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).

I remember this being a feature request a couple of years ago, but I don't think it was ever implemented. Then again, I haven't kept up to date in recent times, so I might have missed something. — Bart, Jul 06 '13 at 09:54

score 9 · Answer 1 · edited Apr 13 '16 at 08:49

9

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();

edited Apr 13 '16 at 08:49

Toby Speight

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answered Apr 12 '16 at 03:08

ZHANG Zikai

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It would be better to include more of the answer in your answer rather than just linking. – Dave Schweisguth Apr 12 '16 at 03:30
@DaveSchweisguth Thanks. I've just added an example to make it clear. – ZHANG Zikai Apr 13 '16 at 03:00

score 5 · Accepted Answer · answered Jul 06 '13 at 11:28

5

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.

answered Jul 06 '13 at 11:28

peppe

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Detaching a started process

2 Answers2

Linked