Ruby

https://sourabhbajaj.com/mac-setup/Ruby/

macOS comes with Ruby installed, but as we don't want to be messing with operating system core files we're going to use the tools rbenv and ruby-build to manage and install our Ruby versions for our development environment.

$ brew install rbenv ruby-build rbenv-default-gems rbenv-gemset
$ echo 'eval "$(rbenv init -)"' >> ~/Projects/config/env.sh
$ source ~/.zshrc # Apply changes

rbenv install 2.6.3




https://rvm.io/rubies/default
rvm --default use 2.6.3

$ ruby -v

https://makandracards.com/makandra/21545-rbenv-how-to-switch-to-another-ruby-version-temporarily-per-project-or-globally

If you need to change manually, you have several options:

1. rbenv shell
2. rbenv local
3. rbenv global

You probably want rbenv shell.

Temporarily: rbenv shell

Changes your Ruby version on your current shell:

COPY
$ ruby -v
ruby 1.9.3p484 (...)

$ rbenv shell 2.0.0-p353
$ ruby -v
ruby 2.0.0p353 (...)

Per project: rbenv local

Looks like rbenv shell…

COPY
$ ruby -v
ruby 1.9.3p484 (...)

$ rbenv local 2.0.0-p353
$ ruby -v
ruby 2.0.0p353 (...)

…but actually writes that version to a .ruby-version in your current directory. Use this only when you want to change the Ruby version on a project, not to change it temporarily (as you'd change your project's file or clutter whatever directory you are currently in with that file).

Globally: rbenv global

This will also change your Ruby version, but only the one you are using whenever no other version is specified, e.g. via a .ruby-version file or RBENV_VERSION variable.

COPY
$ ruby -v
ruby 1.9.3p484 (...)

$ rbenv global 2.0.0-p353
$ ruby -v
ruby 2.0.0p353 (...)

$ echo "1.9.3p484" > .ruby-version
$ rbenv global 2.0.0-p353
$ ruby -v
ruby 1.9.3p484 (...)

https://stackoverflow.com/questions/24736204/rbenv-cant-change-global-ruby-version/24736330

Did you add the following lines to your ~/.bash_profile?

export PATH="$HOME/.rbenv/bin:$PATH"
eval "$(rbenv init -)"

http://bundler.io/man/bundle-install.1.html
https://en.wikipedia.org/wiki/RubyGems
https://help.dreamhost.com/hc/en-us/articles/115001070131-Using-Bundler-to-install-Ruby-gems


https://stackoverflow.com/questions/2619695/gem-install-permission-problem

qichunren@zhaobak:~> gem install hpricot
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions into the /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8 directory.

Do not use sudo because you will install them as root and not have access to them when you're using your normal user. Use RVM and gemsets.

For a systemwide Ruby install, become root. For example:

$ sudo gem install hpricot

However, the modern approach in many circumstances, including in development, is to use a tool that lets you easily install and use Ruby as a normal user. This lets you avoid having to become root. There are a few such tools, and the one I use is RVM.

# install rvm into your ~
$ \curl -sSL https://get.rvm.io | bash -s stable

# install latest version of ruby into your ~
$ rvm install ruby

# installs a gem into your ~
$ gem install $SOME_GEM_NAME