ls (list files and directories) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the ls command do in Linux?

The ls command lists files and directories in the current folder or a specified path.

beginner

How do you list all files, including hidden ones, using ls?

Use ls -a to show all files, including those starting with a dot (hidden files).

beginner

What does the -l option do with ls?

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

intermediate

How can you list files sorted by modification time using ls?

Use ls -lt to list files sorted by modification time, newest first.

intermediate

What does ls -R do?

The -R option lists directories and their contents recursively, showing all nested files and folders.

Which ls option shows hidden files?

A -R

B -l

C -t

D -a

The -a option includes hidden files (those starting with a dot).

What does ls -l display?

A Detailed info like permissions and size

B Hidden files only

C Files sorted by size

D Only file names

-l shows detailed information about files and directories.

How do you list files sorted by modification time, newest first?

A ls -R

B ls -lt

C ls -a

D ls -lh

ls -lt sorts files by modification time, newest first.

Which command lists all files and directories inside subfolders too?

A ls -R

B ls -a

C ls -l

D ls -t

ls -R lists contents recursively inside all subdirectories.

What does the plain ls command show by default?

A All files including hidden

B Only directories

C Files and directories except hidden files

D Detailed file info

Plain ls lists files and directories except hidden ones.

Explain how to use ls to see detailed info about all files, including hidden ones.

Combine options to get detailed and hidden files listed.

Describe how to list files recursively in all subdirectories using ls.

Think about how to see inside folders inside folders.

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