CODEWITHSUNDEEP
c++filefile-handling
Siddhartha Sinha
Siddhartha Sinha

Reputation: 61

Error in File handling C++

The code goes like this 

ofstream f("bank.dat", ios::app);
ifstream fa("bank.dat");
int n = 0, flag = 0;
struct bac
{
    char name[10];
    char amt[5];
} s;

void add()
{ 
    cout << "\nenter the details ";
    cin >> s.name >> s.amt;
    f.write((char *)&s, sizeof(bac));

}

void ser()
{
    ifstream fa("bank.dat");
    fa.seekg(0);
    char x[10];
    cout << "\nenter value to be searched ";
    cin >> x;

    while (fa && flag == 0)
    {
        n++;
        fa.read((char *)&s, sizeof(bac));
        if (strcmp(s.name, x) == 0)
        {
            flag = 1;
            break;
        }
    }
    if (flag == 1)
    {
        cout << "\nfound";
        cout << "\nAmount " << s.amt;
    }


}

void mod()
{
    ser();
    cout<<" "<<n;
    if (flag == 1)
    {
        f.seekp((n - 1) * sizeof(bac));
    //  cout<<f.tellp();
        cout<<"\nnew details ";
        add();
    }
}


int main()
{f.seekp(0);
    int ch;

        cout << "\nBANK MANAGEMENT SYSTEM \n";
        cout << "enter choice ";
        cout << "\n1.add\n2.search\n3.delete and overwrite ";
        cin >> ch;
        if (ch == 1)
        {
            add();
        }
        if (ch == 2)
        {
            ser();
        }
        if (ch == 3)
        {
            mod();
        }

    return 0;
}

What I am trying to do is to make a program with search , display and modify functions ;

ERROR

The record gets appended at the last , even when i use 

f.seekp((n - 1) * sizeof(bac));

OPERATIONS PERFORMED

*add sid , sar named entries with amts 5,6 respectively

*replace sid named entry with name : sid (same as original ) amt :7

THE OUTPUT IN FILE

EXPECTED sid 7 sar 6

FOUND sid 5 sar 6 sid 7

Upvotes: 0

Views: 147

Answers (2)

Kevin MOLCARD
Kevin MOLCARD

Reputation: 2218

I think this is because you are using ios::app flag.

As it is written here:

app:    (append) Set the stream's position indicator to the end of the stream before each output operation.

Upvotes: 1

Amit
Amit

Reputation: 697

Reinitialize 'n = 0' at the beginning of ser() operation. Currently you keep increasing 'n' everytime search is called and that's the reason record gets appended to the end of file. I would advise not to use global vars 'n' and 'flag', rather return these values e.g. 

int ser()
{
    // return n if search succeeds else return '-1'.
}

I see it could be improved in various ways, perhaps take a look at example code on IO in standard book.

Upvotes: 1

Related Questions