From: Christopher Brown <cbrown@...>
Date: 2006-08-03T23:30:34+09:00
Subject: Re: How to tell when IO::popen is finished?

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If the IO::popen is creating a child process, how about calling  
Process.waitpid?  Once that returns, the subprocess will have  
completed and the file should be complete.

Cheers,
Chris

On 03 Aug 2006, at 6:29 AM, Daniel N wrote:

> Hi,
>
> I've just installed and had some success with the gnuplot library.
>
> I'm saving the output to a png file (plot.terminal "png") and this  
> all works
> well, but when I try to use the file it isn't finished writing it  
> yet and I
> get an exception.
>
> I've used
>
> Gnuplot.open(  ) do |gp|
> ....
> end
>
> while(!File.exists?("/test2.png") || File.zero?("/test2.png") )
> sleep 0.1
> end
>
> In an attempt to wait until the file is written before I try to do  
> anything
> with it, but this seems a bit too hackish.
>
> Can I capture the Gnuplot.open into a variable and check it?  The last
> statement in the Gnuplot.open is a call to
> IO::popen( cmd, "w") { |io| yield io }
>
> but if I test the class of what is returned it is
> Gnuplot::Plot
>
> not anything to do with IO
>
> Is there a way that I can test the IO::popen to tell when it's  
> finished?

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