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sudo rvm get head
sudo rvm install ruby-2.7.4-railsexpress
rvm use --default ruby-2.7.4-railsexpress
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rvm list known
rvm install ruby@latest
ruby -v
## If it still shows you ruby 2.0., run rvm use ruby-X.X.X --default.
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/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew install ruby
echo 'export PATH="/usr/local/opt/ruby/bin:$PATH"' >> ~/.bash_profile
source ~/.bash_profile