Thread: Printing files to the screen console

Hi there,

I made a program which contains car info... the car make and the mpg. Each car make/mpg is put into a structure and written into a file called cars.dat.

From there, I open the file cars.dat and go through to see if the mpg is > 30 or < 30. If it's >30 it gets put into the file Over30.dat, otherwise it gets put into Under30.dat. The program works well so far.

Here is my problem:

I'm having trouble figuring out how to print the contents from all 3 files to the screen. Essentially I want to print cars.dat, Over30.dat, and Under30.dat to the screen console so the program actually looks like it's doing something instead of doing everything "behind the scenes"

Code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

// put the data into a structure
struct Car {
	string make;
	int mpg;
};

int main()
{
	Car c1, c2, c3, c4, c5, c6, c7;
	
	// define each car
	c1.make = "Prius";
	c1.mpg = 45;
	c2.make = "Civic";
	c2.mpg = 35;
	c3.make = "Suburban";
	c3.mpg = 12;
	c4.make = "BMW";
	c4.mpg = 18;
	c5.make = "Mercedes";
	c5.mpg = 20;
	c6.make = "Siena";
	c6.mpg = 22;
	c7.make = "Focus";
	c7.mpg = 32;

	// put all the car info into cars.dat
	ofstream fout;
	fout.open("cars.dat", ios::binary);
	fout << c1.make << " " << c1.mpg << "\n";
	fout << c2.make << " " << c2.mpg << "\n";
	fout << c3.make << " " << c3.mpg << "\n";
	fout << c4.make << " " << c4.mpg << "\n";
	fout << c5.make << " " << c5.mpg << "\n";
	fout << c6.make << " " << c6.mpg << "\n";
	fout << c7.make << " " << c7.mpg << "\n";

	// open cars.dat and go through the structure classes and put the cars in their associated new files (either over30.dat
	// or under30.dat)

	fout.open("cars.dat");

	if(c1.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c1.make << " " << c1.mpg << "\n";
	}
		else {
			ofstream fout;
			fout.open("under30.dat", ios::app);
			fout << c1.make << " " << c1.mpg << "\n";
		}

	if(c2.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c2.make << " " << c2.mpg << "\n";
	}
		else {
			ofstream fout;
			fout.open("under30.dat", ios::app);
			fout << c2.make << " " << c2.mpg << "\n";
		}

	if(c3.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c3.make << " " << c3.mpg << "\n";
	}
		else {
			ofstream fout;
			fout.open("under30.dat", ios::app);
			fout << c3.make << " " << c3.mpg << "\n";
		}

	if(c4.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c4.make << " " << c4.mpg << "\n";
	}
		else {
			ofstream fout;
			fout.open("under30.dat", ios::app);
			fout << c4.make << " " << c4.mpg << "\n";
		}

	if(c5.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c5.make << " " << c5.mpg << "\n";
	}
		else {
			ofstream fout;
			fout.open("under30.dat", ios::app);
			fout << c5.make << " " << c5.mpg << "\n";
		}

	if(c6.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c6.make << " " << c6.mpg << "\n";
	}
		else {
			ofstream fout;
			fout.open("under30.dat", ios::app);
			fout << c6.make << " " << c6.mpg << "\n";
		}

	if(c7.mpg > 30) {
		ofstream fout;
		fout.open("over30.dat", ios::app);
		fout << c7.make << " " << c7.mpg << "\n";
	}
		else {
		ofstream fout;
		fout.open("under30.dat", ios::app);
		fout << c7.make << " " << c7.mpg << "\n";
		}

		// here is where i'm having trouble:
		char buf[80];
		ifstream printCars;
		printCars.open ("cars.dat", ios::in); 
		if (printCars.is_open() && printCars.eof())
		for(int i=0;i<80;i++)
			cout << buf[i];

		printCars.close();
		return 0;
}

I'm having trouble towards the bottom.

If someone could help me out with this, that'd be killer.

What exactly is the problem, other than the fact that you have 17 different variables named "fout" and who knows which ones are related? You will have to close your cars.dat file before you can try to read from it.

How exactly do I display the contents of all 3 files? Ok, say I close my cars.dat file...

I then put something like this:

Code:

		char buf[80];
		ifstream printCars;
		printCars.open ("cars.dat", ios::in); 
		if (printCars.is_open() && printCars.eof())
		for(int i=0;i<80;i++)
			cout << buf[i];

		printCars.close();

And it still won't output anything onto the screen.

You have to read from printCars into buf before you can print it.

Kinda confused. My apologies... can you point me into the right direction with some literature on this? I've been searching, but can't quite find anything to get me past this hump.

If "<<" goes out, then I would guess ">>" goes in.

Ok, cool. Got it. Thanks.