Command-Line Calculator with Python

Create a command-line calculator app, mycal, using Python and argparse. Run it from the Terminal like:

mycal -s "+" -f "100" -n "200"

Follow these steps to build it:

Step 1: Create the Python Script

Create a file named mycal and add the following script:

#!/usr/bin/env python3
import argparse

def calculate(sign, first, second):
    try:
        first = float(first)
        second = float(second)

        if sign == "+":
            return first + second
        elif sign == "-":
            return first - second
        elif sign == "*":
            return first * second
        elif sign == "/":
            return first / second
        else:
            return "Invalid operator!"
    except Exception as e:
        return f"Error: {e}"

def main():
    parser = argparse.ArgumentParser(description="Simple CLI Calculator")

    parser.add_argument('-s', '--sign', required=True, help='Operator: +, -, *, /')
    parser.add_argument('-f', '--first', required=True, help='First number')
    parser.add_argument('-n', '--second', required=True, help='Second number')

    args = parser.parse_args()

    result = calculate(args.sign, args.first, args.second)
    print(f"Result: {result}")

if __name__ == "__main__":
    main()

Step 2: Make It Executable

In the Terminal, run:

chmod +x mycal

Move it to your path:

mv mycal /usr/local/bin/

Now, use it like:

mycal -s "+" -f "100" -n "200"

Output:

Result: 300.0

Notes

• -s for sign/operator

• -f for the first number

• -n for the second number

• Use full names: --sign, --first, --second if preferred

Interested in expanding functionality with power (**), modulus (%), or string expressions? Let me know!

Issue with Missing Directory and Operation Permission

The user is experiencing two issues on their macOS system:

1. Missing Directory: The /usr/local/bin directory does not exist, only /usr/local is present. This might require creating the directory if needed by running:

   mkdir /usr/local/bin

   Ensure you have the proper permissions or use sudo if necessary.

2. Permission Error: When trying to move a file to /bin using:

   sudo mv mycal /bin

   The operation fails with "Operation not permitted". This could be due to system integrity protection (SIP) preventing modifications to system directories.

Suggestions

• Create Missing Directory: If you need /usr/local/bin, create it with:

  sudo mkdir -p /usr/local/bin

• Address Operation Not Permitted: Try using a different directory such as /usr/local/bin:

  sudo mv mycal /usr/local/bin

Ensure SIP is not overly restrictive for necessary operations or consider alternative directories like /usr/local/bin for installing custom binaries.

If you're using macOS and need to move CLI tools to a secure location, follow these steps. System Integrity Protection (SIP) in macOS restricts access to certain system folders like /bin.

💡 Recommended Approach: Create a Custom Bin Directory

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🔧 Step-by-Step Guide

1. Create a Custom CLI Tools Folder

mkdir -p $HOME/.mybin

2. Transfer Your Script

If mycal is in the current directory:

mv mycal $HOME/.mybin/

3. Update Your PATH Variable

Edit your shell configuration file:

• zsh: ~/.zshrc

• bash: ~/.bash_profile or ~/.bashrc

Add this line:

export PATH="$HOME/.mybin:$PATH"

Reload your shell configuration:

source ~/.zshrc   # or source ~/.bash_profile

✅ Verify It

Run your script:

mycal -s "+" -f "100" -n "200"

Expected output:

Result: 300.0

You can edit mycal anytime in $HOME/.mybin. For features like history or logging, feel free to reach out!