Thread: FILE I/0 and Structures

Hey;

I'm in the process of building a program that requires the use of a .txt file, however the values have to be loaded into a structure. In the end, the load process has to be in it's own function but i'm not worried about that at the moment. Here is something that i've been messing around with:

Code:

#include <iostream.h>
#include <conio.h>
#include <stdlib.h>
#include <fstream.h>

struct data
{
	char title[50];
	char author[50];
	int pages;
};


int main(void)
{
	int i;
                /*used for testing*/
	/*char title[20];
	char author[20];
	int pages;*/

//	void openFile(struct data structure[]);

	struct data structure[2];
	
	fstream in_file;

	in_file.open("a:test.txt",ios::in);

	if(!in_file)
	{
		cout<<" \nFile could not be found\nPress <ENTER> to exit..."<<endl;
		getch();
		exit(1);
	}

	
	while(!in_file.eof())
	{
		i++;
		in_file>>structure[i].title>>structure[i].author>>structure[i].pages;

		//used for testing
		/*in_file<<title<<author>>pages;
		cout<<" \n"<<title<<"\n"<<author<<"\n"<<pages<<endl;*/
		in_file.get();
	}

	in_file.close();

	cout<<"\n\n"<<structure[0].title
		<<"\n"<<structure[0].author 
		<<"\n"<<structure[0].pages
		<<endl;

	getch();

return 0;
}

Another problem that i'm running in to is that everytime i run the program, it creates the file, i don't want this to happen. I want my file check routine to kick in if the file isn't there. The file contains:
Book_Title Author 56

I'm pretty sure that the probem is in logic somewhere, but i just can see it.

Thanks in advanced;
S0n1C!

Code:

while(!in_file.eof())
	{
		i++; //could be anything
		in_file>>structure[i].title>>structure[i].author>>structure[i].pages;

		//used for testing
		/*in_file<<title<<author>>pages;
		cout<<" \n"<<title<<"\n"<<author<<"\n"<<pages<<endl;*/
		in_file.get();
	}

Don't control file input using eof().
Also i looks uninitialized - could have any value (including 0).

(Since you can't know how much data you are going to have, consider using std::vector<data>. Same goes for using std::string instead of char arrays - there's no telling how long a title may be.)

To stop it from creating a new file, don't use fstream - use ifstream, which is an input stream and just fails if the file doesn't exist.

Thanks, I'm pretty new to C++, if you couldn't tell, so i'm still getting use to the new language. Thanks for the suggestions, and help. I was wondering how to assign values to variables without knowing the length of the string.

Thank you for the help;
S0n1C!

Why not thank you guys? I am a n00b and i know that. so i bow down to you and thank you again for answering my n00b questions.

S0n1C!