CODEWITHSUNDEEP
c++line
user3668051
user3668051

Reputation: 77

How to read line by line

i am just a beginer in c++ so please do not judge me hard. Probably this is silly question but i want to know.

i have a text file like this(there always will be 4 numbers, but the count of rows will vary):

5 7 11 13
11 11 23 18
12 13 36 27
14 15 35 38
22 14 40 25
23 11 56 50
22 20 22 30
16 18 33 30
18 19 22 30

And here is what i want to do: i want to read this file line by line and put each number into variable. Then i will do some functions with this 4 numbers and then i want to read the next line and again do some functions with this 4 numbers. How can i do that? This is as far as i am

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

int main()
{
    int array_size = 200;
    char * array = new char[array_size];
    int position = 0;

    ifstream fin("test.txt");

    if (fin.is_open())
    {

        while (!fin.eof() && position < array_size)
        {
            fin.get(array[position]); 
            position++;
        }
        array[position - 1] = '\0'; 

        for (int i = 0; array[i] != '\0'; i++)
        {
            cout << array[i];
        }
    }
    else
    {
        cout << "File could not be opened." << endl;
    }
    return 0;
}

but like this i am reading whole file into array, but i want to read it line by line, do my function and then read the next line.

Upvotes: 4

Views: 1151

Answers (1)

Malcomar
Malcomar

Reputation: 124

For reading data from file I find the stringstream really helpful.

What about something like this?

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <sstream>

using namespace std;

int main()
{
  ifstream fin("data.txt");
  string line;

  if ( fin.is_open()) {
    while ( getline (fin,line) ) {
      stringstream S;
      S<<line; //store the line just read into the string stream
      vector<int> thisLine(4,0); //to save the numbers
      for ( int c(0); c<4; c++ ) {
        //use the string stream as a new input to put the data into a vector of int    
        S>>thisLine[c]; 
      }
      // do something with these numbers
      for ( int c(0); c<4; c++ ) {
        cout<<thisLine[c]<<endl;
      }  
   }
}
else
{
   cout << "File could not be opened." << endl;
}
return 0;
}

Upvotes: 2

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