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

@hornzach - You were so close and with a much simpler answer than the rest.

To hide the error message in (win 7 at least) redirect to the standard error output (2) to nul (a special file, that quietly discards the output "bit-bucket")

set /a varCheck = %var% 2>nul

Then the rest of your answer works for the 4 test cases.

Full Answer With Test Cases:

call :CheckNumeric AA  "#NOT A VALID NUMBER"
call :CheckNumeric A1  "#NOT A VALID NUMBER"
call :CheckNumeric 1A  "#NOT A VALID NUMBER"

call :CheckNumeric 11  "#A VALID NUMBER"

call :CheckNumeric 1.23456789012345678901234567890.123456  "#NOT A VALID NUMBER"
goto :EOF

:CheckNumeric
@ECHO.

@ECHO Test %1
set /a num=%1 2>nul

if {%num%}=={%1} (
    @ECHO %1 #A VALID NUMBER, Expected %2
    goto :EOF
)

:INVALID
    @ECHO %1 #NOT A VALID NUMBER, Expected %2

Outputs:

Test AA
AA #NOT A VALID NUMBER, Expected "#NOT A VALID NUMBER"

Test A1
A1 #NOT A VALID NUMBER, Expected "#NOT A VALID NUMBER"

Test 1A
1A #NOT A VALID NUMBER, Expected "#NOT A VALID NUMBER"

Test 11
11 #A VALID NUMBER, Expected "#A VALID NUMBER"

Test 1.23456789012345678901234567890.123456
1.23456789012345678901234567890.123456 #NOT A VALID NUMBER, Expected "#NOT A VALID NUMBER"