Your First Ruby Program

Create a file called hello.rb with this one line:

puts "Hello, world!"

Then run it from the folder that contains the file:

ruby hello.rb

Expected output

Hello, world!

That's a complete Ruby program. There is no main function and no required boilerplate — Ruby runs the file from top to bottom.

• puts ("put string") prints a value followed by a new line.
• "Hello, world!" is a string — a piece of text in quotes.
• Parentheses around method arguments are optional: puts("Hello, world!") does exactly the same thing. Ruby style usually leaves them off for puts.

A slightly longer program runs line by line:

puts "Hello, world!"
puts "I am learning Ruby."
puts 2 + 3

Hello, world!
I am learning Ruby.
5

Common mistakes

• Running ruby hello.rb from the wrong folder gives No such file or directory. Use cd to move into the folder first.
• Mismatched quotes such as puts "Hello' cause an unterminated string syntax error.

Practice

Write a program that prints your name on one line and your favorite food on the next.

puts "Ada"
puts "Pizza"