gistfile1.rb

#! /usr/bin/env ruby
# -*- conding: utf-8 -*-

require 'nkf'

unless ARGV.size == 1
  warn 'pleese set directory'
  exit
end

Dir["#{ARGV[0]}/*.html"].each do |f|
  puts "converting #{f}..."
  File.open(f, 'rb+') do |io|
    body = NKF.nkf('-wS', io.read)
    io.rewind
    io.write body
  end
end