Editing text file via console app

I'm trying to learn to alter a line of text within a text file via a console app. So far I can open the file, read each line into a string, identify the text I'd like to alter & alter the string. I can also set the cursor to the position of the begining of the line I want to alter. but when I write to the file it always appends instead of overwriting the line.

This is the text in the file I'm working with:

Code:

This is a text file for testing.
I plan to use it to develop my fixPath program.
I hope it works.

What I'd like to do is remove the word "fixPath from the 2nd line.

Here is the code so far:

Code:

#include <QtCore/QCoreApplication>
#include <QTextStream>
#include <QString>
#include <QFile>
 
QTextStream cout(stdout, QIODevice::WriteOnly);
QTextStream cerr(stderr, QIODevice::WriteOnly);
 
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QString str1, str2(" fixPath");
    QFile file("fixPath.txt");
 
 
    if(file.open(QIODevice::ReadWrite))
    {
        QTextStream fileStream(&file);
        while (not fileStream.atEnd())
        {
          str1 = fileStream.readLine();
          if (str1.contains(str2))
          {
              str1.remove(str2);
              fileStream.seek(34);
              fileStream.operator<<(str1);
              cout << fileStream.pos()<<endl;
          }
        }
        file.close();
    }
 
    //return a.exec();
}

Any help is appreciated.

Ed