问题场景：

新mac使用brew命令时 显示

zsh : command not found :brew

分析：

未安装brew命令

解决：

安装brew命令就好了啊
1.去homebrew官网(https://brew.sh/)，使用官方提供的命令行

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

2.国内用户会遇到以下问题，链接github失败

fatal: unable to access ‘https://github.com/Homebrew/brew/’: Failed to connect to github.com port 443: Operation timed out
Error: Fetching /usr/local/Homebrew failed!

3.替换homebrew安装源
替换homebrew默认源

cd "$(brew --repo)" 
git remote set-url origin git://mirrors.ustc.edu.cn/brew.git

替换homebrew-core源

cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin git://mirrors.ustc.edu.cn/homebrew-core.git

重新安装重试
4.如果还没有解决

Cloning into '/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core'...
fatal: unable to access 'https://github.com/Homebrew/homebrew-core/': LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443 
Error: Failure while executing: git clone https://github.com/Homebrew/homebrew-core /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core --depth=1
Error: Failure while executing: /usr/local/bin/brew tap homebrew/core
Failed during: /usr/local/bin/brew update --force

不要急，我们手动处理
依次输入以下命令行

cd /usr/local/Homebrew/Library/Taps/
mkdir homebrew
cd homebrew
git clone https://mirrors.ustc.edu.cn/homebrew-core.git
brew update

到这应该就能解决问题啦~~~

tips：意外情况
在下载过程中如果出现了

Failed to connect to 127.0.0.1 port 1080: Connection refused

这种拒绝链接的提示，只要 查看并取消代理proxy
强势取消代理命令

$ unset http_proxy
$ unset ftp_proxy
$ unset all_proxy
$ unset https_proxy
$ unset no_proxy

取消代理后重试一下，看一看是否能够链接成功。

记录一下踩得这些坑😭