edit: trouble checking if file is empty or not, what am I doing wrong?

Question

Edit: changed my question to be more accurate of the situation

I'm trying to open up a text file (create it if it doesnt exist,open it if it doesnt). It is the same input file as output.

ofstream oFile("goalsFile.txt");
fstream iFile("goalsFile.txt");
string goalsText;   
string tempBuffer;
//int fileLength = 0;
bool empty = false;

if (oFile.is_open())
{
    if (iFile.is_open())
    {
        iFile >> tempBuffer;
        iFile.seekg(0, iFile.end);
        size_t fileLength = iFile.tellg();
        iFile.seekg(0, iFile.beg);
        if (fileLength == 0) 
        {
            cout << "Set a new goal\n" << "Goal Name:"; //if I end debugging her the file ends up being empty
            getline(cin, goalSet);
            oFile << goalSet;
            oFile << ";";
            cout << endl;

            cout << "Goal Cost:";
            getline(cin, tempBuffer);
            goalCost = stoi(tempBuffer);
            oFile << goalCost;
            cout << endl;
        }
    }
}

Couple of issues. For one, if the file exist and has text within it, it still goes into the if loop that would normally ask me to set a new goal. I can't seem to figure out what's happening here.

Answer 1

The problem is simply that you are using buffered IO streams. Despite the fact that they reference the same file underneath, they have completely separate buffers.

// open the file for writing and erase existing contents.
std::ostream out(filename);
// open the now empty file for reading.
std::istream in(filename);
// write to out's buffer
out << "hello";

At this point, "hello" may not have been written to disk, the only guarantee is that it's in the output buffer of out. To force it to be written to disk you could use

out << std::endl;  // new line + flush
out << std::flush; // just a flush

that means that we've committed our output to disk, but the input buffer is still untouched at this point, and so the file still appears to be empty.

In order for your input file to see what you've written to the output file, you'd need to use sync.

#include <iostream>
#include <fstream>
#include <string>

static const char* filename = "testfile.txt";

int main()
{
    std::string hello;

    {
        std::ofstream out(filename);
        std::ifstream in(filename);
        out << "hello\n";
        in >> hello;
        std::cout << "unsync'd read got '" << hello << "'\n";
    }

    {
        std::ofstream out(filename);
        std::ifstream in(filename);
        out << "hello\n";

        out << std::flush;
        in.sync();

        in >> hello;
        std::cout << "sync'd read got '" << hello << "'\n";
    }
}

The next problem you'll run into trying to do this with buffered streams is the need to clear() the eof bit on the input stream every time more data is written to the file...