From: Brian Candler <B.Candler@...>
Date: 2003-04-05T20:59:34+09:00
Subject: Re: reading from $stdout ???

On Sat, Apr 05, 2003 at 06:43:04PM +0900, Meinrad Recheis wrote:
> thanks brian, that sounds good. but is very complicated for capturing 
> the whole output of a large program.
> 
> i would like to connect a pipe to the $stdout (i have no gess how to do 
> it, but hope that you understand my intention) and in one location of my 
> main loop (in the display procedure)
> i would like to read whatever is on the stream and print it to my 
> graphical output.

Ah, in that case probably what you want is:

  $defout = File.open("log.txt","w")
  puts "hello"    # goes to log file

However, any sub-processes which you spawn which write to stdout will write
their output directly to the operating system's stdout, bypassing Ruby
altogether.

The only ways round that that I know of are:

(1) explicitly capture the stdout of the child process, using `` or IO.popen
    as described before, and write it to $defout yourself

(2) when spawning the child process, redirect its stdout to a file, e.g.
        system("ls >log2.txt")

(3) redirect stdout before you start the ruby interpreter itself, e.g.

        ruby myprog.rb >log.txt

Regards,

Brian.