Shell concept (Bash, Zsh) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a shell in Linux?

A shell is a program that lets you type commands to control the computer. It acts like a translator between you and the system.

beginner

Name two popular shells used in Linux.

Bash and Zsh are two popular shells. Bash is common and simple, Zsh has more features and customization.

beginner

What does the command prompt in a shell represent?

The prompt shows that the shell is ready to accept your commands. It often shows your username, computer name, and current folder.

beginner

How does a shell script help you?

A shell script is a file with commands you want to run automatically. It saves time by doing tasks for you without typing each command.

intermediate

What is the difference between Bash and Zsh?

Bash is the default shell on many systems and is simple to use. Zsh offers more features like better auto-completion, themes, and plugins for easier use.

What is the main role of a shell in Linux?

A To store files on the computer

B To display images on the screen

C To accept and run commands typed by the user

D To manage internet connections

The shell takes commands you type and runs them on the system.

Which shell is known for having many features and customization options?

A Zsh

B Cmd

C Bash

D PowerShell

Zsh offers advanced features like themes and plugins.

What does a shell script do?

A Runs a set of commands automatically

B Creates a new user account

C Formats the hard drive

D Displays system hardware info

Shell scripts automate tasks by running commands in order.

What information might you see in a shell prompt?

A Weather forecast

B Username and current folder

C List of installed apps

D Battery percentage

Prompts often show your username and where you are in the file system.

Which shell is usually the default on many Linux systems?

A Tcsh

B Zsh

C Fish

D Bash

Bash is the default shell on many Linux distributions.

Explain what a shell is and why it is useful in Linux.

Think of the shell as your helper to talk to the computer.

Describe the main differences between Bash and Zsh shells.

Compare their features and user experience.

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