nginx dynamic change root of subdomain to folder on same level - linux

Question

I have this hierarchy on my server:
/var/www/domain.tld/web
/sub
The root in the /etc/nginx/sites-available/domain.tld is set like this:
server {
root /var/www/domain.tld/web;
index index.html index.php index.htm;
...
location / {
try_files $uri $uri/ =404;
}
How can I make the nginx to dynamically forward to specific folder so if I make folder in /sub for example /var/www/domain.tld/sub/subdomain so if I make request http://subdomain.domain.tld it will forward to this folder in folder sub?
So again something.domain.tld would be going to /var/www/domain.tld/sub/something but domain.tld would be going to /var/www/domain.tld/web
Thank you!

Answer 1

First off, welcome to StackOverflow! :)
There are probably a few ways of achieving this, but I would try a simple map to set a $my_subdir variable from the $host, which you can then use in your root. The $host variable is set automatically from the incoming request.
In this example, we're using a regular expression to check if the $host matches subdomain.domain.tld. If it does, capture the subdomain part - the bit in brackets - and use that to make the value "sub/subdomain" ($1 means use the first thing captured from the regular expression). If it doesn't match, it defaults to "web".
That way,
when the request comes in as something like http://domain.tld/foo.html, the response served is /var/www/domain.tld/web/foo.html
if the request comes in as something like http://bar.domain.tld/foo.html, the response served is /var/www/domain.tld/sub/bar/foo.html
map $host $my_subdir {
~^(?:www\.)?((?!www\.)[^.]+)\.domain\.tld$ sub/$1;
default web;
}
server {
root /var/www/domain.tld/$my_subdir;
index index.html index.php index.htm;
...
location / {
try_files $uri $uri/ =404;
}