How can I format a data table in Qt?

[viniltc]

Hi,

I am not familiar with file formatting in Qt. I have a txt file containing the data log from a device, as below:

=== USAGE_LOG ===
Phase	count	min time ms	max time ms	total time ms
0	1738	5	70933790	117611680
1	376	18	4103927	7104930
2	339	432	105935	2167343
3	288	298	96749	1955551
4	261	225	79872	1051601
5	94	639	2000	185639

and I need to modify it ideally would like:

=== USAGE_LOG ===
Phase	  count  	min time 	max time  total time 
Rest	  1738	        0.05	        70933	  117611
Open_1	  376	        0.018	        4103	  7104
Move	  339	        0.432	        105       2167
Grip_1	  288	        0.298	        96	  1955
Grip_2    261	        0.225	        79	  1051
Open_3	  94	        0.639	        2	  185

The first column changed from numbers to words, and all the time columns are changed from milliseconds to seconds. Can anyone suggest an efficient way to do this?

[jsulm]

@viniltc What exactly is the problem?
Read the file line by line and in each line change what you need to change and write it to another file.
Writing to a text file can be done using https://doc.qt.io/qt-6/qtextstream.html

[viniltc]

@jsulm Hi.

I can read line by line whole content of the file to a text browser as follows:

    QString fname = "logfile.txt";
    QFile file(fname);

    file.open(QIODevice::ReadOnly|QIODevice::Text);

    QTextStream instream(& file);

    while (!instream.atEnd()){
        QString line = instream.readLine();
        ui->textBrowser->append(line); 
    }


    file.close();

But I'm not sure how to read a particular line, for example. Read 3rd line:

0	1738	5	70933790	117611680

and change it to:

Rest	  1738	        0.05	        70933	  117611

It would be very helpful if someone showed me an example

[jsulm]

@viniltc said in How can I format a data table in Qt?:

But I'm not sure how to read a particular line, for example. Read 3rd line:

Read lines until you got line number 3 (counting lines should really not be an issue).
"and change it to" - if you know which columns you want to change you can use https://doc.qt.io/qt-6/qstring.html#split to split the line, then change the columns you want to change and merge the substrings into one string again (https://doc.qt.io/qt-6/qstringlist.html#join for example).

[viniltc]

@jsulm Thanks.

I have a basic question:

I opened an old log file in the readonly mode and stored content in QTextStream, and closed it

I opened another file to write and tried to read line by line and write it into the new file. As an initial step, I just want to see each line read on Debug, but nothing is showing. Any idea what's wrong here?

    QString oldfilename = "log_file";
    QString newfilename = "new_log_file";

    QString path1 = QCoreApplication::applicationDirPath()+"/"+oldfilename +".txt";
    QString path2 = QCoreApplication::applicationDirPath()+"/"+newfilename+".txt";

    QFile readfile(path1);
    if(!readfile.open(QIODevice::ReadOnly | QIODevice::Text)){

        qDebug() << "Error opening file: "<<readfile.errorString();
    }

    QTextStream instream(& readfile);
    readfile.close();


    QFile writefile(path2);
    if(file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        int nb_line(0);
        while(!instream.atEnd())
        {
            QString line = instream.readLine();
            
           if(nb_line == 1 )
            {
               qDebug () << line ;
            }
            if(nb_line == 2 )
            {
                qDebug () << line ;
            }

            if(nb_line == 3 )
            {
               qDebug () << line ;
            }
            
        ++nb_line;
       
          }
        
     writefile.close();
    }

[JonB]

@viniltc said in How can I format a data table in Qt?:

QTextStream instream(& readfile);
readfile.close();

You are closing the underlying readfile before reading from it. Move readfile.close() to after the loop which reads from it/the QTextStream wrapper.