之后：
gem install rvm
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/universal-darwin18/rbconfig.rb:215: warning: Insecure world writable dir /usr/local/bin in PATH, mode 040757
Successfully installed rvm-1.11.3.9
Parsing documentation for rvm-1.11.3.9
Done installing documentation for rvm after 0 seconds
1 gem installed
我做到了
which rvm
得到了
Command not found
???