Console output in a Qt GUI app?

Question

I have a Qt GUI application running on Windows that allows command-line options to be passed and under some circumstances I want to output a message to the console and then

Answer 1

No way to output a message to console when using QT += gui.

fprintf(stderr, ...) also can't print output.

Use QMessageBox instead to show the message.

Answer 2

It may have been an oversight of other answers, or perhaps it is a requirement of the user to indeed need console output, but the obvious answer to me is to create a secondary window that can be shown or hidden (with a checkbox or button) that shows all messages by appending lines of text to a text box widget and use that as a console?

The benefits of such a solution are:

• A simple solution (providing all it displays is a simple log).
• The ability to dock the 'console' widget onto the main application window. (In Qt, anyhow).
• The ability to create many consoles (if more than 1 thread, etc).
• A pretty easy change from local console output to sending log over network to a client.

Hope this gives you food for thought, although I am not in any way yet qualified to postulate on how you should do this, I can imagine it is something very achievable by any one of us with a little searching / reading!

Answer 3

Make sure Qt5Core.dll is in the same directory with your application executable.

I had a similar issue in Qt5 with a console application: if I start the application from Qt Creator, the output text is visible, if I open cmd.exe and start the same application there, no output is visible. Very strange!

I solved it by copying Qt5Core.dll to the directory with the application executable.

Here is my tiny console application:

#include <QCoreApplication>
#include <QDebug>

int main(int argc, char *argv[])
{
    int x=343;
    QString str("Hello World");
    qDebug()<< str << x<<"lalalaa";

    QTextStream out(stdout);
    out << "aldfjals alsdfajs...";
}

Answer 4

One solution is to run powershell and redirect the output to whatever stream you want.

Below is an example of running powershell from cmd.exe and redirecting my_exec.exe output to both the console and an output.txt file:

powershell ".\my_exec.exe | tee output.txt"

Answer 5

First of all you can try flushing the buffer

std::cout << "Hello, world!"<<std::endl;

For more Qt based logging you can try using qDebug.