How to install and use different versions of ruby?

There are two major Ruby version managers out there from which you can choose:

• rbenv and ruby-build
• RVM

These allow you to keep multiple versions of Ruby on the same system. Once you've installed a version manager, and installed your own Ruby version, you won't mess with your system's Ruby and its Gems, which is the greatest benefit. No more sudo! No more permissions errors and Gem conflicts.

Which one should I choose?

Both do the same thing, but they follow different philosophies. The choice is up to you.

I personally recommend rbenv for its simplicity. I've been using it for years and it has always worked well.

How do I install them?

If you choose rbenv:

• Follow the all the installation and setup instructions.
• Install ruby-build
• Run rbenv install x.x.x where x.x.x is the version (use rbenv install --list to see which ones are available
• Run rbenv global x.x.x to change your global Ruby version

If you choose RVM:

• Use the secure installation method
• Read the installation instructions — you probably want the single-user configuration
• Use rvm list known to list available Rubies and then run rvm install x.x.x to install a specific version.
• Use rvm use x.x.x --default to change your default Ruby

I think rbenv deserves at least its own answer.

There is a constant battle between fans of rbenv and those of RVM but I personally like rbenv a lot more. As the Sam Stephenson (the author) states, rbenv it solely concerned with switching Ruby versions (as opposed to RVM, which does a lot more).

On OS X, it's especially easy to give it a try. Just follow the excellent installation instructions on the Github page (if you have Homebrew installed, it's basically just a brew install rbenv ruby-build).

As for switching Rails versions, I once wrote an article about that which my be of interest for you.

Assuming you have installed the rbenv ruby version: run,

rbenv init

Then;

eval "$(rbenv init - zsh)" 

To confirm the switched version, run;

which ruby

It should be something like;

/Users/MacbookAir/.rbenv/shims/ruby

This is what worked for me, I don't have sudo:

#!/usr/bin/env bash

ruby -v
if ! command -v ruby &> /dev/null
then
    echo "Going to try to install ruby (ideally 3.1.2)"
    # - install rebenv (following ruby-build really is needed eventhough it doesn't look like it)
    mkdir -p ~/.rbenv
    cd ~/.rbenv
    git clone https://github.com/rbenv/rbenv.git .
    # if $HOME/.rbenv/bin not in path append it, otherwise don't change it
    echo $PATH | tr ':' '\n' | awk '{print "  " $0}';
    if [[ ":$PATH:" != *":$HOME/.rbenv/bin:"* ]]; then
      echo "might want to put $HOME/.rbenv/bin in your path"
      export PATH="$HOME/.rbenv/bin:$PATH"
#      echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc.lfs
    fi
    eval "$(rbenv init -)"
    rbenv -v

    # - install ruby-build, odd, this really is needed for ruby to install despite it not looking like ruby build is need at the bottom
    mkdir -p ~/.ruby-build
    cd ~/.ruby-build
    git clone https://github.com/rbenv/ruby-build.git .
    # if $HOME/.ruby-build/bin not in path append it, otherwise don't change it
    echo $PATH | tr ':' '\n' | awk '{print "  " $0}';
    if [[ $PATH != *"$HOME/.ruby-build/bin"* ]]; then
      echo "might want to put $HOME/.ruby-build/bin in your path"
      export PATH="$HOME/.ruby-build/bin:$PATH"
#      echo 'export PATH="$HOME/.ruby-build/bin:$PATH"' >> ~/.bashrc.lfs
    fi
    ruby-build --version

    # - install ruby without sudo -- using rbenv
    mkdir -p ~/.local
    #    ruby-build 3.1.2 ~/.local/
    rbenv install 3.1.2
    rbenv global 3.1.2
fi
ruby -v

# - wontfix: above worked but what was ruby's official way to do this? doesn't matter but answer might be here some day: https://discuss.rubyonrails.org/t/what-is-the-official-way-to-install-ruby-ideally-3-1-2-on-ubuntu/82226

# -old prover bot ignore doesn't work on SNAP
# Proverbot's way to install ruby
#    # First, install Ruby, as that is for some reason required to build the "system" project
#    git clone https://github.com/rbenv/ruby-build.git ~/ruby-build
#    mkdir -p ~/.local
#    PREFIX=~/.local ./ruby-build/install.sh
#    ~/.local/ruby-build 3.1.2 ~/.local/
# ref: https://superuser.com/questions/340490/how-to-install-and-use-different-versions-of-ruby/1756372#1756372

see this for more general answers: https://askubuntu.com/questions/339/how-can-i-install-a-package-without-root-access

related: https://stackoverflow.com/questions/75330125/why-would-only-using-rbenv-and-ruby-build-work-to-install-ruby