std::getline does not work inside a for-loop

c++, getline

Solution

You can see why this is failing if you output what you stored in `local` (which is a poor variable name, by the way :P):

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;
int main()
{
    int n;
    cin >> n;
    for(int i = 0; i < n; i++)
    {
        string local;
        getline(cin, local);
        std::cout << "> " << local << std::endl;
    }

    //............................
    return 0;
}

You will see it prints a newline after `>` immediately after inputting your number. It then moves on to inputting the rest.

This is because `getline` is giving you the empty line left over from inputting your number. (It reads the number, but apparently doesn't remove the `\n`, so you're left with a blank line.) You need to get rid of any remaining whitespace first:

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;
int main()
{
    int n;
    cin >> n;
    cin >> ws; // stream out any whitespace
    for(int i = 0; i < n; i++)
    {
        string local;
        getline(cin, local);
        std::cout << "> " << local << std::endl;
    }

    //............................
    return 0;
}

This the works as expected.

Off topic, perhaps it was only for the snippet at hand, but code tends to be more readable if you don't have `using namespace std;`. It defeats the purpose of namespaces. I suspect it was only for posting here, though.

Problem

Original source