From: Matthieu Riou <matthieu.riou@...>
Date: 2007-07-07T14:18:00+09:00
Subject: Immediately terminating a pipe

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Hi,

I'm opening a pipe and forking a command using popen3 to send it some data.
However the data "accumulates" so even if I close the stream, the command
continues running for a little while. In my case I'd like to find a way to
stop it immediately. This explanation doesn't sound very clear so let me
elaborate with an example.

Say that I want to stream some music to mpg123 to get it played. I can do
something like:

require 'open3'
mpg_in, mpg_out, mpg_err = Open3.popen3("mpg123 -q -")
f = File.new("Placebo - Pure Morning.mp3")
200.times { mpg_in.write f.read(1024) }
mpg_in.close

You'll notice that the music continues playing after exiting the loop for a
little while even though the input stream has been closed. I'd like it to
stop immediately. I guess there must be a buffer or something.

The only solution I've found so far is to kill the forked process (in that
case mpg123) when I really want it to stop. And there's one more problem
here: popen3 doesn't give you the forked process id . So I have to hack
Open3 to give me the forked process id.

Anybody has a better idea? Any more elegant alternative than killing?

Thanks!
Matthieu

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