Thread: Reading text file twice, can it be done once?

  1. #1
    Registered User
    Join Date
    Jan 2006

    Reading text file twice, can it be done once?

    I am reading a text file of two-column numeric data. I do not know the number of rows that the file will contain. Currently, I read the file twice: Once to ascertain the length and the second time to fill the arrays with the data. Is there a way to create and populate the arrays while only having to read the text file once?

    Here is my current code:
    FILE* fid;
    double tempx, tempy;
    fid = fopen("c:/file.txt","rt");
    int i=0;
    while( fscanf(fid,"%le%le", &tempx, &tempy )!= EOF )
    rewind( fid );
    x = new double[i];
    y = new double[i];
    while (fscanf(fid,"%le%le", x+i, y+i)!= EOF)
    Thanks for your time.

  2. #2
    Frequently Quite Prolix dwks's Avatar
    Join Date
    Apr 2005
    x = new double;
    That's C++.

    If you're using C, go with realloc().

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  3. #3
    Registered User
    Join Date
    Jan 2006


    Good point, I really should have posted this in c++, but I was hesitant, because I wanted to stick with C file handling rather than c++ file handling.

    I'll move the post to the c++ board.

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