2

Hey I'm trying to mess around with Qt and for some reason the following code will create the desired text file, but never writes anything to it. Am I doing something wrong? I believe I've copied the example in the documentation pretty accurately. 

qDebug() << output

works as expected, but even though the file is created, nothing is ever written to it.

#include <QCoreApplication>
#include <QtDebug>
#include <QString>
#include <QDateTime>
#include <QTextStream>

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

QString filename = "";
filename.append(QString::number(QDateTime::currentMSecsSinceEpoch()));
filename.append(".txt");

QFile file(filename);
file.open(QIODevice::WriteOnly);
QTextStream out(&file);

QString output = "TEST";

qDebug() << output;
out << output;
return a.exec();
}
druckermanly
  • 2,694
  • 15
  • 27

1 Answers1

4

The data does not get written to disk immediately: It sits in a buffer until it's flushed.

Close the file after you've finished writing.

(In my experience, the file is closed anyway when you quit the program, but it's good practice to do this explicitly)

JKSH
  • 2,658
  • 15
  • 33
  • Ah, I didn't know it would sit in buffer. Thanks for the assistance! – druckermanly Nov 19 '13 at 01:58
  • You're welcome. :) If the answer solves your problem, please indicate this by clicking the tick mark on the left. This is how StackOverflow users find answers to existing questions. – JKSH Nov 19 '13 at 04:10
  • 1
    @user2899162 You should also note, that [`QFile::open()`](http://qt-project.org/doc/qt-5.0/qtcore/qfile.html#open-2) returns `true` if the file was opened successfully. It is good practice to check this. If it fails, you can check the error with [`QFile::errorString()`](http://qt-project.org/doc/qt-5.0/qtcore/qiodevice.html#errorString). – thuga Nov 19 '13 at 07:29