/dev/null

输出到空设备

>/dev/null 2>&1
1>/dev/null 2>&1
2>/dev/null

printf "%-40s %40s\n" "Stopping Nginx" "[ OK ]"

参考：

https://blog.csdn.net/wuruixn/article/details/8535378
https://blog.51cto.com/meiling/2057676