First Linux commands in Linux CLI - Commands & Configuration

Introduction

Linux commands let you talk to your computer using text. They help you see files, move around folders, and check what is inside your computer.

When you want to see what files are in a folder on your computer

When you need to know which folder you are currently working in

When you want to create a new folder to organize your files

When you want to move into a different folder to work with files there

When you want to see the contents of a file quickly

Commands

This command shows you the full path of the folder you are currently in. It helps you know your exact location in the computer's folder system.

Terminal

pwd

Expected Output

/home/user

This command lists all files and folders in your current folder. It helps you see what is inside without opening anything.

Terminal

ls

Expected Output

Documents Downloads Music Pictures Videos

→

-l - Shows detailed information about files and folders

→

-a - Includes hidden files in the list

This command creates a new folder named 'myfolder' in your current location. Use it to organize your files better.

Terminal

mkdir myfolder

Expected Output

No output (command runs silently)

This command moves you into the folder named 'myfolder'. It changes your current working folder to where you want to work.

Terminal

cd myfolder

Expected Output

No output (command runs silently)

This command shows the content of the file named 'example.txt' right in the terminal. It helps you read files quickly without opening an editor.

Terminal

cat example.txt

Expected Output

This is an example text file.

It has multiple lines.

Key Concept

If you remember nothing else, remember: 'pwd' shows where you are, 'ls' shows what's there, 'mkdir' makes a folder, and 'cd' moves you around.

Common Mistakes

Typing 'cd' with a folder name that does not exist

The command fails because the folder is not found, so you stay in the same place.

Use 'ls' first to check the folder name, then type 'cd' with the exact folder name.

Using 'ls' without flags and expecting detailed info

'ls' alone only shows names, not details like size or date.

Add '-l' flag to see detailed information: 'ls -l'.

Trying to 'cat' a file that does not exist

The command returns an error because the file is missing.

Check the file name with 'ls' before using 'cat'.

Summary

Use 'pwd' to find your current folder location.

Use 'ls' to list files and folders inside the current folder.

Use 'mkdir' to create a new folder.

Use 'cd' to move into a folder.

Use 'cat' to read the contents of a file.

Practice

1. Which Linux command shows the current directory you are in?

easy

A. pwd

B. ls

C. cd

D. mkdir

Solution

1. Step 1: Understand the purpose of pwd

   The pwd command stands for "print working directory" and shows the current folder path.

2. Step 2: Compare with other commands

   ls lists files, cd changes directory, and mkdir creates a folder, so they don't show the current directory.

3. Final Answer:

   pwd -> Option A

4. Quick Check:

   Current directory command = pwd [OK]

Hint: Remember: pwd = print working directory [OK]

Common Mistakes:

• Confusing ls with pwd
• Using cd to show directory
• Thinking mkdir shows current folder

2. Which of the following is the correct syntax to create a new directory named projects?

easy

A. mkdir projects

B. mk projects

C. create projects

D. newdir projects

Solution

1. Step 1: Identify the command to create directories

   The standard Linux command to make a directory is mkdir.

2. Step 2: Check the syntax

   The correct syntax is mkdir directory_name, so mkdir projects is correct.

3. Final Answer:

   mkdir projects -> Option A

4. Quick Check:

   Create directory command = mkdir [OK]

Hint: mkdir means make directory; use it to create folders [OK]

Common Mistakes:

• Using mk instead of mkdir
• Typing create instead of mkdir
• Using newdir which is not a command

3. What will be the output of the following commands?

mkdir testdir
cd testdir
pwd

medium

A. /testdir

B. /home/testdir

C. /home/username/testdir

D. testdir

Solution

1. Step 1: Understand the commands

   mkdir testdir creates a folder named testdir. cd testdir moves into that folder. pwd prints the full path of the current directory.

2. Step 2: Determine the full path

   Assuming the user starts in their home directory (like /home/username), after changing into testdir, pwd will show /home/username/testdir.

3. Final Answer:

   /home/username/testdir -> Option C

4. Quick Check:

   pwd after cd into testdir = full path /home/username/testdir [OK]

Hint: pwd shows full path, not just folder name [OK]

Common Mistakes:

• Expecting just folder name output
• Assuming root directory path
• Confusing relative and absolute paths

4. You run the command cd myfolder but get an error: bash: cd: myfolder: No such file or directory. What is the most likely cause?

medium

A. You do not have permission to use cd

B. The folder myfolder does not exist in the current directory

C. The cd command is misspelled

D. You need to use mkdir before cd

Solution

1. Step 1: Analyze the error message

   The error says "No such file or directory", meaning the folder named myfolder is not found in the current location.

2. Step 2: Check other options

   cd is a basic command and usually not misspelled here. Permissions errors give different messages. mkdir creates folders but is not required before cd if the folder exists.

3. Final Answer:

   The folder myfolder does not exist in the current directory -> Option B

4. Quick Check:

   cd error means folder missing [OK]

Hint: Check folder exists before cd [OK]

Common Mistakes:

• Assuming permission error
• Thinking cd needs mkdir first
• Misspelling cd command

5. You want to create a new folder named backup inside your current directory and then move into it. Which sequence of commands will do this correctly?

hard

A. mkdir
cd backup

B. cd backup
mkdir backup

C. cd backup
cd backup

D. mkdir backup
cd backup

Solution

1. Step 1: Create the folder first

   The command mkdir backup creates the folder named backup in the current directory.

2. Step 2: Change directory into the new folder

   After creating it, cd backup moves you inside that folder.

3. Step 3: Check other options

   cd backup mkdir backup tries to cd into backup before it exists, causing an error. mkdir cd backup misses the folder name in mkdir. cd backup cd backup tries to cd twice without creating the folder.

4. Final Answer:

   mkdir backup cd backup -> Option D

5. Quick Check:

   Create then cd = mkdir then cd [OK]

Hint: Always mkdir before cd into new folder [OK]

Common Mistakes:

• Trying cd before mkdir
• Omitting folder name in mkdir
• Repeating cd without folder