Building a Ruby CLI (Let's Build a Ruby Gem, Ep 03)

In the third episode of the series, I build a command-line interface for the Converty gem driven out by RSpec tests to show how to assert against stdout and stderr. This allows people to call out to Converty right from the terminal, for example: `converty 5 --from km --to mi --round 1` which outputs 3.1. Table of contents: 00:00 - Intro 01:25 - Help docs 08:53 - Parsing arguments 12:40 - Calling out to our gem code 23:01 - Requiring arguments 32:39 - CLI demo OptionParser docs: https://ruby-doc.org/stdlib-2.7.1/libdoc/optparse/rdoc/OptionParser.html Thor, an alternative to OptionParser: http://whatisthor.com/ View the code from this episode: https://github.com/monoso/converty/commit/ee73f072e62473ef05a46ed52016919452aaf995 Ruby version: 2.6.5 Bundler version: 2.2.16 Ruby Gem version: 3.0.6