程序调试中需要保存qDebug的打印信息，首先想到的是Linux重定向输出到一个文件中，但是qdebug不行。google发现Qt已经自带了保存log的方法。

#include <QtGui/QApplication>
#include <QTextCodec>

#include <QDebug>
void customMessageHandler(QtMsgType type, const char *msg)
{
        QString txt;
        switch (type) {
        //调试信息提示
        case QtDebugMsg:
                txt = QString("Debug: %1").arg(msg);
                break;
        //一般的warning提示
        case QtWarningMsg:
                txt = QString("Warning: %1").arg(msg);
        break;
        //严重错误提示
        case QtCriticalMsg:
                txt = QString("Critical: %1").arg(msg);
        break;
        //致命错误提示
        case QtFatalMsg:
                txt = QString("Fatal: %1").arg(msg);
                abort();
        }

        QFile outFile1("debuglog1.txt");
        QFile outFile2("debuglog2.txt");
        outFile1.open(QIODevice::WriteOnly | QIODevice::Append);
        if(outFile1.size() >= 1024*10 )
        {
           outFile1.close();
           outFile2.remove();
           QFile::copy("debuglog1.txt","debuglog2.txt");
           outFile1.remove();

           QFile outFile3("debuglog1.txt");
           outFile3.open(QIODevice::WriteOnly | QIODevice::Append);
           QTextStream ts(&outFile3);
           ts << txt << endl;
        }
        else
        {
            QTextStream ts(&outFile1);
            ts << txt << endl;
        }
}

int main(int argc, char *argv[])
{
        QApplication a(argc, argv);
        qInstallMsgHandler(customMessageHandler);
      
        MainServer mainWin;

        mainWin.show();

        return a.exec();
}

debuglog1.txt 如果大于10k了，就复制到debuglog2.txt,同时删除debuglog1.txt,重新开始写

PS:bool QFile::copy ( const QString & fileName, const QString & newName ) [static]
This is an overloaded function.


Copies the file fileName to newName. Returns true if successful; otherwise returns false.


If a file with the name newName already exists, copy() returns false (i.e., QFile will not overwrite it).