How to create a working calculator script in shell?

Creating a Working Calculator Script in Shell

Creating a calculator script in Shell can be a useful tool for performing quick calculations, automating repetitive mathematical tasks, or even integrating calculations into more complex shell scripts. In this guide, we'll walk through the steps to create a simple yet effective calculator script in Shell.

Understanding Shell Scripting

Before we dive into the calculator script, it's important to have a basic understanding of shell scripting. Shell scripts are text files that contain a series of commands that the shell (such as Bash, Zsh, or Ksh) can execute. These scripts can automate various tasks, including file management, system administration, and, in our case, mathematical calculations.

Designing the Calculator Script

The core functionality of our calculator script will be to take two numbers and an operator as input, perform the requested calculation, and display the result. Here's a high-level overview of the steps involved:

Implementing the Calculator Script

Now, let's put this plan into action by creating the calculator script. We'll use the Bash shell for this example, but the same principles can be applied to other shell environments.

#!/bin/bash

# Function to perform the calculation
calculate() {
    local num1=$1
    local num2=$2
    local operator=$3

    case $operator in
        "+") result=$((num1 + num2));;
        "-") result=$((num1 - num2));;
        "*") result=$((num1 * num2));;
        "/") result=$(echo "scale=2; $num1 / $num2" | bc);;
        *) result="Invalid operator";;
    esac

    echo "$result"
}

# Get user input
read -p "Enter the first number: " num1
read -p "Enter the operator (+, -, *, /): " operator
read -p "Enter the second number: " num2

# Validate input
if ! [[ "$num1" =~ ^-?[0-9]+([.][0-9]+)?$ ]] || ! [[ "$num2" =~ ^-?[0-9]+([.][0-9]+)?$ ]]; then
    echo "Error: Invalid number(s) entered."
    exit 1
fi

# Perform the calculation
result=$(calculate "$num1" "$num2" "$operator")
echo "Result: $result"

Let's break down the script:

1. The calculate() function takes three arguments: num1, num2, and operator. It performs the requested calculation based on the operator and returns the result.
2. The script prompts the user to enter the first number, the operator, and the second number.
3. The script validates the input to ensure that the user has entered valid numbers.
4. The calculate() function is called with the user's input, and the result is displayed.

Explanation of the Mermaid Diagram

The Mermaid diagram in this example illustrates the high-level flow of the calculator script. It starts with the user providing input, which is then validated. If the input is valid, the calculation is performed, and the result is displayed. If the input is invalid, the script prompts the user to re-enter the values.

Real-world Example

Imagine you're a small business owner who needs to perform various calculations, such as calculating the total cost of an order, including taxes and shipping. Instead of using a separate calculator app or spreadsheet, you can create a custom calculator script that integrates seamlessly with your daily workflow. This way, you can quickly perform calculations without switching between different tools, saving you time and improving your productivity.

In conclusion, creating a calculator script in Shell is a straightforward process that can be a valuable tool in your shell scripting arsenal. By understanding the basics of shell scripting and following the steps outlined in this guide, you can create a customized calculator that meets your specific needs.