What is Bundler?

Bundler provides a consistent environment for Ruby projects by tracking and installing the exact gems and versions that are needed.

Bundler is an exit from dependency hell, and ensures that the gems you need are present in development, staging, and production. Starting work on a project is as simple as bundle install.

Getting Started

Getting started with bundler is easy! Open a terminal window and run this command:
$ gem install bundler

Specify your dependencies in a Gemfile in your project's root:
source 'https://rubygems.org'
gem 'nokogiri'
gem 'rack', '~>1.1'
gem 'rspec', :require => 'spec'
Learn More: Gemfiles
Install all of the required gems from your specified sources:
$ bundle install
$ git add Gemfile Gemfile.lock
Learn More: bundle install
The second command adds the Gemfile and Gemfile.lock to your repository. This ensures that other developers on your app, as well as your deployment environment, will all use the same third-party code that you are using now.
Inside your app, load up the bundled environment:
require 'rubygems'
require 'bundler/setup'

# require your gems as usual
require 'nokogiri'
Learn More: Bundler.setup
Run an executable that comes with a gem in your bundle:
$ bundle exec rspec spec/models

In some cases, running executables without bundle exec may work, if the executable happens to be installed in your system and does not pull in any gems that conflict with your bundle.

However, this is unreliable and is the source of considerable pain. Even if it looks like it works, it may not work in the future or on another machine.

Finally, if you want a way to get a shortcut to gems in your bundle:
$ bundle install --binstubs
$ bin/rspec spec/models
The executables installed into bin are scoped to the bundle, and will always work.
Learn More: Executables

Use Bundler with

Get involved

Bundler has a lot of contributors and users, and they all talk to each other quite a bit. If you have questions, try the IRC channel or mailing list. If you're interested in contributing to the project (no programming skills needed), read the contributing guide. While participating in the Bundler project, please keep the code of conduct in mind, and be inclusive and friendly towards everyone. If you have sponsorship or security questions, please contact the core team directly.

Edit this document on GitHub if you caught an error or noticed something was missing.