How do i convert a text file input to an array in c++

Question

Hi I have a text file of the format phonenumber housenumber firstname lastname

I'm trying to read all the data ans store it in an array. I have used the code below. But it is reading only first line data. Can anyone help me why this is happening.

#include <iostream>
#include <iomanip>
#include <fstream>
#include <string.h>
#define Size 200

unsigned long long int mobilenumber[Size];
char seatnumber[Size][4];
char firstname[Size][30],lastname[Size][30];

using namespace std;
int main()
{
    //delcares the files needed for input and output//
    ifstream infile;
    ofstream outfile;

    infile.open("reservations.txt",ios::in);
    //opens files needed for output//
    outfile.open("pricing.txt");
    int i=0;
    if (infile.is_open())
    {
        infile>> mobilenumber[i]>>seatnumber[i]>>firstname[i]>>lastname[i];
        i++;
        numberofbooking++;
    }
    infile.close();
    for(int i=0;i<=numberofbooking;i++)
    {
    cout<< mobilenumber[i]<<" "<< seatnumber[i]<<" "<< firstname[i]<<" "<< lastname[i];
    }
return 0;
}

Thanks in advance

You need a loop to read more than the first line. Instead of infile>> mobilenumber[i]>>seatnumber[i]>>firstname[i]>>lastname[i]; you want while (infile>> mobilenumber[i]>>seatnumber[i]>>firstname[i]>>lastname[i]) { i++; numberofbooking++;} — drescherjm
– drescherjm, Commented Apr 13, 2020 at 15:58
I did not post an answer because this is a very common type of problem. I expect there is a duplicate. — drescherjm
– drescherjm, Commented Apr 13, 2020 at 16:04

Object object · Accepted Answer · 2020-04-13 16:16:33Z

1

The reason it is reading only one line of data is because that is all you have told it to do. Here:

...
 if (infile.is_open())
    {
        infile>> mobilenumber[i]>>seatnumber[i]>>firstname[i]>>lastname[i];
        i++;
        numberofbooking++;
    }
...

This will run once, I think what you meant was a while loop:

while  (infile>> mobilenumber[i]>>seatnumber[i]>>firstname[i]>>lastname[i])
    {

        i++;
        numberofbooking++;
    }

This will do what you want, as long as 0 <= i <= 199, if i is outside that range then you will get undefined behaviour.

edited Apr 13, 2020 at 16:16

answered Apr 13, 2020 at 16:04

Object object

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Comments

dj1986 · Accepted Answer · 2020-04-13 17:21:21Z

0

Assuming you don't have data more than 200 in data file or your program will fail.

You are only reading once from the file so getting only first line data. You need to red from file till the EOF. add a while loop inside if(infile.is_open()){} . Read till EOF as below.

if (infile.is_open())
        {
            while (infile >> mobilenumber[i] >> seatnumber[i] >> firstname[i] >> lastname[i]) {
                cout << "Reading file" << endl;
                i++;
                numberofbooking++;
            }
        }

I don't see any benefit of i++ other than indexing. I think you can use numberofbooking for indexing as well.

Whenever you face such kind of issues, Try adding logs to check what is happening or use debugger. Hope this will help you.

edited Apr 13, 2020 at 17:21

answered Apr 13, 2020 at 16:39

dj1986

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1 Comment

dj1986 Over a year ago

@drescherjm make sense. Edited as per suggestion.

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