How do I get a list of files that have been `required` in Ruby?

Question

This is purely an experiment, but I'm wondering if it's possible to get a list of the require'd gems at runtime via some kind of metaprogramming. For example, say I have:

require 'rubygems'
require 'sinatra'
require 'nokogiri'

# don't know what to do here

How can I print out the following at runtime?

this app needs rubygems, sinatra, nokogiri

Answer 1

You can't do this exactly, because requiring one file may require others, and Ruby can't tell the difference between the file that you required and the file that someone else required.

You can check out $LOADED_FEATURES for a list of every single thing that's been required. But you should use Bundler if you want to specify dependencies explicitly.

Here's a thoroughly imperfect way to guess at the gem names and enumerate everything:

ruby-1.9.2-p180 :001 > $LOADED_FEATURES.
   select { |feature| feature.include? 'gems' }.
   map { |feature| File.dirname(feature) }.
   map { |feature| feature.split('/').last }.
   uniq.sort
 => ["1.9.1", "action_dispatch", "action_pack", "action_view", "actions", "active_model", "active_record", "active_support", "addressable", "agent", "array", "aws", "builder", "bundler", "cache_stores", "cancan", "cdn", "class", "client", "common", "compute", "connection", "control", "controllers", "core", "core_ext", "core_extensions", "css", "data_mapper", "decorators", "dependencies", "dependency_detection", "deprecation", "devise", "digest", "dns", "encodings", "encryptor", "engine", "errors", "excon", "ext", "failure", "faraday", "fields", "fog", "formatador", "geographer", "haml", "hash", "helpers", "heroku_san", "hmac", "hooks", "hoptoad_notifier", "html", "http", "i18n", "idna", "importers", "inflector", "initializers", "instrumentation", "integrations", "interpolate", "interval_skip_list", "jquery-rails", "json", "kaminari", "kernel", "lib", "mail", "metric_parser", "mime", "mixins", "model_adapters", "models", "module", "mongo_mapper", "mongoid", "multibyte", "new_relic", "node", "nokogiri", "numeric", "oauth", "object", "omniauth", "orm_adapter", "package", "parser", "parsers", "plugin", "pp", "providers", "queued", "rack", "rails", "railtie", "redis", "request", "request_proxy", "resp    ruby-1.9.2-p180 :008 >onse", "resque", "retriever_methods", "routing", "ruby_extensions", "ruby_flipper", "rubygems", "runtime", "samplers", "sass", "sax", "script", "scss", "selector", "sequel", "ses", "shell", "signature", "simple_geo", "state_machine", "stats_engine", "storage", "strategies", "string", "tar_reader", "template", "terremark", "thor", "tokens", "tree", "treetop", "twitter", "us", "util", "vendor", "version_specific", "visitors", "warden", "xml", "xml_mini", "xpath", "xslt"]