如果没有安装curl
curl sudo apt-get install curl
查看rvm是否安装
rvm -v
未安装时
\curl -sSL https://get.rvm.io | bash -s stable
安装成功后：rvm list known 查看版本
rvm install 2.7.2
提示：
Press ENTER to install Homebrew in the default location /usr/local
or type a custom path (needs to be writable for the current user)
: 按一下 enter
Warning: The Ruby Homebrew installer is now deprecated and has been rewritten in
Bash. Please migrate to the following command:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
执行命令：/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
然后在执行：rvm install 2.7.2
