安裝方式有兩種 curl 或 wget 

curl 方式:    
sh -c "$(curl -fsSL https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh)" 

wget 方式:
sh -c "$(wget https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh -O -)" 

安裝報錯

Cloning Oh My Zsh...
xcrun: error: active developer path ("/Users/guokai/Desktop/Xcode.app/Contents/Developer") does not exist
Use `sudo xcode-select --switch path/to/Xcode.app` to specify the Xcode that you wish to use for command line developer tools, or use `xcode-select --install` to install the standalone command line developer tools.
See `man xcode-select` for more details.
Error: git clone of oh-my-zsh repo failed
 

先輸入下面命令在執行安裝zsh指令

sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer

安裝成功介面