You should use QProcess rather than low-level system call because it is a nice abstraction in a Qt codebase. Otherwise, you will end up dealing with platform specific bits. QProcess
already solves that for you. If you happen to be fine with a blocking approach, aka. sync, you could write something like that code below.
QProcess process;
process1.start("gnuplot arg1 arg2 etc");
// Wait for it to start
if(!process.waitForStarted())
return 0;
bool retval = false;
QByteArray buffer;
while ((retval = process.waitForFinished()));
buffer.append(process.readAll());
if (!retval) {
qDebug() << "Process 2 error:" << process.errorString();
msgBox.setText(buffer);
return 1;
}
If you would not like to block while the gnuplot script of yours is running, you could connect a slot, or simply lambda with C++11 and on, to the readyRead() signal. For sure, you would also need to connect to the error() signal. The code without lambda to work with pre C++11 environments would look something like this:
GnuPlotReader::GnuPlotReader(QQProcess *process, QObject *parent)
: QObject(parent)
, m_process(process)
, m_standardOutput(stdout)
{
connect(m_process, SIGNAL(readyRead()), SLOT(handleReadyRead()));
connect(m_process, SIGNAL(error(QProcess::ProcessError)), SLOT(handleError(QProcess::ProcessError)));
connect(&m_timer, SIGNAL(timeout()), SLOT(handleTimeout()));
m_timer.start(5000);
}
GnuPlotReader::~GnuPlotReader()
{
}
void GnuPlotReader::handleReadyRead()
{
m_readData = m_process->readAll();
if (!m_timer.isActive())
m_timer.start(5000);
}
void GnuPlotReader::handleTimeout()
{
if (m_readData.isEmpty()) {
m_standardOutput << QObject::tr("No data was currently available for reading from gnuplot") << endl;
} else {
m_standardOutput << QObject::tr("GnuPlot successfully run")<< endl;
}
}
void GnuPlotReader::handleError(QProcess::ProcessError processError)
{
if (processError == QProcess::ReadError) {
m_standardOutput << QObject::tr("An I/O error occurred while reading the data, error: %2").arg(m_process->errorString()) << endl;
messageBox.setText(m_readData);
}
}