Qt / c ++：如果此进程未运行，则启动该进程

Question

I have wrote an app in Qt/c++, The app is currently checking some state and start a new process in case the statement become true.

I'm able to start the new process when the statement is true but the app will have to periodically check the statement through a timer. I want to make sure that in case the statement become true and and stay at true I will not start the application multiple times.

here is the current code

QProcess *process = new QProcess();
process->startDetached(fileBrowserExecutablePath);

I know the process can be checked using

process->state() == QProcess::NotRunning

but to check this I need first to start the process otherwise process don't know what to check. I mean which process to check.

Any idea on how to check the process ?

I have tried to init the process with the application I want to start but it failed to build.

Something like :

QProcess *process = new QProcess(fileBrowserExecutablePath);

Thanks

Answer 1

You can't do it with Qt(if you didn't create the process with QProcess earlier, of course). You have to use a platform specific API to check if the process is running.

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But if you did start the process then you can use the QProcess object to check its state. You do it like this:

QProcess *process = new QProcess();
process->start(fileBrowserExecutablePath);
///...
p->state() == QProcess::Running

That way you can use the process object to check the state. But note, that if you don't have the process object than you have to use the native API to check if the process is running.