From: James Gray <james@...>
Date: 2008-01-17T22:28:14+09:00
Subject: Re: Quit, if a specific key is hit

On Jan 16, 2008, at 11:43 PM, Pavankumar Kulkarni wrote:

> Excuse me, if this is already discussed... but from from here <http://www.rubyrailways.com/implementing-15-exercises-for-learning-a-new-programming-language/ 
> >.. the author concludes that the following problem cannot be  
> solved.. whats the reason?
> "Display series of numbers (1,2,3,4, 5....etc) in an infinite loop.  
> The program should quit if someone hits a specific key (Say ESCAPE  
> key)."

It can definitely be solved.  Here's a solution that works on most  
Unix-like operating systems, for example:

   #!/usr/bin/env ruby -wKU

   require "io/wait"

   state = `stty -g`
   begin
     system "stty raw -echo cbreak isig"

     1.upto(1.0/0.0) do |n|
       puts n
       exit if $stdin.ready? and $stdin.getc == 27
     end

   ensure
     system "stty #{state}"
   end

   __END__

What the author actually said was that it can't solve it without  
writing some platform specific code or threads.  I don't know how to  
do it without using one of those tricks either.

The reason is that all terminals are different and you are needing to  
interact with it on two levels at once (reading while writing).  This  
is what introduces the need for the platform specific code.

James Edward Gray II