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Tools for working with command line arguments.

Stable Releases and Dependency Information

Latest stable release: 0.3.5

Leiningen dependency information:

[org.clojure/tools.cli "0.3.5"]

Maven dependency information:


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The function has been superseded by, and should not be used in new programs.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 forseeable 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
   ["-v" nil "Verbosity level"
    :id :verbosity
    :default 0
    :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:

  • Short options may be grouped together.

    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 option arguments may be specified with an equals sign.

    --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 falsy 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

The namespace is available for use in ClojureScript programs! Both parse-opts and summarize have been ported, and have complete feature parity with their Clojure counterparts.

ClojureScript Versions 0.0-2080 and above are supported, but earlier versions are likely to work as well.

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 assoc-fn to create non-idempotent options
    :assoc-fn (fn [m k _] (update-in m [k] inc))]
   ["-h" "--help"]])

(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

  • Release 0.3.5 on 2016-05-04
    • Fix summarize in cljs after renaming during TCLI-36 below TCLI-85.
  • Release 0.3.4 on 2016-05-01
    • Clarify use of summarize via expanded docstring and make both of the functions it calls public so it is easier to build your own :summary-fn. TCLI-36.
  • Release 0.3.3 on 2015-08-21
  • Add :missing to option specification to produce the given error message if the option is not provided (and has no default value). TCLI-12
  • Add :strict to parse-opts: If true, treats required option arguments that match other options as a parse error (missing required argument). TCLI-10
  • Release 0.3.2 on 2015-07-28
    • Add :no-defaults to parse-opts: Returns sequence of options that excludes defaulted ones. This helps support constructing options from multiple sources (command line, config file).
    • Add get-default-options: Returns sequence of options that have defaults specified.
    • Support multiple validations TCLI-9
    • Support in-order arguments TCLI-5: :in-order processes arguments up to the first unknown option; A warning is displayed when unknown options are encountered.
  • Release 0.3.1 on 2014-01-02
    • Apply patch for TCLI-8: Correct test that trivially always passes
    • Apply patch for TCLI-7: summarize throws when called with an empty sequence of options
  • Release 0.3.0 on 2013-12-15
  • Release 0.2.4 on 2013-08-06
    • Applying patch for TCLI-2 (support an assoc-fn option)
  • Release 0.2.3 on 2013-08-06
    • Add optional description string to prefix the returned banner
  • Release 0.2.2 on 2012-08-09
    • Applying patch for TCLI-1 (do not include keys when no value provided by :default)
  • Release 0.2.1 on 2011-11-03
    • Removing the :required option. Hangover from when -h and --help were implemented by default, causes problems if you want help and dont provide a :required argument.
  • Release 0.2.0 on 2011-10-31
    • Remove calls to System/exit
    • Remove built-in help options
  • Release 0.1.0
    • Initial import of Clargon codebase


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

The use and distribution terms for this software are covered by the Eclipse Public License 1.0 ( which can be found in the file epl.html at the root of this distribution. By using this software in any fashion, you are agreeing to be bound by the terms of this license.

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

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