From: "ara.t.howard" <ara.t.howard@...>
Date: 2008-06-03T01:46:45+09:00
Subject: Re: Traping signals on child processes




On Jun 2, 2008, at 10:17 AM, Mário Lopes wrote:

>
> Tried that with the following example just for testing..
>
> fork { exec "echo 'start'; sleep 20; echo 'end'" }
>
> And if I issue a SIGINT the warning gets printed but the 'end' never
> gets printed meaning that the process ended abruptly. That's what I'm
> trying to avoid :-/
>
> Mário

you have to avoid races, programs which install their own handlers  
(like ruby), and confusing the issue by shelling out three child   
processes in instead of one:

cfp:~ > cat a.rb
ready = :ready

pipe = IO.pipe

trap('INT'){ STDERR.puts "#{ Process.pid } killed" }

pid = fork{
   pipe.first.close
   pipe = pipe.last
   pipe.puts ready
   sleep
}

trap 'INT', 'DEFAULT'

pipe.last.close
pipe = pipe.first
ready = pipe.gets

STDERR.puts "parent: #{ Process.pid }"
STDERR.puts "child: #{ pid }"

Process.kill 'INT', pid

Process.waitpid pid, Process::WUNTRACED


cfp:~ > ruby a.rb
parent: 25227
child: 25228
25228 killed



basically ruby is, by default, going to relay the signal to the child,  
you need to catch it and do something sensible with it.


a @ http://codeforpeople.com/
--
we can deny everything, except that we have the possibility of being  
better. simply reflect on that.
h.h. the 14th dalai lama