From: Gary Wright <gwtmp01@...>
Date: 2007-04-05T14:09:43+09:00
Subject: Re: Forking and copying variables


On Apr 5, 2007, at 12:19 AM, Joel VanderWerf wrote:
> Are you using the win32/process version of fork? If so, what you  
> are seeing is one of the differences between that and native fork  
> on unix/linux.
>
> For example, this code:
>
>   puts "foop"
>
>   Process.fork do
>     puts "fork"
>   end
>
> on linux produces the following output:
>
> foop
> fork
>
> and on windows (requiring 'win32/process' first) produces:
>
> foop
> foop
> fork


This seems like a typical IO buffering problem rather than
different semantics regarding process data shared across
forks.

It looks like in the Windows version stdout is buffered such
that 'foop' is not written before the fork.  After the fork
the output buffer still has 'foop\n' in it.  At some point
the parent flushes its buffer (with just 'foop\n') and then
later the child flushes its buffer (with 'foop\nfork\n')
giving you the result you see.

This is a common 'gotcha' in Unix if stdout is going to
a file and so it isn't line buffered.  If stdout goes to
a terminal device it is line buffered and so the problem
doesn't occur since each call to puts flushes a line of
output.

I'm not a Windows guy but that's what seems to be happening
in Joel's example.

I'm still not sure what problem the original poster is
encountering.  Some sample code and output would help.


Gary Wright