Variable $1 is Empty

[Maxim Dounin]

Hello!

On Thu, Oct 14, 2010 at 05:56:34PM +0700, Indra Setiawan wrote:

> Hi everyone,
> 
> This is my first time installing nginx. I install it on my Debian
> 5.0.3 VPS and use Debian's repository to install it (version: 0.6.32).
> 
> I'm having problem with using regular expression at server_name.
> Here's my configuration:
> 
> server {
>   listen    80;
>   server_name    ~^(.+)\.mydomain\.com$;
>   location / {
>     root    /home/$1/public_html;
>     index    index.html  index.htm;
>   }
> }
> 
> When I hit myusername.mydomain.com, where
> /home/myusername/public_html/ is exist. It gives me a 404 error. And
> when I view the log file, seems like $1 is null or something.
> 
> 2010/10/14 10:47:08 [error] 4924#0: *3 "/home//public_html/index.html"
> is not found (2: No such file or directory), client: 173.245.73.113,
> server: ~^(.+)\.mydomain\.com$, request: "GET / HTTP/1.1", host:
> "myusername.mydomain.com"
> 
> Am I doing wrong?
> Any helps will be appreciated, thanks in advance.

Changes with nginx 0.7.44:

...
    *) Bugfix: if there is the single server for given address:port pair, 
       then captures in regular expressions in a "server_name" directive 
       did not work.
...

Adding another server listening on the same socket should resolve 
the issue, though I would recommend to upgrade.  0.6.* branch is 
legacy and not supported, and you are using an old version from 
this branch.

Additionally, it's *really bad* idea to use enumerated captures in 
server_name.  Things may be screwed up easily - it's enough to add 
another regexp to config (e.g. regexp location) to break anything.  

There are two possible safe aproaches:

1. Use named captures as available in nginx 0.8.25+.

    server {
        server_name ~^(P<name>.+)\.mydomain\.com$;
        root /home/$name/public_html;
        ...
    }

See http://nginx.org/en/docs/http/server_names.html for details.

2. For old versions - use server-level if, i.e.

    server {
        server_name *.mydomain.com;

        set $name "";
        if ($host ~ "^(.+)\.mydomain\.com$") {
            set $name $1;
        } 

        root /home/$name/public_html;

        ...
    }

Maxim Dounin