fish是帅当时我买了macbook之后就帮我装的，后来重装了一次系统，我就自己手动装了一次。
前提是我已经安装好了homebrew，如果没有安装homebrew也可以在github上，找到fish的安装包，或者百度一下。
1、安装 fish
打开终端，输入： brew install fish
brew开始执行安装，安装结果如下：
[LXMAJS]:issues lxmajs$ brew install fish
Updating Homebrew...
==> Homebrew has enabled anonymous aggregate formulae and cask analytics.
Read the analytics documentation (and how to opt-out) here:
https://docs.brew.sh/Analytics
==> Auto-updated Homebrew!
Updated 1 tap (homebrew/core).
==> Updated Formulae
alexjs chakra
==> Installing dependencies for fish: pcre2
==> Installing fish dependency: pcre2
==> Downloading https://homebrew.bintray.com/bottles/pcre2-10.32.mojave.bottle.tar.gz
######################################################################## 100.0%
==> Pouring pcre2-10.32.mojave.bottle.tar.gz