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

/*
 *
 * Demostrates failure when piping a large ( +100KB ) file to a child process
 *
 */

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

int test_write(const QString &aFile)
{
    printf ("test_write: Write '%s' to child's stdin that will write "
            "it to '%s.out'\n", aFile.toLocal8Bit().constData(),
            aFile.toLocal8Bit().constData());

    QProcess p;

    QFile f (aFile);
    if (f.open (QIODevice::ReadOnly))
    {
        QString aOutFile = aFile + ".out";

        p.start ("child",
                 QStringList() << "0" << aOutFile,
                 QIODevice::WriteOnly);

        if (p.waitForStarted())
        {
            while (!f.atEnd())
            {
                //QByteArray ba = f.read (2048);
                //QByteArray ba = f.read (32768);
                QByteArray ba = f.read (65536);

                p.write (ba);

                p.waitForBytesWritten (-1);
            }

            //p.close();
            p.closeWriteChannel();

            p.waitForFinished();
            printf ("Process finished with %d (%d)\n",
                    p.exitCode(), p.exitStatus());
        }
        else
            printf ("waitForStarted() failed\n");

        f.close();
    }
    else
        printf ("Can't open output file %s\n",
                aFile.toLatin1().constData());

    return 0;
}

int test_read(const QString &aFile, bool aToStdErr)
{
    const char *ext = aToStdErr ? "err" : "out";

    printf ("test_read: Read '%s' from child's std%s "
            "and write it to '%s.%s'\n", aFile.toLocal8Bit().constData(),
            ext, aFile.toLocal8Bit().constData(), ext);

    QString aOutFile = aFile + "." + ext;
    QProcess p;
    QFile f (aOutFile);

    p.setReadChannel (aToStdErr ? QProcess::StandardError :
                                  QProcess::StandardOutput);

    if (f.open (QIODevice::WriteOnly))
    {
        p.start ("child",
                 QStringList() << (aToStdErr ? "2" : "1") << aFile,
                 QIODevice::ReadOnly);

        if (p.waitForStarted())
        {
            while (p.waitForReadyRead() || p.bytesAvailable())
            {
                QByteArray ba = p.read (p.bytesAvailable());

                f.write (ba);
            }

            p.waitForFinished();
            printf ("Process finished with %d (%d)\n",
                    p.exitCode(), p.exitStatus());
        }
        else
            printf ("waitForStarted() failed\n");

        f.close();
    }
    else
        printf ("Can't open output file %s\n",
                aOutFile.toLatin1().constData());

    return 0;
}

int test_sleep()
{
    printf ("test_sleep: start a 3s sleepy and wait for termination.\n");

    QProcess p;

    p.start ("cmd",
             QStringList() << "/c" <<
             "process-sync-helper.cmd" << "sleep");

    if (p.waitForStarted())
    {
        p.waitForFinished();
        printf ("Process finished with %d (%d)\n",
                p.exitCode(), p.exitStatus());
    }
    else
        printf ("waitForStarted() failed\n");

    return 0;
}

int test_delayed_write()
{
    printf ("test_sleep: start a 3s delayed write to child's stdin " 
            "and wait until written.\n");

    QProcess p;

    p.start ("cmd",
             QStringList() << "/c" <<
             "process-sync-helper.cmd" << "delayed_write",
             QIODevice::ReadWrite);

    if (p.waitForStarted())
    {
        p.write (QByteArray("Hello from parent.\n"));
        p.waitForBytesWritten();

        if (p.waitForReadyRead()) {
            QByteArray ba = p.read (p.bytesAvailable());
            printf ("Child says:\n%s\n", ba.constData());
        }

        p.waitForFinished();
        printf ("Process finished with %d (%d)\n",
                p.exitCode(), p.exitStatus());
    }
    else
        printf ("waitForStarted() failed\n");

    return 0;
}

int test_delayed_read()
{
    printf ("test_sleep: start a 3s delayed read from child's stdout " 
            "and wait until read.\n");

    QProcess p;

    p.start ("cmd",
             QStringList() << "/c" <<
             "process-sync-helper.cmd" << "delayed_read",
             QIODevice::ReadOnly);

    if (p.waitForStarted())
    {
        if (p.waitForReadyRead()) {
            QByteArray ba = p.read (p.bytesAvailable());
            printf ("Child says:\n%s\n", ba.constData());
        }

        p.waitForFinished();
        printf ("Process finished with %d (%d)\n",
                p.exitCode(), p.exitStatus());
    }
    else
        printf ("waitForStarted() failed\n");

    return 0;
}

int test_hang()
{
    printf ("test_hang: start cmd /c pause and wait for termination. "
            "Requires killing cmd.exe.\n");

    QProcess p;

    p.start ("cmd",
             QStringList() << "/c" << "pause");

    if (p.waitForStarted())
    {
        p.waitForFinished();
        printf ("Process finished with %d (%d)\n",
                p.exitCode(), p.exitStatus());
    }
    else
        printf ("waitForStarted() failed\n");

    return 0;
}

int main( int argc, char *argv[] )
{
    if (argc >= 3)
    {
        QScopedPointer <QApplication> app;
        if (argc == 4 && qstrcmp (argv [3], "gui") == 0)
            app.reset (new QApplication (argc, argv));
         
        if (qstrcmp (argv [1], "read_out") == 0)
            return test_read (QLatin1String (argv [2]), false);
        if (qstrcmp (argv [1], "read_err") == 0)
            return test_read (QLatin1String (argv [2]), true);
        if (qstrcmp (argv [1], "write") == 0)
                return test_write(QLatin1String (argv [2]));
        }
        else
    if (argc == 2)
    {
        if (qstrcmp (argv [1], "sleep") == 0)
                return test_sleep();
        if (qstrcmp (argv [1], "hang") == 0)
                return test_hang();
        if (qstrcmp (argv [1], "delayed_write") == 0)
                return test_delayed_write();
        if (qstrcmp (argv [1], "delayed_read") == 0)
                return test_delayed_read();
    }

    printf ("Usage: testcase read_out|read_err|write <filename>\n"
            "       testcase sleep|hang\n");

    return 0;
}