From: Robert Dober <robert.dober@...>
Date: 2006-03-25T00:32:31+09:00
Subject: Re: redirecting stdout to a String

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On 3/24/06, Mark Volkmann <r.mark.volkmann@gmail.com> wrote:
>
> On 3/24/06, James Edward Gray II <james@grayproductions.net> wrote:
> > On Mar 24, 2006, at 7:50 AM, Mark Volkmann wrote:
> >
> > > I wrote a unit test for a method that writes to stdout. I got it to
> > > work, but I'm not sure my approach was the best. Is there a more
> > > recommended way to do this?
> > >
> > >     # Create a String with a singleton write method
> > >     # that allows it to take the place of stdout.
> > >     actual =3D '''
> > >     def actual.write(data); self << data; end
> >
> > See the standard library, StringIO.
>
> Thanks!  I have that working, but it's not clear to me how that is
> better. In fact, it seems to take more code to do it that way. I now
> have this.
>
>   require 'stringio'
>
>   sio =3D StringIO.new
>   old_stdout, $stdout =3D $stdout, sio
>   # Invoke method to test that writes to stdout.
>   $stdout =3D old_stdout # restore stdout
>   actual =3D sio.string
>
> Am I overcomplicating this?
>
> --
> R. Mark Volkmann
> Object Computing, Inc.
>
>
I made a benchmark of both solutions, but I was surprised how small the
difference was.
StringIO is faster, as I expected. See below for results.
Apart from that I feel that stringio will have adavantages for giving you a
complete API.
But for a quick solution the singleton method seems elegant and I like it a
lot, after all
you do not require( which was not benchmarked!!!) 'stringio' and run a core
script.

But for reusable code I'll defenitely go for stringio.

Cheers
Robert

---------------------------------- 8< -------------------------------------


 cat stringio.rb;ruby stringio.rb
#!/usr/bin/env ruby
   # Create a String with a singleton write method
   # that allows it to take the place of stdout.
 require 'benchmark'
 require 'stringio'

 n =3D 500000
 r1 =3D r2 =3D nil
 Benchmark.bm do
        |bm|
        bm.report "single string" do
            actual =3D ''

            def actual.write(data); self << data.to_s; end
            old_stdout, $stdout =3D $stdout, actual
            n.times{ |i| $stdout.write i }
            $stdout =3D old_stdout
            r1=3D actual
        end # do

        bm.report "stringio     " do
                 sio =3D StringIO.new
                 old_stdout, $stdout =3D $stdout, sio
                 n.times{ |i| $stdout.write i}
                 # Invoke method to test that writes to stdout.
                 $stdout =3D old_stdout # restore stdout
                 r2 =3D sio.string
        end # do
 end # do

 raise Exception unless r1 =3D=3D r2


      user     system      total        real
single string  1.460000   0.000000   1.460000 (  1.823057)
stringio       1.320000   0.010000   1.330000 (  1.828039)


--
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

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