Install Ruby 2.2 on MAC Osx Catalina with Ruby-Install

Ruby installation (2.2.2) fails in macOS Big Sur

EDIT

It looks like OP edited the error in the original message so the below answer is no longer relevant. Leaving it here for posterity.

Updated Answer

Based on discussion in a couple of Github issues on the rbenv repo,

https://github.com/rbenv/ruby-build/issues/1480
https://github.com/rbenv/ruby-build/issues/1489

it sounds like Apple changed the default CFLAGS as part of xcode 12, which makes some of the native extension installations go haywire. It sounds like the solution proposed in those issues is

CFLAGS="-Wno-error=implicit-function-declaration" rbenv install 2.2.2

Original answer

The error states it failed due to issues with extensions

The Ruby readline extension was not compiled.
The Ruby zlib extension was not compiled.
ERROR: Ruby install aborted due to missing extensions

so I would suggest trying to install those extensions manually first, then retrying the ruby install.

With brew:

brew install readline
brew install zlib

There are some issues on ruby-build's github that might help as well:

https://github.com/rbenv/ruby-build/issues/1076
https://github.com/rbenv/ruby-build/issues/832#issuecomment-160906530

how to install ruby-Tk on mac OSX catalina 10.15.4, ruby-2.6.3

Below guide assumes you have Xcode already installed. If not install it first from the apple app store.

1) Install ActiveTcl for macOS from https://www.activestate.com
under applications/utilities, there will be a new app wish.app. run this app and if you get the wish console to open, then, it installed ok

2) Using your command line do the following

brew install ruby #this will install latest version of ruby
gem install tk

3) then add other ruby gems that you need for your development environment.

Unable to update Ruby on macOS Catalina version 10.15.3

First you need add gpg key.

gpg --keyserver hkp://pool.sks-keyservers.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB

Then install rvm via CURL. If you don't have CURL, install it via Homebrew brew install curl

curl -sSL https://get.rvm.io | bash

then rvm list to get installed version of ruby.

then rvm list known to get the available version.

then rvm install 2.7.0 to install ruby 2.7.0.

then rvm --default use 2.7.0 to use it.