Re: return DECLINED or OK?

[Raymond Wan <suppressed>]

Hi,


J. Peng wrote:
> On Fri, Feb 29, 2008 at 7:03 PM, Torsten Foertsch
> <suppressed> wrote:
>   
> >  Example continued: The entry /var/www/a/b exists on disk either as file or as
> >  directory but /var/www/a/b/c does not. Then after MapToStorage $r->filename
> >  is /var/www/a/b and $r->path_info is /c/d/e.
> >     
> Sorry I can't understand for this. If /var/www/a/b exists but
> /var/www/a/b/c not, why user requests it? What's $r->path_info? How to
> get path_info from filename? thanks again.
>   


I'm not sure if I can help by cutting in here as I'm some what learning 
Apache and modperl myself.

$r is not a file or a filename.  This is Perl, remember?  :-)  So, $r is 
a scalar variable and, to be precise, the global variable for the Apache 
RequestRec object.  Take a look at:

http://perl.apache.org/docs/2.0/api/Apache2/RequestRec.html

and

http://perl.apache.org/docs/2.0/api/Apache2/RequestRec.html#C_path_info_

to see what Torsten meant by the "path_info".

As for /var/www/a/b/c, a user can request for a file that does not 
exists.  The key is what Torsten said about "walking the hierarchy".  
So, if /var/www/a/b/c/d/e does not exist, it sees if /var/www/a/b/c/d 
exists.  If not, it tries /var/www/a/b/c/.  It continues doing this, 
"walking [up] the hierarchy", until it finds a match.  In Torsten's 
example, this would be:

/var/www/a/b/

Then, the RequestRec object now stores two parts.  A filename 
"/var/www/a/b/" and a path_info "/c/d/e".  Why would you want to do 
that.  Well, an example that I saw in the Mason Book (Note:  don't 
confuse yourself with learning this right now, but I just want to 
mention where I got the example from) which helped me understand this 
was as follows.  Say you have a news site like:

http://example.com/archive/news/2008/02/29/index.html

A user might request that, but it wouldn't make sense to have 365 
"index.html"'s every year (ok, 366 this year :-) ).  Instead, you could 
do a trick above and keep going up the hierarchy until you have a 
filename "/var/www/archive/news/" and a path_info 
"/2008/02/29/index.html".  You can then use the path_info as a query 
string to some database to retrieve today's news.  i.e., you don't 
actually have a file sitting at:

/var/www/archive/news/2008/02/29/index.html

but the user doesn't know this and probably doesn't care as long as s/he 
can see today's news.

I hope this helps and I hope I didn't mess up your example, Torsten.  If 
so, please correct me for my benefit, as well!  :-)

Ray