Question about seekg() function of ifstream in C++?

I am testing the following code:

int _tmain(int argc, _TCHAR* argv[])
{
    int sum = 0;
    int x;
    ifstream inFile;

    inFile.open("test.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1); // terminate with error开发者_开发知识库
    }

    while (inFile >> x) {
        cout << x << endl;
    }
    cout << "-----------------------------" << endl;
    // Reading from beggining file again
    inFile.seekg(0, ios::beg);
    while (inFile >> x) {
        cout << x << endl;
    }

    inFile.close();

    return 0;
}

In the above code, I want to read the file then moving the pointer to the beginning of the file and read again. I have used inFile.seekg(0, ios::beg); to get back to the beginning of the file but it does not work? Can anyone help me, please? Thanks

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Before you seek to the beginning, you need to clear all error flags, else no operations are done on the stream:

inFile.clear();
inFile.seekg(0,std::ios::beg);

That's because the eof bit will be set, because you reached the end of the file before.

---

I think you have to reset the error flags of the ifstream by inFile.clear(). Otherwise it still thinks it has reached the end of file.

---

int autoinc()   //auto incriment no//
{
    fstream fp;

    fp.open("birthreg.dat",ios::in);

    fp.seekg(0,ios::beg) ; **//what used this function**

        int t=0;

    while(fp.read((char*)&st,sizeof(birthreg)))

    t=reg_no;

    fp.close();

    return t;

}