QT writes data to file, logging

Project scenario:

In QT applications, sometimes it is necessary to record error information in a log file, or to output data to a file for comparison and viewing.

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Create a log file, if the file exists, do not create it

                QDir dir(QCoreApplication::applicationDirPath()+"/recv_data");
                if(dir.exists())
                {
    
    

                }
                else
                {
    
    
                    dir.mkdir(QCoreApplication::applicationDirPath()+"/recv_data");//只创建一级子目录，即必须保证上级目录存在
                }
                QString filename = QCoreApplication::applicationDirPath()+"/recv_data/" +QString("%1").arg(QDateTime::currentDateTime().toString ("yyyyMMddhhmmss").toLatin1().data());
                data_name =filename +".log";

---

Open file and write data

               QFile file(data_name);
               if (file.open(QIODevice::WriteOnly | QIODevice::Append))
               {
    
    

               }
               QTextStream streamFile(&file);
               streamFile << QString("%1").arg(data, 5, 'f', 2, QLatin1Char('0')) << "     "<< << "\n" ;