Bash Script to Find Smallest of Three Numbers

Use a Bash script with if statements to compare three numbers and print the smallest, like: if [ "$a" -le "$b" ] && [ "$a" -le "$c" ]; then echo "$a"; elif [ "$b" -le "$a" ] && [ "$b" -le "$c" ]; then echo "$b"; else echo "$c"; fi.

Examples

Input3 5 1

Output1

Input10 10 10

Output10

Input-2 0 -5

Output-5

How to Think About It

To find the smallest of three numbers, compare the first number with the other two using -le (less or equal) operator. If it is smaller or equal to both, it is the smallest. Otherwise, compare the second number with the other two. If neither the first nor second is smallest, the third must be the smallest.

Algorithm

1

Get the three numbers as input.

2

Check if the first number is less than or equal to both the second and third numbers.

3

If yes, return the first number as smallest.

4

Otherwise, check if the second number is less than or equal to both the first and third numbers.

5

If yes, return the second number as smallest.

6

Otherwise, return the third number as smallest.

Code

bash

#!/bin/bash
read -p "Enter three numbers separated by space: " a b c
if [ "$a" -le "$b" ] && [ "$a" -le "$c" ]; then
  echo "$a"
elif [ "$b" -le "$a" ] && [ "$b" -le "$c" ]; then
  echo "$b"
else
  echo "$c"
fi

Output

1

Dry Run

Let's trace input '3 5 1' through the code

1

Input values

a=3, b=5, c=1

2

Check if a <= b and a <= c

3 <= 5 is true, 3 <= 1 is false, so condition false

3

Check if b <= a and b <= c

5 <= 3 is false, so condition false

4

Else case

Print c = 1

Step	Condition	Result
1	3 <= 5 and 3 <= 1	false
2	5 <= 3 and 5 <= 1	false
3	Print c	1

Why This Works

Step 1: Compare first number

We use -le to check if the first number is less than or equal to the other two numbers.

Step 2: Compare second number

If the first is not smallest, we check if the second number is less than or equal to the other two.

Step 3: Default to third number

If neither first nor second is smallest, the third number must be the smallest.

Alternative Approaches

Using array and sort

bash

#!/bin/bash
read -p "Enter three numbers: " a b c
arr=($a $b $c)
sorted=($(printf "%s\n" "${arr[@]}" | sort -n))
echo "${sorted[0]}"

This method uses sorting but is less efficient for just three numbers.

Using arithmetic expansion

bash

#!/bin/bash
read -p "Enter three numbers: " a b c
min=$a
if (( b < min )); then min=$b; fi
if (( c < min )); then min=$c; fi
echo "$min"

This uses arithmetic comparison which is simpler and more readable.

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

Time Complexity

The script performs a fixed number of comparisons (at most two), so it runs in constant time.

Space Complexity

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

Which Approach is Fastest?

Direct comparisons with if statements are fastest and simplest; sorting is slower and unnecessary for just three numbers.

Approach	Time	Space	Best For
Direct if comparisons	O(1)	O(1)	Small fixed inputs, fastest
Array sort	O(n log n)	O(n)	When needing sorted output, less efficient here
Arithmetic expansion	O(1)	O(1)	Simple numeric comparisons, readable