|  | Home

# A non-GUI example

This example shows how to use the single-application functionality in a console application. It does not require the `QtGui` library at all.

The only differences from the GUI application usage demonstrated in the other examples are:

1) The `.pro` file should include `qtsinglecoreapplication.pri` instead of `qtsingleapplication.pri`

2) The class name is `QtSingleCoreApplication` instead of `QtSingleApplication`.

3) No calls are made regarding window activation, for obvious reasons.

console.pro:

     TEMPLATE   = app
     CONFIG    += console
     SOURCES   += main.cpp
     include(../../src/qtsinglecoreapplication.pri)
     QT -= gui

main.cpp:

     /****************************************************************************
     **
     ** This file is part of a Qt Solutions component.
     **
     ** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
     **
     ** Contact:  Qt Software Information (qt-info@nokia.com)
     **
     ** Commercial Usage
     ** Licensees holding valid Qt Commercial licenses may use this file in
     ** accordance with the Qt Solutions Commercial License Agreement provided
     ** with the Software or, alternatively, in accordance with the terms
     ** contained in a written agreement between you and Nokia.
     **
     ** GNU Lesser General Public License Usage
     ** Alternatively, this file may be used under the terms of the GNU Lesser
     ** General Public License version 2.1 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.LGPL included in the
     ** packaging of this file.  Please review the following information to
     ** ensure the GNU Lesser General Public License version 2.1 requirements
     ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
     **
     ** In addition, as a special exception, Nokia gives you certain
     ** additional rights. These rights are described in the Nokia Qt LGPL
     ** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
     ** package.
     **
     ** GNU General Public License Usage
     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.GPL included in the
     ** packaging of this file.  Please review the following information to
     ** ensure the GNU General Public License version 3.0 requirements will be
     ** met: http://www.gnu.org/copyleft/gpl.html.
     **
     ** Please note Third Party Software included with Qt Solutions may impose
     ** additional restrictions and it is the user's responsibility to ensure
     ** that they have met the licensing requirements of the GPL, LGPL, or Qt
     ** Solutions Commercial license and the relevant license of the Third
     ** Party Software they are using.
     **
     ** If you are unsure which license is appropriate for your use, please
     ** contact the sales department at qt-sales@nokia.com.
     **
     ****************************************************************************/

     #include "qtsinglecoreapplication.h"
     #include <QtCore/QDebug>

     void report(const QString& msg)
     {
         qDebug("[%i] %s", (int)QCoreApplication::applicationPid(), qPrintable(msg));
     }

     class MainClass : public QObject
     {
         Q_OBJECT
     public:
         MainClass()
             : QObject()
             {}

     public slots:
         void handleMessage(const QString& message)
             {
                 report( "Message received: \"" + message + "\"");
             }
     };

     int main(int argc, char **argv)
     {
         report("Starting up");

         QtSingleCoreApplication app(argc, argv);

         if (app.isRunning()) {
             QString msg(QString("Hi master, I am %1.").arg(QCoreApplication::applicationPid()));
             bool sentok = app.sendMessage(msg);
             QString rep("Another instance is running, so I will exit.");
             rep += sentok ? " Message sent ok." : " Message sending failed.";
             report(rep);
             return 0;
         } else {
             report("No other instance is running; so I will.");
             MainClass mainObj;
             QObject::connect(&app, SIGNAL(messageReceived(const QString&)),
                              &mainObj, SLOT(handleMessage(const QString&)));
             return app.exec();
         }
     }

     #include "main.moc"