Check environment

$ gem env

$ bundle env

List installed gems

$ bundle list

Gems included by the bundle:
  * addressable (2.7.0)
  * ...

Names of directories:

$ ls vendor/bundle/ruby/2.6.0/gems

addressable-2.7.0           i18n-0.9.5      ...
...

Find gem locally

For a gem installed locally such as minima theme.

Show path:

$ bundle show minima

<PATH_TO_REPO>/vendor/bundle/ruby/2.6.0/gems/minima-2.5.1

Open VS Code in that directory. Use open to use your file browser.

$ code $(bundle show minima)

Gem CLI

Calling gem from the shell.

See also plugins page.

Help

$ gem COMMAND --help
$ gem help COMMAND

Install

$ gem install GEMNAME
$ gem install GEMNAME --user-level

Update

Upgrade target gem.

$ gem update GEMNAME

Usage: gem update GEMNAME [GEMNAME ...] [options]

Upgrade many gems.

$ gem update
$ gem update --system

gem help update
Usage: gem update GEMNAME [GEMNAME ...] [options]

  Options:
      --system                     Update the RubyGems system software

Ruby gem command

Calling gem from inside Ruby code including a Gemfile.

See Gem versions page.

Bundler command

Gemfile should like this:

gem 'foo'
gem 'bar', '~> 2.5'

Then Bundler will use that.

$ bundle install

Install from GitHub

gem 'bar', git: 'https://github.com/foo/bar'