Ruby script that returns version of a gem included in `Gemfile.lock` file

bundler_version.rb

#!/usr/bin/env ruby

require 'bundler'

puts Bundler::LockfileParser.new(Bundler.read_file(Bundler.default_lockfile)).specs.find { |s| s.name == ARGV[0] }.version.version

# Requires `Gemfile.lock` file with required dependency included (eg: `bundle install rubocop`)
# Use case : gem install rubocop -v $(ruby bundler_version.rb rubocop) --no-document
# Can be useful in CI jobs (do not install all dependencies through `bundle install` when you only need to pass linter for example)