IGem - run gem executables with forking, thus save the loading time. Can be used to speed up Rails generate, Rails server startup or Rake from minutes to seconds.

igem.rb

=begin

IGem - run gem executables with forking, thus save the loading time. Can be used to speed up Rails generate, Rails server startup or Rake from minutes to seconds.

Usage:
$ rails console
>> IGem.run "rake db:migrate"
>> IGem.run "rails server", wait: false
>> IGem.run "rake --tasks", fork: false

The first word of the command can be:
* a gem executable:               rspec
* a gem name and an executable:   rspec-core#rspec
* a path to a ruby file:          script/something.rb

Options and default values:
fork: true    to fork the process or just run in this one (! rails generate and some others will stop the process after running)
wait: true    if fork is true, wait for the forked process with Process.wait
env: {}        update the environment with these values

! you cannot always change environments this way because bundler will not load gems from other envs
=end

module IGem
  def self.run cmdline, opts={}
    opts = {
      :fork=>Process.respond_to?(:fork),
      :wait=>true,
      :env=>{}
    }.merge(opts)

    # split cmdline
    cmd, *args = cmdline.scan(/(?:[^"\s]+|"[^"]+")+/).map{|s|s.chars.grep(/[^"]/).join}
    
    # find executable
    case cmd
    when /\//
      # for example scripts/something.rb
      executable = cmd
    when /#/
      # for example rspec-core#rspec
      executable = Gem.bin_path(*cmd.split("#"))
    else 
      # for example rspec
      executable = Gem.bin_path(nil, cmd)
    end

    # if fork is requested
    if opts[:fork]
      fork do
        ENV.update opts[:env]
        ARGV.replace args
        load executable
      end

      # wait if requested
      Process.wait if opts[:wait]
    else
      # run without forking

      ENV.update opts[:env]
      ARGV.replace args
      load executable
    end
  end
end

Hi, cle, I tried to use your gist with "rails s" command and it throws "Gem::Exception: no default executable for rails-3.2.7", couldn't figure out why. Any thoughts?

Gem.bin_path was called the wrong way. I also added a possibility to execute arbitrary ruby files, or to specify both the gem and the executable name.

Also see my irails gist, this is probably faster for rails server.