You do not say how you eval'ed the TWO expressions.

If you are in the scratch buffer and place the cursor at the end of the 2nd line, and hit C-j, emacs is only going to eval that line, which is the last sexp before the cursor.

Try putting your cursor at the end of this, and hit C-j:

(progn

  (setq file-name "test")
 
(describe-variable 'file-name))


Or eval each line one after the other.


>________________________________
>From: filebat Mark <filebat.mark@gmail.com>
>To: Drew Adams <drew.adams@oracle.com>
>Cc: help-gnu-emacs@gnu.org
>Sent: Thursday, October 27, 2011 12:47:44 PM
>Subject: Re: what's the mystery of file-name variable?
>
>
>Hi Adams
>
>Thanks a lot for your quick response.
>
>After clean start with emacs -Q, the problem remain.
>
>Below is my emacs-version:
>Emacs 23.3.2 (i686-pc-linux-gnu, GTK+ Version 2.20.1) of 2011-04-06 on wei-laptop
>
>
>
>On Fri, Oct 28, 2011 at 12:44 AM, Drew Adams <drew.adams@oracle.com> wrote:
>
>> (setq file-name "test")
>>> (describe-variable 'file-name)
>>
>>>  file-name's value is nil
>>>
>>>  Documentation:
>>>  Not documented as a variable."
>>
>>It works for me.  Says file-name's value is "test" (and not documented etc.).
>>
>>Give a recipe starting from emacs -Q.
>>
>>
>
>
>-- 
>Thanks & Regards
>
>Denny Zhang
>
>
>
>