Shell concept (Bash, Zsh) in Linux CLI - Mini Project: Build & Apply

Basic Shell Scripting with Variables and Loops

📖 Scenario: You are learning how to automate simple tasks in the Linux shell using Bash or Zsh. Imagine you want to keep track of your favorite fruits and print a message for each one.

🎯 Goal: Create a shell script that stores a list of fruits, sets a greeting message, loops through the fruits, and prints a personalized message for each fruit.

📋 What You'll Learn

Create a variable called fruits containing the exact list: apple, banana, cherry

Create a variable called greeting with the exact text: "I love"

Use a for loop with variable fruit to iterate over fruits

Print the message combining greeting and fruit exactly as shown

💡 Why This Matters

🌍 Real World

Shell scripts like this help automate repetitive tasks such as processing lists of files, users, or data entries.

💼 Career

Basic shell scripting is essential for system administrators, developers, and anyone working with Linux servers or automation.

1

Create the list of fruits

Create a variable called fruits and assign it the exact string: "apple banana cherry"

Linux CLI

# Create the variable fruits with the exact value
# Your code here

Hint

Use quotes to assign multiple words to a variable in shell.

2

Add a greeting message

Create a variable called greeting and assign it the exact text: "I love"

Linux CLI

fruits="apple banana cherry"
# Create the variable greeting with the exact value
# Your code here

Hint

Remember to use quotes for strings with spaces.

3

Loop through the fruits

Use a for loop with variable fruit to iterate over fruits and inside the loop print the message combining greeting and fruit separated by a space.

Linux CLI

fruits="apple banana cherry"
greeting="I love"

# Use a for loop to iterate over fruits
# Inside the loop, print the greeting and fruit
# Your code here

Hint

Use for fruit in $fruits; do ... done and echo to print.

4

Run the script and see the output

Run the script and print the output. The output should show each fruit with the greeting on its own line.

Linux CLI

fruits="apple banana cherry"
greeting="I love"

for fruit in $fruits; do
    echo "$greeting $fruit"
done

# Run the script to print the output
# Your code here

Hint

Run the script in your shell or use bash script.sh if saved in a file.

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