irb on Linux and Mac, fxri on Windows

Before starting to write scripts, let's take a look at irb, the Interactive Ruby Shell. A REPL (Read Evaluate Print Loop) that can help you explore the languages. Just type irb on the command line and it will give you its own prompt. There you can type in ruby statements.

$ irb
irb(main):001:0> 42
=> 42
irb(main):002:0> 'hello'
=> "hello"
irb(main):003:0> 19+23
=> 42
irb(main):004:0> puts 42
=> nil
irb(main):005:0> a = 19
=> 19
irb(main):006:0> b = 23
=> 23
irb(main):007:0> a+b
=> 42
irb(main):008:0> exit

Simply typing in numerical or string expressions will print the result. Calling the puts ruby function will also print to the screen, but then the REPL will print the "result" of puts, which is nil. We can assign values to variables, and then use them in other expressions. Finally exit will let us leave the Interactive Ruby session.