Linux CLI Essentials¶
A comprehensive guide to working effectively on the Linux command line. These guides take you from "I can type commands" to understanding how the shell actually works and using it productively.
Each topic is covered in its own guide. Start anywhere - they're self-contained, but the order below follows a natural learning path.
Guides¶
Shell Basics¶
What the shell is, how it starts up, and how it processes your input. Covers shell types, configuration files, the PATH variable, variables, quoting rules, and the full set of shell expansions (brace, tilde, parameter, arithmetic, command substitution, and globbing).
Streams and Redirection¶
How programs communicate through STDIN, STDOUT, and STDERR. Covers basic redirection, appending, /dev/null, here documents, here strings, file descriptor manipulation, pipelines (exit status, PIPESTATUS, named pipes), tee, subshells, and process substitution.
Text Processing¶
The core toolkit for searching, transforming, and analyzing text. Covers grep (with regular expressions - basic, extended, and POSIX classes), sed (substitution, addresses, in-place editing), awk (fields, patterns, BEGIN/END, variables), cut, sort, uniq, tr, wc, head, tail, and tee.
Finding Files¶
Searching directory trees and operating on the results. Covers find (name, type, size, time, permission, and owner tests, depth control, logical operators, and actions) and xargs (null-delimited input, placeholder substitution, parallel execution).
File Permissions¶
The Linux permission model explained. Covers reading ls -l output, chmod (symbolic and octal modes), chown, chgrp, umask, and special permission bits (setuid, setgid, sticky bit) with real-world examples.
Job Control¶
Managing processes from the terminal. Covers foreground/background processes, Ctrl-Z/bg/fg/jobs, signals (SIGTERM, SIGKILL, etc.), kill/killall/pkill, nohup, disown, ps, top/htop, and terminal multiplexers (screen and tmux).
Scripting Fundamentals¶
Writing reliable bash scripts. Covers exit codes, conditionals (test/[ ]/[[ ]] and their differences), if/elif/else, case, for/while/until loops, functions (arguments, return values, local variables), and error handling (set -euo pipefail, trap).
Disk and Filesystem¶
Managing storage. Covers df (filesystem usage), du (directory sizes), mount/umount, /etc/fstab, lsblk, partition management (fdisk/parted), mkfs, and fsck.
Networking¶
Essential networking from the command line. Covers ping/traceroute/mtr, curl/wget, ssh (keys, config, port forwarding, jump hosts), scp/rsync, ss/ip, dig/nslookup, and nc (netcat).
System Information¶
Understanding what's running on a system. Covers uname, uptime (and how to interpret load averages), free (and what buff/cache means), lscpu, lsof, vmstat, the /proc and /sys virtual filesystems, and dmesg.
Archiving and Compression¶
Bundling and compressing files. Covers tar (with gzip, bzip2, and xz), standalone gzip/bzip2/xz, zip/unzip, and guidance on when to use each format.
Best Practices¶
Conventions that prevent real bugs. Covers set -euo pipefail, quoting variables, [[ ]] vs [ ], $() vs backticks, mktemp, shellcheck, avoiding ls parsing, using arrays, portability considerations, and a script template.