From: Stefano Crocco <stefano.crocco@...>
Date: 2008-06-16T00:27:58+09:00
Subject: Re: How !isset in Ruby

On Sunday 15 June 2008, Alexey Tafintsev wrote:
> Thank you Marc!!!! I rewrite this example :-)))
> ---------------------
> #!c:/ruby/bin/ruby.exe
>
> $kcode = "windows-1251"
>
> require 'cgi'
> cgi = CGI.new
>
> def auth_lang
>   myauthlang = ENV['HTTP_ACCEPT_LANGUAGE']
>      case myauthlang
>        when /ru/
>            alang = "Ошибка 401: Необходима авторизация"
>        else
>            alang = "Error 401: Authorization Required"
>      end
> end
>
> user = ENV['AUTH_USER']
> password = ENV['AUTH_PASSWD']
>
> unless defined? user
>         puts cgi.header({"Status" => "401 Authorization Required",
> "Type" => "text/html", "WWW-Authenticate" => "Basic realm=\"Web
> Password\""})
>         puts auth_lang
> else
>        if user == nil
>          puts cgi.header({"Status" => "401 Authorization Required",
> "Type" => "text/html", "WWW-Authenticate" => "Basic realm=\"Web
> Password\""})
>          puts auth_lang
>        else
>          real_password=password
>           if real_password!=password
>              puts cgi.header({"Status" => "401 Authorization Required",
> "Type" => "text/html", "WWW-Authenticate" => "Basic realm=\"Web
> Password\""})
>              puts auth_lang
>           end
>        end
> end
> ---------------------

If I'm reading your code correctly, I think your use of defined? is wrong. The 
user local variable will always be defined, because you assign to it. If ENV 
doesn't contain the 'AUTH_USER' entry, user will be nil, but it will be 
defined. If you want to check whether the 'AUTH_USER' environment variable 
exists, you can use

ENV.has_key?('AUTH_USER')

or 

ENV['AUTH_USER'].nil?

If you try running your code, you'll see that the branch corresponding to 
'AUTH_USER' being undefied is never executed, whether that environment 
variable exists or not.

Stefano