12 Factor CLI Apps with Cobra - Markus Zimmermann - cosee

CLIs had a bit of a renaissance in recent years with powerful tooling like Docker and Kubernetes. They are faster and more productive to use than their visual counterparts. What makes these CLIs that good? Heroku defined 12 factors for great applications and did the same for CLIs. Good help documentation and shell completion are, for example, a very important factor. Modern CLIs take these factors into account to improve the user experience. Besides great UX, a powerful library is needed and Cobra takes this spot for Go. All the popular CLIs written in Go use Cobra.
In this talk, we want to look at the 12 factors that make CLIs successful and show how to implement a great CLI in Cobra.

Transcript

1. cosee GmbH, Markus Zimmermann, @markus_zm 12 Factor CLI Apps with Cobra
2. About me Cloud Developer Master Thesis about npm Security (Analysis written in Go) Co-organizer Gophers Darmstadt
3. Section one Why should we still use CLIs in 2020?
4. Old technology? Source: Unsplash - Anastasia Dulgier
5. Nope - still modern and very powerful Scripting with Bash CI/CD automation Machine Readable Output Usable for API interactions Rapid prototyping
6. Section two UX for CLIs Multi-Cloud?
7. Bad UX in GUIs Source: UX Planet
8. Bad UX in CLIs Do you remember how to extract a tar? tar -C /usr/local -xzf sample.tar.gz
9. “A user interface is like a joke. If you have to explain it, it’s not that good.” Martin LeBlanc, CEO of Iconfinder
10. Section three The snakes that power Go CLIs
11. The two libraries for Go CLIs
12. Powers many popular CLIs
13. Cobra Features Automatic generation of bash completion, man pages and help Intelligent suggestions Different flag types Code generator
14. Viper integration App Configuration Reads config files Reads from Environment Variables Reading from remote config systems like etcd Live watching and re-reading
15. Demo Time
16. Section four 12 Factor CLIs
17. Credit to Jeff Dickey @jdxcode
18. Great help is essential $ git $ git --help $ git help $ git -h # get help for subcommand $ git subcommand --help $ git subcommand -h
19. Determine based on number of arguments (1 argument is fine) Order of flags can be random - arguments not Prefer flags to args copy --from /tmp --to /home
20. git version git --version => git version 2.17.1 What version am I on?
21. Mind the streams stdout get written to file or can be piped stderr get printed on terminal stdin accepted as input for root command
22. Handle things going wrong Informative Errors: Error Code Error title Fix for the Error URL with more information
23. Prompt if you can Never require a prompt - impedes automation! Dangerous actions can require a prompt Prompts can be visualized with Checkboxes or Radio buttons promptui https://github.com/manifoldco/promptui
24. And some more... Be fancy! Use tables Be speedy! Encourage contributions Be clear about subcommands Follow XDG-spec
25. for listening! Source: Tomasz Sroka – unsplash Thanks
26. blog.cosee.biz cosee.jobs