Notes from David Bryant Copeland’s “Build Awesome Command-Line Applications in Ruby 2”

The experience of writing and running automated checks, as well as building some personal apps that run on the terminal, in recent years, has given me a keen sense of appreciation on how effective command-line applications can be as tools. I’ve grown fond of quick programming experiments (scraping data, playing with Excel files, among others), which are relatively easy to write, powerful, dependable, and maintainable. Tons of libraries online help interface well with the myriad of programs in our desktop or out in the web.

Choosing to read “Build Awesome Command-Line Applications in Ruby 2” is choosing to go on an adventure about writing better CLI apps, finding out how options are designed and built, understanding how they are configured and distributed, and learning how to actually test them.

Some notes from the book:

  • Graphical user interfaces (GUIs) are great for a lot of things; they are typically much kinder to newcomers than the stark glow of a cold, blinking cursor. This comes at a price: you can get only so proficient at a GUI before you have to learn its esoteric keyboard shortcuts. Even then, you will hit the limits of productivity and efficiency. GUIs are notoriously hard to script and automate, and when you can, your script tends not to be very portable.
  • An awesome command-line app has the following characteristics:
    • Easy to use. The command-line can be an unforgiving place to be, so the easier an app is to use, the better.
    • Helpful. Being easy to use isn’t enough; the user will need clear direction on how to use an app and how to fix things they might’ve done wrong.
    • Plays well with others. The more an app can interoperate with other apps and systems, the more useful it will be, and the fewer special customizations that will be needed.
    • Has sensible defaults but is configurable. Users appreciate apps that have a clear goal and opinion on how to do something. Apps that try to be all things to all people are confusing and difficult to master. Awesome apps, however, allow advanced users to tinker under the hood and use the app in ways not imagined by the author. Striking this balance is important.
    • Installs painlessly. Apps that can be installed with one command, on any environment, are more likely to be used.
    • Fails gracefully. Users will misuse apps, trying to make them do things they weren’t designed to do, in environments where they were never designed to run. Awesome apps take this in stride and give useful error messages without being destructive. This is because they’re developed with a comprehensive test suite.
    • Gets new features and bug fixes easily. Awesome command-line apps aren’t awesome just to use; they are awesome to hack on. An awesome app’s internal structure is geared around quickly fixing bugs and easily adding new features.
    • Delights users. Not all command-line apps have to output monochrome text. Color, formatting, and interactive input all have their place and can greatly contribute to the user experience of an awesome command-line app.
  • Three guiding principles for designing command-line applications:
    • Make common tasks easy to accomplish
    • Make uncommon tasks possible (but not easy)
    • Make default behavior nondestructive
  • Options come in two-forms: short and long. Short-form options allow frequent users who use the app on the command line to quickly specify things without a lot of typing. Long-form options allow maintainers of systems that use our app to easily understand what the options do without having to go to the documentation. The existence of a short-form option signals to the user that that option is common and encouraged. The absence of a short-form option signals the opposite— that using it is unusual and possibly dangerous. You might think that unusual or dangerous options should simply be omitted, but we want our application to be as flexible as is reasonable. We want to guide our users to do things safely and correctly, but we also want to respect that they know what they’re doing if they want to do something unusual or dangerous.
  • Thinking about which behavior of an app is destructive is a great way to differentiate the common things from the uncommon things and thus drive some of your design decisions. Any feature that does something destructive shouldn’t be a feature we make easy to use, but we should make it possible.
  • The future of development won’t just be manipulating buttons and toolbars and dragging and dropping icons to create code; the efficiency and productivity inherent to a command-line interface will always have a place in a good developer’s tool chest.
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