how can i cast float to char to write on a file using write function in c++?

Question

I need to write float price on a file using write function not << operator but it crashes

int addDevice(fstream & f, Device & d)
    {
        char buffer[200];
        strcpy(buffer, d.id);
        strcat(buffer, "#");
        strcat(buffer, d.name);
        strcat(buffer, "#");
        short length = strlen(buffer) + sizeof(d.price);
        char c = '$';
            f.seekp(0, ios::end);
            f.write((char*) & c, 1);
            f.write((char*)&length, sizeof(length));
            f.write(buffer, length);
            f.write((char *) & d.price, sizeof(float));
            f.write((char *)'#', 1);
            f.seekp(0, ios::beg);
            return length;
    }

Answer 1

The problem is likely to be the line

f.write((char *)'#', 1);

This reinterprets the numerical value of '#' (ie, 35) as a memory address, dereferences that address and would write the byte at that address into f if that address were valid, which it isn't. This is where you get undefined behaviour and probably a crash (although you can't depend on it that this sort of thing always crashes).

I think you want

f.put('#');