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I want to read the file(.txt) line by line but not in while loop(once reading whole fle). Currently I am reading the file once as whole. BUT what I want to do is to read one line than go back to normal MAIN function than later on call
and read the next line. Any help would be appreciated

NOTE:: Lines in .txt file are not same in size
5:50:12:560:434,    Rx, 7,  0x1E3,       00 80 2B 00 77 00 7D
5:50:12:560:615,    Ax, 4,  0x760,       00 12 84 41
5:50:12:560:826,    gc, 5,  0x2f1,       64 5A 43 20 4E

READ File function
	QString LFileName = "P_1.trc";
    QFile logfile(LFileName );
      QTextStream in(&logfile);
      while (!in.atEnd())
          QString fileLine = in.readLine(); //


What I have tried:

What i think i need to do is to keep previous line in pointer. And net time previous+1. but dont know how to read a specific line inside the document. if .txt file contain 1000000 line. how i can read line#670000 ???
Updated 21-Jun-16 4:01am

See : getline (string) - C++ Reference[^]
and count the lines until you get where you want (since you have variable length lines).
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XamBEE 21-Jun-16 7:39am    
BUT i want to avoid to read lines (n-1) to goto line n
Mehdi Gholam 21-Jun-16 9:18am    
You could create a line pointer index, but that is the same as reading all the lines in the first place (although if you intend to read the same file multiple times then it would make sense).
XamBEE 21-Jun-16 10:03am    
I just added the sample function of reading file. would be nice if you can tell me how to add line pointer.
Mehdi Gholam 21-Jun-16 10:06am    
Read each line and store the file pointer offset in an array, save that array for later.
Sergey Alexandrovich Kryukov 21-Jun-16 11:55am    
Since the lines of the file have different lengths, I see just two options, you either
  • Read the file line by line (that is call multiple times getline).

  • Read the file in big chunks and skip the unwanted lines in memory.
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XamBEE 21-Jun-16 8:23am    
Can you explain first options a bit. I dont know exactly how?
CPallini 21-Jun-16 8:44am    
It is what Mehdi Gholam already suggested. I know you don't like it, but there are no alternatives (other than finding yourself the newlines, as in option 2) because the file lines haven't the same length.
Sergey Alexandrovich Kryukov 21-Jun-16 11:55am    

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