Shell script to convert binary to decimal

Binary and decimal are two fundamental number systems used in computing. While humans typically interact with decimal numbers (0-9), computers internally store and process data using binary digits (0s and 1s). Converting between these systems is often necessary when working with computer programs or manipulating data. This article explores how to write a shell script that converts a binary number to its decimal equivalent.

Understanding the Conversion Process

Converting a binary number to decimal involves multiplying each binary digit by its corresponding power of 2, starting from the rightmost digit as the exponent and increasing by 1 for each subsequent digit to the left. Finally, we sum the products of these individual multiplications to obtain the decimal equivalent.

Given a binary number as input, we need to make a conversion from a binary number to its equivalent decimal number.

Examples: 

Input : 1011
Output : 11
Input : 1111
Output : 15

Binary to decimal 

The idea is to retain the decimal number from the binary number, so, take the binary number and traverse from right to left, taking one by one the last digit of the binary number. 

Pick the last digit and multiply by the proper base (power of two) and add it to the final variable (say num).

Repeat this process until the binary number is not equal to zero and then print the result (that is, num).

For example, let's consider the binary number

Example 1 :

n =  10101 (Binary number)

• Rightmost digit (1) * 2^0 = 1
• Second digit (0) * 2^1 = 0
• Third digit (1) * 2^2 = 4
• Fourth digit (0) * 2^3 = 0
• Leftmost digit (1) * 2^4 = 16

Summing these values: 1 + 0 + 4 + 0 + 16 = 21
Therefore, the decimal equivalent of 10101 is 21.

Example 2: 

n =  101 (Binary number)

num = 1*(2^2) + 0*(2^1) + 1*(2^0) = 6 (resultant decimal)

Example 3: 

n =  1101 (Binary number)

num =1*(2^3) + 1*(2^2) + 0*(2^1) + 1*(2^0) = 13 (resultant decimal)

Here We will extract the decimal number from the given binary number.

Shell Script to Convert Binary to Decimal

#!/bin/bash

# Take input as binary number
echo "Enter Binary Number: "
read n

# Validate input
if [[ ! "$n" =~ ^[01]+$ ]]; then
echo "Error: Invalid binary number."
exit 1
fi

# Initialize variables
i=0
num=0

# Convert binary to decimal
while [ $n -ne 0 ]; do
digit=$((n % 10))
num=$((num + digit * 2**i))
n=$((n / 10))
let "i++"
done

# Print the result
echo "Resultant Decimal Number: $num"

Step by Step Explanation of the Shell Script to Convert Binary to Decimal

1. Setting up the script:

• #!/bin/bash: This tells the system to use the bash interpreter to run the script.
• echo "Enter Binary Number: " : This displays a message asking the user to enter a binary number.
• read n: This reads the user's input and stores it in the variable n.

2. Validating the input:

• if [[ ! "<span class="math-inline">n" \=\~ ^\[01\]\+</span> ]]; then: This checks if the input n contains only 0s and 1s using regular expressions.
  • !: This negates the expression, meaning it checks for the absence of valid characters.
  • ^: This matches the beginning of the string.
  • [01]+: This matches one or more repetitions of 0s or 1s.
  • $: This matches the end of the string.
• echo "Error: Invalid binary number.": If the input is invalid, this displays an error message.
• exit 1: This exits the script with an error code of 1.

3. Initializing variables:

• i=0: This initializes the variable i to 0. This variable will be used as a counter later.
• num=0: This initializes the variable num to 0. This variable will store the final decimal number.

4. Converting binary to decimal:

• while [ $n -ne 0 ]; do: This starts a loop that continues until the value of n becomes 0.
  • <span class="math-inline">n \-ne 0\: This checks if `n` is not equal to 0. * `digit=((n % 10)): This calculates the rightmost digit of the binary number stored innand assigns it to the variabledigit`.
  • %: This is the modulus operator which gives the remainder of dividing n by 10.
  • <span class="math-inline">\(\(\.\.\.\)\)\: This is a bash expression used for arithmetic operations. * `num=((num + digit * 2**i)): This adds the value ofdigitmultiplied by 2 raised to the power ofito the variablenum`.
  • 2**i: This raises 2 to the power of i.
  • +: This adds the two values.
• n=$((n / 10)): This removes the rightmost digit from the binary number stored in n.
  • /: This is the division operator.
• let "i++": This increments the value of the variable i by 1.
• done: This ends the loop.

5. Printing the result:

• echo "Resultant Decimal Number: $num": This displays the final decimal number stored in the variable num.

How to execute the bash files?

Write the bash code into a text file using text editors. In this example we are using Vim text editor and saving our file with `.sh` extension.

Open terminal and execute the file using below command:

vim Binary.sh

Making Script Executable

chmod +x Binary.sh

Execute the Script

./Binary.sh

Output:

Conclusion

In this article we discussed how to write a shell script to convert binary to decimal . To sum it up, this article is about turning computer language (binary) into numbers we humans use (decimal). It explains the process step by step and gives an easy-to-use script (like a computer recipe) using a program called Bash. The article shows why it's important to understand this conversion, gives examples, and helps people practice it with the provided script. It's like learning a new language and then using a simple tool to speak it.