How to spawn several processes from the Windows shell and wait for them all to complete?

Question

I want to do the following from a Windows batch script:

start proc1.exe

start proc2.exe

...

start procN.exe

<wait for all N processes to complete> <-- What do I put here?

How do I wait for all spawned processes to complete?

Answer 1

This is ugly, but you could wrap each command in another batch file that runs the command and then signals that the command is complete. Your main batch file would call each of those batch files asynchronously and sit in a loop waiting for the signals.

For example:

main.bat

start cmd /c proc1.bat
start cmd /c proc2.bat
:wait
sleep 1
IF NOT EXIST proc1done GOTO wait
IF NOT EXIST proc2done GOTO wait
del proc1done
del proc2done
echo All processes are complete

proc1.bat

proc1.exe
echo Done > proc1done

The sleep command is available in Windows Server 2003 Resource Kit Tools. If you don't have that, you could use a ping on localhost just to slow down that tight loop.

Answer 2

I found a good solution in using an alternative shell called "Yori". You can read more about it and download it from http://www.malsmith.net/yori/. Yori is open source and its code repository is at https://github.com/malxau/yori.

Yori makes it easy to implement parallel process execution and wait for them to finish. In essence, what you need to do is to start the different sub-processes as so-called "jobs" and then use the internal command "wait" to wait for them to finish. You can start any process as a job by adding the special characters "&!" at the end of the command. Something like this:

ping localhost &!
ping someotherhost &!
wait

You can put your Yori-dependent commands in a separate batch-file (with the Yori-batch extension ".ys1") and invoke that from your Windows-batch for example with the following command:

echo Let Yori do the parallel execution of some lengthy operations...
start /wait /b /belownormal yori.exe -c "your-yori-script.ys1"
echo All the lengthy operations are finished, continue with the next steps...