Printing all messages and warning on terminal to a file?

Question

I want to generate Log in my application i.e whatever i get on terminal window or cmd window to be generated as log in a text file.

e.g. I have a client server program so whatever message or warnings i get on terminal to be printed on log file along with timestamp.

Any Idea,Are QxtLog or log4Qt do the same that i want?

I'm not sure, maybe [this answer](http://stackoverflow.com/questions/4954140/how-to-redirect-qdebug-qwarning-qcritical-etc-output) will help you (if you're using `Qt 4.*`? Else if you're using `Qt 5.*` then read [this](http://qt-project.org/doc/qt-5.0/qtcore/qtglobal.html#qInstallMsgHandler) : the API has been changed a bit, deprecating the previous one! — Nawaz, Nov 19 '13 at 09:56
@Nawaz: I tried that but qInstallMsgHandler() doesn't work it shows it doesn't exist. — CowboY, Nov 19 '13 at 10:10
then try `qInstallMessageHandler()`, as I said, [the API has been changed since Qt 5.0](http://qt-project.org/doc/qt-5.0/qtcore/qtglobal.html#qInstallMsgHandler). — Nawaz, Nov 19 '13 at 11:01
*"still not working"* is almost always equal to NO information. — Nawaz, Nov 19 '13 at 12:16
@Nawaz: Sorry buddy for that.I am getting this error:I used it as you told as i use Qt5 so have to replace qInstallMessageHandler() but it is showing error as follows:invalid conversion from 'void ()(QtMsgType, const char)' to 'QtMessageHandler {aka void (*)(QtMsgType, const QMessageLogContext&, const QString&)}' [-fpermissive] — CowboY, Nov 20 '13 at 10:15

score 3 · Answer 1 · answered Nov 19 '13 at 10:42

3

Install your Qt message handler.

FILE *fd;

void myMessageOutput(QtMsgType type, const char *msg)
{
    QString timeStamp = QTime::currentTime().toString("hh:mm:ss:zzz");
    switch (type) {
    case QtDebugMsg:
        fprintf(fd, "[%s]", timeStamp.toStdString().c_str());
        fprintf(fd, "[Debug] %s\n", msg);
        break;
    case QtWarningMsg:
        fprintf(fd, "[%s]", timeStamp.toStdString().c_str());
        fprintf(fd, "[Warning] %s\n", msg);
        break;
    case QtCriticalMsg:
        fprintf(fd, "[%s]", timeStamp.toStdString().c_str());
        fprintf(fd, "[Critical] %s\n", msg);
        break;
    case QtFatalMsg:
        fprintf(fd, "[%s]", timeStamp.toStdString().c_str());
        fprintf(fd, "[Fatal] %s\n", msg);
        abort();
    }
}

int main(int argc, char **argv)
{
    fd = fopen("log.txt", "a");
    qInstallMsgHandler(myMessageOutput);
    QApplication app(argc, argv);
    ...
    return app.exec();
}

answered Nov 19 '13 at 10:42

liuyi.luo

1,219
7
11

Will it print all messages on terminal be it warning,error messages etc ?I mean does these msgtypes cover all the messages appearing on cmd,terminal? – CowboY Nov 19 '13 at 12:12
1

Yes. There are four debug level in Qt. Four global functions are used to write out warning and debug message. They are `qDebug()`, `qWarning()`, `qCritical()` and `qFatal()`. – liuyi.luo Nov 20 '13 at 01:37
I used it as you told as i use Qt5 so have to replace qInstallMessageHandler() but it is showing error as follows:invalid conversion from 'void (*)(QtMsgType, const char*)' to 'QtMessageHandler {aka void (*)(QtMsgType, const QMessageLogContext&, const QString&)}' [-fpermissive] – CowboY Nov 20 '13 at 10:14
Sorry, I have no experience on Qt5. I hope [this](http://stackoverflow.com/questions/14643293/how-does-qt5-redirect-qdebug-statements-to-the-qt-creator-2-6-console) can help you. – liuyi.luo Nov 20 '13 at 10:26

score 1 · Answer 2 · answered Nov 19 '13 at 09:56

One quick and simple approach would be to pipe the output of your software to a file.

For a more sophisticated approach I suggest considering log4cplus (http://sourceforge.net/p/log4cplus/wiki/Home/) - I don't know log4Qt, but I guess it might have a similar interface.

Log4Cplus allows to create different channels/priorities for your logs, so you can also filter your output in terms of importance, which might be interesting depending on the size of your project.

Printing all messages and warning on terminal to a file?

2 Answers2