🐧 Chapter 6: The Ultimate Linux Command Lab

This guide combines theory review, sequential hands-on problems, and real-world troubleshooting scenarios. It is designed to take you from a terminal beginner to a confident CLI user.

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🏗️ PART 1: Knowledge & Logic Check (Theory Review)

Test your understanding before touching the keyboard.

🔹 Section A: Multiple Choice Questions

1. Which command displays the current logged-in username?
   • A) who
   • B) whoami
   • C) user
   • D) id
2. Which of the following is an "Absolute Path"?
   • A) Documents/notes.txt
   • B) ../home/student
   • C) /home/student/Desktop
   • D) ./Images
3. To view long file content page-by-page, which command is best?
   • A) cat
   • B) more
   • C) view
   • D) show
4. In the permission string -rwxr-xr--, what does the first - represent?
   • A) Directory
   • B) Regular file
   • C) Hidden file
   • D) Executable
5. Which numeric value represents 'Read' and 'Write' but NO 'Execute'?
   • A) 7
   • B) 5
   • C) 6
   • D) 4

🔹 Section B: Command Logic

1. How do you exit the bc (calculator) environment?
2. Write the command to create nested directories School/Std11/Computer in one go.
3. Explain why rmdir fails if a directory contains even one hidden file.
4. If you use cat > myfile.txt on an existing file, what happens to the old data?
5. What is the difference between the * and ? wildcards?

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💻 PART 2: Hands-on Command Lab (50 Problems)

Execute these in your terminal to build muscle memory.

🎯 Level 1: System Awareness (1-7)

1. Shell Check: Check which shell you are currently using.
2. Calendar: Display the calendar for January 2024 and the entire year 2024.
3. Date: Display today's date in mm/dd/yy format.
4. Calculator: Use bc to calculate 45 * 23 + 17 and find sqrt(625).
5. Variable: Create a variable "name" and echo "Hello, [name]!".
6. Cleanup: Clear your terminal screen.
7. Help: Access the manual for mkdir.

📂 Level 2: Directory Operations (8-12)

8. Structure: Create subfolders math, science, and english inside a folder named studies.
9. Location: Verify your path with pwd.
10. Jump: Go back to your home directory from math using a single command.
11. Remove: Delete the english folder.
12. Batch: Create temp1 through temp4 simultaneously.

📄 Level 3: File Operations (13-20)

13. Create: Use cat > notes.txt to write three lines about Linux.
14. Display: View the content of notes.txt.
15. Append: Add "Learning never stops" to the end of notes.txt.
16. Merge: Concatenate notes.txt and more_notes.txt into all_notes.txt.
17. Stats: Find the line, word, and character count of all_notes.txt.
18. Copy: Create a backup_notes.txt from notes.txt.
19. Rename: Change backup_notes.txt to archived_notes.txt.
20. Purge: Delete the temp folders and the archived file.

🚀 Level 4: Advanced Filters & Wildcards (21-30)

21. Hidden: List all files including hidden ones.
22. Secret: Create a file named .secret and see if ls shows it.
23. Pattern: List all files starting with 'a', 'b', or 'c'.
24. Slice: Extract the first 10 characters of notes.txt using cut.
25. CSV: Extract the 1st column from a comma-separated data.txt.
26. Sort: Sort data.txt by the second field (Age).
27. Search: Find the line containing "John" in data.txt.
28. Snippet: Show only the first 2 and last 2 lines of a file.
29. Compare: Find the differences between two similar text files.
30. Join: Use paste to join two files horizontally.

🔐 Level 5: Permissions & Security (31-34)

31. Status: Check the long-format listing (ls -l) of a script.
32. CHMOD: Set permissions to 744 (Owner: all, Others: read).
33. Restrict: Remove your own write permission.
34. Vault: Create a private directory accessible only to you.

⚡ Level 6: Redirection & Piping (35-40)

35. Export: Save your directory list to files.txt.
36. Count: Count how many files are in /bin using a pipe.
37. Users: Save the top 5 users from /etc/passwd to users.txt.
38. Bash: Find all users using the bash shell.
39. Pipeline: Sort data.txt and save it to final.txt.
40. Transform: Convert a file's text to all UPPERCASE using tr.

🛠️ Level 7: Troubleshooting (42-50)

42. Force delete a non-empty directory.
43. Find a command related to "copy" using apropos.
44. Identify the owner and group of a system file.
45. Rename a file that has a space in its name (e.g., my file.txt).
46. Search for a specific word inside all .txt files in a folder.
47. Find the differences between config.old and config.new.
48. Count how many times the word "error" appears in a log file.
49. See the last 10 commands you typed (Hint: use history).
50. The Master Pipeline: List → filter .doc → sort → save to list.txt.

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🏆 PART 3: The Capstone Challenges

Complex tasks that require multiple commands to solve.

🏔️ Challenge 1: The Master Flow Lab

1. Find your username and current date.
2. In Home, create Project/Codes and Project/Notes.
3. Move into Project/Notes.
4. Create intro.txt, data.txt, and final.doc.
5. Write "Linux Master" into intro.txt.
6. Move final.doc into the Codes folder using a relative path.
7. Copy intro.txt to backup.txt.
8. Change backup.txt permission to 400.
9. Go back to Project and delete the Notes folder and everything inside it.

🏗️ Challenge 2: The Comprehensive Project

41. The Linux Organizer:
    • Create linux_practice with subfolders documents, scripts, and logs.
    • Create report1.txt and report2.txt inside documents.
    • Merge them into final_report.txt.
    • Create a recursive inventory of the whole project and save it to system_map.txt.
    • Make every file in scripts executable.

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💡 Final Mentor's Tip

"Commands are like vocabulary. The more you use them in real scenarios, the faster you will speak the language of Linux. Don't just read—type!" 🐧🚀

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