CODEWITHSUNDEEP
c++qtqtcoreqprocess
JVE999
JVE999

Reputation: 3517

How to stop a detached process in qt?

After starting a process with QProcess::startDetached, how can I stop it later?

Say the main program runs, then starts the detached process, which runs independently. The user closes the main program, then later opens it up again and wants to stop the process. How would I find the process and then stop it?

Upvotes: 4

Views: 3588

Answers (2)

JVE999
JVE999

Reputation: 3517

Here's the answer I figured out:

I first start the detached process that generates a unique id. That process write to a file whenever it runs (was a 1 minute timer). When it runs, it writes its id to a file. Then, if there happens to be another one that ran, if it sees a previous one ran, it just writes its id to the file and doesn't run, then, when the next one runs, it sees if its id is already in the file and if it is, it shuts itself off and clears the file, then the next run ends up running freely, being the only one running. This may end up skipping some time.

You can add a timestamp, too, as that might indicate it wasn't run recently and help with deciding whether or not to shut it down. The issue was if I just write the id to a file, when I turn the phone off, the file will say it's still running. The same applies to if it crashes.

Upvotes: 0

László Papp
László Papp

Reputation: 53225

Is there a way I could prevent the application from the same process twice?

No, it will be decoupled from your application. You could get the the PID of it and then send a SIGSTOP on Linux, but this is platform specific and will not work without POSIX support, like with msvc. You would need to hand-craft your version therein.

Is there a way I could prevent the application from the same process twice?

Yes, by using lock file in the detached process. If that detached process happens to be written in at least partially Qt, you could use the QLockFile class.

If you happen to detach some platform specific process, then you have the same recurring issue again, for sure.

Upvotes: 1

Related Questions