how to run one program and check the existence of output periodically while running the program - ruby

Question

I want to run a script which is generating some files and want check the existence of the script genrated file in every 3 min.
I did the following,
def periodic_method time, block
t = EventMachine::PeriodicTimer.new(time) {eval(block)}
begin
yield
ensure
t.cancel
end
end
periodic_method(60, "if File.exists(file1.txt) then puts 'done with step 1' else puts 'running generator'") do
generator.rb
end
While running i am getting error wrong no of arguments.
Here is the stacktrace:-
wrong number of arguments (1 for 0)
/tools/simulation/simulation_assemble/test.rb:652:in `eval'
(eval):1:in `block in periodic_block'
/tools/simulation/simulation_assemble/test.rb:652:in `eval'
/tools/simulation/simulation_assemble/test.rb:652:in `block in periodic_block'
/tool/pandora64/.package/ruby-1.9.2-p136/lib/ruby/gems/1.9.1/gems/eventmachine-1.0.0.beta.4
/lib/em/timers.rb:52:in `call'
/tool/pandora64/.package/ruby-1.9.2-p136/lib/ruby/gems/1.9.1/gems/eventmachine-1.0.0.beta.4/lib/em/timers.rb:52:in `fire'
/tool/pandora64/.package/ruby-1.9.2-p136/lib/ruby/gems/1.9.1/gems/eventmachine-1.0.0.beta.4/lib/eventmachine.rb:206:in `call'
/tool/pandora64/.package/ruby-1.9.2-p136/lib/ruby/gems/1.9.1/gems/eventmachine-1.0.0.beta.4/lib/eventmachine.rb:206:in `run_machine'
/tool/pandora64/.package/ruby-1.9.2-p136/lib/ruby/gems/1.9.1/gems/eventmachine-1.0.0.beta.4/lib/eventmachine.rb:206:in `run'
generator.rb:195:in `block in run'
generator.rb:168:in `standard_exception_handling'
generator:191:in `run'
generator:28:in `< main>'
Can anyone help in achieving my task?
Is there any other way to do this task?

Answer 1

I would use rufus-scheduler for that
require 'rufus-scheduler'
scheduler = Rufus::Scheduler.new
scheduler.every '3m' do
# run script here; would this do?
puts "running generator..."
`ruby generator.rb`
puts "done generating..."
# now when the script is done,
# check if File.exists?
end
scheduler.every '3m' do
# do other things in another thread
end
scheduler.join
sleep 1 while true # in order for your program to stay alive