ls (list files and directories) in Linux CLI - Mini Project: Build & Apply

Listing Files and Directories with ls

📖 Scenario: You are organizing your files on your computer. You want to see what files and folders are inside a specific folder to decide what to do next.

🎯 Goal: Learn how to use the ls command to list files and directories in a folder.

📋 What You'll Learn

Use the ls command to list files

Use ls with options to show hidden files

Use ls to list files with detailed information

Use ls to list files sorted by size

💡 Why This Matters

🌍 Real World

Listing files is a daily task when managing files on any computer or server. Knowing how to see hidden files and details helps you understand your files better.

💼 Career

System administrators, developers, and anyone working with computers use <code>ls</code> to quickly check files and folders. It is a fundamental skill for working in command-line environments.

1

Create a test folder with files

Create a folder called test_folder and inside it create three files named file1.txt, file2.txt, and .hiddenfile.

Linux CLI

# Create the folder and files using mkdir and touch commands
# Your code here

Hint

Use mkdir test_folder to make the folder and touch to create files.

2

List files in the folder

Use the ls command to list the files inside test_folder.

Linux CLI

mkdir test_folder
cd test_folder
touch file1.txt file2.txt .hiddenfile

# Use ls to list files
# Your code here

Hint

Just type ls to see visible files.

3

List all files including hidden ones

Use the ls -a command to list all files, including hidden files, inside test_folder.

Linux CLI

mkdir test_folder
cd test_folder
touch file1.txt file2.txt .hiddenfile

# Use ls with -a option to show hidden files
# Your code here

Hint

The -a option shows hidden files starting with a dot.

4

List files with details and sort by size

Use the ls -lS command to list files with detailed information sorted by size inside test_folder.

Linux CLI

mkdir test_folder
cd test_folder
touch file1.txt file2.txt .hiddenfile

# Use ls with -lS options to show details and sort by size
# Your code here

Hint

The -l option shows details like size and date, and -S sorts by size.

Practice

1. What does the ls command do in Linux?

easy

A. Creates a new directory

B. Deletes files from the current folder

C. Lists files and directories in the current folder

D. Moves files to another folder

Solution

1. Step 1: Understand the purpose of ls

   The ls command is used to show what files and folders are inside a directory.

2. Step 2: Identify the correct description

   Among the options, only listing files and directories matches what ls does.

3. Final Answer:

   Lists files and directories in the current folder -> Option C

4. Quick Check:

   ls = list files [OK]

Hint: Remember: ls = list files and folders [OK]

Common Mistakes:

• Confusing ls with commands like rm or mkdir
• Thinking ls deletes or moves files
• Assuming ls creates directories

2. Which of these is the correct syntax to list all files including hidden ones in a directory?

easy

A. ls -l

B. ls -r

C. ls -h

D. ls -a

Solution

1. Step 1: Recall option meanings for ls

   -a shows all files including hidden (those starting with a dot).

2. Step 2: Match option to requirement

   Only ls -a lists hidden files; others do different things like long format or reverse order.

3. Final Answer:

   ls -a -> Option D

4. Quick Check:

   -a means all files [OK]

Hint: Use -a to see hidden files starting with . [OK]

Common Mistakes:

• Using -l instead of -a to see hidden files
• Confusing -r (reverse) with -a
• Thinking -h shows hidden files

3. What will be the output of the command ls -l /tmp if the /tmp directory contains two files named file1.txt and file2.log?

medium

A. file1.txt file2.log

B. Detailed list showing permissions, owner, size, and date for file1.txt and file2.log

C. Only hidden files in /tmp

D. An error saying /tmp does not exist

Solution

1. Step 1: Understand -l option with ls

   The -l option shows a detailed list including permissions, owner, size, and modification date.

2. Step 2: Apply to /tmp directory contents

   Since /tmp has two files, the command will show detailed info lines for both files.

3. Final Answer:

   Detailed list showing permissions, owner, size, and date for file1.txt and file2.log -> Option B

4. Quick Check:

   ls -l = detailed list [OK]

Hint: -l means long detailed listing [OK]

Common Mistakes:

• Expecting just filenames without details
• Thinking it lists only hidden files
• Assuming it shows an error if directory exists

4. You run ls -la /home/user but get an error: ls: cannot access '/home/user': No such file or directory. What is the most likely cause?

medium

A. /home/user directory does not exist

B. You forgot to add the -a option

C. You need to run the command as root

D. The ls command is misspelled

Solution

1. Step 1: Analyze the error message

   The error says the directory '/home/user' cannot be accessed because it does not exist.

2. Step 2: Check other options

   Options -a and running as root do not cause this error; misspelling ls would cause a different error.

3. Final Answer:

   /home/user directory does not exist -> Option A

4. Quick Check:

   Directory missing = cannot access error [OK]

Hint: Check if directory exists before blaming options [OK]

Common Mistakes:

• Assuming missing -a causes error
• Thinking root is always needed
• Confusing command misspelling with directory missing

5. You want to list all files in the directory /var/log sorted by modification time, newest first, including hidden files. Which command should you use?

hard

A. ls -lat /var/log

B. ls -ltr /var/log

C. ls -al /var/log

D. ls -lh /var/log

Solution

1. Step 1: Identify options needed

   -a shows hidden files, -t sorts by modification time, newest first, and -l gives detailed listing.

2. Step 2: Match options to command

   Only ls -lat /var/log combines all needed options correctly.

3. Final Answer:

   ls -lat /var/log -> Option A

4. Quick Check:

   -lat = list all, sort by time [OK]

Hint: Use -lat to list all files sorted by time [OK]

Common Mistakes:

• Using -ltr which sorts oldest first
• Forgetting -a to show hidden files
• Using -lh which shows size but not sorting