Spawn process thats loops and get stdout continuosly in ruby - ruby

Question

i need to spwan a program in a ruby script.
This program periodically print a JSON and in the main script i need to intercept this and made calculation.
Thanks
Something like this:
MAIN:
Spawn a process
//This generates stdout periodically
//End call
Intercept its stdout
//REST of the code
How to?
I need to use eventmachine? Somewhat?
I clarify with this code
timer = EventMachine.add_periodic_timer POLLING_INTERVAL do
if memcached_is_running
ld 'reading from device'
begin
IO.popen("HostlinkPollerLight -p #{SERIAL_PORT} -v #{SERIAL_BAUDRATE} -r #{MODEL_CONFIG} 2> /dev/null") do |payload|
$_data = JSON.parse payload.readlines[0]
end
if $data['success']
memcache.set( MEMCACHE_DATA_KEY, _to_json( $data[ 'result' ], _mapping ))
timer.interval = POLLING_INTERVAL
else
log_this " read fault: error_code #{$data['fault']}"
timer.interval = FAULT_INTERVAL
end
rescue Errno::ENOENT
log_this 'Unable to read output'
rescue JSON::ParserError
log_this 'Malformed data'
end
else
timer.interval = FAULT_INTERVAL
system("on_red_led.sh 2")
end
log_this "elapsed time: #{Time.now.to_f - delta}"
ld "## end read: #{counter}"
counter += 1
end
I need to spwan only one time the program opened with popen and get the stdout every time its print stdout.

Answer 1

The way I do this is, that I create a class, which creates a new Thread with infinite loop, which alters object's instance variable. Then I can access those variables via its getters. Example:
class Stopwatch
def initialize
#seconds = 0
end
def start
#thread = Thread.new do
loop {
sleep(1)
#seconds += 1
}
end
end
def seconds
#seconds
end
def stop
#thread.kill
end
def reset
#seconds = 0
end
end
stoper = Stopwatch.new
stoper.start
sleep(5)
stoper.seconds #=> 5