QString appRootPath = qApp->applicationDirPath();

    QProcess *process = new QProcess();
    process->setWorkingDirectory(appRootPath + "/BG/");
    process->start(appRootPath + "/BG/TestApp.exe");


    QObject::connect(process, &QProcess::readyRead, [=](){
        QByteArray procOutput = process->readAll();
        qDebug()<<"TestApp："<< procOutput.data();
    });

子程序有标准输出流时，会发出QProcess::readyRead信号，通过此信号可以获取子进程的标准输出流内容。

二：子程序的日志，重定向到文件 setStandardOutputFile

    QString appRootPath = qApp->applicationDirPath();

    QProcess *process = new QProcess();
    process->setStandardOutputFile("log_1.log");
    process->setWorkingDirectory(appRootPath + "/BG/");
    process->start(appRootPath + "/BG/TestApp.exe");