## Redirect from non-www to www
server {
        server_name example.com;
        # Option 1
        return 301 $scheme://$host$request_uri;

        # Option 2
        rewrite ^ http://$host$request_uri? permanent;
    }

## Default server config

server {
        ...
        listen      192.168.1.1:80 default_server;
        root        /www;
        server_name www.example.com;

选项2似乎与curl一起使用,但是在浏览器调用时它不会重定向,并且返回代码是临时重定向的代码,尽管重写指令设置为permanent：

curl -I example.com
 HTTP/1.1 302 Moved Temporarily
 Server: Nginx
 ...
 Location: http://www.example.com/
 ...