Ruby Online Compiler | Free Online Compiler

Code

puts "Hello, Ruby!"
if ARGV.length > 0
    puts "First arg: #{ARGV[0]}"
end

STDIN (optional)

Args (space separated)

Output

What Is the Ruby Online Compiler?

This tool lets you run Ruby scripts directly in your browser without installing Ruby or any gems on your machine. Whether you are learning Ruby for the first time or quickly testing blocks, iterators, and object-oriented patterns, this compiler provides a fast way to write and execute Ruby code online.

Ruby does not require a main function. You can write executable statements directly at the top level, define classes and modules, and call methods immediately. Use puts or print to display output and gets to read input from standard input.

All code executes on a remote sandboxed server powered by the Piston API. Your browser sends the source code to the server, which runs it with the Ruby interpreter inside an isolated container. Ruby's dynamic typing, duck typing, and runtime error handling all work as they would in a local environment.

How It Works

Write your Ruby code in the editor panel. The editor starts with a simple "Hello, Ruby!" example using puts, but you can replace it with any valid Ruby script.
Provide input in the STDIN field if your script reads from standard input using gets or $stdin.read. Leave this field empty if your script does not require input.
Add command-line arguments in the Args field if your script reads from ARGV. Enter arguments separated by spaces.
Click the Run button to send your code to the Piston execution server. The server runs your Ruby script with the interpreter and captures all output.
View the results in the Output panel. You will see everything your script prints to standard output, along with any errors including syntax errors, NoMethodError, TypeError, or other runtime exceptions.

Step-by-Step Example

Suppose you want to write a script that reads names from standard input and uses blocks with iterators to format and display them. Here is how you would do it using this compiler:

First, type the following code into the editor panel:

class Greeter
  def initialize(greeting)
    @greeting = greeting
  end

  def greet(names)
    names.each_with_index do |name, i|
      puts "#{i + 1}. #{@greeting}, #{name.strip.capitalize}!"
    end
  end
end

input = gets&.chomp || ""
names = input.split(",")

greeter = Greeter.new("Hello")
greeter.greet(names)

puts "\nTotal: #{names.length} name(s)"

This example demonstrates several Ruby features: class definition with an initializer, instance variables with @, the each_with_index iterator with a block, string interpolation with #{}, and the safe navigation operator &. for nil handling.

Next, go to the STDIN field and type some names, for example alice,bob,carol. These values will be read by gets when the script runs.

Now click the Run button. The interpreter executes your Ruby script with the provided input. After a moment, the Output panel displays the result:

1. Hello, Alice!
2. Hello, Bob!
3. Hello, Carol!

Total: 3 name(s)

You can modify the STDIN values and click Run again to test with different input. This workflow makes it easy to experiment with Ruby's blocks, iterators, and object-oriented features interactively.

Use Cases

Learning Ruby fundamentals. Beginners can experiment with variables, strings, arrays, hashes, blocks, and control flow in a zero-setup environment.
Testing blocks and iterators. Quickly verify how each, map, select, reduce, and custom blocks behave with different data.
Practicing object-oriented design. Define classes with inheritance, modules with mixins, and explore Ruby's flexible OOP model including method_missing and open classes.
Exploring regular expressions. Test Ruby's powerful regex support with match, scan, gsub, and named capture groups on sample text.
Preparing for coding interviews. Many interview questions can be solved in Ruby. Use this compiler to practice problems, test edge cases, and refine solutions quickly.

Limitations and Notes

Single file execution only. This compiler runs a single Ruby file (main.rb). Multi-file projects with separate require files are not supported.
No gem installation. RubyGems and Bundler are not available. You cannot install or require external gems beyond the Ruby standard library.
No web frameworks. Ruby on Rails, Sinatra, and other web frameworks are not available. This compiler supports standalone Ruby scripts only.
Standard library is available. You can use built-in modules like JSON, Set, Date, Time, and other standard library classes that do not require gem installation.
No file I/O access. The sandboxed environment does not allow reading from or writing to the filesystem. File operations will fail at runtime.
Execution timeout applies. Scripts that take too long or enter infinite loops are terminated automatically to prevent resource exhaustion.
Interpreted language. Ruby code is interpreted directly without a separate compilation step. Syntax errors are reported at runtime when the interpreter encounters them.

Frequently Asked Questions

What Ruby version does this compiler use?

It uses the latest Ruby version available through the Piston execution engine.

Can I install gems?

No, RubyGems and Bundler are not available. Only the Ruby standard library is accessible.

Can I use gets for input?

Yes, use gets or gets.chomp in your code and provide the input data in the STDIN field before running.

Do blocks and iterators work?

Yes, Ruby blocks, procs, lambdas, and iterators like each, map, select, and reduce all work as expected.

Can I use classes and modules?

Yes, you can define classes with inheritance, modules with mixins, and use Ruby's full object-oriented features in a single file.

Can I run Rails applications?

No, Ruby on Rails and other web frameworks are not available. This compiler supports standalone Ruby scripts only.

Do regular expressions work?

Yes, Ruby regular expressions are fully supported including match, scan, gsub, and the =~ operator.

Can I use ARGV for command-line arguments?

Yes, use the ARGV array to access command-line arguments. Enter arguments in the Args field separated by spaces.

Ruby Compiler