band.rb

INTERFACE = ARGV[0] || 'wlan0'

class Float; def to_mb; self / 1048576; end; end

initial   = (ARGV[1] || 0  ).to_f
available = (ARGV[2] || 100).to_f
delay     = (ARGV[3] || 5  ).to_f
left      = 0

initial = File.read('.band') if !ARGV[1] && File.exists?('.band')

trap('INT') do
  File.open('.band', ?w) { |f| f.write left.to_s }
	abort
end

while true
	begin
		tx = File.read("/sys/class/net/#{INTERFACE}/statistics/tx_bytes").to_f.to_mb
		rx = File.read("/sys/class/net/#{INTERFACE}/statistics/rx_bytes").to_f.to_mb
		left = (tx + rx + initial) - available
		
		puts "#{(left).round(4)}mb left"
	rescue
		puts "Waiting for #{INTERFACE}..."
	end

	sleep delay
end