source: tests/process/process-sync2/process-sync2.cpp

#include <QFile>
#include <QDebug>
#include <QProcess>

int main (int argc, char *argv[])
{
        if (argc < 4)
        {
            qDebug("Usage: %s <in_file> <out_file> <child> [<child_arguments>]\n\n"
                   "Sends <in_file> to stdin of <child> and puts its stdout to"
                   "<out_file>.", argv [0]);
            return 0;
        }

    QByteArray data;

    QFile qfIn (argv [1]);
    if (qfIn.open (QIODevice::ReadOnly))
    {
        data = qfIn.readAll();
        qfIn.close();
        qDebug() << "Read" << data.size() << "bytes from" << argv [1];
    }
    else
    {
        qDebug() << "Couldn't open" << argv [1] << "for reading";
        return 1;
    }

    qint64 bytes;
    QProcess proc;

#if 0
    proc.setProcessChannelMode (QProcess::ForwardedChannels);
#endif

    QStringList args;
    for (int i = 4; i < argc; ++ i)
        args << argv [i];

    proc.start (argv [3], args, QIODevice::ReadWrite);

    if (!proc.waitForStarted())
    {
        qDebug() << "Failed to start" << argv [3] <<":" << proc.errorString();
        return 1;
    }

    qDebug() << "Started" << argv [3];

    bytes = proc.write (data);
    qDebug() << "Wrote" << bytes << "bytes to child process";

    proc.closeWriteChannel();
    qDebug() << "Waiting for child termination...";

    if (!proc.waitForFinished())
    {
        qDebug() << "Child ended abnormally:" << proc.errorString();
    }
    else
    {
        qDebug() << "Child ended normally";
    }

    data = proc.readAllStandardOutput();
    qDebug() << "Read" << data.size() << "bytes from child process";
    
    QFile qfOut (argv [2]);
    if (qfOut.open (QIODevice::WriteOnly))