Check if input is a number in command prompt script!?

To check if the input is a number, you can do a simple check using if and a regular expression (RegEx) in a batch script. However, there is no direct support for regular expressions in CMD, but you can use the set /a statement to ensure that only valid numbers are processed.

1. Here is the commented code in English:
2. Summary

1.) Here is the commented code in English:

@echo off
:: Prevents commands from being displayed in the terminal.

:start
:: Defines the starting point of the loop.

chcp 65001 >nul
:: Sets the code page to UTF-8 and suppresses output.

echo Addition
echo Please enter the 2 numbers you want to add. Confirm each number with ENTER.

:: Input of the first number
set /p num1=First number:
:: Prompts the user to enter the first number.

call :check_if_number %num1%
:: Calls the subroutine to check if the input is a valid number.

if errorlevel 1 (
:: If the input is invalid, an error message is displayed.
echo Error: "%num1%" is not a valid number.
goto start
:: Returns to the starting point.
)

:: Input of the second number
set /p num2=Second number:
:: Prompts the user to enter the second number.

call :check_if_number %num2%
:: Calls the subroutine again to check the second input.

if errorlevel 1 (
:: If the second input is invalid, an error message is displayed.
echo Error: "%num2%" is not a valid number.
goto start
:: Returns to the starting point.
)

echo %num1% + %num2%?
pause
:: Displays the entered values and pauses to let the user confirm.

:: Calculation of the sum
set /a Answer=%num1%+%num2%
:: Adds the two numbers and stores the result in the variable "Answer".

echo Result: %Answer%
:: Outputs the result.

pause
:: Pauses to allow the user to view the result.

goto start
:: Returns to the starting point to perform another addition.

:e
:: Marks the end of the program (currently unused).
echo Done!
pause
exit /b
:: Exits the script.

:: Subroutine to check if the input is a number
:check_if_number
:: Begins the subroutine to validate numeric input.

echo %1 | findstr /r "^[0-9]" >nul
:: Checks if the input starts with a digit (regular expression).

if errorlevel 1 (
:: If no number is found, the subroutine returns an error status.
exit /b 1
)

exit /b 0
:: Exits the subroutine with status 0 (success) if the input is valid.

2.) Summary