server
{

    # 在server块添加以下代码
    # 设置默认值
	set $uid "-";
 
    # 存在值则赋值
	if ( $http_cookie ~* "at_uvid=(\S+)(;.*|$)"){
		set $uid $1; 
	}
	
    # 最后一段数据是该cookie值
	log_format  uid_log  '$remote_addr - $remote_user [$time_local] "$request" '
				  '$status $body_bytes_sent "$http_referer" '
				  '"$http_user_agent" "$http_x_forwarded_for" "$uid"';
				  
	access_log  /var/log/nginx/gretheer.com.log  uid_log;	
    #到此结束

}