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Read/Write from File into Array

closed account (2hTDizwU)
A bit different from my last post.

This assignment/program is suppose to read an external txt file (which looks like):
Book Title
Author
Price
Book Title
Author
Price
Etc...

change the price by giving it a 20% discount, and then write the information to a different txt file. We are suppose to use a header file, main file, and body file for some reason (practice, I guess). My program compiled without errors, but when I try to launch it, it gives a a bunch of errors stating:

Error 1 error LNK2005: "int bookCounter" (?bookCounter@@3HA) already defined in book.obj C:\Users\blind_000\documents\visual studio 2013\Projects\Lab02\Lab02\main.obj Lab02

Error 2 error LNK2005: "class std::basic_ifstream<char,struct std::char_traits<char> > infile" (?infile@@3V?$basic_ifstream@DU?$char_traits@D@std@@@std@@A) already defined in book.obj C:\Users\blind_000\documents\visual studio 2013\Projects\Lab02\Lab02\main.obj Lab02

and about 5 more like that. I have no idea what they mean. Any help would be appreciated.

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  //Header

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

using namespace std;

#ifndef BOOK_H
#define BOOK_H

ifstream infile;
ofstream outfile;
int bookCounter;

struct bookTable {
	string title, author;
	double price, newPrice;
};

void readCalc();

#endif 


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//book.cpp body

#include "book.h"

void readCalc() {

        bookTable Book[100];
        bookCounter = 0;

	infile.open("books.txt");

	if (!infile) {
		cout << "Unable to open Books.txt" << endl;
		return;
	}

	for (int i=0; !infile.eof(); i++) {

		getline(infile,Book[i].title);
		getline(infile, Book[i].author);
		infile >> Book[i].price;

		Book[i].newPrice = Book[i].price * .8;
 		
		bookCounter++;
	}

	infile.close();


	outfile.open("sales.txt");

	for (int i = 0; i <= bookCounter; i++) {

		outfile << Book[i].title << endl;
		outfile << Book[i].author << endl;
		outfile << Book[i].newPrice << endl;
	}

	outfile.close();
}


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//main.cpp file

#include "book.h"

int main() {

	readCalc();

	cout << "Sales.txt has been created." << endl;

	return 0;
}
Last edited on
ne555 (10692)
closed account (2hTDizwU)
I'm not sure I fully understand the difference between define and declare. I've updated my code as can be see in the original post. It removed one of the 5 errors of when I try to run the program but the rest are still there. I have no idea what I'm missing :(
ne555 (10692)
> when I try to run the program
No, the error is at build time, there is no program to run because it was not generated.


In your header
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extern ifstream infile;
extern ofstream outfile;
extern int bookCounter;


In one source file 
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ifstream infile;
ofstream outfile;
int bookCounter;



¿Do you really need them to be global?
Last edited on
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