Verify unique instance of application in Qt

unique_app_instance_Qt.cpp

#include <QSharedMemory>

int main(int argc, char *argv[])
{
    //  Verify unique instance of application
    QSharedMemory sharedMemory("service");
    if (sharedMemory.attach())
        return EXIT_FAILURE;
    if (!sharedMemory.create(1))
        return EXIT_FAILURE;
...
}