Wait for multiple applications run asynchronously from batch file to finish

Question

There is a simple Windows batch file that runs multiple instances of application:

start app.exe param1
start app.exe param2

Is there a way

Answer 1

Adapting on @dbenham answer, here's how i made it to work inside a for and for unlimited number of processes:

setlocal enabledelayedexpansion
for %%a in (*.*) do start "" 9>"%temp%/wait!random!.lock" /b /low "myprogram.exe" -program_parameters

:wait
ping /n 2 ::1 > nul
echo waiting processes to finish...
2>nul del "%temp%\wait*.lock" > nul
if exist "%temp%\wait*.lock" goto :wait

... more commands ...

Here %random% don't work, cause it's expanded when for is called, therefore making all numbers the same. So I enabledelayedexpansion and use !random!.

On the loop I try to delete all files. 2>nul will make sure any error won't show on screen. It will only go through when all can be deleted (if exist).