dat.eof()

I got few questions about this code.

dat - is that a class in iostream? I tried looking it up on google, with no results. Weird.

Is "fstream" analogous to C's FILE structure?

I'd also like to know why my dat.write() wont work.

When i enter some data, and call dat.write to write the structure, the data doesnt appear in my file.

I also couldnt find dat.eof() with google. Is there a site that tells about these functions?

Code:

#include <iostream>
#include <fstream>
#include <cstdlib>

using namespace std;

struct tstudent {
	int mat_br;
	char prez_ime[35];
	int g_stu;
};

tstudent student;
fstream dat;
char naziv_datoteke[40];

void kreiranje_datoteke();
void unos_podataka_u_datoteku();
void ispis_podataka_o_svim_studentima();
void ispis_podataka_o_zadanom_studentu(int mb);

int main()
{
     
    int izbor,mbr;
    	cout << "Unesite naziv datoteke u koju cete spremati podatke:";
    	cin >> naziv_datoteke;
    do{
    	cout <<"Izaberite :" <<endl<<endl;
    	cout <<"1. Kreiranje datoteke"<<endl;
    	cout <<"2. Unos podataka u datoteku"<<endl;
    	cout <<"3. Ispis svih slogova iz datoteke"<<endl;
    	cout <<"4. Ispis podataka o zadanom studentu"<<endl;
    	cout <<"9. Izlaz iz programa"<<endl;
    	cin >> izbor;
    	switch (izbor){
    		case 1:kreiranje_datoteke();break;
    		case 2:unos_podataka_u_datoteku();break;
    		case 3:ispis_podataka_o_svim_studentima();break;
    		case 4:
    				cout << "Maticni broj studenta:";
    				cin >> mbr;
    				ispis_podataka_o_zadanom_studentu(mbr);
                    break;
        }
    } while (izbor != 9);

}

void kreiranje_datoteke(){
	char promjena;
	dat.open(naziv_datoteke,ios::in | ios::binary);
	if (!dat){
		dat.open(naziv_datoteke,ios::out | ios::binary);
		dat.close();
	}
	else

	{
		cout << "Datoteka " << naziv_datoteke << " vec postoji na disku." << endl;
		cout << "Ako ostane isti naziv datoteke, sadrzaj ce biti izbrisan."<<endl;
		cout << "Hocete li promijeniti naziv datoteke? (d/n) "<<endl;
		cin >> promjena;
		if (promjena=='n') return;
		cout << "Unesite naziv datoteke u koju cete spremati podatke:";
		cin >> naziv_datoteke;
		dat.open(naziv_datoteke,ios::out | ios::binary);
		dat.close();
	};
};

void unos_podataka_u_datoteku(){
	char dalje;
	dat.open(naziv_datoteke,ios::app | ios::binary);
	do{
		cout << "Maticni broj:";
		cin >> student.mat_br;
		cout << "Prezime i ime:";
		cin >> student.prez_ime;
		cout << "Godina studija:";
		cin >> student.g_stu;
		dat.write((char *) &student,sizeof(student));
		cout << "Dalje? (d/n)";
		cin >> dalje;
	} while (dalje=='d');
	dat.close();
};

void ispis_podataka_o_svim_studentima(){
	dat.open(naziv_datoteke,ios::in | ios::binary);
	while (1){
		dat.read((char *) &student, sizeof(student));
		if (dat.eof()) break;
		cout << "Maticni broj: " << student.mat_br << endl;
		cout << "Prezime i ime: " << student.prez_ime << endl;
		cout << "Godina studija: " << student.g_stu << endl;
	}
	dat.close();
};

void ispis_podataka_o_zadanom_studentu(int mb){
	int brojac=0;
	dat.open(naziv_datoteke,ios::in | ios::binary);
	while (dat.eof() == 0){
		dat.read((char *) &student, sizeof(student));
		if (student.mat_br==mb){
			cout << "Maticni broj: " << student.mat_br << endl;
			cout << "Prezime i ime: " << student.prez_ime << endl;
			cout << "Godina studija: " << student.g_stu << endl;
			brojac++;
		}
	}
	if (brojac==0)
		cout << "Student s maticnim brojem " << mb << " nije nadjen u datoteci."<<endl;
	dat.close();
};

dat is a variable in your code, of type fstream. Yes, fstream serves much the same purpose as FILE.

Originally Posted by Tool

dat - is that a class in iostream?

No, look at this line:

Code:

fstream dat;

Originally Posted by Tool

Is "fstream" analogous to C's FILE structure?

Yes, you might say that.

Originally Posted by Tool

I also couldnt find dat.eof() with google. Is there a site that tells about these functions?

There are many, e.g., cppreference.com

Code:

void unos_podataka_u_datoteku(){
	char dalje;
	dat.open(naziv_datoteke,ios::app | ios::binary);
	do{
		cout << "Maticni broj:";
		cin >> student.mat_br;
		cout << "Prezime i ime:";
		cin >> student.prez_ime;
		cout << "Godina studija:";
		cin >> student.g_stu;
		dat.write((char *) &student,sizeof(student));
		cout << "Dalje? (d/n)";
		cin >> dalje;
	} while (dalje=='d');
	dat.close();
};

Im still confused why this function wont write stuff to the file.

I tried dat.flush(), didnt help.

Change this line:

Code:

dat.open(naziv_datoteke,ios::app | ios::binary);

To this:

Code:

dat.open(naziv_datoteke, ios::out | ios::app | ios::binary);

That should get it to work.

Oh...make sure you take the semicolon off the end of that function. You have a semicolon after the closing curly-brace in the code you posted.

And some suggestions I have: try using ofstream instead of fstream, and try using the << (stream output) operator. Granted...it's not necessary that you do this, but it's what I suggest