Command Line
The command line is where data and AI work actually happens — running scripts, wrangling files, inspecting servers. Learn the practical Unix shell: navigation, finding and filtering text, pipes, permissions, processes, and enough scripting to automate the boring parts.
- Chapter 01
Shell Basics
4 lessons - 01 What is the shell? Understand what the terminal, the shell, and bash/zsh actually are — and why the command line is worth learning.
- 02 Navigating the filesystem Learn pwd, ls, and cd so you always know where you are and can move anywhere in the filesystem with confidence.
- 03 Working with files & directories How to create, copy, move, rename, and delete files and folders from the terminal — without losing work.
- 04 Viewing files: cat, less, head, tail How to read any file — tiny config or 2 GB log — from the terminal without opening an editor.
- Chapter 02
Finding & Filtering
4 lessons - 05 Searching with grep Learn to search file contents with grep — the fastest way to find which files contain a pattern, on what line, and in what context.
- 06 Finding files with find Use find to locate files by name, type, size, and age — then act on them with -delete or -exec.
- 07 Pipes & redirection Learn how to chain small commands together using pipes and redirection — the heart of the Unix philosophy.
- 08 Text processing: sort, uniq, wc, cut Master the Unix text-wrangling toolkit — sort, uniq, wc, cut, and tr — and learn to compose them into powerful data-analysis pipelines without leaving the terminal.
- Chapter 03
Power Tools
3 lessons - 09 Permissions & sudo Why you see 'Permission denied' and how to fix it safely using chmod, chown, and sudo.
- 10 Processes & jobs See every running process, move jobs between foreground and background, and kill a runaway script cleanly — or forcefully when you have no other choice.
- 11 Environment variables & PATH Learn what environment variables are, how PATH controls where the shell finds commands, and why 'command not found' happens — and how to fix it.
- Chapter 04
Beyond the Basics
3 lessons - 12 ssh, scp & curl Log into a remote GPU box, copy files to it, and hit a REST API — all from the terminal using ssh, scp, and curl.
- 13 Shell scripting basics Turn a sequence of commands into a reusable script you can run with one word — variables, arguments, conditionals, loops, and exit codes explained.
- 14 Productivity: aliases, history, xargs Master the habits that make terminal power users fast: history navigation, aliases, command chaining, xargs, and line-editing shortcuts.
- End of section 0 / 14 complete
Make it stick — pass every quiz.
Each lesson has a short quiz at the bottom. Passing the quiz is what marks the lesson complete and counts toward your certificate.
Section complete 14 / 14 lessonsNice work — you finished Command Line.
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Command Line — frequently asked questions
Straight answers to the questions people ask most about command line.
What is the difference between the terminal, the shell, and bash?
The terminal is the application window that shows text, the shell is the program running inside it that reads your commands and executes them, and bash and zsh are specific shells (zsh is the macOS default). In short, the terminal is the screen, the shell is the interpreter, and bash or zsh are particular brands of that interpreter.
Read the lessonWhat is the difference between grep and find?
grep searches inside files for lines matching a text pattern, while find locates the files themselves by name, size, type, or modification time. Use grep to answer 'which files contain this text?' and find to answer 'where are the files with these properties?' — and they are often combined in one pipeline.
Read the lessonWhat is the difference between a single and double redirect in the shell?
A single greater-than sign redirects a command's output to a file and overwrites whatever was there, while a double greater-than sign appends the output to the end of the file instead. Use append when adding to a log you want to keep, and overwrite only when you intend to replace the file's contents.
Read the lessonHow do I make a shell script executable?
Add a shebang line such as #!/usr/bin/env bash at the top, run chmod +x on the file to give it execute permission, then run it with ./script.sh. The shebang tells the system which interpreter to use, and the execute bit is what lets you run the file directly.
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