From: Bedo Sandor <bsanyi@...>
Date: 2003-10-17T16:46:30+09:00
Subject: Re: Thread + fork warning

On Wed, Oct 15, 2003 at 11:16:43PM +0900, Yukihiro Matsumoto wrote:
> Hi,
> 
> In message "Re: Thread + fork warning"
>     on 03/10/15, Bedo Sandor <bsanyi@sunserv.kfki.hu> writes:
> 
> |% chmod +x thread.rb ; ./thread.rb
> |./thread.rb:4: warning: fork terminates thread at ./thread.rb:8
> |
> 
> When you fork, all other threads are terminated in the child process.

But only in the child process!?  This is exactly what I
want!  In my program the main process forks&execs other
processes, and in the main process creates a thread to
wait/waitpid the forked process, and log the time and
the pid when done.  I don't need thread in the Ruby
interpreter in the child processes, they only execs an
external command.  I think the correct behavior would
be in a threaded Ruby program that fork does not harm
threads in the main process, but starts an other
interpreter without threads running only with the
commands in the block passed to the Kernel.fork.


> The simplest solution is not mixing fork and threads, for example, use
> system instead of fork+exec.

I have two problems with system():

- I can't log the termination of the spawned
  process.

- Don't know if this is a correct way to start
  background processes: (I need background processes,
  so I have to continue the main Ruby program!)

		def startInBg(unixCommand)
			system(unixCommand.to_s + "&")
		end
	      ...
		startInBg 'zcat /var/log/messages*.gz | logClassifier'

	It works, and there's no warnin, but what
	do You think about  +"&"  ?

-- 
bSanyI