# Twelve Days of Shell

6 Hacker News commenters recommended Twelve Days of Shell and 11 criticized it, November 2025 to November 2026. It was recommended in 1 of 13 months.

**Verdict:** A free, browser-based set of challenges that lets people practice command-line skills without setting up full projects. Critics say the answer checker often rejects valid commands and gives no output on wrong answers.

## What people warn about

- Rejects valid commands as wrong (4 comments): "I think a beginner could be doing it right but then be told they are wrong as you aren't evaluating actual commands" ([source](https://news.ycombinator.com/item?id=46190909)) "It accepts ls -a as and answer and ls -l but not ls -al" ([source](https://news.ycombinator.com/item?id=46193156)) "it's rejecting valid commands as incorrect" ([source](https://news.ycombinator.com/item?id=46191398))
- Shows no output on wrong answers (2 comments): "You don't see the (wrong) output if you don't get it right the first time" ([source](https://news.ycombinator.com/item?id=46190818)) "Doesn't tell you without looking at the answer." ([source](https://news.ycombinator.com/item?id=46196020))
- Weak shell escaping handling (2 comments): "But doesn’t seem to do enough shell escaping or correctly." ([source](https://news.ycombinator.com/item?id=46190810)) "doesn’t seem to do enough shell escaping or correctly." ([source](https://news.ycombinator.com/item?id=46191177))
- Unclear which previous problem applies (2 comments): "It's difficult to know that it is following from the previous problem" ([source](https://news.ycombinator.com/item?id=46191749)) "That's pretty confusing especially since users are primed with file contents from the previous exercises already." ([source](https://news.ycombinator.com/item?id=46191034))

## Alternatives hackers recommend

- [CSS-Tricks](https://hackerapproved.com/p/css-tricks.md): 23 recommend
- [Learn OpenGL](https://hackerapproved.com/p/learn-opengl.md): 15 recommend
- [Patterns.dev](https://hackerapproved.com/p/patterns-dev.md): 12 recommend
- [Fintech Engineering Handbook](https://hackerapproved.com/p/fintech-engineering-handbook.md): 12 recommend
- [vimtutor](https://hackerapproved.com/p/vimtutor.md): 8 recommend

## Cite as

Hacker Approved, "Twelve Days of Shell", https://hackerapproved.com/p/twelve-days-of-shell/ (counts from 1,795,640 Hacker News comments, November 2025 to November 2026).