extract email bandwidth usage for a domain grouped by day

email_bandwidth.rb

cmd = 'grep @domain.com /var/log/maillog | grep retr= | awk {\'print $6" "$1" "$2" "$3" "$11\'} | grep -v retr=0'

output = []
r, io = IO.pipe
fork do
  system(cmd, out: io, err: :out)
end
io.close

list = {}
r.each_line{|l|
  res = l.split(' ')
  email = res[0].gsub('pop3(','')+'-'+res[1]+res[2]
  byte = (res[4].split('/').last[0..-2].to_f/1024/1024).round(4)
  if list.has_key?(email)

    list[email][:size] +=byte
  else
    list[email] = { size: byte }
  end

  puts 'key: ' + email + ", size: "+ byte.to_s

}

puts "result==========="
list.keys.each do |key|
  puts key+": "+list[key][:size].round(4).to_s+"MB"
end

puts 'done.'