ruby bundler

abstract

Bundler is a Ruby gem which installs Ruby gems. Bundler installs a separate bundle of gems for each software project on a machine. Keeping projects' gems separated helps developers avoid dependency hell.

basics

Open a terminal and cd to a project's top-level folder.
Create a Gemfile listing the project's required gems and version constraints.
Run bundle to install all gems in the Gemfile and their dependencies.
Bundler creates a Gemfile.lock file listing pinned versions of all installed gems.
Bundler automatically updates Gemfile.lock on subsequent runs.

commands

The rake gem is used here as an example.

system commands
`gem install bundler`	install Bundler
`gem uninstall bundler`	uninstall Bundler
`gem update bundler`	update Bundler

project commands
`bundle clean`	remove unused gems
`bundle exec gem list`	show installed gems
`bundle exec irb`	start interactive Ruby
`bundle exec ruby path/to/script.rb`	run a Ruby script
`bundle init`	create a minimal `Gemfile` in current folder
`bundle install`	install all gems in `Gemfile`
`bundle show rake`	show path to `rake`
`bundle update rake`	update `rake`

dependencies

Ruby >= 2.3.0
RubyGems >= 2.5.0

examples

Example Gemfile file:

ruby '~> 2.3'
source 'https://rubygems.org' do
    gem 'nokogiri'
    gem 'rails', '3.0.0.beta3'
    gem 'rack',  '>=1.0'
    gem 'thin',  '~>1.1'
end

Example .gitignore file:

.bundle/           # Bundler config files
vendor/bundle      # Locally-installed gem files

faq

Where are the official docs?: Bundler docs; Bundler workflow; Gemfile.lock reference