Ruby Syntax Basics

A few rules cover most of what Ruby code looks like.

One statement per line. No semicolons are needed at the end of a line. (You can put two statements on one line separated by ;, but it's rarely done.)

puts "one"
puts "two"

Blocks of code end with end. Where other languages use curly braces, Ruby uses keywords:

if 10 > 5
  puts "Ten is bigger"
end

Ten is bigger

Indentation is two spaces. Unlike Python, Ruby doesn't require indentation — end marks where a block stops — but every Ruby project indents with two spaces, so code stays readable.

Case matters. name and Name are different: names starting with a lowercase letter are variables and methods; names starting with a capital letter are constants and classes.

Method calls can drop parentheses. puts("hi") and puts "hi" are the same. The convention: leave them off for simple statements like puts, and include them when a call is part of a bigger expression.

Everything returns a value. Even if produces a value, which is why irb always shows a => result.

Common mistakes

• Forgetting an end. Ruby reports syntax error, unexpected end-of-input — count your if/def/do openers against your ends.
• Putting a space between a method name and its opening parenthesis, as in puts ("a", "b"). Ruby reads the space as the start of a single argument and fails. Write puts("a", "b") or puts "a", "b".