How to display the output of a process in a TextEdit widget in real time?

[qtzcute]

Hi,

I have an application that when run from shell, gives many messages, variable and their data as output in the same shell.

Now, i am running that application with the help of QProcess and i want the resulting ouput to display in my Text Edit widget of my GUI in real time....i.e. as the appication is producing output, it should be appearing in TextEdit concurrently.

I browse the google for the problem and found that people are using readLineStdout() which seems like not a slot provided by QProcess but they are using it as if it is.

[spirit]

all what you need it's to use QProcess::readyReadStandardOutput/QProcess::readyReadStandardError signals and create slots for these signals, then in these slots you should call QProcess::readAllStandardOutput/QProcess::readAllStandardError and add results in a text edit.

[qtzcute]

hmmm..right. I used following code but doesn't display anything in my TextEdit.

...
QObject::connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError(myProcess)));
QObject::connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText(myProcess)));
 myProcess->start(program);

...
QObject::connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError(myProcess)));
QObject::connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText(myProcess)));
 myProcess->start(program);

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Definition of updateError and updateText:

void MainWindow::updateError(QProcess *myProcess)
{
 QByteArray data = myProcess->readAllStandardError();
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText(QProcess *myProcess)
{
   QByteArray data = myProcess->readAllStandardOutput();
   textEdit_verboseOutput->append(QString(data));
}

void MainWindow::updateError(QProcess *myProcess)
{
 QByteArray data = myProcess->readAllStandardError();
  textEdit_verboseOutput->append(QString(data));
}

void MainWindow::updateText(QProcess *myProcess)
{
   QByteArray data = myProcess->readAllStandardOutput();
   textEdit_verboseOutput->append(QString(data));
}

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[spirit]

sigh, you code won't work.
try this

connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError()));
connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText()));
myProcess->start(program);
...
void MainWindow::updateError()
{
 QByteArray data = myProcess->readAllStandardError();
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText()
{
   QByteArray data = myProcess->readAllStandardOutput();
   textEdit_verboseOutput->append(QString(data));
}

connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError()));
connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText()));
myProcess->start(program);
...
void MainWindow::updateError()
{
 QByteArray data = myProcess->readAllStandardError();
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText()
{
   QByteArray data = myProcess->readAllStandardOutput();
   textEdit_verboseOutput->append(QString(data));
}

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BUT, myProcess must be a class member of MainWindow or you can cast QObject::sender to QProcess.
PS, you should read more about Signal&Slot mechanism.

[qtzcute]

Still not working. The process is however running fine but TextEdit widget remains empty.
My MainWindow class

class MainWindow : public QMainWindow, private Ui::MainWindow
{
Q_OBJECT
public:
QProcess *myProcess;
MainWindow(QMainWindow *parent = 0);

private slots:
void updateError();
void updateText();
};

MainWindow.cpp

void MainWindow::On_pushButton_startAnalysis_Click()
{
	QObject *parent;
	myProcess= new QProcess(parent);
 
	QString program = "./memviz ";
	QCoreApplication::processEvents();		
	connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError()));
	connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText()));
	myProcess->start(program);
}
 
void MainWindow::updateError()
{
 QByteArray data = myProcess->readAllStandardError();
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText()
{
   QByteArray data = myProcess->readAllStandardOutput();
   textEdit_verboseOutput->append(QString(data));
}

void MainWindow::On_pushButton_startAnalysis_Click()
{
	QObject *parent;
	myProcess= new QProcess(parent);

	QString program = "./memviz ";
	QCoreApplication::processEvents();		
	connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError()));
	connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText()));
	myProcess->start(program);
}

void MainWindow::updateError()
{
 QByteArray data = myProcess->readAllStandardError();
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText()
{
   QByteArray data = myProcess->readAllStandardOutput();
   textEdit_verboseOutput->append(QString(data));
}

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Is some error still hiding there from my egle eyes?

[spirit]

what do you see in console when this code works?

void MainWindow::On_pushButton_startAnalysis_Click()
{
    QObject *parent;
    myProcess= new QProcess(parent);
 
    QString program = "./memviz ";
    QCoreApplication::processEvents();      
    qDebug() << connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError()));
    qDebug() << connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText()));
    myProcess->start(program);
}
 
void MainWindow::updateError()
{
 QByteArray data = myProcess->readAllStandardError();
 qDebug() << data;
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText()
{
   QByteArray data = myProcess->readAllStandardOutput();
 qDebug() << data;
   textEdit_verboseOutput->append(QString(data));
}

void MainWindow::On_pushButton_startAnalysis_Click()
{
    QObject *parent;
    myProcess= new QProcess(parent);
 
    QString program = "./memviz ";
    QCoreApplication::processEvents();      
    qDebug() << connect(myProcess, SIGNAL(readyReadStdError()), this, SLOT(updateError()));
    qDebug() << connect(myProcess, SIGNAL(readyReadStdOutput()), this, SLOT(updateText()));
    myProcess->start(program);
}
 
void MainWindow::updateError()
{
 QByteArray data = myProcess->readAllStandardError();
 qDebug() << data;
  textEdit_verboseOutput->append(QString(data));
}
 
void MainWindow::updateText()
{
   QByteArray data = myProcess->readAllStandardOutput();
 qDebug() << data;
   textEdit_verboseOutput->append(QString(data));
}

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[qtzcute]

Oh its giving following error

Object::connect: No such signal QProcess::readyReadStdError()
Object::connect:  (receiver name: 'MainWindow')
Object::connect: No such signal QProcess::readyReadStdOutput()
Object::connect:  (receiver name: 'MainWindow')

Object::connect: No such signal QProcess::readyReadStdError()
Object::connect:  (receiver name: 'MainWindow')
Object::connect: No such signal QProcess::readyReadStdOutput()
Object::connect:  (receiver name: 'MainWindow')

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But this error should also have appeared in the texEdit_verboseOutput.

I said the program is working fine because i was actually generating an xml file with my 'memviz' application which is generated finely. Sorry din check the console earlier.

[qtzcute]

Any idea about this error? Isn't it weird QProcess::readyReadStdError() is a signal provided by QProcess as i see it in Qt Assistant but still i am getting 'no such signal error'.

[spirit]

take a look at docs: there are only these signals QProcess::readyReadStandardError && QProcess::readyReadStandardOutput.

[wagmare]

set the
void QProcess::setProcessChannelMode ( ProcessChannelMode mode )

to QProcess::MergedChannels

[qtzcute]

Ah...stupid me.

Thanks. It's working now.