Creating executable gems

This is not necessarily the correct way of creating executable gems but a method which worked for me.

Assuming we are working in folder just for this gem we need a structure like this:

my_gem/
   my_gem.gemspec
   bin/
      my_gem #<-script with no file extension
   lib/
      my_gem.rb #<- Actual class file

my_gem.gemspec

require 'rake/gempackagetask'
spec = Gem::Specification.new do |s|
   s.name         = 'my_gem'
   s.version      = '0.0.1'
   s.platform     = Gem::Platform::RUBY
   s.summary      = 'Report memory usage on Mac OS X, Linux and Unix.'
   s.homepage     = 'http://amaras-tech.co.uk/software/memory_usage'
   s.authors      = "Morgan Prior"
   s.email        = "memory_usage_gem@amaras-tech.co.uk"
   s.description  = "Reports memory used by all current user processes"
   s.files        = ['bin/my_gem', 'lib/my_gem.rb']
   s.bindir       = 'bin'   
   s.executables  = ['my_gem']
   s.has_rdoc     = false

   s.post_install_message = "To use 'my_gem' as a standalone application your gems folder must be on your path"   
end
Rake::GemPackageTask.new(spec).define

bin/my_gem

#!/usr/bin/env ruby

require 'rubygems'
require 'my_gem'

a = MyGem.new(ARGV)
a.report

lib/my_gem.rb

class MyGem
    #Any command Line options set are passed in as array argv
    # You cannot have arguments as CONSTANTS plus if it was 
    # ARGV it would clash with the built in ARGV.
    def initialize(argv=[""])
      @msg = "HelloWorld!"
    end

    def report
       puts @msg.to_s
    end
 end

Then :

$ gem build my_gem.gemspec

and you can test the install via:

$ gem install my_gem-0.0.1.gem

Test then uninstall:

$ gem uninstall my_gem

Push to RubyGems:

$ gem push my_gem-0.0.1.gem

Then install from ruby Gem:

$ gem install my_gem

Done, Remember to replace ‘my_gem’ with a unique but relevant name.