One other tool that is worth mentioning, and that comes with your Ruby runtime,
irb. You can start it by typing
irb in your shell and hitting enter.
Its name is short for “Interactive Ruby Shell”, and yes, it is another kind of
shell: Just like the shell running in your terminal
irb is also a program
that interactively waits for you to type something, and hit enter. However,
since this is a Ruby shell, it will expect that you type Ruby code instead of
IRB is pretty handy for quickly trying something out, and it is a great tool for exploring the language Ruby, and things that come built in.
$ irb > puts "Hello world!" Hello world! => nil >
The first line starts the IRB program. Notice how the “prompt” indicator
changes. The prompt will look a little different depending on your system and
shell configuration, but often
$ is used to indicate that this is a
system shell prompt, while
> is used by IRB to indicate that this is an
interactive Ruby shell.
The second line is a piece of Ruby code. When you type this line and hit enter then Ruby will execute the code, and print out the text “Hello world!”.
It will then also print out the return value for this statement, which in this
nil. This is something that you can simply ignore for the time being.
On the last line you see IRB again waiting for input with a prompt.
You can exit the IRB session, and get back to your system shell, by typing
exit and hitting enter. Or you can also just hit
ctrl-d, which does the