From: Joel VanderWerf <vjoel@...>
Date: 2005-09-04T10:33:37+09:00
Subject: Re: Detecting a hung/stalled child process

junk5@microserf.org.uk wrote:
> Hi all
> 
> I need to be able to start an external process (as one might do by
> using backquotes, e.g. `ls some-dir`) but then kill that process some
> time later if it has not completed. I cannot assume that the program I
> call will ever complete (i.e. it potentially has an infinite loop), so
> I want to be able to let the program run for 4000 microseconds (or
> whatever) and if it hasn't completed, kill it.
> 
> I'd be very grateful if anyone could advise me on how to do this. It
> would be desirable if the solution was as platform-neutral as possible.
> 
> Many thanks in advance.
> 
> Chris
> 

Someone just put a fork-based library for this on RAA:
  http://raa.ruby-lang.org/project/forkedtimeout/
but fork doesn't port well. The following might work, and I'm pretty
sure it works on both windows and linux/unix:

require 'timeout'

Thread.new do
  begin
    Timeout.timeout(1) do
      `sleep 2` # or system "sleep 2"
      puts "done"
    end
  rescue TimeoutError
    puts "timed out"
  end
end

10.times do
  puts "waiting"
  sleep 0.5
end

__END__

output:

waiting
waiting
waiting
timed out
waiting
waiting
waiting
waiting
waiting
waiting
waiting

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407