Ruby Hello World Example: How To Write and Execute Ruby Program on Unix OS

Question: I would like to understand the basics of how to write and execute a ruby program on Linux OS. Can you explain it with a simple example?

Answer: In this article, let us review very quickly how to write a basic Hello World ruby program and execute *.rb program on Linux or Unix OS.

1. Write a Hello World Ruby Program

Create the helloworld.rb program using a Vim editor as shown below.

$ vim helloworld.rb

#!/usr/bin/ruby

# Hello world ruby program

puts "Hello World!";

2. Verify ruby Interpreter availability

Make sure ruby interpreter is installed on your system as shown below.

$ whereis ruby
ruby: /usr/bin/ruby /usr/bin/ruby1.8 /usr/lib/ruby /usr/share/man/man1/ruby.1.gz

$ which ruby
/usr/bin/ruby

Installing Ruby

If you don’t have Ruby, install it as shown below.

$ sudo apt-get install ruby

3. Execute Ruby Program

You can either execute using “ruby helloworld.rb” or “./helloworld.rb”.

$ ruby helloworld.rb
Hello World!

( or )

$ chmod u+x helloworld.rb

$ ./helloworld.rb
Hello World!

Note: As Ruby is an interpreted language, you don’t have the compilation step similar to the C program.

Executing Ruby one liner

You can also execute Ruby from the command line as shown below. This will print Hello World!.

$ ruby -e 'puts "Hello World!\n"'