GLI, the Git-Like Interface Command Line Parser

GLI allows you to create command-line app in Ruby that behaves like git in that it takes subcommands to perform a series of complex action, e.g. git remote add.

<img src=“” alt=“Build Status” />

What Problem does GLI Solve?

Creating a command-line app that uses subcommands, each of which might accept different command-line options, is somewhat difficult with Ruby’s built-in OptionParser. GLI provides an API that wraps OptionParser so that you can create a subcommand-based command-line app with minimal boilerplate. This API also produces complete documentation for your command-line app.

Why is GLI’s solution different from others?

There are other RubyGems that allow you to create a command-line app that takes subcommands. These solutions are often quite limited (e.g. they don’t allow deeply nested subcommand structures or sophisticated command-line options per subcommand), or require more code that we think is needed. Some solutions make it difficult or impossible to properly document your command-line app.

What you need to know to use GLI

You should know Ruby, and have a basic understanding of how the UNIX command line works: standard input, standard output, standard error, and exit codes.


Install if you need to:

gem install gli

You can validate you have installed it correctly by running gli help. You should see formatted help output.

If you are using GLI in another application, add it to your Gemfile:

gem "gli"

You can test your install via Bundler by running bundle exec gli help. This should produce formatted help output from GLI.

Getting Started

The simplest way to get started is to create a scaffold project

gli init todo list add complete

(note if you installed via Bundler you will need to execute bundle exec gli init todo list add complete)

This will create a basic scaffold project in ./todo with:

  • executable in ./todo/bin/todo. This file demonstrates most of what you need to describe your command line interface.

  • an empty test in ./todo/test/default_test.rb that can bootstrap your tests

  • a gemspec shell

  • a README shell

  • Rakefile that can generate RDoc, package your Gem and run tests

  • A Gemfile suitable for use with Bundler to manage development-time dependencies

Now, you are ready to go:

> cd todo
> bundle exec bin/todo help
    todo - Describe your application here

    todo [global options] command [command options] [arguments...]


    -f, --flagname=The name of the argument - Describe some flag here (default: the default)
    --help                                  - Show this message
    -s, --[no-]switch                       - Describe some switch here

    add      - Describe add here
    complete - Describe complete here
    help     - Shows a list of commands or help for one command
    list     - Describe list here

> bundle exec bin/todo help list
    list - Describe list here

    todo [global options] list [command options] Describe arguments to list here

    -f arg - Describe a flag to list (default: default)
    -s     - Describe a switch to list

All you need to do is fill in the documentation and your code; the help system, command-line parsing and many other awesome features are all handled for you.

Get a more detailed walkthrough on the main site

Supported Platforms

See ‘.circleci/config.yml` for the supported rubies, but general we’re running tests on the all MRI rubies receiving support, which tends to be the most recent four versions.

GLI should work on older Rubies and JRuby, but it’s too much work to keep tests passing for those.


Extensive documentation is available at the wiki.

API Documentation is available here. Recommend starting with GLI::DSL or GLI::App.



Dave Copeland (davetron5000 at g mail dot com)


Copyright © 2010 by Dave Copeland


Distributes under the Apache License, see LICENSE.txt in the source distro

gli CLI documentation