CODEWITHSUNDEEP
c++qt
jdl
jdl

Reputation: 6323

Program termination callback in QT?

I want to dump data to a file on program termination, whether it be "Ctrl-C" or some other means in Linux.

Not sure how to capture the program closing or terminating event/s?

Upvotes: 1

Views: 608

Answers (3)

Yves
Yves

Reputation: 187

QCoreApplication (and thus QApplication) has a signal aboutToQuit() that will be emitted when the application is about to quit the main event loop. Connect it to a slot that dumps your data and you should be fine.

Upvotes: 1

Cory Klein
Cory Klein

Reputation: 55620

You need to handle Linux-style signals. Note - this will not work on Windows or Mac if you are trying to be cross platform.

See the Qt article Calling Qt Functions From Unix Signal Handlers.

Here is a minimal setup example extracted from the article:

class MyDaemon : public QObject
{
    ...
public:
    static void hupSignalHandler(int unused);

public slots:
    void handleSigHup();

private:
    static int sighupFd[2];

    QSocketNotifier *snHup;
};

MyDaemon::MyDaemon(...)
{
    if (::socketpair(AF_UNIX, SOCK_STREAM, 0, sighupFd))
       qFatal("Couldn't create HUP socketpair");
    snHup = new QSocketNotifier(sighupFd[1], QSocketNotifier::Read, this);
    connect(snHup, SIGNAL(activated(int)), this, SLOT(handleSigHup()));
}

static int setup_unix_signal_handlers()
{
    struct sigaction hup;
    hup.sa_handler = MyDaemon::hupSignalHandler;
    sigemptyset(&hup.sa_mask);
    hup.sa_flags = 0;
    hup.sa_flags |= SA_RESTART;
    if (sigaction(SIGHUP, &hup, 0) > 0)
       return 1;
    return 0;
}

void MyDaemon::hupSignalHandler(int)
{
    char a = 1;
    ::write(sighupFd[0], &a, sizeof(a));
}

void MyDaemon::handleSigHup()
{
    snHup->setEnabled(false);
    char tmp;
    ::read(sighupFd[1], &tmp, sizeof(tmp));

    // do Qt stuff

    snHup->setEnabled(true);
}

Upvotes: 1

levengli
levengli

Reputation: 1121

It appears as though you are trying to capture a system signal. If so, see here

Upvotes: 1

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