From: Markus Schirp <mbj@...>
Date: 2007-10-15T04:29:18+09:00
Subject: Re: Capturing the output of an external program line by line

Am Mon, 15 Oct 2007 04:23:41 +0900
schrieb Aditya Mahajan <adityam@umich.edu>:

> Hi,
> 
> I want to run an external program in ruby. The external program takes 
> a long time to execute. While running, it gives the information on 
> stdout about what it is doing. How can I run the external program 
> inside ruby so that I can capture this information, and display it on 
> stdout? I tried %x{...}, `...` and system("...."), but all of them 
> give me a result AFTER the external program has finished executing, 
> not during its execution.
> 
> Thanks,
> Aditya
> 

in,out = IO.popen($command)

in refers to standart input of the program
out to the standart output

you can receive lines from the program using in.gets. Beware, "in" may
be a reserved word in ruby.