Write/Read struct array data table C++ - c++

Question

Im fairly new to c++ and I've spent about six hours on this, sadly with no result.
im trying to do the following. (for my own practice)
Make a navigation menu like in cmd. #done
Create two structs with the concept of "uml aggregation" #done
Make function for input, output, sort by a value, etc. #done
Write everything to a file #Struggling from this point.
Read back from the file.
Use the data later(sort by name, delete last object, add new...etc)
I have a massive code that I think will be silly to post (and a waste of time) so I'll just post a simpler version.
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string.h>
using namespace std;
struct man{
char name[20];
int age;
};
struct group{
man* men[3];
};
void fill( man &y);
void show( man &y);
void input(group &x, man &y);
void output(group &x, man &y);
int main(){
man q;
group w;
input(w, q);
cout<<endl;
output(w, q);
ofstream w1file("B.dat");
for (int i=0; i<2; i++){
w1file.write((char*) &w.men[i]->name, 20);
w1file.write((char*) &w.men[i]->age, sizeof(int));
}
w1file.close();
ifstream r1file("B.dat");
while(r1file.good()){
r1file.read((char*) &w.men[0]->name, 20);
r1file.read((char*) &w.men[0]->age, sizeof(int));
r1file.read((char*) &w.men[1]->name, 20);
r1file.read((char*) &w.men[1]->age, sizeof(int));
}
output(w, q);
r1file.close();
system("pause");
return 0;
}
void fill( man &y){
gets(y.name);
cin>>y.age;
cin.ignore();
}
void show( man &y){
cout<<y.name<<endl;
cout<<y.age<<endl;
}
void input(group &x, man &y){
x.men[2]= new man[2];
for (int i=0; i<2;i++){
fill(y);;
x.men[i]= new man(y);
}
}
void output(group &x, man &y){
for (int i=0; i<2;i++){
show(*x.men[i]);
}
}
if i remove the writing part, then the program just crashes as soon as i press run.
ive tried it like this, and with file>>"variable"... ive tried it with only first element...tried to copy the whole thing to an array, write the array and then read it, but nothing works :(
I also want it to output the data in the file like this: (example)
#in the txt, dat, whatever
John 21
Pier 18...etc
So i can edit the data directly from the written file.
but what im getting is this:
John н# А…J { Adam ed н# А…J Х
My initial idea was to make a program that outputs data to files in the form of tables(hope you understand me)
exmpl.
name1 age1 wage1 married/not married1
name2 age2 wage2 married/not married2
name3...age3...etc
Can someone from heaven please help me with this and if possible explain what im doing wrong?

Answer 1

for (int i; i<2; i++){
Looks at this line, until you see the problem. Keep looking at it, until you do.
Hint: what do you expect the first value of i to be, in this loop?
P.S.: Why are you allocating a single instance of man, for men[0] and men[1], and two instances of man, for men[2]?

Answer 2

There are several problems:
The writing for uses an uninitialized variable i, so that it starts with an undetermined value. Try :
for (int i=0; i<2; i++){ //i=0 !!
Then you write binary data in a file open in the default text mode. This can, depending on the binary value and the operating system alter what is effectively written in the file. So:
ofstream w1file("B.dat", ios::binary); // binary mode instead of text mode
The same applies of course to the reading stream.
Note that you could have from 0 to 3 men in the group. It would be wise to write at the beginning of the group the number of items. So when reading the group you could first read the number of items to be expected and loop until you have read them all. Your current reading loop is weird, as it will read the file and constantly overwrite the 2 first mens (if there are more data in the file).
The way you could properly read would be:
const int maxmen=3;
for (int i=0; i<maxmen && r1file.read((char*) &w.men[i]->name, 20)
&& r1file.read((char*) &w.men[0]->age, sizeof(int)); i++)
cout << "Successfuly read item "<<i<<endl;
}
Note also that this code is heavily leaking memory.