Server name

http://nginx.org/en/docs/http/server_names.html

• server_name
• server_name _;

https://stackoverflow.com/questions/45318758/nginx-variable-for-subdomain

server {
    listen       80;
    server_name  ~^(?<name>.+)\.example\.com$;
    return       301 http://example.com/$name$request_uri;
}

See also

• Nginx: nginx -t, nginx.conf, /etc/nginx/fastcgi.conf, Nginx Sample Configurations, server, ssl_certificate, redirect, return, rewrite, sendfile, request_uri, server_name, listen, /etc/nginx/snippets/, /etc/nginx/sites-enabled/default
• Web server: Nginx: /etc/nginx/nginx.conf, nginx -t, Nginx logs, Nginx change log, PHP, php-fpm, Let's encrypt, Nginx directives, Reverse Proxy, Configure HTTP redirection Nginx, Return, proxy_pass (Reverse proxy), ngx_http_rewrite_module, /etc/nginx/sites-enabled/, error.log, access.log, /nginx status, AIO