role_hax.rb

#!/usr/bin/env ruby

require 'chef'
require 'chef/knife'
require 'getoptlong'

def print_help
  puts "#{File.basename(__FILE__)} OPTS"
  puts '  --> Help is on a help yourself basis.'
end

args = Mash.new(
  :kind => 'default'
)

opts = GetoptLong.new(
  ['--default', '-d', GetoptLong::NO_ARGUMENT],
  ['--override', '-o', GetoptLong::NO_ARGUMENT],
  ['--role-name', '-r', GetoptLong::REQUIRED_ARGUMENT],
  ['--attribute', '-a', GetoptLong::REQUIRED_ARGUMENT],
  ['--value', '-v', GetoptLong::REQUIRED_ARGUMENT],
  ['--cast', '-c', GetoptLong::REQUIRED_ARGUMENT],
  ['--help', '-h', GetoptLong::NO_ARGUMENT]
)
opts.each do |opt,arg|
  case opt
  when '--default'
    args[:kind] = 'default'
  when '--override'
    args[:kind] = 'override'
  when '--role-name'
    args[:role_name] = arg
  when '--attribute'
    args[:attribute] = arg
  when '--value'
    args[:value] = arg
  when '--cast'
    args[:cast] = arg
  else
    print_help
    exit 1
  end
end

%w(kind role_name attribute value).each do |req|
  next if args[req]
  puts "Missing required data for update: #{req}"
  exit 2
end

Chef::Knife.new.configure_chef

if(args[:cast])
  case args[:cast]
  when 'integer'
    args[:value] = args[:value].to_i
  when 'float'
    args[:value] = args[:value].to_f
  when 'bool'
    args[:value] = args[:value] == 'true'
  else
    puts "Unsupported cast type provided: #{args[:cast]}"
  end
end

begin
  role = Chef::Role.load(args[:role_name])
  attributes = role.send("#{args[:kind]}_attributes")
  attribute_path = args[:attribute].split('.')
  dest = attribute_path.slice(0, attribute_path.size - 1).inject(attributes) do |memo, key|
    if(memo[key].nil? || !memo[key].is_a?(Hash))
      memo[key] = {}
    end
    memo[key]
  end
  dest[attribute_path.last] = args[:value]
  role.save
  puts "Role successfully updated!"
rescue => e
  $stderr.puts "Failed to update role. Reason: #{e}"
  exit 3
end