Cannot find the end of an array when opening a file

Question

So I want to open a file and display the contents. Thing is, I don't know how many elements are used and how many elements are empty. So, when I try to display the elements the first few are shown but the rest are random numbers. How do I find and display the exact number of elements?

file:

10011   Ali         Doha        12355555    11-5-14     3434    7890 
10015   Ahmed       Al-Khor     51244444    13-6-14     3425    4455 
10014   Mohammed    Al-Wakra    53344333    17-7-14     5566    1234 
10012   Omar        Doha        56666666    10-8-14     1234    5678 
10013   Youssef     Al-Khor     7555512     5-5-14      88000   4532 
10019   Hamad       Al-Wakra    81234567    8-6-14      3125    1265     
10018   Jassim      Doha        86753541    9-7-14      9875    5566

code:

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

using namespace std;


int main()
{
    const int isize=10;
    ifstream datafile;
    datafile.open("D:\customers.txt");
    int customer_number[isize];
    string customer_name[isize]; 
    string customer_address[isize]; 
    long contact[isize]; 
    string Due_date[isize]; 
    int water_consumption[isize]; 
    int electricity_consumption[isize];
    double total_bill[isize];
    if (!datafile)//to know if the file is exist or not
         cout << "error" << endl;
    else
    {
        for(int i=0; i<1000; i++)
        {
            datafile >> customer_number[i];
            datafile>> customer_name[i];
            datafile>> customer_address[i];
            datafile>> contact[i];
            datafile>> Due_date[i];
            datafile>> water_consumption[i];
            datafile>> electricity_consumption[i];}
    }

        for(int i=0; i<isize; i++)
        {
              if(customer_number[i] == '\0')
                      break;
          else
                  cout << customer_number[i] << "\t" << customer_name[i] << "\t" << customer_address[i] << "\t" << contact[i] << "\t"
                      << Due_date[i] << "\t" << water_consumption[i] << "\t" << electricity_consumption[i] << "\t" <<  endl;

   }
      datafile.close();
     return 0;
 }

I can't understand what do you want, can you please tell me what are you trying to do? What is empty and what are you trying to display... — Ahmed Hamdy, May 28 '14 at 18:10
see here's the thing, each array is 1000 elements long, but only 7 are used, how do I find out they're 7? — user3684811, May 28 '14 at 18:16
Each array is 1000 elements? Not in the posted code. They're all `const int isize=10;` dimensioned. Anything more than 10 iterations and you're blowing out your array. Not that you'd know it since you never check any boundaries nor any IO operations. — WhozCraig, May 28 '14 at 18:29
You have three options here. 1) add a number in the beginning telling you the number of preceding elements in the array. 2) add the each array element in a separate line. 3) make a separator, I mean assume that a character like `$` is the separator between each array elements and that char can't be used as a normal char — Ahmed Hamdy, May 28 '14 at 18:38
After the post modification, I saw the file better. You can easily read line by line and then split on space, or tab? — Ahmed Hamdy, May 28 '14 at 18:40
@user3684811 refer to this post, I think this is what you want >> [C++ Read file line by line then split each line using the delimiter](http://stackoverflow.com/questions/3910326/c-read-file-line-by-line-then-split-each-line-using-the-delimiter) — Ahmed Hamdy, May 28 '14 at 18:41

score 1 · Accepted Answer · answered May 28 '14 at 19:40

Looks like each text line is a record, thus use std::getline with std::string to read a record.

When the number of records is unknown, you need a dynamic container, such as std::vector, std::list or std::map, not a fixed size array.

You will need to research the std::string methods and also std::istringstream for parsing the text line into native format fields. There are lots of examples on StackOverflow on how to do this.

So stop using fixed size arrays and use std::vector instead.

Cannot find the end of an array when opening a file

1 Answers1