Bash Script to Find Largest of Two Numbers

Use a Bash script with an if statement to compare two numbers and print the larger one, like if [ $a -gt $b ]; then echo $a; else echo $b; fi.

Examples

Inputa=5, b=3

Output5

Inputa=10, b=10

Output10

Inputa=-2, b=7

Output7

How to Think About It

To find the largest of two numbers, compare them using the greater-than operator -gt in Bash. If the first number is greater or equal, print it; otherwise, print the second number.

Algorithm

1

Get the first number as input and store it in variable a

2

Get the second number as input and store it in variable b

3

Compare if a is greater than or equal to b

4

If yes, print a

5

Otherwise, print b

Code

bash

#!/bin/bash
read -p "Enter first number: " a
read -p "Enter second number: " b
if [ $a -ge $b ]; then
  echo "$a is the largest number"
else
  echo "$b is the largest number"
fi

Output

Enter first number: 8
Enter second number: 3
8 is the largest number

Dry Run

Let's trace the input a=8 and b=3 through the code

1

Input values

a=8, b=3

2

Compare a and b

Is 8 >= 3? Yes

3

Print result

Print '8 is the largest number'

Step	a	b	Condition (a >= b)	Output
1	8	3	true	8 is the largest number

Why This Works

Step 1: Read inputs

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

Step 2: Compare numbers

The if [ $a -ge $b ] checks if a is greater than or equal to b using the numeric comparison operator -ge.

Step 3: Print largest

If the condition is true, it prints a; otherwise, it prints b, showing the largest number.

Alternative Approaches

Using ternary-like syntax with && and ||

bash

read -p "Enter first number: " a
read -p "Enter second number: " b
[ $a -ge $b ] && echo "$a is the largest number" || echo "$b is the largest number"

This is shorter but less readable for beginners.

Using arithmetic expansion

bash

read -p "Enter first number: " a
read -p "Enter second number: " b
max=$(( a > b ? a : b ))
echo "$max is the largest number"

Uses Bash arithmetic to find max in one line, good for compact scripts.

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

Time Complexity

The script performs a single comparison operation, so it runs in constant time regardless of input size.

Space Complexity

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

Which Approach is Fastest?

All approaches run in constant time; using arithmetic expansion is slightly more concise but functionally equivalent.

Approach	Time	Space	Best For
if-else statement	O(1)	O(1)	Clear and beginner-friendly
&& and || operators	O(1)	O(1)	Short scripts, less readable
Arithmetic expansion	O(1)	O(1)	Compact code, slightly advanced