🐚 Bash Course: From Zero to Claude Level

24 lessons. Every lesson has the same four files:

File	What it is
Lesson-N.md	the teaching: concepts, examples, gotchas
Code.md	every part of the script explained, plus experiments
Code.sh	the real, runnable script (safe: works in its own demo folder and cleans up)
Resources.md	cheat sheet, exercises, answers, common errors, habits, extra reading

Start with LESSON.md (the roadmap), then follow the lessons in order.

---

How to study (the loop that works)

1. Read Lesson-N.md (30 to 40 minutes). Type the examples yourself in a terminal.
2. Run bash Code.sh and compare the output with Code.md.
3. Break it: do the experiments at the end of Code.md.
4. Do the exercises in Resources.md before opening the answers.
5. Next day: redo two exercises from memory.

Practice inside ~/bash-practice. Never practice on your important folders.

---

The lessons

🟢 Level 1: Survival

#	Lesson
1	Meet Bash: echo, pwd, ls, cd
2	Files & folders: mkdir, touch, cp, mv, rm, cat
3	Reading & finding: less, head, tail, wc, find, grep
4	Help yourself: man, --help, type, PATH, history, aliases

🟡 Level 2: Power Tools

#	Lesson
5	Pipes & redirection
6	Wildcards & globbing, brace expansion
7	Text tools: sort, uniq, cut, tr, sed, awk
8	Permissions & users: chmod, chown, sudo, umask

🟠 Level 3: Real Scripting

#	Lesson
9	Your first script: shebang, running, exit codes
10	Variables & quoting
11	User input & arguments
12	Conditions: if, [[ ]], case
13	Loops: for, while, until
14	Functions

🔴 Level 4: Professional

#	Lesson
15	Arrays & associative arrays
16	String manipulation
17	Error handling: set -euo pipefail, trap
18	Argument parsing: getopts, --long options, subcommands
19	Regular expressions

🟣 Level 5: Automation

#	Lesson
20	Processes & jobs: background, wait, parallel work
21	Scheduling: cron, systemd timers, locking
22	Networking & APIs: curl, jq, ssh, rsync

⚫ Level 6: Claude Level

#	Lesson
23	Real projects: backup, log analyzer, organizer, scaffolder, deployer
24	Mastery: debugging, speed, portability, testing, security, style

---

Requirements

• Linux, WSL, or macOS with Bash. Lessons 1 to 14 work with any Bash; Lessons 15 to 24 want Bash 4+ (macOS ships 3.2: brew install bash).
• Some scripts use GNU tools (stat -c, date -d, touch -d). On macOS: brew install coreutils gnu-sed grep.
• Optional but recommended: shellcheck, jq, bats, git, curl, python3.

Check your version: bash --version.

Running a lesson

cd lesson-10
bash Code.sh          # always run with bash, not sh

Every Code.sh writes only inside ~/bash-practice/lessonNN-demo and removes it at the end (Lesson 22 also starts and stops a tiny local web server on 127.0.0.1; Lesson 21 never touches your real crontab).

To keep the files a demo creates (for example the tools from Lesson 23), comment out the rm -r "$DEMO" line near the bottom.

---

Built to take you from "I don't know a single line of Bash" to writing, testing and shipping real tools. Keep one rule: automate something every week. 🎓