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An argument is a token passed after the command name. For instance, given the foo greet command, when an user types foo greet Luca, then Luca is considered an argument. A command can accept none or many arguments. An argument can be declared as required.

#!/usr/bin/env ruby
require "bundler/setup"
require "dry/cli"

module Foo
  module CLI
    module Commands
      extend Dry::CLI::Registry

      class Greet < Dry::CLI::Command
        argument :name, required: true, desc: "The name of the person to greet"
        argument :age, desc: "The age of the person to greet"

        def call(name:, age: nil, **)
          result = "Hello, #{name}."
          result = "#{result} You are #{age} years old." unless age.nil?

          puts result

      register "greet", Greet
$ foo greet Luca
Hello, Luca.
$ foo greet Luca 35
Hello, Luca. You are 35 years old.
$ foo greet
ERROR: "foo greet" was called with no arguments
Usage: "foo greet NAME"

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