connect(&cmd, SIGNAL(readyReadStandardError()), this, SLOT(slotStderr()));
    connect(&cmd, SIGNAL(readyReadStandardOutput()), this, SLOT(slotStdout()));
    connect(&cmd, SIGNAL(finished(int,QProcess::ExitStatus)), this, SLOT(slotFinished(int,QProcess::ExitStatus)));

....


void CCreateMapGeoTiff::slotStderr()
{
    textBrowser->setTextColor(Qt::red);
    textBrowser->append(cmd.readAllStandardError());
}

void CCreateMapGeoTiff::slotStdout()
{
    textBrowser->setTextColor(Qt::blue);
    QString str = cmd.readAllStandardOutput();

    textBrowser->insertPlainText(str);
    textBrowser->verticalScrollBar()->setValue(textBrowser->verticalScrollBar()->maximum());
}