source: de.wigbels.ruby/hothotread/hothotpiper_gas.rb@ b62bf13

#!/usr/bin/env ruby

require 'pi_piper'
include PiPiper

mypath = File.expand_path(File.dirname(__FILE__))
trigger_step = 0.01
trigger_watch = 0
counter = 0.0
timestamp =  Time.now.to_i

def last_rrd_count(concretepath)
  val = 0.0
  handle = IO.popen("rrdtool lastupdate #{concretepath}")
  handle.each_line do |line|
    m = line.match("^[0-9]*: ([0-9.]*) [0-9.]*")
    if m
      val = m[1].to_f
      break
    end
  end
  return val
end

watch :pin => 4, :trigger => :falling do 
  puts('triggered watch to 1')
  trigger_watch = 1
end

rrdpath = mypath + "/gasneu.rrd"
counter = last_rrd_count(rrdpath)
puts('Counter restored to: '+counter.to_s)

loop do
  if trigger_watch == 1 then
    counter = counter + trigger_step
    system("rrdtool update #{rrdpath} N:#{counter}:#{trigger_step}")
    puts('Counter updated to: '+counter.to_s)
    timestamp =  Time.now.to_i
    trigger_watch = 0
  elsif Time.now.to_i - timestamp > 3600
    system("rrdtool update #{rrdpath} N:#{counter}:0")
    timestamp = Time.now.to_i
  end
  sleep(1)
end