From: "Carlo E. Prelz" <fluido@...>
Date: 2013-01-25T02:56:10+09:00
Subject: Re: Processes and forks

	Subject: Processes and forks
	Date: Fri 25 Jan 13 02:04:38AM +0900
Sorry for the delay!

Quoting baq s. (lists@ruby-forum.com):

> Hi all, I have a quick problem that I am sure someone here has an
> elegant solution for.
> 
> I have a ruby script that runs in a loop an external linux process via
> gdb:
> 
> ...
> until checks.empty? do
> ...
>     begin
>         Timeout::timeout(5) {
>             system("/usr/bin/gdb --args #{proc} 2>/dev/null")}
>         rescue Timeout::Error
>     end
> ...
> end
> ...
> 
> What I am trying to do is have gdb terminate after 5 seconds of activity
> and move on to debugging the next task. What I am finding however is
> that after 5 seconds, my ruby script quits and returns to the command
> line and the gdb and debugged processes are left running in the
> background.
> 
> I can then hit fg and it will start again but this is not what I want; I
> want my script to execute gdb and launch it to debug a program, after 5
> seconds to terminate debugging and move on to the next binary to
> debug.

The biggest reason why your process does not die is most probably
because you use system (which starts a shell). The signal reaches the
shell but not gdb. I believe that gdb has a bit special way to
handle interrupts.

So, instead of system, you should use Process::spawn. But even then,
read carefully the doc: if you pass a command line (like in your
example), you will still have a shell process in the middle. To avoid
that, you must pass the parts of the command in an array. Every time I
do this, I have to spend a decent amount of time finding how to
correctly split the command.

Anyway, you may try with something like:

pid=Process::spawn(array)

begin
  Timeout::timeout(5) do
    Process::waitpid(pid)		        
  end
rescue Timeout::Error
  Process::kill(pid,'KILL')		    
  Process::waitpid(pid)		    
end

You will have to experiment...

Carlo

-- 
  *         Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as             che bisogno ci sarebbe
  *               di parlare tanto di amore e di rettitudine? (Chuang-Tzu)