How to check if a parameter (or variable) is a number in a Batch script

Question

I need to check if a parameter that is passed to a Windows Batch file is a numeric value or not. It would be good for the check to also works for variables.

I found a

Answer 1

Does the same thing as above. Have problems with special characters. However, the solution is of a different approach.

@echo off
cls
setlocal enabledelayedexpansion

if "%1"=="" (goto:eof) else (set _VAR2CHECK=%1)

for /l %%a in (0,1,9) do (
   if defined _VAR2CHECK (set "_VAR2CHECK=!_VAR2CHECK:%%a=!") else (goto :end)
)

:end
if defined _VAR2CHECK (echo %1 #NOT A VALID NUMBER) else (echo %1 #A VALID NUMBER)

set "_VAR2CHECK="
endlocal

Test scenarions:

C:\>ISNUM 1A
1A  #NOT A VALID NUMBER

C:\>ISNUM 11
11  #A VALID NUMBER