Mac OS 10.13.1后删除了telnet命令，telnet是明文密码所以为了安全起见，苹果就取消这个了。
好了我们来解决这个问题：
首先我们直接安装telnet
//在终端输入
brew install telnet
C0199BD4-F5A3-4872-8498-88D4CFE2CC79.png
这是没有安装Homebrew造成的
我们也可以终端输入
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
196101AF-E2A0-44CD-98BC-9CC4FB1875BE.png
/usr/local/Cellar is not writable. You should change the ownership and permissions of /usr/local/Cellar back to your user account 这时候按照它的的提示做就OK，终端输入
sudo chown -R $(whoami) /usr/local/Cellar
7E930F98-621B-4FB9-8BC5-DA7EE5F32DA3.png
Already up-to-date.
Error: Could not link:
/usr/local/share/man/man1/brew.1
Please delete these paths and run `brew update`.
Error: Could not link:
/usr/local/share/doc/homebrew
那我们就终端删除这几个文件：
jiangs:~ liangc$ rm /usr/local/share/man/man1/brew.1
override rw-rw-r-- root/wheel for /usr/local/share/man/man1/brew.1? y
jiangs:~ liangc$ rm -rf /usr/local/share/doc/homebrew
8FDA1E13-E30F-4DAD-BF90-EDFB97FD822C.png
终端输入
sudo chmod -R 777 /usr/local/share/doc/homebrew
然后终端执行
jiangs:homebrew liangc$ rm -rf /usr/local/share/doc/homebrew
jiangs:homebrew liangc$ ruby -e "$(curl -fsSL --insecure https://raw.githubusercontent.com/Homebrew/install/master/install)"
OK成了，我们来安装吧
brew install telnet
AAD72E8F-815A-4CE0-9C9E-F18090A7094F.png
快去更新XCode吧！
