#!/usr/bin/env ruby
# encoding: utf-8
#
# lock 
#

LOCK_FILE = 'lockfile'
COUNT_FILE = 'count'
def lock
  open(LOCK_FILE, 'a') do |st|
    st.flock(File::LOCK_EX)
    yield
    st.flock(File::LOCK_UN)
  end
end

def new_id
  count = nil
  lock do
    count = File.read(COUNT_FILE).to_i
    count += 1
    open(COUNT_FILE, "w") do |out|
      out.print count
    end
  end
  count 
end