Inputting values into an array from a file with C++

Question

The file does open and I get the message "File opened successfully". However I can't input data from the array in file "random.csv" into my inputFile object.

The data in random.csv is:

Boston,94,-15,65

Chicago,92,-21,72

Atlanta,101,10,80

Austin,107,19,81

Phoenix,112,23,88

Washington,88,-10,68

Here is my code:

#include "main.h"

int main() {

    string item; //To hold file input
    int i = 0;
    char array[6];
    ifstream inputFile;
    inputFile.open ("random.csv",ios::in);

    //Check for error
    if (inputFile.fail()) {
        cout << "There was an error opening your file" << endl;
        exit(1);
    } else {
        cout << "File opened successfully!" << endl;
    }

    while (i < 6) {
        inputFile >> array[i];
        i++;
    }

    for (int y = 0; y < 6; y++) {
        cout << array[y] << endl;
    }


    inputFile.close();

    return 0;
}

Hint: `char array[6]` can only hold 5 characters (1 byte each) — CinCout, Sep 24 '18 at 05:01
Don't forget arrays of chars should be terminated with null! — TheEngineer, Sep 24 '18 at 05:05
Better: Don't use arrays of `char` for strings in C++. Use `std::string`. — Swordfish, Sep 24 '18 at 05:08
@TheEngineer good point but that is not their problem. Output will terminate properly if he manages to read from file to buffer correctly. — teukkam, Sep 24 '18 at 05:08
That should print out B o s t o n, one character per line. Is it doing something else? — Shawn, Sep 24 '18 at 05:16
Program looks good to me (as far as it goes). What do you see when you try to run it? 'I can't input data' is not a good enough problem description. — john, Sep 24 '18 at 06:19
@CinCout A char array of size 6 can hold 6 chars. What makes you think any different? There's no requirement in the OPs program for a nul terminator. — john, Sep 24 '18 at 06:20
Possible duplicate of [Using getline with CSV](https://stackoverflow.com/questions/12234678/using-getline-with-csv) — kelalaka, Sep 24 '18 at 08:13

Constantinos Glynos · Answer 1 · 2018-09-24T11:32:20.817

Hello and welcome to Stack Overflow (SO). You can use std::getline() to read each line from the file, and then use boost::split() to split each line into words. Once you have an array of strings for each line, you can use a container of your liking to store the data.

In the example below I've used an std::map that stores strings and a vector of ints. Using a map will also sort the entrances using the key values, which means that the final container would be in alphabetical order. The implementation is very basic.

#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <fstream>
#include <boost/algorithm/string.hpp>
#include <boost/algorithm/string/split.hpp>
#include <ctype.h>

typedef std::map<std::string,std::vector<int>> ContainerType;

void extract(ContainerType &map_, const std::string &line_)
{
    std::vector<std::string> data;

    boost::split(data, line_, boost::is_any_of(","));

    // This is not the best way - but it works for this demo.
    map_[data[0]] = {std::stoi(data[1]),std::stoi(data[2]),std::stoi(data[3])};
}

int main()
{
    ContainerType map;

    std::ifstream inputFile;
    inputFile.open("random.csv");

    if(inputFile.is_open())
    {
        std::string line;
        while( std::getline(inputFile,line))
        {
            if (line.empty())
                continue;
            else
                extract(map,line);
        }
        inputFile.close();
    }

    for (auto &&i : map)
    {
        std::cout<< i.first << " : ";
        for (auto &&j : i.second)
            std::cout<< j << " ";
        std::cout<<std::endl;
    }
}

Hope this helps.

Inputting values into an array from a file with C++

1 Answers1