From: Jp Hastings-spital <jphastings@...>
Date: 2009-03-20T06:00:47+09:00
Subject: Re: Wrapping applications in Ruby

Robert,
Thanks very much for your reply - its helped no end! However I'm still 
having problems:

Firstly (though really this isn't vitally important, as I only *need* 
stdout):
Open3.popen3 doesn't appear to work when I drop it in place of IO.popen 
(where |stdout| is replaced with |stdin,stdout,stderr|).
The called program is definitely running, however even the following 
code outputs nothing:

Open3.popen3 "./counting.rb" do |stdin,stdout,stderr|
  p stdout.read
end

But as I say, I only really need the stdout pipe. The problem here is 
that the program I'm calling doesn't appear to send the \n character at 
all (its the output from HandBrake's CLI), and as such the io block only 
gets called once, at the end of the program's execution. Here's some 
code:

$ HandBrakeCLI {options} 2> /dev/null
\rEncoding: task 1 of 1, 0.09 %\rEncoding: task 1 of 1, 0.13 
%\rEncoding: task 1 of 1, 0.18 %\rEncoding: task 1 of 1, 0.23 %

$ cat wrapper.rb
input = "input.avi"
output = "output.mp4"
IO.popen("/usr/local/bin/HandBrakeCLI -i \"#{input}\" -o \"#{output}\"") 
{ |stdout|
  p stdout.read
}

This prints nothing! Am I right in thinking that the popen block gets 
called every time a \n character is captured by the pipe? (Your 
'counting.rb' uses \n rather than \r - and works) Any ideas (other than 
say, passing the output through sed or something similar)?

Thanks again, JP
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