Chef (1) Install Chef Development Kit and Basic Ruby Syntax

1. Install Chef Development Kit:

Down load the deb for Ubuntu from https://downloads.chef.io/chefdk.

$ sudo dpkg -i <deb filename>
$ echo 'eval "$(chef shell-init bash)"' >> ~/.bashrc
$ source ~/.bashrc

Check the installation:

$ ls /opt/chefdk/bin
$ which ruby # ruby is installed with chef

2. Ruby Syntax:

Open the Ruby REPL in the terminal:

$ irb

Ruby is similar to Python. We don't need to declare the variable type. Let's define a variable.

> variable = 3
> variable

if statement in Ruby.

num = 2
if num%2 == 0
  puts "even"
else
  puts "odd"
end

3. Ruby String and Heredoc:

The #{} operator performs expression substitution inside a string literal.

apple_num = 10
bob_say = "I have #{apple_num} apples."

Heredoc is convenient to represent a long string. The Heredoc expression starts with << operator.

apple_num = 10
<<APPLE
I like to eat apple. 
I have #{apple_num} apples.
APPLE

4. Ruby Array:

arr = ["alice", "bob", "cat", "dog", "echo", "frog"]
puts arr.first
puts arr.last
puts arr[2]

puts arr[1..3] 
# ["bob", "cat", "dog"]

The .. operator creates a range from start point to end point inclusive.

5. Ruby Hash:

Hash in Ruby is similar to the dictionary in Python.

person = {name: "bob", age: 30}

person[:name]
# "bob"

person[:age]
# 30

If you want to use the string literal as the key, you can use Hash Rocket (=>) operator to define Hash.

person = {"name"=> "bob", "age"=> 30}

person["name"]
# "bob"

person["age"]
# 30

6. Methods, Classes, and Modules

class Bacon
  def cook(temperature)
    #...
  end
end

module Edible
  # ...
end