https://blog.wongcw.com/2020/11/10/%e8%98%8b%e6%9e%9c%e9%87%8d%e6%96%b0%e8%ae%93unix-shell-ios%e6%87%89%e7%94%a8%e9%80%b2%e5%85%a5%e6%87%89%e7%94%a8%e5%95%86%e5%ba%97/