From: "M. Edward (Ed) Borasky" <znmeb@...>
Date: 2006-07-31T14:10:25+09:00
Subject: Re: Environment variables with empty value missing from ENV?

M. Edward (Ed) Borasky wrote:
> Clifford Heath wrote:
>> Under Windows XP (using cygwin's bash, but native Ruby), I
>> found the following six-legged feature:
>>
>> $ ruby -v
>> ruby 1.8.2 (2004-12-25) [i386-mswin32]
> Have you tried this with Ruby 1.8.4? What does "which ruby" say?
>
>> $ unset FOO; env|grep FOO; ruby -e 'p ENV["FOO"]'
>> nil
>> $ FOO= env |grep FOO
>> FOO=
> Is this legitimate? I've never seen anyone use this construct ("FOO= ")
> What happens when you do    FOO=''   ?
>> $ FOO= ruby -e 'p ENV["FOO"]'
>> nil
> What does  ruby -e 'p "" '   do?
>> $ FOO=xyz ruby -e 'p ENV["FOO"]'
>> xyz
>> $
>>
>> The problem is that ENV doesn't contain the key FOO in
>> the 2nd case, where the value is zero-length.
>>
>> What possible justification could there be for this behaviour?
> I'm not sure ... is this construct useful to you in some way? Setting 
> an environment variable to an empty string and reading it in Ruby?
>
>>
>> Clifford Heath.
>>
>>
>
>
>
On Gentoo Linux:


znmeb@DreamGate ~ $ export FOO=
znmeb@DreamGate ~ $ set|grep FOO
FOO=
_=FOO
znmeb@DreamGate ~ $ export FOO=""
znmeb@DreamGate ~ $ set|grep FOO
FOO=
_=FOO
znmeb@DreamGate ~ $ which ruby
/usr/bin/ruby
znmeb@DreamGate ~ $ ruby -v
ruby 1.8.5 (2006-06-22) [i686-linux]
znmeb@DreamGate ~ $ ruby -e 'p ""'
""
znmeb@DreamGate ~ $ ruby -e 'p ENV["FOO"]'
""
znmeb@DreamGate ~ $ bash --version
GNU bash, version 3.1.17(1)-release (i686-pc-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
znmeb@DreamGate ~ $


Happy to help ... at least it works the way I expected it to work on 
Linux with Ruby 1.8.5 (pre something, IIRC). I still don't see how it's 
useful, though. :)