Interactive Ruby (IRB) is an interactive shell where you can try out your code or just play around. IRB comes in really handy to try out small pieces of code. For the rest of the chapter, you can try out the code examples in IRB or create files and execute them. In the examples, we will be doing both so that you can be comfortable using either.
IRB comes along with Ruby. So, installing Ruby will also install the correct irb.
irb on your command line to start the shell:
2.0.0-p195 :001 > puts "Hello World!" Hello World! => nil
=> nil that you see is the return value of the statement executed. So you don't need to worry about it much.
You can run any valid Ruby code in irb. Use it to play around with objects and ...