A command line interface for smithing new Ruby gems.
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A command line interface for smithing new Ruby gems.

Table of Contents





  1. A UNIX-based system.
  2. Ruby 2.4.x.
  3. RubyGems.
  4. Bundler.



For a secure install, type the following from the command line (recommended):

gem cert --add <(curl --location --silent https://www.alchemists.io/gem-public.pem)
gem install gemsmith --trust-policy MediumSecurity

NOTE: A HighSecurity trust policy would be best but MediumSecurity enables signed gem verification while allowing the installation of unsigned dependencies since they are beyond the scope of this gem.

For an insecure install, type the following (not recommended):

gem install gemsmith


This gem can be configured via a global configuration:


It can also be configured via XDG environment variables as provided by the Runcom gem.

The default configuration is as follows:

:year: <current year>
:github_user: "<Git config GitHub user>",
  :label: "Undefined"
  :name: "undefined"
  :path: "undefined"
  :class: "Undefined"
  :platform: "Gem::Platform::RUBY"
  :url: "https://github.com/<author>/<gem name>"
  :license: "MIT"
  :name: "<Git config user name>"
  :email: "<Git config user email>"
  :url: ""
  :name: ""
  :url: ""
  :ruby: "<current Ruby version>"
  :rails: "5.1"
  :cli: false
  :rails: false
  :security: true
  :pry: true
  :guard: true
  :git_cop: true
  :rspec: true
  :reek: true
  :rubocop: true
  :scss_lint: false
  :git_hub: false
  :code_climate: false
  :gemnasium: false
  :circle_ci: false
  :patreon: false
  :sign: false

Feel free to take this default configuration, modify, and save as your own custom configuration.yml.

Existing Gems

If you have gems that were not originally crafted by Gemsmith, you can add Gemsmith support to them by modifying the following files:

Add the following to your gem's *.gemspec file:

spec.add_development_dependency "gemsmith"

Replace or add a modified version of the following to your gem's Rakefile:

# frozen_string_literal: true

  require "gemsmith/rake/setup"
rescue LoadError => error
  puts error.message

NOTE: Ensure require "bundler/gem_tasks" is removed as Gemsmith replaces Bundler functionality.

With those changes, you can leverage the benefits of Gemsmith within your existing gem.


Command Line Interface (CLI)

From the command line, type: gemsmith --help

gemsmith -c, [--config]        # Manage gem configuration.
gemsmith -g, [--generate=GEM]  # Generate new gem.
gemsmith -h, [--help=COMMAND]  # Show this message or get help for a command.
gemsmith -o, [--open=GEM]      # Open a gem in default editor.
gemsmith -r, [--read=GEM]      # Open a gem in default browser.
gemsmith -v, [--version]       # Show gem version.

For more gem generation options, type: gemsmith --help --generate

[--cli], [--no-cli]                    # Add CLI support.
[--rails], [--no-rails]                # Add Rails support.
[--security], [--no-security]          # Add security support.
                                       # Default: true
[--pry], [--no-pry]                    # Add Pry support.
                                       # Default: true
[--guard], [--no-guard]                # Add Guard support.
                                       # Default: true
[--git-cop], [--no-git-cop]            # Add Git Cop support.
                                       # Default: true
[--rspec], [--no-rspec]                # Add RSpec support.
                                       # Default: true
[--reek], [--no-reek]                  # Add Reek support.
                                       # Default: true
[--rubocop], [--no-rubocop]            # Add Rubocop support.
                                       # Default: true
[--scss-lint], [--no-scss-lint]        # Add SCSS Lint support.
[--git-hub], [--no-git-hub]            # Add GitHub support.
[--code-climate], [--no-code-climate]  # Add Code Climate support.
[--gemnasium], [--no-gemnasium]        # Add Gemnasium support.
[--circle-ci], [--no-circle-ci]        # Add Circle CI support.
[--patreon], [--no-patreon]            # Add Patreon support.


Once a gem skeleton has been created, the following tasks are available (i.e. bundle exec rake -T):

rake build                 # Build example-0.1.0.gem package
rake clean                 # Clean gem artifacts
rake code_quality          # Run code quality checks
rake doc                   # Update README (table of contents)
rake git_cop               # Run Git Cop
rake install               # Install example-0.1.0.gem package
rake publish               # Build, tag as v0.1.0 (unsigned), and push example-0.1.0.gem to RubyGems
rake reek                  # Check for code smells
rake rubocop               # Run RuboCop
rake rubocop:auto_correct  # Auto-correct RuboCop offenses
rake spec                  # Run RSpec code examples

When building/testing your gem locally, a typical workflow is:

  1. bundle exec rake install
  2. Test your gem locally.
  3. Repeat until satisfied.

When satified with your gem, builds are green, and ready to publish, run:

bundle exec rake publish


To test, run:

bundle exec rake


Git Signing Key

To securely sign your Git tags, install and configure GPG:

brew install gpg
gpg --gen-key

When creating your GPG key, choose these settings:

  • Key kind: RSA and RSA (default)
  • Key size: 4096
  • Key validity: 0
  • Real Name: <your name>
  • Email: <your email>
  • Passphrase: <your passphrase>

To obtain your key, run the following and take the part after the forward slash:

gpg --list-keys | grep pub

Add your key to your global Git configuration in the [user] section. Example:

  signingkey = <your GPG key>

Now, when publishing your gems with Gemsmith (i.e. bundle exec rake publish), signing of your Git tag will happen automatically. You will be prompted for the GPG Passphrase each time but that is to be expected.

Gem Certificates

To create a certificate for your gems, run the following:

cd ~/.ssh
gem cert --build you@example.com
chmod 600 gem-*.pem

The resulting *.pem key files can be referenced via the :private_key: and :public_key: keys within the ~/.gemsmithrc file.

To learn more about gem certificates, read the following:

Private Gem Servers

By default, the following Rake task will publish your gem to RubyGems:

bundle exec rake publish

You can change this behavior by adding metadata to your gemspec that will allow the Rake tasks, mentioned above, to publish your gem to an alternate/private gem server instead. This can be done by updating your gem specification and RubyGems credentials.

Gem Specification Metadata

Add the following metadata to your gemspec:

Gem::Specification.new do |spec|
  spec.metadata = {
    "allowed_push_key" => "example_key",
    "allowed_push_host" => "https://gems.example.com"

The gemspec metadata keys and values must be strings per the RubyGems Specification. Each key represents the following:

  • allowed_push_key: Provides a reference (look up) to the key defined the RubyGems credentials file so that sensitive credentials are not used within your gemspec.
  • allowed_push_host: Provides the URL of the private gem server to push your gem to.

Gem Credentials

With your gem specification metadata established, you are ready to publish your gem to a public or private server. If this is your first time publishing a gem and no gem credentials have been configured, you'll be prompted for them. Gem credentials are stored in the RubyGems ~/.gem/credentials file. From this point forward, future gem publishing will use your stored credentials instead. Multiple credentials can be stored in the ~/.gem/credentials file. Example:

:rubygems_api_key: 2a0b460650e67d9b85a60e183defa376
:example_key: "Basic dXNlcjpwYXNzd29yZA=="

Should you need to delete a credential (due to a bad login/password for example), you can open the ~/.gem/credentials in your default editor and remove the line(s) you don't need. Upon next publish of your gem, you'll be prompted for the missing credentials.


Once your gem is released, you might want to let the world know about your accomplishment:


When running bundle exec rake install or bundle exec rake publish with modified, staged, or uncommitted Git changes, the rake task will throw an error to this effect. When this occurs, it is recommended that you commit your changes or stash them before proceeding.


Read Semantic Versioning for details. Briefly, it means:

  • Major (X.y.z) - Incremented for any backwards incompatible public API changes.
  • Minor (x.Y.z) - Incremented for new, backwards compatible, public API enhancements/fixes.
  • Patch (x.y.Z) - Incremented for small, backwards compatible, bug fixes.

Code of Conduct

Please note that this project is released with a CODE OF CONDUCT. By participating in this project you agree to abide by its terms.


Read CONTRIBUTING for details.


Copyright (c) 2011 Alchemists. Read LICENSE for details.


Read CHANGES for details.


Developed by Brooke Kuhlmann at Alchemists.