Writing your own Hammer plugin

In this tutorial we will create a simple hello world plugin.

Hammer plugins are nothing but gems. Details on how to build a gem can be found for example at rubygems.org. In the first part of this tutorial we will briefly guide you through the process of creating a very simple gem. First of all you will need the rubygems package installed on your system.

Create the basic gem structure in a project subdirectory of your choice: $ cd ./my_first_hammer_plugin/ $ touch Gemfile $ touch hammer_cli_hello.gemspec $ mkdir -p lib/hammer_cli_hello $ touch lib/hammer_cli_hello.rb $ touch lib/hammer_cli_hello/version.rb

Example Gemfile: “`ruby source “rubygems.org

gemspec “`

Example hammer_cli_hello.gemspec file: “`ruby $:.unshift File.expand_path(“../lib”, FILE) require “hammer_cli_hello/version”

Gem::Specification.new do |s|

s.name = “hammer_cli_hello” s.authors = [“Me”] s.version = HammerCLIHello.version.dup s.platform = Gem::Platform::RUBY s.summary = %q{Hello world commands for Hammer}

s.files = Dir s.require_paths = [“lib”]

s.add_dependency 'hammer_cli', '>= 0.0.6' end “` More details about the gemspec structure is again at rubygems.org.

We'll have to specify the plugin version in lib/hammer_cli_hello/version.rb: ruby module HammerCLIHello def self.version @version ||= Gem::Version.new '0.0.1' end end

This should be enough for creating a minimalist gem. Let's build and install it. $ gem build ./hammer_cli_hello.gemspec $ gem install hammer_cli_hello-0.0.1.gem

Place your module's config file into ~/.hammer/cli.modules.d/hello_world.yml. yaml :hello: :enable_module: true

Verify the installation by running: $ hammer -v > /dev/null

You should see a message saying that your module was loaded (second line in the sample output). [ INFO 2013-10-16 11:19:06 Init] Initialization of Hammer CLI (0.1.0) has started... [ INFO 2013-10-16 11:19:06 Init] Extension module hammer_cli_hello loaded [ INFO 2013-10-16 11:19:06 Init] Configuration from the file /root/.hammer/cli_config.yml has been loaded [ INFO 2013-10-16 11:19:06 Init] Configuration from the file /root/.hammer/cli.modiles.d/hello.yml has been loaded [ INFO 2013-10-16 11:19:06 HammerCLI::MainCommand] Called with options: {"verbose"=>true}

Done. Your first hammer plugin is installed. Unfortunately it does not contain any commands yet. So let's start adding some to finally enjoy real results.

Optionally you can add a Rakefile and build and install the gem with rake install ruby # ./Rakefile require 'bundler/gem_tasks'