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 an answer to a similar question, where the findstr command is used with a regular expression.

I did try that solution, but it’s not working like I hoped (at least on Windows 7).

My test scenarios are as follows:

AA  # not a valid number
A1  # not a valid number
1A  # not a valid number

11  # a valid number

Solution 1

SET "var="&for /f "delims=0123456789" %%i in ("%1") do set var=%%i
if defined var (echo %1 NOT numeric) else (echo %1 numeric)

Replace %1 with %yourvarname% as appropriate

Solution 2

for ± integers (test also for leading zero):

echo(%~1|findstr "^[-][1-9][0-9]*$ ^[1-9][0-9]*$ ^0$">nul&&echo numeric||echo not numeric

Solution 3

You could try this. The variable passed is for example var and %var% is equal to 500.

set /a varCheck=%var%
if %varCheck% == %var% (goto :confirmed) else (exit /B)
exit /B

:confirmed
:: You can use %var% here, and it should only be executed if it is numerical!

if %var% is equal to e.g. a3453d, then it would set varCheck to be 0, and because 0 is not equal to a3453d, then it will exit batch processing.

(The exit on line 3 is just in case the if statement decides not to execute for some reason ... XD.)

Solution 4

The easiest for positive integers should be:

IF 1%1 NEQ +1%1 echo Notnumeric!

If negative numbers (hyphen) are also to be considered, this will work

SET number=%1
if 1%1 EQU +1%1 echo positive number
if %1==-%number:-=% echo negative number

Learned from this article here

Solution 5

@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"

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