sorting C file numerically

Question

I have some structs in my file and I have to sort them numerically (I have to sort the ID of students for example) I wrote this but it doesn't work :

        int i = 0;
        fseek(fileKALAJADIDptr, 0, SEEK_SET);
        while (fread(&KJadid, sizeof(struct KalaJadid), 1, fileKALAJADIDptr))
        {
            int j = i + 1;
            fseek(fileKALAJADIDptr2, j * sizeof(struct KalaJadid), SEEK_SET);
            while (fread(&KJadid2, sizeof(struct KalaJadid), 1, fileKALAJADIDptr2))
            {
                if (KJadid.Tedad > KJadid2.Tedad)
                {
                    struct KalaJadid swap = KJadid;
                    KJadid = KJadid2;
                    KJadid2 = swap;

                    fwrite(&KJadid2, sizeof(struct KalaJadid), 1, fileKALAJADIDptr2);
                    fseek(fileKALAJADIDptr, i * sizeof(struct KalaJadid), SEEK_SET);
                    fwrite(&KJadid, sizeof(struct KalaJadid), 1, fileKALAJADIDptr);
                }
                j++;
            }
            i++;
        }

        fclose(fileKALAJADIDptr);
        fclose(fileKALAJADIDptr2);

first of all I point at the beginning of the file with fseek, then we have "while" for sorting ( I use selection sort ) but it doesn't work and I get run time error... what should I do?

openning file part :

FILE* fileKALAJADIDptr = fopen(fileKALAJADID, "r+b");
FILE* fileKALAJADIDptr2 = fopen(fileKALAJADID, "r+b");

if (fileKALAJADIDptr == NULL)
{
    fopen(fileKALAJADID, "w+");
}

here's the code: https://code.sololearn.com/c8Bh9vtao0C0/#cpp

Answer 1

Hey guys I found my answer.. I had to copy data in a structure array and sort the array then rewriting file with sorted structure array.