Ruby

https://www.ruby-lang.org/en/

Dynamically typed open-source programming language known for its simplicity, flexibility, and focus on developer happiness.

Not my main language but it's an easy language to pick up so I've written a few bits and pieces over the years eg. check_puppet.rb.

Popularity Over the Years
Poignant Guide to Ruby
IRB
- JIRB
Gem
RVM - Ruby Version Manager
- RVM Install
- RVM Usage
Code
JRuby
- Rubinius
- Ludicrous
RubyMine

Popularity Over the Years

IMO was at peak popularity in the late 2000s when Puppet was the big thing (Puppet was written in Ruby) and was the first widely used configuration language (CFengine wasn't as widely used).

Update: a quick Google found this article showing Ruby actually peaked in the mid 2000s rather than the late 2000s. I probably should have made more notes here at that time...

Poignant Guide to Ruby

A popular source for learning Ruby.

https://poignant.guide/book/

http://www.rubyinside.com/media/poignant-guide.pdf

IRB

Interactive Ruby interpreter.

(if you need to install the irb Gem see next section)

Start the irb interactive ruby interpreter:

irb

JIRB

JRuby interactive Ruby interpreter.

Start the jirb interactive ruby interpreter:

jirb

GUI irb using swing:

jruby -S jirb_swing

java_import java.lang.System
version = System.getProperties["java.runtime.version"]

Gem

Install Gems

gem install "$name"

Install the mdl gem for markdown linting (used heavily to check the docs in this repo):

gem install mdl

Run mdl to check an .md file:

mdl README.md

Interesting Gems

irb - Interactive Ruby interpreter
mdl - Markdown lint
lolcat - turns text into rainbow colours
gitlab - GitLab CLI
jgrep
httparty
gist
kramdown

List Installed Gems

gem list

Configure gem command to install gems to user writable $HOME/.gem/ruby/<version>/gems/ directory:

In $HOME/.gemrc:

gem: --user-install

gem install then installs to ~/.gem/ruby/<version>/gems.

Then make sure to add $HOME/.gem/ruby/<version>/bin to $PATH environment to be able to run commands installed by gems:

gem env

Runs server on http://localhost:8808 to show installed gems:

gem server

gem install ruby-debug

gem install cheat

Install from Custom Gem Server

gem install --source http://server

RVM - Ruby Version Manager

https://rvm.io/

Installs multiple Ruby environments, interpreters and gem commands under

Like VirtualEnv in Python - multiple ruby environments, interpreters and gems

RVM Install

Install GPG Keys:

gpg2 --keyserver keyserver.ubuntu.com \
     --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 \
                 7D2BAF1CF37B13E2069D6956105BD0E739499BDB

On Mac, had to do this instead:

gpg --keyserver hkps://keys.openpgp.org \
    --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 \
                7D2BAF1CF37B13E2069D6956105BD0E739499BDB

Prompts to import GPG keys if you skipped the step above:

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

or with Ruby-on-Rail (compiles, takes ages):

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

You will likely get a warning to remove the user gem setting from $HOME/.gemrc as it'll clash with RVM:

In $HOME/.gemrc, remove:

gem: --user-install

RVM Usage

https://rvm.io/rvm/basics

See available interpreters:

rvm list known

Install a recent Ruby interpreter:

rvm install ruby

Further help:

rvm help

Code

Code	Description
`foo`	local variable (default: `NameError: undefined local variable` exception)
`$foo`	global variable (default: `nil`)
`@foo`	instance variable (default: `nil`)
`@@foo`	class variable (default: `NameError` exception)
`^[A-Z]...`	constant (default: `NameError` exception)

puts object.inspect

object.to_yaml

Path to code modules:

$LOAD_PATH

JRuby

Run Ruby on the Java JVM with full access to Java libraries.

Rubinius

https://github.com/rubinius/rubinius#readme

JIT for Ruby

Ludicrous

http://rubystuff.org/ludicrous/