Ruby CLI Playground Online

Simulate a Ruby terminal in your browser to test scripts and practice syntax quickly.

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Sample

🚀 222,513 total executions (1,339 this month)

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💡 Ruby Basics Guide for Beginners

1. Declaring Variables and Constants

Ruby is dynamically typed. Constants start with uppercase letters and are not meant to change.

x = 10
pi = 3.14
name = "Alice"
is_active = true

MAX_USERS = 100
APP_NAME = "CodeUtility"

2. Conditionals (if / case)

Use if, elsif, else, or case for control flow.

x = 2
if x == 1
  puts "One"
elsif x == 2
  puts "Two"
else
  puts "Other"
end

case x
when 1
  puts "One"
when 2
  puts "Two"
else
  puts "Other"
end

3. Loops

Use while, until, or iterators like each.

i = 0
while i < 3
  puts i
  i += 1
end

[1, 2, 3].each do |n|
  puts n
end

4. Arrays

Arrays store ordered lists of elements. Access using indexes.

fruits = ["apple", "banana", "cherry"]
puts fruits[0]
puts fruits.length

5. Array Manipulation

Use push, pop, slice, and reverse for working with arrays.

fruits.push("kiwi")
fruits.pop
puts fruits[1..2]
puts fruits.reverse

# Array comprehension
squares = (1..5).map { |x| x * x }
puts squares

6. Console Input/Output

Use gets.chomp to read input and puts/print for output.

print "Enter your name: "
name = gets.chomp
puts "Hello, #{name}"

7. Functions

Define functions using def. You can pass arguments and return values.

def greet(name)
  "Hello, #{name}"
end

puts greet("Alice")

8. Hashes

Hashes are key-value pairs, like dictionaries or maps.

person = { "name" => "Bob", "age" => 25 }
puts person["name"]

# Symbol keys
person = { name: "Alice", age: 30 }
puts person[:name]

9. Exception Handling

Use begin-rescue-end to catch exceptions and handle errors gracefully.

begin
  raise "Something went wrong"
rescue => e
  puts e.message
end

10. File I/O

Read and write files using File methods or IO classes.

File.write("file.txt", "Hello File")
content = File.read("file.txt")
puts content

11. String Manipulation

Ruby strings support many methods: length, gsub, split, etc.

text = " Hello World "
puts text.strip
puts text.upcase
puts text.gsub("Hello", "Hi")
puts text.split

12. Classes & Objects

Ruby is fully object-oriented. Use initialize to define constructors.

class Person
  def initialize(name)
    @name = name
  end

  def greet
    "Hi, I'm #{@name}"
  end
end

p = Person.new("Alice")
puts p.greet

13. References (Object Mutation)

All variables hold references to objects. Modifying an object inside a function affects the original.

def modify(arr)
  arr << "changed"
end

data = ["original"]
modify(data)
puts data.inspect  # ["original", "changed"]