How to get subdomain of URL in NGINX

Question

I am wanting to do a redirect based on what subdomain the user is entering.

For example:

<subdomain>.example.com/admin -> <subdomain>.myurl.com

Ideally I want to pass <subdomain> as a parameter to my redirect URL.

I was looking at something along the lines of this:

location ~ (sub).(somewhere).(com)/(some)(thing)/(something)(else) {
  set $var1 = $1; # = sub in above example
  set $var2 = $2; # = somewhere in above example
  set $var3 = $3; # = com in above example
  set $var4 = $4; # = some in above example
  set $var5 = $5; # = thing in above example
  set $var6 = $6; # = something in above example
  set $var7 = $7; # = else in above example
  rewrite ^ $1/$2 last; # would be sub/somewhere
}

based on this post here: Manipulate or split string (I think the syntax of the variable set is wrong in this example but you get the gist).

Answer 1

The domain name part of the URL is not tested by the location directive. You will need to use a named capture in the server_name directive. See this document for details.

For example:

server {
    server_name ~^(?<name>\w+)\.example\.com$;

    location /admin {
        return 301 $scheme://$name.myurl.com/;
    }
}