Why is my Library Management program not writing to file - c++

Question

I am creating a library Management which you can add books, dvds and students to. The books and dvds can then be issued to the Students. The books, dvds and students are written to a .dat file.
The problem I am having is that the program doesn't seem to be writing the students to the .dat file and therefore when I search for a student or try to issue a book student it doesn't find the student, it gives me an error saying student not found. Can someone tell me what I am doing wrong.
I have included some of the code below.
Main.cpp
#include <iostream>
#include "Library.h"
int main() {
Library lib1;
while(1)
{
char studentOption;
char name[30];
std::cout<<"1 to add a new student\n";
std::cout<<"2 to search for a student\n";
std::cin.getline( name, 80);
studentOption = name[0];
switch(studentOption){
case '1':
lib1.insertStudent();
break;
case '2':
char regno[6];
std::cout<<"Enter the registration no. of the student you want to search: \n";
std::cin>>regno;
lib1.searchStudent(regno);
break;
}
};
return 0;
};
Library.h
#ifndef _Library_H_
#define _Library_H_
#include <stdio.h>
class Library
{
public:
void insertStudent();
void searchStudent(char regno[]);
};
#endif
Library.cpp
#include <iostream>
#include <fstream>
#include "Library.h"
#include "Student.h"
Student student1;
void Library::insertStudent()
{
std::fstream file;
file.open("student.dat",std::ios::out|std::ios::app);
student1.newStudent();
file.write((char*)&student1,sizeof(Student));
file.close();
}
void Library::searchStudent(char regno[])
{
std::fstream file;
int flag=0;
file.open("student.dat",std::ios::in);
while(file.read((char*)&student1,sizeof(Student)))
{
if((strcmp(student1.retregistrationNo(),regno)==0))
{
student1.displayStudent();
flag=1;
}
}
file.close();
if(flag==0)
std::cout<<"Error: Student not found in the system. \n";
}
Student.cpp
#include "Student.h"
void Student::newStudent()
{
std::cout<<"Enter the registration no. \n";
std::cin>>registrationno;
std::cin.ignore();
std::cout<<"Enter the name of the student \n";
fgets(name, sizeof(name), stdin);
stbookbar[0]='/0';
std::cout<<"Student added to system.\n";
}
void Student::displayStudent()
{
std::cout<<"Enter the registration no. : \n";
std::cin>>registrationno;
std::cin.ignore();
std::cout<<"Enter the name of the student: \n";
puts(name);
}
Student.h
#ifndef STUDENT_H_
#define STUDENT_H_
#include <iostream>
#include <fstream>
class Student
{
char registrationno[6];
char name[20];
char stbookbar[6];
char stdvdbar[6];
public:
void newStudent();
void displayStudent();
char* retregistrationNo()
{
return registrationno;
}
};
#endif

Answer 1

Although the following my not be the exact cause of your issue, they may lead to issues.
Use string not char*
There are soo many ways that a program can fail by using C-Style (char *) strings. There is also the issue of memory management.
Use std::string instead. If you need fixed record lengths, this can be handled at the point when you write the data. All other times you should be using std::string.
Also, you can use operator == with std::string instead of strcmp. The strcmp function will invoke undefined behavior if the two strings are not nul terminated.
Avoid fgets
There are buffer overflow and other issues with fgets. Use std::getline and std::string instead. This combination will handle expanding a string as required. It's safer.
Don't cross the streams
Be consistent, use C++ streams or C-style I/O, don't mix the two. For example, you use cout and in the same function, puts. There is a possibility that the two can use different I/O buffers. I don't see why you don't use cout << name;.
Use Boolean types, not 1 & 0
The C++ language has a type to represent true and false values. The type is bool, use it. The 1 and 0 representation of Boolean values is sooo old fashioned (like circa 1966). Move on to more readable code.
With integers, is the value 3 true or false? What about -1? From reading the code, there are a lot more reasons why an integer is set to 0 than setting a Boolean variable to false.
Readable code prevents many defects.
Use block statements, always.
All if, for, while, do-while should use blocks
Change your coding style to use '{' and '}' for single line and multi-line statements.
Avoid Magic Numbers
A magic number is a numeric constant without any description. Prefer named identifiers instead. Named identifiers make the code easier to read and easier to maintain.
For example, say you have a text field that has a capacity of 23 characters. If you change the capacity to 32, you will have to find every occurrence of 23, figure out if the instance applies to the text field, then modify them. With a named identifier, you would only make 1 change, and that is where the identifier is declared.
Use a debugger
Invest time now to learn to use a debugger. You'll find issues a lot faster on you own rather than having to wait for somebody to answer your post.
Use test cases
Design your program so it can read test cases. Place your data into a file and feed it to your program. Create test cases that pass. Create invalid test cases, these are the ones that will break your program. Can your program handle invalid input?
The test cases allow for automated testing your program. They also allow for consistent operation while you are debugging issues.
Edit 1: Comparing strings
Example:
std::string s1 = "Taco";
std::string s2 = "Salad";
if (s1 == s2)
{
cout << "s1 == s2\n";
}
if (s1 == "burrito")
{
cout << "s1 == burrito\n";
}

Answer 2

As #NathanOliver already pointed out in the comments, you need to open the file in binary mode in order to read bytes and put them in the student1 variable
file.open("student.dat",std::ios::in | std::ios::binary);
and correct the inner code of
displayStudent()
as it will not display the desired results