Batch File input validation - Make sure user entered an integer

Question

I\'m experimenting with a Windows batch file to perform a simple operation which requires the user to enter a non-negative integer. I\'m using simple batch-file techniques t

Answer 1

You're probably not doing this in a DOS batch file. Or at least, support for set /p is unheard of for me in DOS :-)

You could use substrings. In fact I have written a parser for a specific regular language that way once, but it's cumbersome. The easiest way would probably be to assign the contents of %userinput% to another variable, using set /a. If the result comes out as 0 you need to check whether the input itself was 0, otherwise you can conclude it was a non-number:

@echo off
setlocal enableextensions enabledelayedexpansion
set /p UserInput=Enter a number: 
set /a Test=UserInput
if !Test! EQU 0 (
  if !UserInput! EQU 0 (
    echo Number
  ) else (
    echo Not a number
  )
) else (
  echo Number
)

However, this works only for numbers in the range of Int32. If you just care for any number (possibly floating-point as well) then you need to resort to the loop-based approach of dissecting it.

NOTE: Updated to solve the space issues. However, there is still a problem lurking: Entering 123/5 yields "number", since set /a can evaluate this ...

Answer 2

:ASK
SET /P number= Choose a number [1 or 2]: 
IF %number% EQU 1 GOTO ONE
IF %number% NEQ 1 (
  IF %number% EQU 2 GOTO TWO
  IF %number% NEQ 2 (
    CLS
    ECHO You need to choose a NUMBER: 1 OR 2.
    ECHO.
    GOTO ASK
  )
)

It works fine to me. If he chooses numbers less or greater, strings, floating number etc, he wil receive a message ("You need to choose a NUMBER: 1 OR 2.") and the INPUT will be asked again.

Answer 3

you can reinvent the wheel and grow a few white hairs doing string validation in batch, or you can use vbscript

strInput = WScript.Arguments.Item(0)
If IsNumeric(strInput) Then
    WScript.Echo "1"
Else
    WScript.Echo "0"
End If

save it as checkdigit.vbs and in your batch

@echo off
for /F %%A in ('cscript //nologo checkdigit.vbs 100') do (
        echo %%A
        rem use if to check whether its 1 or 0 and carry on from here
)

Answer 4

I know this is years old, but just to share my solution.

set /p inp=Int Only : 
:: Check for multiple zeros eg : 00000 ::
set ch2=%inp%-0
if %inp% EQU 0 goto :pass
if [%inp%]==[] echo Missing value && goto :eof
if %inp:~0,1%==- echo No negative integers! && goto :eof
set /a chk=%inp%-10>nul
if %chk%==-10 echo Integers only! && goto :eof
:pass
echo You shall pass
:eof

Tested and working on Windows 8.

Answer 5

You can also use a quite simple trick:

echo %userinput%|findstr /r /c:"^[0-9][0-9]*$" >nul
if errorlevel 1 (echo not a number) else (echo number)

This uses findstr's regular expression matching capabilities. They aren't very impressive but useful at times.

Answer 6

You can validate any variable if its number:

SET "var="&for /f "delims=0123456789" %i in ("%a") do set var=%i
if defined var (echo."NIC">nul) else (echo."number")