An example knife-plugin that displays Hello World and a user name.

knife-hello_world.rb

#
#
#
#

# Loads the knife classes and code to be used. 
require 'chef/knife'

module ExamplePlugin
# This module is arbritary and mainly for keeping your plugin code
# seperate. The module name can be anything that can help organize 
# your code. 
    class HelloWorld < Chef::Knife
    # This class will be displayed as the banner below.
    # When putting the words HelloWorld are capitalized as such
    # Chef will split by the capital words, but if the World was not
    # capitalized, then it would be shown as one word. 

        # This is the "show help" bit. Doing the -h also shows the 
        # options defined below as well as the default ones. 
        banner "knife hello world -U USERNAME (options)"

        # This method loads dependencies and require's only when this plugin
        # is being used. 
        deps do 
            # Nothing here yet
        end

        # This defines the command line options, and there are more of them
        # Its preferable to have as many options as possible. 
        option :user_name,
        :short => "-U USER",
        :long => "--ser_name USER",
        :description => "This is just a user name.",
        :default => "default_user"

        # This is what is ran when the knife plugin is executed.
        def run
            puts "Hello World #{config[:user_name]}"
        end
    end

    class HelloYou < Chef::Knife
        banner "knife hello you (options)"

        deps do
            #
        end

        def run
            puts "Hello You! I don't have a name."
        end
    end

    class HelloUser < Chef::Knife
        deps do
            #
        end

        banner "knife hello user NAME (options)"

        def run
            puts "Hello #{ARGV[2]}"
            puts "Hello #{name_args.first}"
        end
    end

    class HelloToMe < Chef::Knife
        deps do
            #
        end

        banner "knife hello to me USER (options)"

        def run
            puts "Hello to me from #{name_args.first}"
        end
    end
end