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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) 2013 Digia Plc and/or its subsidiary(-ies).
     ** Contact: http://www.qt-project.org/legal
     **
     ** This file is part of the Qt Solutions component.
     **
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
     **   * Redistributions in binary form must reproduce the above copyright
     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
     **     the names of its contributors may be used to endorse or promote
     **     products derived from this software without specific prior written
     **     permission.
     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
     **
     ****************************************************************************/

     #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, 2000);
             QString rep("Another instance is running, so I will exit.");
             rep += sentok ? " Message sent ok." : " Message sending failed; the other instance may be frozen.";
             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"