#!/usr/bin/env ruby
require 'nkf'

sender	= ENV['SENDER']
rcpt	= ENV['RECIPIENT']

if sender == nil || rcpt == nil then
  STDERR.puts "$SENDER and $RECIPIENT not set. exit."
  exit 0		# メイル用プログラムはエラーでも exit 0 すべき
elsif /.*@.*/ !~ sender then    # メイルアドレス形式でない場合
  STDERR.puts "SENDER address invalid"
  exit 0
end

to	= sender
from	= rcpt
subject = NKF.nkf("-M", 'メイル受信しました')
header	= sprintf("To: %s\nFrom: %s\nSubject: %s\n\n", to, from, subject)
message	= NKF.nkf("-j", "ありがとう\n")
program	= sprintf("| sendmail -f %s %s", from, to)

open(program, "w") do |mail|
  mail.print header
  mail.print message
end