Linux Commands Lecture by Colt Steele

Overview

Colt Steele, an experienced developer and instructor, teaches about 50+ essential Linux commands applicable to Linux, Mac OS, and other Unix-like environments. The lecture includes practical tips, explanations of command structures, and real-world applications.

Introduction

• Colt’s background: Developer and teacher, known for in-person and online web development bootcamps.
• Acknowledgement to Flavio Copez for the Linux Commands Handbook used in the lecture.
• Lecture goal: Cover 50+ useful Linux commands, starting with basics (navigation, file management) and moving to advanced concepts.

Why Learn Linux Commands?

1. Control: More direct control over your system compared to GUI.
2. Speed: Faster execution of tasks once you learn the commands.
3. Automation: Automate repetitive tasks using scripts.
4. Availability: Standardized across Unix-like systems, essential for developers, sysadmins, engineers, etc.
5. Requirement: Many tech roles require command line proficiency (e.g., web developers, data scientists).
6. Cloud Computing: Many services necessitate command line interaction.
7. Historical Context: Commands are shared across Unix-descended systems like Linux, macOS (due to their Unix heritage).

Key Concepts and Setup

• Unix and Linux Origins: Unix inspired the development of many OS including Linux; Linux distributions (distros) vary but share core commands (Ubuntu, Fedora, etc.).
• Shells: Interface between user and OS; common shells include bash, zsh (default on macOS), and fish.
• Commands Structure: Composed of the command, options (flags), and arguments.
• Installation: Setup guidance for Windows (WSL installation required) and Linux/Mac (terminals pre-installed).

Basic Commands

Who Am I?

• Command: whoami
• Purpose: Prints the currently logged-in user’s name.

Man Pages

• Command: man [command]
• Purpose: Displays the manual page for a command.
• Navigation: Use space to scroll down, q to exit.

Clear Screen

• Command: clear
• Purpose: Clears terminal screen.
• Shortcut: Ctrl + L

Print Working Directory (PWD)

• Command: pwd
• Purpose: Displays current directory path.

List Directory Contents (LS)

• Command: ls
• Purpose: Lists files and directories.
• Options: -l (detailed list), -a (include hidden files), -la (combine).

Change Directory (CD)

• Command: cd [path]
• Purpose: Changes the current directory.
• Special paths: .. (parent directory), ~ (home directory).
• Example: cd ~/Documents

Make Directory (MKDIR)

• Command: mkdir [directory]
• Purpose: Creates a new directory.
• Option: -p (makes parent directories as needed).

Create Files (TOUCH)

• Command: touch [file]
• Purpose: Creates an empty file or updates timestamp on an existing file.

Remove Directory (RMDIR)

• Command: rmdir [directory]
• Purpose: Deletes an empty directory.

Remove Files (RM)

• Command: rm [file]
• Purpose: Removes files or directories.
• Options: -r (recursive for directories), -v (verbose), -i (interactive).

Open Files (MAC ONLY)

• Command: open [file/app]
• Purpose: Opens file or app (works on macOS).
• Alternative on Linux: xdg-open

Intermediate Commands

Move/Rename Files (MV)

• Command: mv [source] [destination]
• Purpose: Moves or renames files and directories.

Copy Files (CP)

• Command: cp [source] [destination]
• Purpose: Copies files and directories.
• Option: -r (recursive for directories).

View File Contents (HEAD and TAIL)

• Commands:
  • head [file] (first 10 lines)
  • tail [file] (last 10 lines)
• Purpose: Views the beginning or end of files.
• Options: -n [number] (specify number of lines), -f (follow for tail).

Print Text (ECHO)

• Command: echo [text]
• Purpose: Prints text to terminal or writes to a file using redirect (>).

Word Count (WC)

• Command: wc [file]
• Purpose: Displays number of lines, words, and bytes in a file.
• Options: -l (lines), -w (words).

Piping

• Operator: |
• Purpose: Pipes output of one command as input to another.

Sort

• Command: sort [file]
• Purpose: Sorts lines in a file.
• Options: -n (numerical), -r (reverse), -u (unique).

Unique (UNIQ)

• Command: uniq [file]
• Purpose: Filters out adjacent duplicate lines.
• Options: -d (only duplicates), -u (non-duplicates), -c (counts occurrences).
• Requires: Files often need sorting first.

Find

• Command: find [path] [criteria]
• Purpose: Searches for files and directories meeting specified criteria.
• Common Criteria: -name, -type, -size, -mtime.
• Example: find . -name '*.txt'

Grep

• Command: grep [pattern] [file]
• Purpose: Searches for text patterns within files.
• Options: -i (case insensitive), -r (recursive), -n (line numbers).
• Supports: Regular expressions.

Disk Usage (DU)

• Command: du [file/folder]
• Purpose: Shows disk usage of files and directories.
• Options: -h (human-readable), -s (summary).

Disk Free (DF)

• Command: df
• Purpose: Shows amount of free disk space on filesystems.
• Option: -h (human-readable).

Advanced Commands

History

• Command: history
• Purpose: Lists command history.
• Recall command: !number
• Search History: history | grep [pattern]

Process Management (PS, TOP, KILL)

• Commands: ps, top, kill
  • ps: Displays processes started by the current user.
  • top: Monitors system resources and running processes interactively.
  • kill [PID]: Kills a process by ID; common signals include -15 (graceful termination) and -9 (forceful).

Advanced Process Management (JOBS, BG, FG)

• Commands: jobs, bg, fg
• Purpose: Manages background and foreground processes.
• Usage:
  • jobs: Lists background jobs.
  • bg [job ID]: Resumes job in the background.
  • fg [job ID]: Brings job to the foreground.

File Compression and Archiving (gzip, tar)

• Commands:
  • gzip [file]: Compresses files with gzip.
  • gunzip [file]: Decompresses gzip files.
  • tar: Archives directories and files.
  • Options: -c (create), -x (extract), -z (gzip), -f (filename)
• Example: tar -czf archive.tar.gz [directories/files]

Text Editor (nano)

• Command: nano [file]
• Purpose: Simple text editor.
• Commands: Ctrl + X (exit), Ctrl + O (save), Ctrl + W (search).

Create Aliases

• Command: alias name='command'
• Purpose: Creates shortcuts for longer commands.
• Permanent Aliases: Add to ~/.bashrc or ~/.zshrc

Environment Variables

• Concept: Variables that affect the behavior of the shell.
• Example: echo $PATH prints the executable search path.
• Exporting: export VAR=VALUE sets a variable.

Input/Output Redirection

• Symbols:
  • > : Redirects output to a file (overwrites).
  • >>: Redirects output to a file (appends).
  • < : Takes input from a file.
  • 2> : Redirects standard error.

Links (ln)

• Commands:
  • Hard link: ln [target] [link_name]
  • Soft link: ln -s [target] [link_name]
• Purpose: Creates links to files or directories (hard and symbolic).

User and Permissions Commands

Who

• Command: who
• Purpose: Displays logged-in users.

Switch User (SU)

• Command: su [username]
• Purpose: Switches to another user.
• Option: - (simulates a full login).

Superuser Do (SUDO)

• Command: sudo [command]
• Purpose: Runs command with superuser (root) privileges.

Password

• Command: passwd [username]
• Purpose: Changes the user’s password.

Change Ownership (CHOWN)

• Command: chown [owner][:group] [file]
• Purpose: Changes file or directory ownership.
• Option: -R (recursive).

Change Permissions (CHMOD)

• Command: chmod [permissions] [file]
• Purpose: Changes file or directory permissions.
• Syntax: [ugoa][+-=][rwx]
• Advanced: Octal notation (e.g., chmod 755).

Conclusion

• Important Concepts: Understanding and combining simple commands is more critical than memorizing everything.
• Practice: Continually practice and refer to man pages as needed.
• Final Note: Thanks to Flavio Copez for resources, and keep exploring Linux commands to improve efficiency.