C/C++ :: File String Replace Algorithm?

I adapted the code from the following: [URL]

To replace a string in my file with another. The file contents look like the following:

abc 123 0

"abc"= The username
"123"= Their password
"0"= The amount in their bank

I want to change their bank amount.

But, it isn't working, nor is it even giving me an error code.

// When the user logs out, make changes to their bank
string strNew = std::to_string(player.bank); // String representation of the revised player bank
ifstream filein("user_accounts.txt"); // Old repository of player data
ofstream fileout("user_accounts_new"); // New repository of player data

[Code].....