A Guide to the Linux Command Line

This guide introduces the essential tools that come with nearly every Linux system and highlights some powerful, modern alternatives for better experience.

Getting Help

The most important commands are those that teach about other commands.

Command	Description
man	The manual. man ls will show you the complete manual page for the ls command, including all its options.
--help	Most commands support a --help flag (e.g., ls --help) for a quick summary of their usage.

Essential GNU Core Utilities (Coreutils)

The coreutils package contains the foundational command-line tools found on virtually every GNU/Linux system. They are the bedrock of command-line work, grouped into three main categories:

• File Utilities: For managing files and directories (e.g., ls, cp, rm, mv, mkdir, chmod, chown, touch).

• Text Utilities: For processing and manipulating text (e.g., grep, cat, sort, head, tail, uniq, cut, sed, awk, wc).

• Shell Utilities: For interacting with the system and shell (e.g., pwd, whoami, date, echo, uname).

Below are the most crucial commands organized by common tasks.

Navigating and Managing Files & Directories

These are the first commands you'll need to learn to move around and interact with the filesystem.

• pwd (Print Working Directory): Shows the full path of the directory you are currently in.

• ls (List): Lists the contents of a directory. A common and more informative usage is ls -la.

• cd (Change Directory): The primary command for navigating between directories. cd .. moves you up one level.

• mkdir (Make Directory): Creates a new directory.

• rmdir: Remove empty directories.

• cp (Copy): Copies files or directories. Example: cp source.txt destination.txt.

• mv (Move): Moves or renames files and directories.

• rm (Remove): Deletes files. To delete a directory and all its contents, use rm -r. Use this command with extreme caution.

• shred: Securely delete a file by overwriting it multiple times, making recovery difficult.

• touch: Creates an empty file or updates the timestamp of an existing file.

• stat: Displays detailed status information about a file or filesystem, such as size, permissions, and access times.

Viewing and Processing Text

These tools are essential for reading, searching, and manipulating the contents of text files.

• cat (Concatenate): Displays the entire content of a file on the screen.

• less: An improved file viewer that allows you to scroll up and down through a file. It's more practical than cat for long files.

• head / tail: Show the first (head) or last (tail) few lines of a file. Useful for checking log files.

• grep (Global Regular Expression Print): Searches for a specific pattern of text within files. Example: grep "error" server.log.

• wc (Word Count): Counts the lines, words, and characters in a file.

• sort: Sorts the lines of a text file alphabetically or numerically.

• uniq: Reports or removes repeated lines from a sorted file.

User and System Information

These commands help you understand your environment, system resources, and user permissions.

• whoami: Prints your current effective username.

• id: Displays user and group information for the current user.

• uname: Prints system information, such as the kernel name and version. Use uname -a for all information.

• df (Disk Free): Reports the amount of available disk space on your filesystems.

• du (Disk Usage): Estimates and displays the disk space used by files and directories.

Modern & Enhanced Command-Line Tools

While the core utilities are powerful, a vibrant ecosystem of modern, third-party tools has emerged to improve on their functionality. These tools are typically more user-friendly, colorful, and feature-rich.

Installation Required!

Unlike the core utilities, these tools are not installed by default. You'll need to install them using your distribution's package manager ( e.g., sudo apt install exa, sudo dnf install bat ).

Enhanced File Listing & Navigation

• exa: A modern replacement for ls. It provides a more user-friendly output with colors, icons, a tree view, and git integration.

• ranger: A console-based file manager with VI key bindings. It provides an interactive, visual way to navigate and manage your files in the terminal.

Modern File Viewing & Editing

• bat (from batcat): A superior cat clone. It offers syntax highlighting for code, Git integration to show modifications, and automatic paging (like less).

• micro: An intuitive and easy-to-use terminal-based text editor. It aims to be a successor to nano, offering more features like plugin support and familiar keybindings out of the box.

Advanced Disk Usage Analysis

• ncdu: An interactive disk usage analyzer. It scans a directory and presents an interactive, navigable list of files and folders, making it easy to see what's consuming your disk space.

• gdu: A very fast disk usage analyzer written in Go. It is similar to ncdu but is significantly faster due to parallel processing.

Powerful File Management & Transfer

• rsync: A fast and versatile tool for synchronizing files and directories, either locally or remotely. It's highly efficient because it only transfers the differences between the source and destination.

• duff: A duplicate file finder. It scans directories to identify and report redundant files, helping you clean up clutter.

• wormhole: A tool for securely sending files and directories from one computer to another. It generates a simple, one-time code to make sharing easy and private.

Detailed Hardware Information

• lshw (List Hardware): A tool that provides extremely detailed information about the hardware configuration of your machine, including memory, CPU, mainboard, and firmware versions.

Reference: Comprehensive GNU Core Utilities List

File Utilities

cat, chgrp, chmod, chown, cp, dd, df, dir, du, install, ln, ls, mkdir, mkfifo, mknod, mktemp, mv, rm, rmdir, shred, sync, touch, truncate, vdir.

Text Utilities

awk, comm, csplit, cut, expand, fmt, fold, grep, head, join, nl, od, paste, ptx, sed, sort, split, sum, tac, tail, tr, unexpand, uniq, wc.

Shell Utilities

basename, chroot, date, dirname, echo, env, expr, factor, false, groups, hostid, id, kill, logname, nice, nohup, nproc, printenv, printf, pwd, readlink, seq, sleep, stat, stty, tee, test, timeout, true, tty, uname, uptime, users, who, whoami, yes.