Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. Copying the file content
Forum Update on Monday, May 27th 2025

Copying the file content

Scheduled Pinned Locked Moved Solved General and Desktop
copyfileqt5file readfile write
32 Posts 6 Posters 7.5k Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • sierdzioS Offline
    sierdzioS Offline
    sierdzio
    Moderators
    wrote on last edited by
    #10

    Yes, start() starts the thread, but it does not mean your writeData() is called. If that were true, you would see your qDebug() output, because it is not in any if conditions - it should be printed every time writeData() is called.

    (Z(:^

    D 1 Reply Last reply
    0
    • sierdzioS sierdzio

      Yes, start() starts the thread, but it does not mean your writeData() is called. If that were true, you would see your qDebug() output, because it is not in any if conditions - it should be printed every time writeData() is called.

      D Offline
      D Offline
      deleted286
      wrote on last edited by deleted286
      #11

      @sierdzio yes you are right. I've called the function. Thread is working now. But copying issue does not work.

      1 Reply Last reply
      0
      • sierdzioS Offline
        sierdzioS Offline
        sierdzio
        Moderators
        wrote on last edited by
        #12

        I don't know either, you have not shown any code or stated how you want it all to work... so all I can say is "read the docs" :D QThread has a nice example and detailed description: https://doc.qt.io/qt-5/qthread.html#details

        (Z(:^

        D 1 Reply Last reply
        0
        • sierdzioS sierdzio

          I don't know either, you have not shown any code or stated how you want it all to work... so all I can say is "read the docs" :D QThread has a nice example and detailed description: https://doc.qt.io/qt-5/qthread.html#details

          D Offline
          D Offline
          deleted286
          wrote on last edited by
          #13

          @sierdzio I just want, when writeData() thread is called, copy the contents into new txt.

          J.HilkJ 1 Reply Last reply
          0
          • D deleted286

            @sierdzio I just want, when writeData() thread is called, copy the contents into new txt.

            J.HilkJ Offline
            J.HilkJ Offline
            J.Hilk
            Moderators
            wrote on last edited by J.Hilk
            #14

            @suslucoder
            QThread has a started signal you connect that signal to your slot


            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.

            D 1 Reply Last reply
            3
            • J.HilkJ J.Hilk

              @suslucoder
              QThread has a started signal you connect that signal to your slot

              D Offline
              D Offline
              deleted286
              wrote on last edited by
              #15

              @J-Hilk My thread has working now. But copying does not occur

              jsulmJ 1 Reply Last reply
              0
              • D deleted286

                @J-Hilk My thread has working now. But copying does not occur

                jsulmJ Offline
                jsulmJ Offline
                jsulm
                Lifetime Qt Champion
                wrote on last edited by
                #16

                @suslucoder So, what does copy() return?

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

                D 1 Reply Last reply
                1
                • jsulmJ jsulm

                  @suslucoder So, what does copy() return?

                  D Offline
                  D Offline
                  deleted286
                  wrote on last edited by
                  #17

                  @jsulm it returns nothing, Either true or false

                  jsulmJ J.HilkJ 2 Replies Last reply
                  0
                  • D deleted286

                    @jsulm it returns nothing, Either true or false

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #18

                    @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");
                    

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

                    D 1 Reply Last reply
                    0
                    • 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 Online
                            JonBJ Online
                            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 Online
                                  JonBJ Online
                                  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 Online
                                      JonBJ Online
                                      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

                                          • Login

                                          • Login or register to search.
                                          • First post
                                            Last post
                                          0
                                          • Categories
                                          • Recent
                                          • Tags
                                          • Popular
                                          • Users
                                          • Groups
                                          • Search
                                          • Get Qt Extensions
                                          • Unsolved