From: Rob Biedenharn <Rob@...>
Date: 2008-05-31T22:35:04+09:00
Subject: Re: getting standard error and output from ruby script in real time


On May 31, 2008, at 8:50 AM, Stefano Crocco wrote:

> On Friday 30 May 2008, Dave Bass wrote:
>> Stefano Crocco wrote:
>>> of KDE. I'd be glad if someone could give
>>> me a hint on this, so that at least
>>> I can know whether I have to look for
>>> documentation about ruby or about
>>> KDE.
>>
>> It's to do with buffering. Buffering takes place within Ruby (I  
>> think)
>> but also in the operating system. Stderr is usually unbuffered  
>> whereas
>> stdout is usually buffered. I.e. the output is accumulated in a  
>> memory
>> buffer until it reaches a certain size, then the block is flushed  
>> to the
>> output stream. This is a lot more efficient that outputting it
>> character-by-character to the output device.
>>
>> In my experience (various languages and OSes), buffering can cause
>> problems that are difficult or impossible to resolve.
>
> Thanks for the information. I think I'll look at the source code of  
> some tool
> which does what I want and see how it works.
>
> Stefano

$stdout.sync = true; $stdout.flush

The #sync setting of true means "unbuffered" (sync'd to the  
destination every time).  If you build up messages, you can call  
#flush on the IO yourself instead.

print "hello "
print "world"
puts "!"
STDOUT.flush

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com