Bash Script to Convert Decimal to Octal Number

Use the Bash command printf '%o' decimal_number to convert a decimal number to octal; for example, printf '%o\n' 10 outputs 12.

Examples

Input10

Output12

Input64

Output100

Input0

Output0

How to Think About It

To convert decimal to octal, think of representing the decimal number in base 8 instead of base 10. Bash's printf command can format numbers in octal using the %o specifier, which directly converts and prints the number in octal form.

Algorithm

1

Get the decimal number input from the user or argument

2

Use the printf command with the '%o' format specifier to convert the decimal number to octal

3

Print the converted octal number

Code

bash

#!/bin/bash

# Read decimal number from user
read -p "Enter a decimal number: " decimal

# Convert decimal to octal and print
printf '%o\n' "$decimal"

Output

Enter a decimal number: 10
12

Dry Run

Let's trace the input 10 through the script

1

Input decimal number

User enters 10, so variable decimal=10

2

Convert decimal to octal

printf '%o\n' 10 converts decimal 10 to octal 12

3

Print result

Output printed is '12'

decimal	printf '%o' output
10	12

Why This Works

Step 1: Reading input

The script reads the decimal number as a string and stores it in a variable.

Step 2: Using printf for conversion

The printf '%o' command formats the decimal number into octal representation.

Step 3: Outputting the octal number

The script prints the octal number with a newline for clear output.

Alternative Approaches

Using bc command

bash

#!/bin/bash
read -p "Enter decimal number: " dec

echo "obase=8; $dec" | bc

This uses the bc calculator to convert decimal to octal; it is flexible but requires bc installed.

Using shell arithmetic expansion

bash

#!/bin/bash
read -p "Enter decimal number: " dec

octal=$((10#$dec))
echo "$(printf '%o' "$octal")"

This ensures the input is treated as decimal before converting to octal with printf.

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

Time Complexity

Conversion using printf or bc is constant time since it processes a single number without loops.

Space Complexity

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

Which Approach is Fastest?

Using printf is fastest and simplest; bc is more flexible but slower due to spawning a process.

Approach	Time	Space	Best For
printf '%o'	O(1)	O(1)	Simple, fast conversion
bc command	O(1)	O(1)	Flexible base conversions
Arithmetic expansion + printf	O(1)	O(1)	Safe input handling