Ifstream.getline() - Only reading first line? - c++

Question

I'm just trying to run a simple c++ program that will format a .txt file with data entries. I have run it with many different text files of the exact same format, and now it just won't work. I'm sure the solution is simple.
Here is a simplified version of the program (I trimmed down everything to only show the parts that are giving me trouble).
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <iomanip>
using namespace std;
int main(){
ifstream filei("in.txt");
ofstream fileo("comlab.txt");
double a, b;
string s;
stringstream ss;
while (getline(filei,s)){
ss<<s;
ss>>a>>b;
fileo<<setw(10)<<a<<setw(10)<<b<<'\n';
}
fileo.close();
}
Here is a sample input for in.txt:
1 11
2 22
3 33
4 44
5 55
Now here is what I want to show up (exactly the same as input):
1 11
2 22
3 33
4 44
5 55
But here is what actually shows up:
1 11
1 11
1 11
1 11
1 11
What is going on? I'm compiling with g++ and following the C++11 standard.

Answer 1

When you execute
ss>>a>>b;
in the first round of execution of the loop. ss is already at the end of the stream. i.e. ss.eof() == true. You need to clear its state and reset state to start reading from the beginning.
while (getline(filei,s)){
ss<<s;
ss>>a>>b;
ss.clear();
ss.seakg(0);
fileo<<setw(10)<<a<<setw(10)<<b<<'\n';
}
A better alternative is to create the object within the scope of the loop.
while (getline(filei,s)){
stringstream ss;
ss<<s;
ss>>a>>b;
fileo<<setw(10)<<a<<setw(10)<<b<<'\n';
}
or even simpler (Thanks to #vsoftco for the suggestion)
while (getline(filei,s)){
stringstream ss(s);
ss>>a>>b;
fileo<<setw(10)<<a<<setw(10)<<b<<'\n';
}