class MyDialog : public QDialog, public Ui_MyDialog {
    Q_OBJECT

public:
    MyDialog();

private:
    QProcess* PtrProcess;

private slots:
    void A();
    void B();
    void C(int);
    void D(int);
    void toPrintStdout();
}  


MyDialog::MyDialog() {

    setupUi(this);

    PtrProcess = new QProcess(this);

    connect(PtrProcess, SIGNAL(readyRead()),   this, SLOT( A()    ));
    connect(PtrProcess, SIGNAL(started()),     this, SLOT( B()    ));
    connect(PtrProcess, SIGNAL(error(int)),    this, SLOT( C(int) ));
    connect(PtrProcess, SIGNAL(finished(int)), this, SLOT( D(int) ));

    connect(pushButton, SIGNAL(clicked()), this, SLOT( DoProcess() ));

    connect(PtrProcess, SIGNAL(readyReadStandardOutput()), this, SLOT( toPrintStdout() ));
} 

void MyDialog::DoProcess() {
    QString program = "./abc/test.exe";
    QStringList arguments;
    arguments << "-abc" << "-def" << "-ghijk"

    PtrProcess->setProgram(program);
    PtrProcess->setArguments(arguments);
    PtrProcess->start();
}


void MyDialog::toPrintStdout() {
    QString rStd = PtrProcess->readAllStandardOutput();
    ....
    ....
}