From: Hugh Sasse <hgs@...>
Date: 2006-11-21T05:45:02+09:00
Subject: Re: fork, trap and exec. Pickaxe typo?

On Tue, 21 Nov 2006, Nate Murray wrote:

> Yeah, but how do I wait for an unknown amount of time? It would seem
> that this would do it:
> 
> trap("CLD") {
>   pid = Process.wait
>   puts "Child pid #{pid}: terminated"
> }
> 
> 1.upto(4) do
>   fork do
>     exec("sleep 3 && echo \"hello $HOSTNAME #{Process.pid}\n\"")
>   end
> end
> 
> Process.waitall

  puts Process.waitall

=begin ri_output
------------------------------------------------------- Process::waitall
     Process.waitall   => [ [pid1,status1], ...]
------------------------------------------------------------------------
     Waits for all children, returning an array of _pid_/_status_ pairs
     (where _status_ is a +Process::Status+ object).
        [...]
=end

  # So while I'm not sure what's happening to the missing signal
  # you should be able to see that all the processes have finished.
> 
> But trap isnt always called on all the children.

> 
> Example output:
> 
        [...]
> Notice that 4137 never called the trap callback even though
> Process.waitall was called.
> 
        Hugh