Executing ruby code

$ ruby
puts "Hello, World!"
^D
Hello, World!

$ ruby -e 'puts "Hello, World!"'
Hello, World!

$ irb
>> puts "Hello, World!"
Hello, World!
=> nil

$ cat > hello.rb
puts "Hello, World!"
^D
$ ruby hello.rb
Hello, World!

$ which ruby
/usr/bin/ruby
$cat > hello.rb
#!/usr/bin/ruby
puts "Hello, World!"
^D
$ chmod +x hello.rb
$ ./hello.rb
Hello, World!