From: ara.t.howard@...
Date: 2006-11-29T23:52:40+09:00
Subject: Re: I'm a process-spawning idiot.

On Wed, 29 Nov 2006, Devin Mullins wrote:

> For reference's sake, I don't need fork. The same trick works with 
> Kernel#system. Some ugly code:
>  inp, out = IO.pipe
>  # start Thread.critical
>  old_stdout = STDOUT.dup
>  STDOUT.reopen out
>  system 'echo', 'matz is nice!'
>  STDOUT.reopen old_stdout
>  # end Thread.critical
>  out.close
>  puts "Hey guess what: #{inp.read}"
> __END__

this is an insanely bad idea: a cross platform way to hang you system.  try
this:

     harp:~ > cat a.rb
     big = 42.chr * 4242
     inp, out = IO.pipe
     old_stdout = STDOUT.dup
     STDOUT.reopen out
     system 'echo', big
     STDOUT.reopen old_stdout


     harp:~ > ruby a.rb
     # hung process

you can't keep writing to a pipe __unless__ someone is guarunteed to be reading
from the other end!

make it easy on yourself:

     harp:~ > cat a.rb
     require 'rubygems'
     require 'systemu'  # gem install systemu

     systemu ['echo', 'matz is nice!'], :stdout=>STDOUT

     systemu ['echo', 'matz is nice!'], :stdout=>stdout=''
     p stdout

     systemu 'cat', :stdin=>['line1', 'line2'], :stdout=>stdout
     p stdout


     harp:~ > ruby a.rb
     matz is nice!
     "matz is nice!\n"
     "matz is nice!\nline1line2"


kind regards


-a
-- 
if you want others to be happy, practice compassion.
if you want to be happy, practice compassion.  -- the dalai lama