升级MacOS 10.13.4 Cocoapods不能正常安装

刚刚将一台恢复出厂的Mac升级到10.13.4，安装cocoapods，输入sudo gem install cocoapods命令后返回结果显示

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /usr/bin directory.

多方查找后得出解决方法，或许是新系统没有创建bin文件夹？
不求甚解，解决命令如下：
sudo gem install -n /usr/local/bin cocoapods

直接顺滑安装，over。