Development/Tutorials/Programming Tutorial KDE 4/KDirWatch

Using KDirWatch

If you want your program to be notified upon file changes, use KDirWatch. Here is an example.


  1. ifndef _KHELLO_H_
  2. define _KHELLO_H_
  1. ifdef HAVE_CONFIG_H
  2. include <config.h>
  3. endif
  1. include <kmainwindow.h>
  2. include <kdirwatch.h>


* @short Application Main Window
* @author Thorsten Staerk <[email protected]>
* @version 0.1

class khello : public KMainWindow {



   KDirWatch dw;
    * Default Constructor
   khello(char* args);
    * Default Destructor
   virtual ~khello();

public slots:

   void slotdirty();


  1. endif // _KHELLO_H_

This subclasses KMainWindow.


  1. include "khello.h"
  1. include <qlabel.h>
  1. include <kdebug.h>
  2. include <kmainwindow.h>
  3. include <klocale.h>
  4. include <kmessagebox.h>

khello::khello(char* args)

   : KMainWindow()


   kdDebug() << "args = " << args << endl;
   kdDebug() << "Watching file " << args << endl;
   connect(&dw, SIGNAL(dirty(const QString & ) ),
          SLOT( slotdirty() ) );


khello::~khello() { }

void khello::slotdirty() {

 kdDebug() << "File has changed" << endl;


  1. include "khello.moc"

First, of course, on line 1 we have to include the header file containing the class declaration.

On line 5, we initialise our text editor with an object. Then on line 6 we use the built-in setCentralWidget() function which tells the KXmlGuiWindow what should appear in the central section of the window.

Finally, KXmlGuiWindow::setupGUI() is called which does a lot of behind-the-scenes stuff and creates the default menu bars (Settings, Help).

Back to main.cpp

In order to actually run this window, we need to add a few lines in main.cpp:



*   Copyright (C) 2004 by Thorsten Staerk
*   thorsten at staerk de
*   This program is free software; you can redistribute it and/or modify  *
*   it under the terms of the GNU General Public License as published by  *
*   the Free Software Foundation; either version 2 of the License, or     *
*   (at your option) any later version.
*   This program is distributed in the hope that it will be useful,
*   but WITHOUT ANY WARRANTY; without even the implied warranty of
*   GNU General Public License for more details.
*   You should have received a copy of the GNU General Public License     *
*   along with this program; if not, write to the
*   Free Software Foundation, Inc.,
*   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

This program reacts on file changes.

  • /

  1. include "khello.h"
  2. include <kapplication.h>
  3. include <kaboutdata.h>
  4. include <kcmdlineargs.h>
  5. include <kdebug.h>
  6. include <klocale.h>

static const char description[] =

   I18N_NOOP("A KDE KPart Application");

static const char version[] = "0.1";

static KCmdLineOptions options[] = {

   { "+[URL]", I18N_NOOP( "Document to open" ), 0 },


int main(int argc, char **argv) {

   KAboutData about("khello", I18N_NOOP("khello"), version, description,
                    KAboutData::License_GPL, "(C) %{YEAR} Thorsten Staerk", 0, 0, "[email protected]");
   about.addAuthor( "Thorsten Staerk", 0, "[email protected]" );
   KCmdLineArgs::init(argc, argv, &about);
   KCmdLineArgs::addCmdLineOptions( options );
   KApplication app;
   khello *mainWin = 0;
       // no session.. just start up normally
       KCmdLineArgs *args = KCmdLineArgs::parsedArgs();
       /// @todo do something with the command line args here
       kdDebug() << argv[1] << endl;
       mainWin = new khello(argv[1]);
   // mainWin has WDestructiveClose flag by default, so it will delete itself.
   return app.exec();



The best way to build the program is to use CMake. All that's changed since tutorial 1 is that mainwindow.cpp has been added to the sources list and any tutorial1 has become tutorial2.


project (tutorial2) find_package(KDE4 REQUIRED KIO KDIRWATCH) include_directories( ${KDE4_INCLUDES} ) set(tutorial2_SRCS


) KDE4_AUTOMOC( ${tutorial2_SRCS} ) kde4_add_executable(tutorial2 ${tutorial2_SRCS}) target_link_libraries( tutorial2 ${KDE4_KDEUI_LIBS} ${KDE4_KIO_LIBS})

Kompile it

To compile, link and run it, use:

cmake . && make && ./tutorial2 /var/log/messages

Moving On

Now you can move on to using KActions.

This page was last edited on 29 June 2011, at 20:54. Content is available under Creative Commons License SA 4.0 unless otherwise noted.