From: Brian Candler <b.candler@...>
Date: 2010-01-05T05:07:45+09:00
Subject: Re: "Dummy" IO object to push and pull data?

Shay Hawkins wrote:
> Test program:
...
>       tstamp("> Time's up! Sending input...")

But that message never appears in the output you showed - and this line 
occurs *before* the puts. So at the moment looks either (a) sleep(5) is 
sleeping indefinitely, or (b) the whole thread has terminated with an 
exception.

A better test would be a standalone pair of ruby programs, because then 
you have something which anyone can reproduce the problem with (*).

Here's your test program, very slightly modified, with a partner 
program.

==> prg1.rb <==
Thread.abort_on_exception = true
require "open3"

command = "ruby prg2.rb"
inline, outline, errline = Open3.popen3(command)

def tstamp(line)
  puts("#{Time.now().to_s().split(" ")[3]}   #{line}")
end

# Read from stderr, thread stdin input
loop do
  tstamp("> Awaiting data...")
  line = errline.gets().strip()
  tstamp("Output: #{line}")

  if(line == "0")
    tstamp("> Received the required line.")

    Thread.new() do
      tstamp("> The thread has been created.")
      sleep(5)

      tstamp("> Time's up! Sending input...")
      inline.puts("EXIT")
      tstamp("> The input has been sent.")
    end
  end
end

==> prg2.rb <==
i = -2
loop do
  $stderr.puts i
  i += 1
  if select([$stdin],nil,nil,2)
    line = $stdin.gets.chomp
    $stderr.puts ">>> Received #{line} <<<"
  end
end

And if I run it under Linux, here's what I get:

$ ruby prg1.rb
19:58:05   > Awaiting data...
19:58:05   Output: -2
19:58:05   > Awaiting data...
19:58:07   Output: -1
19:58:07   > Awaiting data...
19:58:09   Output: 0
19:58:09   > Received the required line.
19:58:09   > The thread has been created.
19:58:09   > Awaiting data...
19:58:11   Output: 1
19:58:11   > Awaiting data...
19:58:13   Output: 2
19:58:13   > Awaiting data...
19:58:14   > Time's up! Sending input...
19:58:14   > The input has been sent.
19:58:14   Output: >>> Received EXIT <<<
19:58:14   > Awaiting data...
19:58:14   Output: 3
19:58:14   > Awaiting data...
19:58:16   Output: 4
19:58:16   > Awaiting data...
19:58:18   Output: 5
19:58:18   > Awaiting data...
^Cprg1.rb:13:in `gets': Interrupt
  from prg1.rb:13
  from prg1.rb:11:in `loop'
  from prg1.rb:11

What happens if you run this under Windows?

Now, this slightly muddies the water because prg2.rb also depends on 
being able to select(), as I wanted it to be able to sleep *and* receive 
data on stdin, the same as your main program does. So it would be also 
interesting to know what happens if you do "ruby prg2.rb" by itself. It 
*should* print a new number every 2 seconds, and if you type something 
onto stdin, it should echo it back as >>> Received ... <<<

What I'm trying to say is, if you can make prg2.rb work properly (or 
make another of version of prg2 work using threads), then you ought to 
be able to make prg1.rb work properly too.

(*) Incidentally: for someone to reproduce this problem, they'll need to 
know exactly what platform you have. You said "Windows Vista" but you 
didn't say which version of Ruby, nor which package (Cygwin? One-Click 
Installer? Other?)

Regards,

Brian.
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