Cannot read QProcess output for some applications

[yagabey]

Hi,
I am trying to read console output of a qt console app from a qt gui app.

void MainWindow::on_pushButton_clicked()
{
    proc= new QProcess(this);
    connect(proc,SIGNAL(readyReadStandardOutput()),this,SLOT(readProcessOutput()));
    proc->setProcessChannelMode(QProcess::MergedChannels);
    proc->start("C:\\Users\\yg\\Documents\\processtest\\debug\\deployFiles.bat");
}
void MainWindow::readProcessOutput()
{
    ui->textEdit->append(proc->readAllStandardOutput());
}

void MainWindow::on_pushButton_clicked()
{
    proc= new QProcess(this);
    connect(proc,SIGNAL(readyReadStandardOutput()),this,SLOT(readProcessOutput()));
    proc->setProcessChannelMode(QProcess::MergedChannels);
    proc->start("C:\\Users\\yg\\Documents\\processtest\\debug\\deployFiles.bat");
}
void MainWindow::readProcessOutput()
{
    ui->textEdit->append(proc->readAllStandardOutput());
}

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I can read the output for "deployFiles.bat" app. But when i change the file to :

proc->start("C:\\Users\\yg\\Documents\\processtest\\debug\\DriverModbus.exe");

proc->start("C:\\Users\\yg\\Documents\\processtest\\debug\\DriverModbus.exe");

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Nothing comes to standartoutput.
DriverModbus is a qt console app that uses qDebug() s to print data on its console.

https://dl.dropboxusercontent.com/u/...iverModbus.rar

What maybe the problem?

Thanks in advance...

[jefftee]

qDebug write to stderr not stdout.

[yagabey]

Hi Jefftee,

I think "proc->setProcessChannelMode(QProcess::MergedChannels) " directs all output to stdout. So that shouldnt be a problem. And i already tried replacing "readyReadStandardOutput to readyReadStandardOutput" and "readAllStandardOutput toreadAllStandardError". Result not changing..

And a few additional information ; i am sure the process is running. When i check its state i see it "running". And When i exit the application i see

QProcess: Destroyed while process ("C:\Users\yg\Documents\processtest\debug\DriverModbus.exe") is still running

QProcess: Destroyed while process ("C:\Users\yg\Documents\processtest\debug\DriverModbus.exe") is still running

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output on the console

[yagabey]

Ok, i discovered one more thing. I can read output when i use:

QTextStream stream(stderr);
    stream << out;

QTextStream stream(stderr);
    stream << out;

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or

QTextStream stream(stdout);
    stream << out;

QTextStream stream(stdout);
    stream << out;

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But cannot read output from:

qDebug() << out    ;

qDebug() << out    ;

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Strange? No idea?

[anda_skoa]

Does the application output appears on a terminal when your run it normally?

Cheers,
_

[yagabey]

Yes, it does..

[anda_skoa]

One thing I could imagine is that the logging framework detects if there is a controlling terminal and output to it if there is.
And if there is not it logs to some system logging factility

Cheers,
_

[yagabey]

Not a solution ;but for now i think i need to use "stdout" ...

[anda_skoa]

Yes, using the correct streams explicitly is a better solution anyway.
More control of which stream something is written to and more control on how the data is formatted, etc.

Cheers,
_