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Forum Update on Monday, May 27th 2025

Copying the file content

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copyfileqt5file readfile write
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  • D deleted286

    @jsulm it returns nothing, Either true or false

    J.HilkJ Offline
    J.HilkJ Offline
    J.Hilk
    Moderators
    wrote on last edited by
    #19

    @suslucoder then the function isn't called.

    Please post what you actually have in your code, otherwise no-one will be able to help you


    Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


    Q: What's that?
    A: It's blue light.
    Q: What does it do?
    A: It turns blue.

    1 Reply Last reply
    0
    • jsulmJ jsulm

      @suslucoder said in Copying the file content:

      it returns nothing, Either true or false

      ?
      It returns a boolean.
      Again: what does it return?!

      qDebug() << QFile::copy("C:/Users/user/Documents/MyThread/deneme.txt", "C:/Users/user/Documents/MyThread/new.txt");
      
      D Offline
      D Offline
      deleted286
      wrote on last edited by
      #20

      @jsulm it returns false. Ekran görüntüsü 2021-01-11 111741.png

      #include "mythread.h"
      #include "mainwindow.h"
      #include <QtCore>
      #include <QDebug>
      #include <QFile>
      #include <QTimer>
      #include <QThread>
      #include <QMutex>
      #include <QQueue>
      #include <QMessageBox>
      #include <QApplication>
      #include <QtWidgets/QApplication>
      #include <QtWidgets/QMainWindow>
      #include <QFileDialog>
      #include <QMainWindow>
      
      QFile file("C:/Users/ilknu/Documents/MyThread/deneme.txt");
      
      
      MyThread::MyThread(QObject* parent)
          : QThread(parent)
      {
          writeData();
      }
      
      MyThread::~MyThread()
      {
      
      }
      
      void MyThread::writeData()
      {
          QFile file2("C:/Users/ilknu/Documents/MyThread/new.txt");
          QFile::copy("C:/Users/ilknu/Documents/MyThread/deneme.txt","C:/Users/ilknu/Documents/MyThread/new.txt" );
          qDebug() << QFile::copy("C:/Users/user/Documents/MyThread/deneme.txt", "C:/Users/user/Documents/MyThread/new.txt");
          qDebug() << "im working in writing thread";
      
          emit writingDone();
      
      }
      
      void MyThread::run()  //Reading file from txt with thread1
      {
      
          if (file.open(QIODevice::ReadOnly))
          {
              QTextStream in (&file);
              while (!in.atEnd())
              {
                  QString line = in.readAll();
                  QStringList list = line.split(QLatin1Char(' '), Qt::SkipEmptyParts);
                  for(const QString &entry : list)
                  {
                      double num = entry.toDouble();
                      queue.enqueue(num);
      
                  }
      
      
                  qDebug()<< "im running on worker thread " <<line;
      
              } // for
          } // while
          file.close();
      } // if
      
      JonBJ SGaistS 2 Replies Last reply
      0
      • sierdzioS Offline
        sierdzioS Offline
        sierdzio
        Moderators
        wrote on last edited by
        #21

        Check if it exists:

        qDebug() << "Source exists?" << QFile::exists("C:/Users/ilknu/Documents/MyThread/deneme.txt");
        qDebug() << "Destination exists?" << QFile::exists("C:/Users/ilknu/Documents/MyThread/new.txt");
        

        You need to check destination because:

        If a file with the name newName already exists, copy() returns false (i.e., QFile will not overwrite it).

        (Z(:^

        D 1 Reply Last reply
        1
        • D deleted286

          @jsulm it returns false. Ekran görüntüsü 2021-01-11 111741.png

          #include "mythread.h"
          #include "mainwindow.h"
          #include <QtCore>
          #include <QDebug>
          #include <QFile>
          #include <QTimer>
          #include <QThread>
          #include <QMutex>
          #include <QQueue>
          #include <QMessageBox>
          #include <QApplication>
          #include <QtWidgets/QApplication>
          #include <QtWidgets/QMainWindow>
          #include <QFileDialog>
          #include <QMainWindow>
          
          QFile file("C:/Users/ilknu/Documents/MyThread/deneme.txt");
          
          
          MyThread::MyThread(QObject* parent)
              : QThread(parent)
          {
              writeData();
          }
          
          MyThread::~MyThread()
          {
          
          }
          
          void MyThread::writeData()
          {
              QFile file2("C:/Users/ilknu/Documents/MyThread/new.txt");
              QFile::copy("C:/Users/ilknu/Documents/MyThread/deneme.txt","C:/Users/ilknu/Documents/MyThread/new.txt" );
              qDebug() << QFile::copy("C:/Users/user/Documents/MyThread/deneme.txt", "C:/Users/user/Documents/MyThread/new.txt");
              qDebug() << "im working in writing thread";
          
              emit writingDone();
          
          }
          
          void MyThread::run()  //Reading file from txt with thread1
          {
          
              if (file.open(QIODevice::ReadOnly))
              {
                  QTextStream in (&file);
                  while (!in.atEnd())
                  {
                      QString line = in.readAll();
                      QStringList list = line.split(QLatin1Char(' '), Qt::SkipEmptyParts);
                      for(const QString &entry : list)
                      {
                          double num = entry.toDouble();
                          queue.enqueue(num);
          
                      }
          
          
                      qDebug()<< "im running on worker thread " <<line;
          
                  } // for
              } // while
              file.close();
          } // if
          
          JonBJ Offline
          JonBJ Offline
          JonB
          wrote on last edited by
          #22

          @suslucoder
          Did you read the documentation of QFile::Copy() for yourself?

          Note that if a file with the name newName already exists, copy() returns false (i.e. QFile will not overwrite it).

          So, does the destination file already exist? Does the source file also exist?

          1 Reply Last reply
          1
          • D deleted286

            @jsulm it returns false. Ekran görüntüsü 2021-01-11 111741.png

            #include "mythread.h"
            #include "mainwindow.h"
            #include <QtCore>
            #include <QDebug>
            #include <QFile>
            #include <QTimer>
            #include <QThread>
            #include <QMutex>
            #include <QQueue>
            #include <QMessageBox>
            #include <QApplication>
            #include <QtWidgets/QApplication>
            #include <QtWidgets/QMainWindow>
            #include <QFileDialog>
            #include <QMainWindow>
            
            QFile file("C:/Users/ilknu/Documents/MyThread/deneme.txt");
            
            
            MyThread::MyThread(QObject* parent)
                : QThread(parent)
            {
                writeData();
            }
            
            MyThread::~MyThread()
            {
            
            }
            
            void MyThread::writeData()
            {
                QFile file2("C:/Users/ilknu/Documents/MyThread/new.txt");
                QFile::copy("C:/Users/ilknu/Documents/MyThread/deneme.txt","C:/Users/ilknu/Documents/MyThread/new.txt" );
                qDebug() << QFile::copy("C:/Users/user/Documents/MyThread/deneme.txt", "C:/Users/user/Documents/MyThread/new.txt");
                qDebug() << "im working in writing thread";
            
                emit writingDone();
            
            }
            
            void MyThread::run()  //Reading file from txt with thread1
            {
            
                if (file.open(QIODevice::ReadOnly))
                {
                    QTextStream in (&file);
                    while (!in.atEnd())
                    {
                        QString line = in.readAll();
                        QStringList list = line.split(QLatin1Char(' '), Qt::SkipEmptyParts);
                        for(const QString &entry : list)
                        {
                            double num = entry.toDouble();
                            queue.enqueue(num);
            
                        }
            
            
                        qDebug()<< "im running on worker thread " <<line;
            
                    } // for
                } // while
                file.close();
            } // if
            
            SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #23

            Hi,

            @suslucoder said in Copying the file content:

            QFile::copy("C:/Users/ilknu/Documents/MyThread/deneme.txt","C:/Users/ilknu/Documents/MyThread/new.txt" );
            qDebug() << QFile::copy("C:/Users/user/Documents/MyThread/deneme.txt", "C:/Users/user/Documents/MyThread/new.txt");

            You do not have the same paths in the qDebug and the previous line.
            You do realise that you are copying it twice ?

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

            D 1 Reply Last reply
            4
            • sierdzioS sierdzio

              Check if it exists:

              qDebug() << "Source exists?" << QFile::exists("C:/Users/ilknu/Documents/MyThread/deneme.txt");
              qDebug() << "Destination exists?" << QFile::exists("C:/Users/ilknu/Documents/MyThread/new.txt");
              

              You need to check destination because:

              If a file with the name newName already exists, copy() returns false (i.e., QFile will not overwrite it).

              D Offline
              D Offline
              deleted286
              wrote on last edited by
              #24

              @sierdzio
              They exists.

              Ekran görüntüsü 2021-01-11 112331.png

              JonBJ sierdzioS 2 Replies Last reply
              0
              • JonBJ Offline
                JonBJ Offline
                JonB
                wrote on last edited by
                #25

                @SGaist , @sierdzio , @J-Hilk
                If QFile::copy() returns false, I don't see anywhere the user can obtain any kind of error message/reason for the failure. Does Qt not supply this by any means?

                1 Reply Last reply
                0
                • SGaistS SGaist

                  Hi,

                  @suslucoder said in Copying the file content:

                  QFile::copy("C:/Users/ilknu/Documents/MyThread/deneme.txt","C:/Users/ilknu/Documents/MyThread/new.txt" );
                  qDebug() << QFile::copy("C:/Users/user/Documents/MyThread/deneme.txt", "C:/Users/user/Documents/MyThread/new.txt");

                  You do not have the same paths in the qDebug and the previous line.
                  You do realise that you are copying it twice ?

                  D Offline
                  D Offline
                  deleted286
                  wrote on last edited by
                  #26

                  @SGaist I fixed it

                  1 Reply Last reply
                  0
                  • D deleted286

                    @sierdzio
                    They exists.

                    Ekran görüntüsü 2021-01-11 112331.png

                    JonBJ Offline
                    JonBJ Offline
                    JonB
                    wrote on last edited by JonB
                    #27

                    @suslucoder said in Copying the file content:

                    They exists.

                    And? We have all said QFile::copy() says:

                    Note that if a file with the name newName already exists, copy() returns false (i.e. QFile will not overwrite it).

                    So you (not we) need to do something about that.

                    Also, as @SGaist has pointed out, you don't even have the same paths on your two QFile::copy() calls.

                    D 1 Reply Last reply
                    1
                    • D deleted286

                      @sierdzio
                      They exists.

                      Ekran görüntüsü 2021-01-11 112331.png

                      sierdzioS Offline
                      sierdzioS Offline
                      sierdzio
                      Moderators
                      wrote on last edited by
                      #28

                      @suslucoder

                      Then the cause is clear: destination exists, so copy() will not overwrite it. You need to remove the destination file first, before calling copy().

                      (Z(:^

                      D 1 Reply Last reply
                      1
                      • JonBJ JonB

                        @suslucoder said in Copying the file content:

                        They exists.

                        And? We have all said QFile::copy() says:

                        Note that if a file with the name newName already exists, copy() returns false (i.e. QFile will not overwrite it).

                        So you (not we) need to do something about that.

                        Also, as @SGaist has pointed out, you don't even have the same paths on your two QFile::copy() calls.

                        D Offline
                        D Offline
                        deleted286
                        wrote on last edited by
                        #29

                        @JonB said in Copying the file content:

                        Also, as @SGaist has pointed out, you don't even have the same paths on your two QFile::copy() calls. I've fixed it, it is my mistake.

                        Even i delete the destination file, for returning true by creating new destination, it returns false.

                        jsulmJ 1 Reply Last reply
                        0
                        • D deleted286

                          @JonB said in Copying the file content:

                          Also, as @SGaist has pointed out, you don't even have the same paths on your two QFile::copy() calls. I've fixed it, it is my mistake.

                          Even i delete the destination file, for returning true by creating new destination, it returns false.

                          jsulmJ Offline
                          jsulmJ Offline
                          jsulm
                          Lifetime Qt Champion
                          wrote on last edited by
                          #30

                          @suslucoder Did you check what @SGaist said? Do NOT call copy twice! Call it once like before but put qDebug() in front of it...

                          https://forum.qt.io/topic/113070/qt-code-of-conduct

                          1 Reply Last reply
                          0
                          • sierdzioS sierdzio

                            @suslucoder

                            Then the cause is clear: destination exists, so copy() will not overwrite it. You need to remove the destination file first, before calling copy().

                            D Offline
                            D Offline
                            deleted286
                            wrote on last edited by
                            #31

                            @sierdzio I'll try it again thank you

                            D 1 Reply Last reply
                            0
                            • D deleted286

                              @sierdzio I'll try it again thank you

                              D Offline
                              D Offline
                              deleted286
                              wrote on last edited by
                              #32

                              @suslucoder it works. thank you

                              1 Reply Last reply
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