Simple read from text file algorithm doesn't work

Simple read from text file algorithm doesn't work

I have a text file that contains keys and values like this:
keyOne=1
keyTwo=734
keyThree=22.3
keyFour=5
The keys are just lower-case and upper-case letters like in my example.
The values are either integers or floats. Each key and value is separated
by an equals sign (=). Now I want to read the values into variables I have
in my program.
This is the code I have tried to read the values: (I omitted the part
where I store the values in my program's variables, and just print them
out now for demonstration.)
std::fstream file(optionsFile, std::fstream::in);
if (file.good()) {
int begin;
int end;
std::string line;
while(std::getline(file, line)) {
// find the position of the value in the line
for (unsigned int i = 0; i < line.length(); i++) {
if (line.at(i) == '=') {
begin = i + 1;
end = line.length();
break;
}
}
// build the string... it starts at <begin> and ends at <end>
const char *string = "";
for (int i = begin; i < end; i++) {
string += line.at(i);
}
// only gibberish is printed in the following line :(
std::cout << "string=" << string << std::endl;
}
}
I don't understand why it won't print the value.. instead only weird stuff
or even nothing is printed
Please help this broke my spirit so hard :(