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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:

 /****************************************************************************
 **
 ** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation ([email protected])
 **
 ** This file is part of a Qt Solutions component.
 **
 ** 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 1.1, 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
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 #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"