Simple code to get the user's home directory. With that information, it is much easier to get to a location on the hard drive such as documents or customization storage.

GetHome.cpp

#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    int myuid;
    passwd *homedir;
    myuid = getuid();
    homedir = getpwuid(myuid);

    string path = homedir->pw_dir;
    path += "/file.txt";
    cout << "File written to: " << path.c_str() << endl;

    ofstream myFile;
    myFile.open(path.c_str());
    myFile << "THIS IS SOME OUTPUT." << endl
           << "Hopefully there was nothing in this file, because it was just overwritten." << endl;
    myFile.close();
}
//NOTE: Unix uses "/" to delimit a directory level, you may need to change
//that in order for your program to work correctly in Windows.

//When putting in a file path for opening a file, you will need to use the c_str() method
//This is because the open method only accepts cstrings. The string type in C++ is a class.