命令行执行命令时报错You don't have wri

这是因为要执行这些操作时必须有管理员的权限(比如更新软件)，比如更新cocoapods时报错：

MyPro:~ MyPro$ gem install cocoapods
ERROR: While executing gem ... (Gem::FilePermissionError) You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.

解决方法：只需要在命令前加上sudo，例如:sudo gem install cocoapods即可。sudo是获取管理员权限，现在按照步骤输入管理员密码即可。

但，接着又报错：

MyPro:~ MyPro$ sudo gem install cocoapods
Password:
ERROR: While executing gem ... (Errno::EPERM) Operation not permitted - /usr/bin/pod

解决办法：

sudo gem install -n /usr/local/bin cocoapods````

###治标不治本，下一次还会再出现，永久解决办法：
命令行工具网址：[http://brew.sh](http://brew.sh/)
运行命令行：

$ /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
$ brew install ruby````