Thread: File I/O difficulty

Hi,

1) Are you aware that arrays start at index position 0? In this code, you are starting at index position 1:

Code:

for (i=1; i <= size ; i++){
  
     infile >> num[i];

    }

How many digits do you think that code reads in? How many do you want to read in?

2)

I am able to read in the data, but since my size is fixed to 11 by the #define size 11 macro, I read 3 9 4 1 4 0 0 0 0 0 0 followed by extra zeros which I don't want to be read, when I just am trying to get
the exact 3 9 4 1 4 to be read, or 2 5 1 4 instead of 2 5 1 4 0 0 0 0 0 0 0.

What do you propose to have in the empty array spots rather than 0's? Junk integers?

3) Do you only want to read from the file once?

4) Is your ultimate goal to get the first 11 digits into an int variable, or do you need to keep them in an array?

Actually when using the >> operator you can do as he did. for example this program will provide the wanted output:

Code:

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

int main()
{
	ifstream fin("test.txt");
	int num;
	while(fin >> num)
		cout << num << endl;
}

In my test.txt I have 10 20 30 40 152 1 4835, which is displayed correctly.

And you can add and substract them since they are integers in the program.

Now to the original problem. I think what you want is a std::vector. Look it up at say www.cppreference.com

I don't really understand this post either:

Originally Posted by treenef

Try something like this.

HOWEVER, remember the number is stored as 'characters' NOT as an integer.
Use the atoi function if you actually want to add or subtract your numbers etc.

Code:

#include<iostream>
#include<fstream>
#include<string.h>

using namespace std;

int main()
{
    fstream file_pointer;
    file_pointer.open("new.txt",ios::in);
    
    char array[81];
    do{
        
        
        file_pointer>>array;
        cout<<array<<endl;
        
        
        
        
        cout<<"The first number is "<<array[0]<<endl;
        
        
        
        
        
      }while(file_pointer.peek()!=EOF); 
      
         
         
       int stop;
       cin>>stop;  
         
}

1)This:

file_pointer>>array;

continually reads one digit into array, and it overwrites the digit that was in array previously. So, after you have read in the whole file, there will be only one digit in array. Also, what's the point of reading in digits as chars, and then converting back to ints? Why not just read in the digits as ints, as the poster did?

2) How did you decide to declare array with a size of 81?

3)

Code:

while(file_pointer.peek()!=EOF);

That is a very inefficient way to loop through a file. It requires reading each number twice: once to peek, and once to actually read it in. This is what I generally do, but I don't know if it's the best way(everybody seems to do it differently ):

Code:

if(!inFile.eof())
{

}

But, when reading chars from a file using cin>> (or if there is a space after the last data in a file) there is a little problem actually reaching eof, so you have to do something like this:

Code:

inFile>>a_char;
while(!inFile.eof())
{
      inFile>>a_char;
}

4) This:

Code:

int stop;
       cin>>stop;

isn't exactly a user friendly way to keep the console window from disappearing. If I hit return, nothing happens. I have to specifically type in an int to get the program to end.