nginx: [error] invalid PID number “” in “/usr/local/var/run/nginx/nginx.pid”

在Mac上用brew安装Nginx，然后修改Nginx配置文件，再重启时报出如下错误：

nginx: [error] invalid PID number "" in "/usr/local/var/run/nginx/nginx.pid"

解决办法：

$ sudo nginx -c /usr/local/etc/nginx/nginx.conf

$ sudo nginx -s reload -c /usr/local/etc/nginx/nginx.conf