Shell concept (Bash, Zsh) in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Bash command?

Consider the following command run in Bash shell:

echo $((3 + 5 * 2))

What will be printed on the screen?

Linux CLI

echo $((3 + 5 * 2))

A 13

B 16

C 10

D Error: invalid arithmetic expression

💡 Hint

Remember the order of operations in arithmetic expressions.

In arithmetic, multiplication happens before addition. So 5 * 2 = 10, then 3 + 10 = 13.

📝 Syntax

intermediate

Which option correctly defines a function in Bash?

You want to create a function named greet that prints 'Hello'. Which of these is the correct syntax?

A function greet { echo 'Hello'; }

B def greet() { echo 'Hello' }

C greet() echo 'Hello'

D function greet() echo 'Hello';

💡 Hint

Bash functions can be declared with or without the 'function' keyword, but syntax matters.

Option A uses the correct Bash syntax: 'function name { commands; }'. Other options have syntax errors or use other languages' syntax.

🔧 Debug

advanced

Why does this script fail to print the variable value?

Given this script:

#!/bin/bash VAR=5 if [ $VAR -gt 3 ] then echo "Value is $var" fi

What is the reason for the output being empty?

Linux CLI

#!/bin/bash
VAR=5
if [ $VAR -gt 3 ]
then
  echo "Value is $var"
fi

A The script lacks execution permission, so it doesn't run.

B Variable names are case-sensitive; $var is empty because VAR was set, not var.

C The if condition syntax is wrong; it should use double brackets [[ ]].

D The echo command is missing quotes around $var.

💡 Hint

Check how variable names are written and used.

Bash variables are case-sensitive. VAR and var are different. The script sets VAR but prints $var, which is empty.

🚀 Application

advanced

Which command lists all files including hidden ones in long format sorted by modification time?

You want to see all files, including hidden ones (those starting with a dot), in your current directory. You want the list in long format and sorted by newest modified first. Which command achieves this?

A ls -l -a -t

B ls -ltr

C ls -lat

D ls -l -a -r -t

💡 Hint

Check what each option means: -l, -a, -t, -r

-l shows long format, -a shows hidden files, -t sorts by modification time newest first, -r reverses order. So -lat lists all files long format sorted newest first.

🧠 Conceptual

expert

What happens when you run this pipeline in Bash?

Consider this command:

echo 'apple banana cherry' | while read word; do echo $word; done

What will be the output?

A

apple
banana
cherry

B

apple banana cherry
apple banana cherry

C No output, the loop does not run

D apple

💡 Hint

Think about how 'read' works with default IFS and how the pipeline feeds input.

The 'read word' command splits the input line on whitespace (default IFS=space/tab/newline), assigning only the first field 'apple' to 'word'. The rest ('banana cherry') is discarded. Since there's only one line, the loop runs once.