Out Parameter In Function Call

Let's say you write a function or procedure or sub program or whatever you want to call it in batch.  How do you pass back a value to the caller?  You can of course set an environment variable, but that's like setting a global variable.  And that's not very nice if you need to call the function multiple times and only use the value after all function calls are made.

Consider this example:

@echo off

call :GETVALUE

set INPUT1=%USERINPUT%

call :GETVALUE

set INPUT2=%USERINPUT%

echo %INPUT1% %INPUT2%

goto :EOF

 

:GETVALUE

set /P USERINPUT=Input?

goto :EOF

Like I said, it's doable, but not very nice.  I find it more soothing to the eyes if I can pass the variable name as an argument to the function.  And here's how you do it:

@echo off

call :GETVALUE INPUT1

call :GETVALUE INPUT2

echo %INPUT1% %INPUT2%

goto :EOF

 

:GETVALUE

set /P %1=Input?

goto :EOF

Nice and simple.  All you need to do is remember that you can use %1 and other %<number> on the left hand side of an assignment.  And it makes you think for a second that you are programming a real scripting language.