From: Jim Weirich <jweirich@...>
Date: 2002-08-18T02:49:19+09:00
Subject: Re: How do I dup file descriptors in ruby?  (diverting STDERR)

    Richard> Thank you for the suggestion, but perhaps I should have
    Richard> been more specific about what I really want to do.  The
    Richard> following is closer to what I'm interested in.  It's a
    Richard> very common lick to play in Korn, perl and C and if I
    Richard> have to go through a symphony to do the same thing in
    Richard> ruby then, to paraphrase the great American poet Chuck
    Richard> Berry, I'll lose the beauty of the melody.

Cute analogy :-)

[... lick elided ...]

Hmmm ... I count 6 extra lines for your lick.

Fortunately, in Ruby you can capture licks in a JamMan effects box and
replay the lick whenever you like.

Write the following file one time and store it somewhere in your
standard Ruby path.

-- File: redirect.rb -------------------------------------------------
    def redirect_to(fn)
      olddefout = $defout
      oldstderr = $stderr
      open(fn, "a") do |file|
        $defout = file
        $stderr = file
        begin
          yield
        ensure
          $defout = olddefout
          $stderr = oldstderr
        end
      end
    end
----------------------------------------------------------------------

Now, to playback your lick, just do  ...

    require 'redirect'
    redirect_to("logfile.txt") {
      puts "output now goes to the log file"
    }

Just three lines of overhead instead of the six.  And it handles
exceptions and early exits properly.

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)