available in both Clojure and ClojureScript.

For the 0.3.x releases, the ClojureScript namespace was and only parse-opts and summarize were available.

Example Usage

(ns cli-example.core
  (:require [cli-example.server :as server]
            [clojure.string :as string]
            [ :refer [parse-opts]])
  (:import ( InetAddress))

(def cli-options
  [;; First three strings describe a short-option, long-option with optional
   ;; example argument description, and a description. All three are optional
   ;; and positional.
   ["-p" "--port PORT" "Port number"
    :default 80
    :parse-fn #(Integer/parseInt %)
    :validate [#(< 0 % 0x10000) "Must be a number between 0 and 65536"]]
   ["-H" "--hostname HOST" "Remote host"
    :default (InetAddress/getByName "localhost")
    ;; Specify a string to output in the default column in the options summary
    ;; if the default value's string representation is very ugly
    :default-desc "localhost"
    :parse-fn #(InetAddress/getByName %)]
   ;; If no required argument description is given, the option is assumed to
   ;; be a boolean option defaulting to nil
   [nil "--detach" "Detach from controlling process"]
   ["-v" nil "Verbosity level; may be specified multiple times to increase value"
    ;; If no long-option is specified, an option :id must be given
    :id :verbosity
    :default 0
    ;; Use :update-fn to create non-idempotent options (:default is applied first)
    :update-fn inc]
   ;; A boolean option that can explicitly be set to false
   ["-d" "--[no-]daemon" "Daemonize the process" :default true]
   ["-h" "--help"]])

;; The :default values are applied first to options. Sometimes you might want
;; to apply default values after parsing is complete, or specifically to
;; compute a default value based on other option values in the map. For those
;; situations, you can use :default-fn to specify a function that is called
;; for any options that do not have a value after parsing is complete, and
;; which is passed the complete, parsed option map as it's single argument.
;; :default-fn (constantly 42) is effectively the same as :default 42 unless
;; you have a non-idempotent option (with :update-fn or :assoc-fn) -- in which
;; case any :default value is used as the initial option value rather than nil,
;; and :default-fn will be called to compute the final option value if none was
;; given on the command-line (thus, :default-fn can override :default)

(defn usage [options-summary]
  (->> ["This is my program. There are many like it, but this one is mine."
        "Usage: program-name [options] action"
        "  start    Start a new server"
        "  stop     Stop an existing server"
        "  status   Print a server's status"
        "Please refer to the manual page for more information."]
       (string/join \newline)))

(defn error-msg [errors]
  (str "The following errors occurred while parsing your command:\n\n"
       (string/join \newline errors)))

(defn validate-args
  "Validate command line arguments. Either return a map indicating the program
  should exit (with a error message, and optional ok status), or a map
  indicating the action the program should take and the options provided."
  (let [{:keys [options arguments errors summary]} (parse-opts args cli-options)]
      (:help options) ; help => exit OK with usage summary
      {:exit-message (usage summary) :ok? true}
      errors ; errors => exit with description of errors
      {:exit-message (error-msg errors)}
      ;; custom validation on arguments
      (and (= 1 (count arguments))
           (#{"start" "stop" "status"} (first arguments)))
      {:action (first arguments) :options options}
      :else ; failed custom validation => exit with usage summary
      {:exit-message (usage summary)})))

(defn exit [status msg]
  (println msg)
  (System/exit status))

(defn -main [& args]
  (let [{:keys [action options exit-message ok?]} (validate-args args)]
    (if exit-message
      (exit (if ok? 0 1) exit-message)
      (case action
        "start"  (server/start! options)
        "stop"   (server/stop! options)
        "status" (server/status! options)))))

Developer Information

Change Log


Copyright (c) Rich Hickey and contributors. All rights reserved.

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You must not remove this notice, or any other, from this software.