pipe multiple files into a single batch file (using explorer highlight)

Question

I can already get a batch file to run when a user right clicks on a file type. How can I make it so that only one instance runs per highlighted group and gets all the files

Answer 1

Normally a file association multi-selection invocation will start several instances of a program and the program itself would have to deal with it on its own (Or with the help of DDE or IDropTarget)

It is going to be very hard to implement this in a batch file, this example should get you started:

@echo off
setlocal ENABLEEXTENSIONS
set guid=e786496d-1b2e-4a49-87b7-eb325c8cc64d
set id=%RANDOM%
FOR /F "tokens=1,2,3 delims=.,:/\ " %%A IN ("%TIME%") DO SET id=%id%%%A%%B%%C
set sizeprev=0

>>"%temp%\%guid%.lock" echo %id%
>>"%temp%\%guid%.list" echo %~1

:waitmore
>nul ping -n 3 localhost
FOR %%A IN (%temp%\%guid%.list) DO set sizenow=%%~zA
if not "%sizeprev%"=="%sizenow%" (
    set sizeprev=%sizenow%
    goto waitmore
)
FOR /F %%A IN (%temp%\%guid%.lock) DO (
    if not "%%A"=="%id%" goto :EOF
    FOR /F "tokens=*" %%B IN (%temp%\%guid%.list) DO (
        echo.FILE=%%B
    )
    del "%temp%\%guid%.list"
    del "%temp%\%guid%.lock"
    pause
)

While this works, it is a horrible horrible hack and will fail badly if you don't wait for the first set of files to be parsed before starting a new operation on another set of files.