Setting Up Your Development Environment

Any text editor can edit Ruby, but one that understands Ruby catches mistakes as you type:

• Visual Studio Code with the Ruby LSP extension (by Shopify) — free and cross-platform. It adds autocomplete, inline errors, formatting, and "go to definition".
• RubyMine by JetBrains — a full commercial IDE for Ruby and Rails.

You also get two tools with Ruby itself:

• irb (Interactive Ruby) — type irb in a terminal, and you can run Ruby one line at a time and see each result immediately. It's the fastest way to experiment. Type exit to leave.
• ruby — runs a whole file: ruby hello.rb.

$ irb
irb(main):001> 2 + 3
=> 5
irb(main):002> "ruby".upcase
=> "RUBY"
irb(main):003> exit

The => line is the value of the expression you typed. Keep an irb session open while you work through these lessons and try every example in it.