From: bob@... (Bob Proulx)
Date: 2004-10-10T13:00:55+09:00
Subject: Re: How to exit properly with a signal?

gabriele renzi wrote:
> Bob Proulx ha scritto:
> >   ruby -e 'sleep 10' ; echo $?
> >   -e:1:in `sleep': Interrupt      from -e:1
> >   1
> 
> I guess you want:
> trap("INT")  { puts "interrupted" }

Thank you for your reply.  Unfortunately that does not work either.
Run, then interrupt:

  ruby -e 'trap("INT") { } ; sleep 10' ; echo $?
  0

The return code is now zero indicating a successful program
completion.  Of course I can exit with an error in the handler such as
in the following example.

  ruby -e 'trap("INT") { exit 1 } ; sleep 10' ; echo $?
  1

But again, this does not return the proper wait(2) status to the
caller.  The caller can't tell that the child process was terminated
with a signal.

In perl one does the following:

    $SIG{$sig} = 'DEFAULT';
    kill($sig,$$);

In C one does the following:

  act.sa_flags = 0;
  act.sa_handler = SIG_DFL;
  sigaction(sig,&act,0);
  raise(sig);

I tried doing in ruby what I would do in perl.  Basically the
following.

    trap sig, "DEFAULT"
    Process.kill sig, $$

But no joy.  Again my efforts were not able to produce the required
results.

  ruby ./signals.rb ; echo $?
  starting program
  signal INT received, cleaning up
  ./signals.rb:5:in `sighandler': Interrupt       from ./signals.rb:7
          from ./signals.rb:7:in `call'
          from ./signals.rb:9:in `sleep'
          from ./signals.rb:9
  1

How can I exit with the same wait(2) status as if the program was
terminated on a signal?  Hopefully someone will know the solution to
this problem.

Thanks
Bob