Detaching a started process

Question

I've started a process using QProcess::start() and I need to detach it afterwards. How can I do it? I haven't found relevant info in the Qt docs.

I'm aware of QProcess::startDetached(), but due to other code in the program, I can't use it (I need to separate the starting and the detaching of the process).

Answer 1

If you take a look into the implementation of QProcess::~QProcess(), you will know how QProcess terminates the process with its destruction. Also, note that QProcess::setProcessState() is protected, which means you could implement a QDetachableProcess inherited from QProcess with a method detach() to call setProcessState(QProcess::NotRunning); as a workaround.

For example:

class QDetachableProcess : public QProcess
{
public:
    QDetachableProcess(QObject *parent = 0) : QProcess(parent){}
    void detach()
    {
        this->waitForStarted();
        setProcessState(QProcess::NotRunning);
    }
};

Then you could do things like this:

QDetachableProcess process;
process.setEnvironment(QStringList() << "SOME_ENV=Value");

process.start();

process.detach();

Answer 2

You can't as of 5.1, see here. There's also a suggestion in the comments, not sure if useful for your case):

Workaround proposal: write a helper process that starts detached processes, and terminates itself when all setting up is completed.