How to run a ruby script within bundler context?

I have a Ruby script called foo.rb, and I want to run it within the context of the bundler environment. How?

bundle exec foo.rb doesn't work, because exec expects a shell script.

Pass the script name to the ruby command:

bundle exec ruby script_name

If you also want the Rails environment:

bundle exec rails runner script_name

For instance, I wanted to use the same version of Rubocop as my Rails app and not the latest system one, so doing this in a script:

require 'bundler'
Bundler.require

# ...

Allowed me to use my app's version of rubocop.

You can just make it a script - add

#!/usr/bin/env ruby

to the start of the file, and make it executable. Then bundle exec foo.rb will work as expected.

(This is on unix or OSX - not sure about Windows)

See http://bundler.io/v1.15/man/bundle-exec.1.html#Loading

Also see https://coderwall.com/p/kfyzcw/execute-ruby-scripts-directly-without-bundler-exec for how to run ruby scripts with bundled dependencies, without needing bundle exec

If you want to create a script that you can run in bundle context within a project, you can invoke Bundler programmatically. E.g., given a project:

foo
├── Gemfile
└── bar
    └── baz.rb

you can put the following at the top of baz.rb to give it access to the gems in the Gemfile:

#!/usr/bin/env ruby

ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
require 'bundler/setup'

# ...etc.

With that, you can invoke the script directly without using bundle exec, and you also don't have to invoke it from within the project directory.