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 to get user input:

@ECHO OFF SET /P UserInput=Please Enter a Number:  

The user can enter any text they want here, so I would like to add some routine to make sure what the user entered was a valid number. That is… they entered at least one character, and every character is a number from 0 to 9. I’d like something I can feed the UserInput into. At the end of the routine would be like an if/then that would run different statements based on whether or not it was actually a valid number.

I’ve experimented with loops and substrings and such, but my knowledge and understanding is still slim… so any help would be appreciated.

I could build an executable, and I know there are nicer ways to do things than batch files, but at least for this task I’m trying to keep it simple by using a batch file.

Answer 1

Thanks all. I was trying to make it harder for myself looking at loops and string manipulation. I used your tips on math evaluation and comparison. Here’s what I finally came up with as my concept script:

:Top @ECHO OFF ECHO. ECHO --------------------------------------- SET /P UserInput=Please Enter a Number:  ECHO. ECHO UserInput = %UserInput% ECHO. SET /A Evaluated=UserInput ECHO Math-Evaluated UserInput = %Evaluated% if %Evaluated% EQU %UserInput% (     ECHO Integer     IF %UserInput% GTR 0 ( ECHO Positive )     IF %UserInput% LSS 0 ( ECHO Negative )     IF %UserInput% EQU 0 ( ECHO Zero )     REM - Other Comparison operators for numbers     REM - LEQ - Less Than or Equal To     REM - GEQ - Greater Than or Equal To     REM - NEQ - Not Equal To ) ELSE (     REM - Non-numbers and decimal numbers get kicked out here     ECHO Non-Integer )  GOTO Top 

This method catches all numbers and can detect whether it’s positive, negative, or zero. Any decimal or string will be detected as non-integers. The only edge case I’ve found is a string with spaces. For example, the text ‘Number 1’ will cause the script to crash/close when the user input is evaluated as math. But in my situation, this is fine. I don’t want my script to go on with invalid input.