Random Access in Text Files

I have an text file that stores the details of objects of an account class. I need to be able to search the text file based on what account number the user has entered. each account number is a 4 digit integer.
I have it working for the first line of a file but i dont know how I can move it on to search the start of the next line of the file. This is the code taht i have so far.

char card[5];
char c;
long int file_pos, last_pos;
string line;

cin >> card;

ifstream in("account.txt") ;

while (!in.eof())
{
getline(in, line);
cout <<line<<endl;
file_pos = line.find(card);
}

Any help would be appreciated. I have not been able to find a tutorial on the web to explain this to me.

You can't use the seek functions (find in the iostream library) for text mode files. Well, you can, but it won't give you the expected results. They can be used only in binary files. You must read the file from the beginning and search for the place you want in memory.