List of installed gems?

This lists all the gems I have installed.

gem query --local

http://guides.rubygems.org/command-reference/#gem-list

See 2.7 Listing all installed gems

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The Gem command is included with Ruby 1.9+ now, and is a standard addition to Ruby pre-1.9.

require 'rubygems'

name = /^/i
dep = Gem::Dependency.new(name, Gem::Requirement.default)
specs = Gem.source_index.search(dep)
puts specs[0..5].map{ |s| "#{s.name} #{s.version}" }
# >> Platform 0.4.0
# >> abstract 1.0.0
# >> actionmailer 3.0.5
# >> actionpack 3.0.5
# >> activemodel 3.0.5
# >> activerecord 3.0.5

Here's an updated way to get a list:

require 'rubygems'

def local_gems
   Gem::Specification.sort_by{ |g| [g.name.downcase, g.version] }.group_by{ |g| g.name }
end

Because local_gems relies on group_by, it returns a hash of the gems, where the key is the gem's name, and the value is an array of the gem specifications. The value is an array of the instances of that gem that is installed, sorted by the version number.

That makes it possible to do things like:

my_local_gems = local_gems()

my_local_gems['actionmailer']
# => [Gem::Specification.new do |s|
#       s.authors = ["David Heinemeier Hansson"]
#       s.date = Time.utc(2013, 12, 3)
#       s.dependencies = [Gem::Dependency.new("actionpack",
#         Gem::Requirement.new(["= 4.0.2"]),
#         :runtime),
#        Gem::Dependency.new("mail",
#         Gem::Requirement.new(["~> 2.5.4"]),
#         :runtime)]
#       s.description = "Email on Rails. Compose, deliver, receive, and test emails using the familiar controller/view pattern. First-class support for multipart email and attachments."
#       s.email = "david@loudthinking.com"
#       s.homepage = "http://www.rubyonrails.org"
#       s.licenses = ["MIT"]
#       s.name = "actionmailer"
#       s.require_paths = ["lib"]
#       s.required_ruby_version = Gem::Requirement.new([">= 1.9.3"])
#       s.requirements = ["none"]
#       s.rubygems_version = "2.0.14"
#       s.specification_version = 4
#       s.summary = "Email composition, delivery, and receiving framework (part of Rails)."
#       s.version = Gem::Version.new("4.0.2")
#       end]

And:

puts my_local_gems.map{ |name, specs| 
  [ 
    name,
    specs.map{ |spec| spec.version.to_s }.join(',')
  ].join(' ') 
}
# >> actionmailer 4.0.2
...
# >> arel 4.0.1,5.0.0
...
# >> ZenTest 4.9.5
# >> zucker 13.1

The last example is similar to the gem query --local command-line, only you have access to all the information for a particular gem's specification.

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Both

gem query --local

and

 ruby -S gem list --local

list 69 entries

While

ruby -e 'puts Gem::Specification.all_names'

gives me 82

I used wc -l to get the numbers. Not sure if that is the right way to check. Tried to redirect the output to text files and diff'ed but that didn't help - will need to compare manually one by one.

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There's been a method for this for ages:

ruby -e 'puts Gem::Specification.all_names'

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Gem::Specification.map {|a| a.name}

However, if your app uses Bundler it will return only list of dependent local gems. To get all installed:

def all_installed_gems
   Gem::Specification.all = nil    
   all = Gem::Specification.map{|a| a.name}  
   Gem::Specification.reset
   all
end

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use this code (in console mode):

Gem::Specification.all_names

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Here's a really nice one-liner to print all the Gems along with their version, homepage, and description:

Gem::Specification.sort{|a,b| a.name <=> b.name}.map {|a| puts "#{a.name} (#{a.version})"; puts "-" * 50; puts a.homepage; puts a.description; puts "\n\n"};nil

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A more modern version would be to use something akin to the following...

require 'rubygems'
puts Gem::Specification.all().map{|g| [g.name, g.version.to_s].join('-') }

NOTE: very similar the first part of an answer by Evgeny... but due to page formatting, it's easy to miss.

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Try it in the terminal:

ruby -S gem list --local

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Maybe you can get the files (gems) from the gems directory?

gemsdir = "gems directory"
gems = Dir.new(gemsdir).entries

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From within your debugger type $LOAD_PATH to get a list of your gems. If you don't have a debugger, install pry:

gem install pry
pry
Pry(main)> $LOAD_PATH

This will output an array of your installed gems.

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