C++/Qt/QFile

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Check file existance and file name with QFile

  
Foundations of Qt Development\Chapter08\fileexist\main.cpp
/*
 * Copyright (c) 2006-2007, Johan Thelin
 * 
 * All rights reserved.
 * 
 * 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 APress 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 <QFile>
#include <QtDebug>
int main( int argc, char **argv )
{
  QFile file( "testfile.txt" );
  
  if( !file.exists() )
  {
    qDebug() << "The file" << file.fileName() << "does not exist.";
    return 0;
  }
  
  if( !file.open( QIODevice::WriteOnly ) )
  {
    qDebug() << "Could not open" << file.fileName() << "for writing.";
    return 0;
  }
  
  qDebug() << "The file opened.";
  
  file.close();
  
  return 0;
}


Create file with QFile

  

Foundations of Qt Development\Chapter08\datastream\main.cpp
/*
 * Copyright (c) 2006-2007, Johan Thelin
 * 
 * All rights reserved.
 * 
 * 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 APress 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 <QFile>
#include <QDataStream>
#include <QList>
#include <QColor>
#include <QtDebug>
struct ColorText
{
  QString text;
  QColor color;
};
QDataStream &operator<<( QDataStream &stream, const ColorText &data )
{
  stream << data.text << data.color;
  
  return stream;
}
QDataStream &operator>>( QDataStream &stream, ColorText &data )
{
  stream >> data.text;
  stream >> data.color;
  
  return stream;
}
void saveList()
{
  QList<ColorText> list;
  ColorText data;
  
  data.text = "Red";
  data.color = Qt::red;
  list << data;
  
  data.text = "Blue";
  data.color = Qt::blue;
  list << data;
  data.text = "Yellow";
  data.color = Qt::yellow;
  list << data;
  data.text = "Green";
  data.color = Qt::green;
  list << data;
  
  QFile file( "test.dat" );
  if( !file.open( QIODevice::WriteOnly ) )
    return;
    
  QDataStream stream( &file );
  stream.setVersion( QDataStream::Qt_4_2 );
  
  stream << list;
  
  file.close();
}
void loadList()
{
  QList<ColorText> list;
  
  QFile file( "test.dat" );
  if( !file.open( QIODevice::ReadOnly ) )
    return;
    
  QDataStream stream( &file );
  stream.setVersion( QDataStream::Qt_4_2 );
  stream >> list;
  
  file.close();
  foreach( ColorText data, list )
    qDebug() << data.text << "(" 
             << data.color.red() << "," 
             << data.color.green() << "," 
             << data.color.blue() << ")";
}
int main( int argc, char **argv )
{
  saveList();
  loadList();
  
  return 0;
}


Create QFile from file path

  
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt 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.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QFile>
#include <QTextStream>
static void process_line(const QByteArray &)
{
}
static void process_line(const QString &)
{
}
int main()
{
    QFile file("in.txt");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return 1;
    while (!file.atEnd()) {
        QByteArray line = file.readLine();
        process_line(line);
    }
}


Open a text file in read-only mode

  
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt 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.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QFile>
#include <QTextStream>
static void process_line(const QByteArray &)
{
}
static void process_line(const QString &)
{
}
int main()
{
    QFile file("in.txt");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return 1;
    while (!file.atEnd()) {
        QByteArray line = file.readLine();
        process_line(line);
    }
}


Open binary file for write-operation

  
#include <QFile>
#include <QTextStream>

int main()
{
    QFile file("out.dat");
    if (!file.open(QIODevice::WriteOnly))
        return 1;
    QDataStream out(&file);
    out << "The magic number is: " << 49 << "\n";
}


Open QFile with WriteOnly flag

  

Foundations of Qt Development\Chapter08\fileexist\main.cpp
/*
 * Copyright (c) 2006-2007, Johan Thelin
 * 
 * All rights reserved.
 * 
 * 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 APress 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 <QFile>
#include <QtDebug>
int main( int argc, char **argv )
{
  QFile file( "testfile.txt" );
  
  if( !file.exists() )
  {
    qDebug() << "The file" << file.fileName() << "does not exist.";
    return 0;
  }
  
  if( !file.open( QIODevice::WriteOnly ) )
  {
    qDebug() << "Could not open" << file.fileName() << "for writing.";
    return 0;
  }
  
  qDebug() << "The file opened.";
  
  file.close();
  
  return 0;
}


Open text file for write-operation

  
#include <QFile>
#include <QTextStream>

int main()
{
    QFile file("out.txt");
    if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
        return 1;
    QTextStream out(&file);
    out << "The magic number is: " << 49 << "\n";
}


Output with QFile

  
#include <QtCore>
#include <iostream>
#include <stdio.h>
using namespace std;
int main(int argc, char* argv[])
{
  QFile in("c:\\a.txt");
  if(!in.open(QIODevice::ReadOnly|QIODevice::Text)) {
    cerr << "File " << argv[1] << " does not exist" << endl;
  }
  QFile out;
  out.setFileName(argv[2]);
  if (out.exists()) {
      cerr << "File" << argv[2] << " already exists" << endl;
      return 1;
  }
  if(!out.open(QIODevice::WriteOnly|QIODevice::Text)) {
      cerr << "Failed to open file " << argv[2] << " for writing" << endl;
      return 1;
  }
  while (!in.atEnd()) {
   QByteArray line = in.readLine();
   if (!line.trimmed().isEmpty() && !line.trimmed().startsWith("#"))
     out.write(line);
  }
  in.close();
  out.close();
  return 0;
}


Read byte array from text file

  
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt 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.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QFile>
#include <QTextStream>
static void process_line(const QByteArray &)
{
}
static void process_line(const QString &)
{
}
int main()
{
    QFile file("in.txt");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return 1;
    while (!file.atEnd()) {
        QByteArray line = file.readLine();
        process_line(line);
    }
}


Read file till file end

  
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt 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.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QFile>
#include <QTextStream>
static void process_line(const QByteArray &)
{
}
static void process_line(const QString &)
{
}
int main()
{
    QFile file("in.txt");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return 1;
    while (!file.atEnd()) {
        QByteArray line = file.readLine();
        process_line(line);
    }
}


Read text file line by line

  
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt 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.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QFile>
#include <QTextStream>
static void process_line(const QByteArray &)
{
}
static void process_line(const QString &)
{
}
int main()
{
    QFile file("modules");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return 1;
    QTextStream in(&file);
    QString line = in.readLine();
    while (!line.isNull()) {
        process_line(line);
        line = in.readLine();
    }
}