Beginner Q: Kernel#puts, STDOUT, $stdout relation

Can anybody help me understanding the relation between Kernel#puts, STDOUT and $stdout?

I thought 'puts' is equivalent to '$stdout.puts'. Why 'puts' doesn't give same result as 'STDOUT.puts'?

class << STDOUT
  def puts(*args)
     args[0] = "I say " + args[0] unless args.empty?
     super(args)
  end
end

puts "hello"
STDOUT.puts "hello"
$stdout.puts "hello"
=> hello
     I say hello

Thank you in advance
-andre

···

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Puts is a method of Kernel.

Andreas S wrote:

···

Can anybody help me understanding the relation between Kernel#puts, STDOUT and $stdout?

I thought 'puts' is equivalent to '$stdout.puts'. Why 'puts' doesn't give same result as 'STDOUT.puts'?

class << STDOUT
def puts(*args)
    args[0] = "I say " + args[0] unless args.empty?
    super(args)
end
end

puts "hello"
STDOUT.puts "hello"
$stdout.puts "hello"
=> hello
    I say hello

Thank you in advance
-andre

_________________________________________________________________
Talk now to your Hotmail contacts with Windows Live Messenger. http://clk.atdmt.com/MSN/go/msnnkwme0020000001msn/direct/01/?href=http://get.live.com/messenger/overview

Can anybody help me understanding the relation between Kernel#puts, STDOUT and $stdout?

I thought 'puts' is equivalent to '$stdout.puts'. Why 'puts' doesn't give same result as 'STDOUT.puts'?

class << STDOUT
def puts(*args)
    args[0] = "I say " + args[0] unless args.empty?
    super(args)
end
end

puts "hello"

This calls $stdout.write "hello\n"

STDOUT.puts "hello"
$stdout.puts "hello"
=> hello
    I say hello

PS:

Please mess with $stdout, not STDOUT, if at all possible.

http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout

···

On Dec 8, 2006, at 14:16 , Andreas S wrote:

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!

From: Daniel Finnie <danfinnie@optonline.net>
Reply-To: ruby-talk@ruby-lang.org
To: ruby-talk@ruby-lang.org (ruby-talk ML)
Subject: Re: beginner Q: Kernel#puts, STDOUT, $stdout relation
Date: Sat, 9 Dec 2006 07:28:20 +0900

Puts is a method of Kernel.

But, doesn't it depend on what IO object $stdout holds? I redefined $stdout 'puts' function, but why it does not affect Kernel's puts method?

···

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Ah, yes, I decided to snoop around in the c files and this fits what I thought I saw in there.

Thanks so much to all.

Regards,

-andre

···

From: Eric Hodel <drbrain@segment7.net>
Reply-To: ruby-talk@ruby-lang.org
To: ruby-talk@ruby-lang.org (ruby-talk ML)
Subject: Re: beginner Q: Kernel#puts, STDOUT, $stdout relation
Date: Sat, 9 Dec 2006 09:39:56 +0900

On Dec 8, 2006, at 14:16 , Andreas S wrote:

Can anybody help me understanding the relation between Kernel#puts, STDOUT and $stdout?

I thought 'puts' is equivalent to '$stdout.puts'. Why 'puts' doesn't give same result as 'STDOUT.puts'?

class << STDOUT
def puts(*args)
    args[0] = "I say " + args[0] unless args.empty?
    super(args)
end
end

puts "hello"

This calls $stdout.write "hello\n"

STDOUT.puts "hello"
$stdout.puts "hello"
=> hello
    I say hello

PS:

Please mess with $stdout, not STDOUT, if at all possible.

http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!

_________________________________________________________________
Talk now to your Hotmail contacts with Windows Live Messenger. http://clk.atdmt.com/MSN/go/msnnkwme0020000001msn/direct/01/?href=http://get.live.com/messenger/overview

It's a tricky relationship, and I'm not quite sure how or why it works
this way, but Kernel#puts does not use STDOUT's (or $stdout, they can
be different) puts. It does use STDOUT/$stdout (I'm not really sure
which) but IIRC Kernel#puts is implemented directly using the write
method. Caveat here though -- the write method is called *twice*, once
for the argument, then again for the newline. So modifying your source
to rewrite "write" instead of "puts":

  class << STDOUT
    def write(*args)
      args[0] = "I say " + args[0] unless args.empty?
      super(args)
    end
  end

  puts "hello"
  STDOUT.puts "hello"
  $stdout.puts "hello"

produces:

  $ ruby test.rb
  I say helloI say

Jacob Fugal

···

On 12/8/06, Andreas S <andreas_s@hotmail.com> wrote:

>From: Daniel Finnie <danfinnie@optonline.net>
>Reply-To: ruby-talk@ruby-lang.org
>To: ruby-talk@ruby-lang.org (ruby-talk ML)
>Subject: Re: beginner Q: Kernel#puts, STDOUT, $stdout relation
>Date: Sat, 9 Dec 2006 07:28:20 +0900
>
>Puts is a method of Kernel.

But, doesn't it depend on what IO object $stdout holds? I redefined $stdout
'puts' function, but why it does not affect Kernel's puts method?