process commands with pid file

launch batchcommands with .pid blocking

#rakefile
require 'rake'
extend FileUtils
PID = '.pid'
task :default => :reset

module Kernel
  def pid
    raise "pid file already exists" if File.exists? PID
    touch PID
    yield
    rm PID
  end
end

desc "deletes PID file"
task :reset do
  rm PID
end

desc "invokes my awkyard command"
task :short do
  pid do
    system 'ls'
  end
end