How to accept an unknown number of lines in c++, each line has two strings

Question

How do I accept an unknown number of lines in c++? Each line has two strings in it separated by a space. I tried the solutions mentioned in This cplusplus forum , but none of the solutions worked for me. One of the solutions works only when Enter is pressed at the end of each line. I am not sure if the \n char will be given at the end of my input lines. What are my options?

My current attempt requires me to press Ctrl+Z to end the lines.

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

int main(){
    string line; 
    while(cin>>line and cin.eof()==false){
        cout<<line<<'\n';
    }
    return 0;
}

I would like to take an unknown number of strings as shown below:

cool toolbox
aaa bb
aabaa babbaab

Please don't flag this as a duplicate, I really tried all I could find, I tried the following solution on the above given link by m4ster r0shi (2201). but it did not work for me.

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

using namespace std;

int main()
{
    vector<string> words;

    string word;
    string line;

    // get the whole line ...
    getline(cin, line);

    // ... then use it to create
    // a istringstream object ...
    istringstream buffer(line);

    // ... and then use that istringstream
    // object the way you would use cin
    while (buffer >> word) words.push_back(word);

    cout << "\nyour words are:\n\n";

    for (unsigned i = 0; i < words.size(); ++i)
        cout << words[i] << endl;
}

And this other solution also did not work: other soln , and I tried this SO post too: Answers to similar ques . This one worked for my example, but when I pass only one line of input, it freezes.

// doesn't work for single line input 
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector> 
using namespace std;

int main(){
    string line ="-1"; 
    vector<string>data;
    while(1){
        cin>>line;
        if(line.compare("-1")==0) break;
        data.push_back(line);
        line = "-1";
    }
    for(int i =0;i<data.size();i+=2){
        cout<<data[i]<<' '<<data[i+1]<<'\n';
    }
    return 0;
}

Answer 1

If each line has two words separated by whitespace, then perhaps you should have a Line struct which contains two std::string s and overloads the >> operator for std::istream .

Then you can just copy from std::cin into the vector.

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>

struct Line {
    std::string first;
    std::string second;
};

std::istream& operator>>(std::istream& i, Line& line) {
    return i >> line.first >> line.second;
}

int main() {
    std::vector<Line> lines;

    std::copy(
      std::istream_iterator<Line>(std::cin),
      std::istream_iterator<Line>(),
      std::back_inserter(lines)
    );

    for (auto &[f, s] : lines) {
        std::cout << f << ", " << s << std::endl;
    }

    return 0;
}

A test run:

% ./a.out                
jkdgh kfk
dfgk 56
jkdgh, kfk
dfgk, 56