Random numbers, Symbols, Characters, in a stream C/C++

Question

Hi guys I'm new here and a little new in c/c++, I dont usually practise streams but when I tried to make one, opening my file created with this code I always get random numbers, chars, symbols and trash in the .txt file created. Like this: Hellothere.txt. I see random symbols, character instead of numbers entered, the name is OK because it shows well, but sometimes when I write long names it will write trash.

Can you help me to solve this?, Here's the code:

---

    struct sample {
       int code; 
       char name [20]; 
    } sampl;

    int main () {
        cout<<" ENTER CODE : "<<endl;
        cin>>sampl.code;

        cout<<" ENTER NAME :"<<endl;
        gets(sampl.name);

        fflush(stdin);

      FILE *fp;
      fp=fopen("Hellothere.txt", "rb+");

      if(fp==NULL) {

          fp=fopen("Hellothere.txt","wb+");
          if(fp==NULL) {
                puts("CANNOT OPEN");
                return 0;
          }
      }

        fwrite(&sampl,sizeof(sampl),1,fp);
        fclose(fp);

        getchar();
    }

Answer 1

You're mixing C++ and older C facilities for input and output. You'll have a much easier time if you stick to just C++.

First, let's replace your struct with the C++ equivalent:

struct sample {
    int code;
    std::string name;
};

Now name can hold as many characters as necessary.

We'll now write a function which will output a sample to a C++ output stream:

std::ostream& write_sample(std::ostream& os, const sample& samp)
{
    os << samp.code << "\n" << samp.name; 
    return os;
}

This will output the code followed by the name, with a newline in between them.

Now let's modify your main() routine to use C++ facilities to fill the struct:

int main()
{
    sample samp;

    cout << "ENTER CODE :\n";
    cin >> samp.code;

    cost << "ENTER NAME :\n";
    cin >> samp.name;
}

Now, we can quickly check whether we've got things right by using our write_sample() function with std::cout, which is a type of output stream:

write_sample(std::cout, samp);

This should repeat what you entered out to the console.

To write to a file instead, we can use C++ facilities to open a file stream:

std::ofstream outfile{"Hellothere.txt"};

Now, we can again use our write_sample() function with this new stream:

write_sample(outfile, samp);

And when your program runs, Hellothere.txt should contain the text you entered.

As a final (slightly more advanced) touch, you might want to rename your write_sample() function to operator<<, which will allow you to use the standard << streaming style:

outfile << samp;

Put it all together and the final code should look like this:

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

struct sample {
    int code;
    std::string name;
};

std::ostream& operator<<(std::ostream& os, const sample& samp)
{
    return os << samp.code << "\n" << samp.name;
}

int main()
{
    using namespace std;

    sample samp;

    cout << "Enter code:\n";
    cin >> samp.code;

    cout << "Enter name:\n";
    cin >> samp.name;

    std::ofstream outfile{"Hellothere.txt"};
    outfile << samp;
}