Homebrew是一个macOS软件包管理器
它的介绍和安装方法其实在官网首页上都有：
https://brew.sh/index_zh-cn.html
注：如果被墙的自己想办法咯，如果执行brew install xxx一直提示brew update，可以按一次ctrl + c，停掉update，直接去下载安装程序
1. 安装
终端输入自动安装()：
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
2. 卸载
终端输入自动卸载：
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
3. 使用
常用命令，在终端中直接敲(注释就不用加了)，比如安装maven：
brew install maven //安装软件
brew uninstall maven //卸载软件
brew search maven //搜索软件
brew upgrade maven //更新软件
brew list //查看已安装列表
brew update //更新Homebrew
4. 如何用Homebrew安装指定版本的软件?
1.查看可安装的软件版本
xxx:~ xxx$ brew search maven
==> Formulae
maven ✔ maven-completion maven-shell maven@3.2 maven@3.3 maven@3.5 ✔
==> Casks
mavensmate
2.指定版本安装
xxx:~ xxx$ brew install maven@3.5
Updating Homebrew...
^C==> Downloading https://www.apache.org/dyn/closer.cgi?path=maven/maven-3/3.5.4/binaries/apache-maven-3.5.4-bin.tar.gz
==> Downloading from http://mirror.bit.edu.cn/apache/maven/maven-3/3.5.4/binaries/apache-maven-3.5.4-bin.tar.gz
######################################################################## 100.0%
==> Caveats
maven@3.5 is keg-only, which means it was not symlinked into /usr/local,
because this is an alternate version of another formula.
If you need to have maven@3.5 first in your PATH run:
echo 'export PATH="/usr/local/opt/maven@3.5/bin:$PATH"' >> ~/.bash_profile
==> Summary
🍺 /usr/local/Cellar/maven@3.5/3.5.4: 104 files, 10.2MB, built in 56 seconds
==>brew cleanuphas not been run in 30 days, running now...
