3 Shell & command line
Every entry filed under Shell & command line and its subtopics.
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What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
21 entries match these filters
- 0420 cron and systemd timers: run something every night Schedule a script with crontab or a systemd timer: the five cron fields, environment and PATH pitfalls, logging, catching up missed runs… Beginner · Step by step · Linux Article cron & timers · Services & systemd 15 Oct 2026
- 0403 Work across Windows and WSL: files, paths and running tools from both sides WSL is most useful when Windows and Linux cooperate: open Linux folders in Explorer, run Windows programs from bash, convert paths with… Beginner · Step by step · Windows Article Basics · WSL 15 Oct 2026
- 0418 Bash scripting fundamentals: variables, conditions, loops, functions The core building blocks of a bash script: variables and quoting, if and test, for and while loops, functions, exit codes and… Beginner · Explains an idea · Linux, macOS Article Basics · Shell scripting 15 Oct 2026
- 0423 Fix: bad interpreter or command not found after a script is copied from Windows (CRLF) A script edited on Windows carries invisible carriage returns, so Linux looks for /bin/bash^M. How to spot CRLF line endings, convert them… Beginner · Fixes an error · Linux, macOS, Windows Article Basics · Shell scripting 15 Oct 2026
- 0392 Install Visual Studio Code on Linux, macOS and Windows Install VS Code from Microsoft's packages, Homebrew or winget, get the code command working in the terminal, and add the extensions you… Beginner · Step by step · Linux, macOS, Windows Article Command-line tools · Installing languages & tools 15 Oct 2026
- 0345 SSH keys: create, copy and use them Generate an ed25519 key pair, install the public key on a server with ssh-copy-id, keep the private key protected with a passphrase… Beginner · Step by step · Linux, macOS, Windows Article Keys & config · SSH 15 Oct 2026
- 0320 Fix: address already in use (EADDRINUSE) Something is already listening on the port your program wants. Find the process with lsof or ss, stop it or pick another… Beginner · Fixes an error · Linux, macOS Article Networking & firewalls · Node.js · Processes & ports 15 Oct 2026
- 0334 Fix: port is already allocated docker run or docker compose up fails with Bind for 0.0.0.0:8080 failed: port is already allocated. Find what holds the port, another… Beginner · Fixes an error · Linux, macOS, Windows Article Docker fixes · Processes & ports 15 Oct 2026
- 0316 Fix: command not found bash: something: command not found means the shell could not find a program with that name in any PATH directory. The usual… Beginner · Fixes an error · Linux, macOS Article Basics · Packages & updates 15 Oct 2026
- 0317 Fix: Permission denied when running a script (chmod +x) bash: ./script.sh: Permission denied means the file exists but you may not execute it. Usually the execute bit is missing; sometimes the… Beginner · Fixes an error · Linux, macOS Article Basics · Users, sudo & hardening 15 Oct 2026
- 0289 What is a process? A process is a running program; the operating system gives each one its own memory and an ID number. Beginner · Explains an idea · Any system Article Processes & ports 15 Oct 2026
- 0290 What is a cron job? A cron job is a command scheduled to run automatically at set times, such as every night at two o'clock. Beginner · Explains an idea · Any system Article cron & timers 15 Oct 2026
- 0284 What is a shell? A shell is the program that reads the commands you type and tells the operating system to run them. Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0285 What is a terminal? A terminal is the window where you type commands; the shell inside it does the actual work. Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0286 What is PATH? PATH is the list of folders your shell searches to find a program when you type its name. Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0287 What is an environment variable? An environment variable is a named value the operating system passes to programs, such as settings or secrets. Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0049 Pipes and redirection: connecting commands A pipe sends one command's output into another command, and redirection sends output to a file. Together they let small tools build… Beginner · Explains an idea · Linux, macOS Article Basics · Text processing 15 Oct 2026
- 0050 File permissions: chmod, chown and what 755 means Every file has an owner, a group and read/write/execute permissions for three kinds of users. chmod changes the permissions and chown changes… Beginner · Explains an idea · Linux, macOS Article Basics 15 Oct 2026
- 0053 Set up SSH keys: ssh-keygen, ssh-copy-id and ~/.ssh/config SSH keys let you log in to servers and push to Git hosts without typing a password. Create an ed25519 key, install… Beginner · Step by step · Linux, macOS, Windows Article Keys & config 15 Oct 2026
- 0051 Environment variables and PATH Environment variables are named settings that every program inherits from the shell. PATH is the one that tells the shell where to… Beginner · Explains an idea · Linux, macOS Article Basics 15 Oct 2026
- 0057 Shell cheat sheet: everyday commands A quick reference for moving around, managing files, viewing and searching text, checking processes and disk space in bash and zsh, with… Beginner · Cheat sheet · Linux, macOS Article Basics · Command-line tools 15 Oct 2026