From: Bill Kelly <billk@...>
Date: 2003-04-06T01:40:55+09:00
Subject: Re: reading from $stdout ???

Hi Meinrad,

From: "Meinrad Recheis" <meinrad.recheis@gmx.dot.at>
>
> so it seems to me, that it is necessary to go the long and slowly way 
> over a log file.
> 
> i have annother idea:
> what do you think about aliasing and overwriting all outputting methods 
> in IO like puts, write, print and so on? would that affect really all 
> output?

I'm still not quite sure I'm clear on what you're trying to do
and why, say, popen() wouldn't do the job for you...  But here's
another popen variation that sounds possibly similar to what
you're describing...  (Did you say what Operating System you're
on?  The following won't work on Windows, I believe, due to lack
of availibilty of fork.  (Probably works under cygwin though (?))

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#!/usr/local/bin/ruby -w

# parent, here, can read everything child sends to stdout
def do_parent_stuff(io)
  io.each {|line| puts "child emitted: #{line}" }
end

# child gets to do both ruby print statements and run
# system commands, all of whose stdout are piped to the parent
def do_child_stuff
  puts "Hello!!!  I'm child #{Process.pid}."
  system("ls -l /usr/lib/ruby/1.6/net")
  puts "Bye now!!!"
end

IO.popen("-") do |io|
  io ? do_parent_stuff(io) : do_child_stuff
end
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

on my system the output is:

child emitted: Hello!!!  I'm child 2743.
child emitted: total 172
child emitted: -rw-r--r--    1 root     root        13968 Jul 24  2002 ftp.rb
child emitted: -rw-r--r--    1 root     root        32781 Jul 24  2002 http.rb
child emitted: -rw-r--r--    1 root     root        52629 Jul 24  2002 imap.rb
child emitted: -rw-r--r--    1 root     root        14189 Jul 24  2002 pop.rb
child emitted: -rw-r--r--    1 root     root        14652 Jul 24  2002 protocol.rb
child emitted: -rw-r--r--    1 root     root        11220 Jul 24  2002 smtp.rb
child emitted: -rw-r--r--    1 root     root        19823 Jul 24  2002 telnet.rb
child emitted: Bye now!!!


Hope this helps,

Bill