Add keywords to your existing octopress posts

Rakefile

desc "add keywords to posts"
task :add_keywords do
  Dir.glob(File.join(File.dirname(__FILE__),"source/_posts/*.markdown")) do |file|
    yaml = YAML.load_file(file)
    keywords = yaml['categories'] || []
    title = yaml['title']

    keywords += title.scan(/'.*'/).map {|kw| kw.gsub("'",'')}
    keywords += title.scan(/\S+[\sv~>]+?\d+\.\d+\.?\d*/)

    title = title.gsub(/[\sv~>]+?\d+\.\d+\.?\d*/,'')
    title = title.gsub(/['\?:\d\.]/,'')

    keywords += title.split()

    keywords_hash = {}
    keywords.each do |keyword|
      keywords_hash[keyword.downcase] = keyword
    end

    %w(# a an i on of to in my from how for the just best own after full if ~> and with when do does not are et up way first set like be there only can one per).each do |word|
      keywords_hash.delete(word)
    end

    system "sed -i '1 a\
    keywords: \"#{keywords_hash.values.join(', ')}\"
    ' #{file}"
  end
end