Nginx multiple domain names point to the same website

Question

My domain name is example.com
I want www.example.com to jump to example.com
My nginx configuration is

server {
       listen 80;
       server_name www.example.com example.com;
       root /var/www/web;

       if ($http_host == "www.example.com") {
                 rewrite ^ http://example.com$request_uri permanent;
       }

no. . .

Answer 1

server {
  listen 80;
  server_name www.example.com;
  return 301 http://example.com/$request_uri;
}

server {
  listen 80;
  server_name example.com;
  root /var/www/web;
}

Answer 2

if ($host = 'www.example.com' ) {
    rewrite ^/(.*)$ http://example.com/$1 permanent;
}

Answer 3

if ($http_host = www.example.com) {
    rewrite  (.*)  http://example.com$1 permanent;
}