Shell concept (Bash, Zsh) in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to list all files in the current directory.

Linux CLI

ls [1]

Drag options to blanks, or click blank then click option'

A-l

B-a

C-x

D-z

Attempts:

3 left

💡 Hint

Common Mistakes

Using options that do not list hidden files

Typing options without dash

The -a option shows all files, including hidden ones.

2fill in blank

medium

Complete the code to print the current working directory.

Linux CLI

[1]

Drag options to blanks, or click blank then click option'

Acd

Bls

Cpwd

Decho

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ls' which lists files

Using 'cd' which changes directory

The pwd command prints the current directory path.

3fill in blank

hard

Fix the error in the command to create a new directory named 'projects'.

Linux CLI

mkdir [1]

Drag options to blanks, or click blank then click option'

Aprojects

Bproject

C-p

Dproject_dir

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular form 'project'

Using option flags instead of directory name

The directory name should be exactly 'projects' to match the requirement.

4fill in blank

hard

Fill both blanks to create a file named 'notes.txt' and write 'Hello World' into it.

Linux CLI

[1] [2] 'Hello World'

Drag options to blanks, or click blank then click option'

Aecho

Bcat

C>

D>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'cat' which reads files

Using '>>' which appends instead of overwriting

echo outputs text, and > redirects it to create or overwrite a file.

5fill in blank

hard

Fill all three blanks to list all files, including hidden ones, in long format sorted by modification time.

Linux CLI

ls [1] [2] [3]

Drag options to blanks, or click blank then click option'

A-a

B-l

C-t

D-r

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-r' which reverses order

Missing the option to show hidden files

-a shows hidden files, -l shows details, and -t sorts by modification time.

Practice

1. What is a shell in Linux or macOS?

easy

A. A programming language for creating websites

B. A program that lets you type commands to control your computer

C. A graphical interface for editing photos

D. A type of hardware component inside the computer

Solution

1. Step 1: Understand the role of a shell

   A shell is a program that takes your typed commands and runs them on the computer.

2. Step 2: Compare options

   Options A, B, and C describe web programming, hardware, and graphics, which are not shells.

3. Final Answer:

   A program that lets you type commands to control your computer -> Option B

4. Quick Check:

   Shell = command program [OK]

Hint: Shell = command line program to control computer [OK]

Common Mistakes:

• Thinking shell is hardware
• Confusing shell with graphical apps
• Mixing shell with programming languages

2. Which of these is the correct way to run a command with an option in Bash?

easy

A. ls -ll

B. ls -l -

C. ls l-

D. ls -l

Solution

1. Step 1: Identify correct option syntax

   Options start with a dash (-) followed by letters, so '-l' is correct.

2. Step 2: Check each option

   A: 'ls -l' is correct. B has extra dash, C has wrong order, D uses '-ll' which repeats the option unnecessarily.

3. Final Answer:

   ls -l -> Option D

4. Quick Check:

   Options start with dash and letter [OK]

Hint: Options start with dash (-) followed by letters [OK]

Common Mistakes:

• Adding extra dash after options
• Writing options without dash
• Combining options incorrectly

3. What will the following Bash command output?

echo "Hello"; echo "World"

medium

A. Hello
World (two lines)

B. Hello\nWorld

C. Hello
World

D. Hello World

Solution

1. Step 1: Understand the echo command

   Each echo prints its argument followed by a new line by default.

2. Step 2: Analyze the command sequence

   First echo prints 'Hello' then newline, second echo prints 'World' then newline, so output is two lines.

3. Final Answer:

   Hello World (two lines) -> Option A

4. Quick Check:

   echo prints with newline [OK]

Hint: echo prints text then newline by default [OK]

Common Mistakes:

• Thinking echo joins output on one line
• Confusing literal \n with newline
• Ignoring semicolon separates commands

4. What is wrong with this Bash script snippet?

for i in 1 2 3
do
echo $i
done

medium

A. Missing semicolon after '3'

B. Incorrect loop syntax, should use parentheses

C. No error, script runs fine

D. Missing 'do' keyword

Solution

1. Step 1: Check for loop syntax

   The for loop syntax 'for i in 1 2 3; do ... done' is correct. The semicolon after '3' is optional if 'do' is on next line.

2. Step 2: Verify keywords and structure

   'do' is present, parentheses are not needed in Bash for this loop, so no syntax error.

3. Final Answer:

   No error, script runs fine -> Option C

4. Quick Check:

   Bash for loop syntax correct without semicolon if newline before do [OK]

Hint: Newline before 'do' replaces semicolon in for loops [OK]

Common Mistakes:

• Thinking semicolon is always required
• Confusing Bash syntax with other languages
• Missing 'do' keyword

5. You want to list all files in a directory including hidden ones, sorted by modification time. Which command should you use?

hard

A. ls -a -t

B. ls -l -h

C. ls -r -S

D. ls -d .*

Solution

1. Step 1: Understand options needed

   '-a' shows all files including hidden, '-t' sorts by modification time.

2. Step 2: Evaluate each option

   A: 'ls -r -S' reverses and sorts by size (no hidden). B: 'ls -l -h' long format with human sizes (no hidden, no time sort). C: 'ls -a -t' shows all including hidden, sorted by mod time. D: 'ls -d .*' shows only dot entries.

3. Final Answer:

   ls -a -t -> Option A

4. Quick Check:

   Show hidden + sort by time = ls -a -t [OK]

Hint: Use -a for hidden, -t for time sort [OK]

Common Mistakes:

• Using -l instead of -a to show hidden
• Confusing -S (size) with -t (time)
• Using -d .* lists only hidden files