Mac 自身版本是2.x  查看ruby版本号 打开终端 ruby -v

1.brew update

  如果报错    这时候brew更新出问题了   

fatal: the remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed

error: RPC failed; curl 18 HTTP/2 stream 3 was reset

fatal: the remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed

Error: Fetching /usr/local/Homebrew failed!

Fetching /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core failed!

这是git 错误 终端执行 我看网上说这是git错误 所以我根据网上继续增加git的大小 

git config http.postBuffer 204288000 （这个大小根据自己需求来）

2.继续执行 brew update  还是报错通第一步一样的错误

  git config --list 可以看 上面的大小是否设置成功

3. git clone git://mirrors.ustc.edu.cn/homebrew-core.git/ /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core --depth=1

fatal: destination path '/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core' already exists and is not an empty directory.

4 .cd "$(brew --repo)"

5.git remote set-url origin https://mirrors.ustc.edu.cn/brew.git

cool_mac@videozudabaoji Homebrew % cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core" 

cool_mac@videozudabaoji homebrew-core % git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git

6. brew update （终于成功了）下图所有命令

7 homebrew-core % brew -v  发现是最新的了

8.继续执行 brew install ruby 

注意如果是mac 13系统以上是配置在这两个文件里面 随便一个就行 如果bash_profile配置了有就删掉

9.echo 'export PATH="/usr/local/opt/ruby/bin:$PATH"' >> ~/.bash_profile

10.source ~/.bash_profile