#include <iostream>   //C++ example
#include <fstream>
#include <cstdlib>
#include <cerrno>     //for errno
#include <cstring>    //for strerror
using namespace std;

int main(int argc, char **argv)
{
	fstream fstr("file", ios_base::in | ios_base::out | ios_base::trunc);
	if (!fstr) {        //if (fstr.operator!()) {
		cerr << "can't open file: "<< strerror(errno) << ".\n";
		return EXIT_FAILURE;
	}

	fstr << "hello\n" << flush;

	cout << "input position == " << fstr.tellg() << "\n";
	if (!fstr) {
		cerr << "can't tellg: " << strerror(errno) << ".\n";
		return EXIT_FAILURE;
	}

	fstr.seekg(0);      //rewind file back to beginning
	if (!fstr) {
		cerr << "can't seekg: " << strerror(errno) << ".\n";
		return EXIT_FAILURE;
	}

	cout << "input position == " << fstr.tellg() << "\n";
	if (!fstr) {
		cerr << "can't tellg: " << strerror(errno) << ".\n";
		return EXIT_FAILURE;
	}

	char buffer[256];   //uninitialized variable
	if (!(fstr >> buffer)) {
		cerr << "can't read from file.\n";
		return EXIT_FAILURE;
	}

	cout << buffer << "\n";
	return EXIT_SUCCESS;
}