Bash Script to Convert Hexadecimal to Decimal Number

Use Bash's built-in arithmetic expansion with $((16#hex_value)) to convert a hexadecimal string to decimal, for example: decimal=$((16#1A)).

Examples

Input1A

Output26

InputFF

Output255

Input0

Output0

How to Think About It

To convert a hexadecimal number to decimal in Bash, treat the hex string as a base-16 number and use Bash's arithmetic expansion syntax with 16# prefix. This tells Bash to interpret the following string as hexadecimal and convert it to decimal automatically.

Algorithm

1

Get the hexadecimal input as a string.

2

Use Bash arithmetic expansion with the prefix <code>16#</code> to convert the hex string to decimal.

3

Store or print the decimal result.

Code

bash

#!/bin/bash
read -p "Enter a hexadecimal number: " hex
# Convert hex to decimal
decimal=$((16#$hex))
echo "Decimal value: $decimal"

Output

Enter a hexadecimal number: 1A
Decimal value: 26

Dry Run

Let's trace the input '1A' through the code

1

Read input

User inputs '1A', stored in variable hex='1A'

2

Convert hex to decimal

Evaluate $((16#1A)) which converts hex '1A' to decimal 26

3

Print result

Output 'Decimal value: 26'

hex	decimal
1A	26

Why This Works

Step 1: Using arithmetic expansion

Bash supports arithmetic expansion with $(( )), allowing calculations inside.

Step 2: Base prefix 16#

Prefixing the number with 16# tells Bash to treat the number as base 16 (hexadecimal).

Step 3: Automatic conversion

Bash converts the hex string to decimal automatically inside the arithmetic expansion.

Alternative Approaches

Using printf

bash

read -p "Enter hex: " hex
printf "%d\n" 0x$hex

Uses printf to convert hex to decimal; simpler but requires 0x prefix.

Using bc command

bash

read -p "Enter hex: " hex
echo "ibase=16; $hex" | bc

Uses bc calculator for conversion; useful if arithmetic expansion is limited.

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

Time Complexity

Conversion is a direct arithmetic operation with no loops, so it runs in constant time.

Space Complexity

Only a few variables are used, so space usage is constant.

Which Approach is Fastest?

Bash arithmetic expansion is fastest and simplest; printf and bc add overhead but offer alternatives.

Approach	Time	Space	Best For
Bash arithmetic expansion	O(1)	O(1)	Simple scripts, fastest
printf command	O(1)	O(1)	Quick one-liners, requires 0x prefix
bc command	O(1)	O(1)	Complex calculations, external tool