Bash Script to Multiply Two Numbers with Output

Use arithmetic expansion in Bash like result=$((num1 * num2)) to multiply two numbers and then print the result with echo.

Examples

Input3 and 4

Output12

Input0 and 5

Output0

Input-2 and 6

Output-12

How to Think About It

To multiply two numbers in Bash, you take the two inputs and use the arithmetic expansion syntax $(( )) with the multiplication operator *. This calculates the product and stores it in a variable, which you then print.

Algorithm

1

Get the first number as input

2

Get the second number as input

3

Multiply the two numbers using arithmetic expansion

4

Store the result in a variable

5

Print the result

Code

bash

#!/bin/bash

read -p "Enter first number: " num1
read -p "Enter second number: " num2

result=$((num1 * num2))
echo "The product is: $result"

Output

Enter first number: 3
Enter second number: 4
The product is: 12

Dry Run

Let's trace multiplying 3 and 4 through the code

1

Input first number

num1 = 3

2

Input second number

num2 = 4

3

Calculate product

result = 3 * 4 = 12

4

Print result

Output: The product is: 12

Step	Variable	Value
1	num1	3
2	num2	4
3	result	12

Why This Works

Step 1: Reading inputs

The script uses read to get two numbers from the user and stores them in variables.

Step 2: Multiplying numbers

It uses Bash arithmetic expansion $(( )) with the * operator to multiply the two numbers.

Step 3: Displaying result

The product is stored in a variable and printed with echo to show the output.

Alternative Approaches

Using expr command

bash

#!/bin/bash
read -p "Enter first number: " num1
read -p "Enter second number: " num2
result=$(expr $num1 \* $num2)
echo "The product is: $result"

Uses external command expr; less efficient but works in older shells.

Using let command

bash

#!/bin/bash
read -p "Enter first number: " num1
read -p "Enter second number: " num2
let result=num1*num2
echo "The product is: $result"

Uses built-in let for arithmetic; simpler but less flexible than $(( )).

Complexity: O(1) time, O(1) space

Time Complexity

Multiplying two numbers is a single arithmetic operation, so it runs in constant time.

Space Complexity

Only a few variables are used to store inputs and output, so space is constant.

Which Approach is Fastest?

Using Bash arithmetic expansion $(( )) is fastest because it is built-in, while expr calls an external program.

Approach	Time	Space	Best For
Arithmetic Expansion $(( ))	O(1)	O(1)	Fast, modern Bash scripts
expr command	O(1)	O(1)	Compatibility with older shells
let command	O(1)	O(1)	Simple arithmetic in Bash