The terminal, files, and paths
By the end of today you can navigate a filesystem from the command line without a mouse, explain the difference between a relative and an absolute path, and say what actually happens when you type a command and press enter.
YesterdayOn Day 7 you learned to narrow a bug down. Most of that narrowing happens in a terminal rather than an editor.
TomorrowTomorrow you use the terminal to install packages and isolate environments.
Why this matters
Every deployment, container, CI job and server you meet later is driven from a shell. Being uncomfortable there caps how far you can go, and the concepts are small enough to learn in one day.
- The shell
- Paths
- Exit codes
- Standard streams
Learn it
70 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
5 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
40 minWithout touching your editor or file manager, create a directory tree three levels deep, add a few files, then find every file containing a chosen word and count the results in one pipeline. Then run a command that fails and check its exit code.
Recall it
20 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
4 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01The shell finds a program on PATH and runs it as a process
- 02Relative paths depend on where you are; absolute paths do not
- 03stdout and stderr are separate so output can be piped while errors stay visible
- 04Exit code 0 means success, and everything else is a kind of failure
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.