C++ Why is this hapenning when trying to read form file and seperate into different variables?

Question

So there is the inputs.txt file looking like this

john connor
neil young
cat stevens

and after seeing this question, I'm trying to read it like this

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

using namespace std;

int main() {

        ifstream inputFile("inputs.txt");

        string s1, s2;
        string line;
        stringstream sline;

        while ( getline(inputFile, line) ) {

                sline.str(line);

                sline >> s1 >> s2;

                cout << "Just read: " << s1 << " " << s2 << endl;
        }

        inputFile.close();
        return 0;
}

but the output I get is

Just read: john connor
Just read: john connor
Just read: john connor

Why is this happening? What am I getting wrong? Any help would be appreciated!

Edit: After fixing my problem using rafix07's comment, I noticed that if I add a few empty lines in the inputs.txt file the output I get is

john connor
neil young

cat stevens

the output I get is

Just read: john connor
Just read: neil young
Just read: neil young
Just read: cat stevens
Just read: cat stevens
Just read: cat stevens

(which is not wanted behavior)

After `>> s1 >> s2`, your stringstream is in bad state - `eof()` returns true (any future read operation must fail, and s1 and s2 are not modified printing data entered in first iteration). So move stringstream into while body scope, or call `clear()` to reset flags before reading new data at every iteration of loop. — rafix07, Mar 13 '20 at 14:18
@rafix07 Thank you, it worked! But why is it in bad sate after the `>> s1 >> s2` expression? — Da Mike, Mar 13 '20 at 14:33

srilakshmikanthanp · Answer 1 · 2020-03-13T15:45:20.583

As mentioned in comment put

    sline.clear();

in while loop,this resets I/O Status.Because after this sline >> s1 >> s2; the eof bit is set to true.

see this:

    while ( getline(inputFile, line) )
    {
            sline.clear();

            sline.str(line);

            sline >> s1 >> s2;

            cout << "Just read: " << s1 << " " << s2 << endl;
    }

You can also simply the code as follow:

 #include <iostream>
 #include <fstream>
 #include <string>
 #include <stdlib.h>

 int main() 
 {

         std::ifstream inputFile("inputs.txt");

         if(inputFile.is_open()==0)
         {
             std::cout<<"File Error";
             exit(1);
         }

         std::string line;

         while ( getline(inputFile, line) )
                    std::cout << "Just read: " <<line << std::endl;

         inputFile.close();
         return 0;
 }

EDIT:

if you want separate two strings try this

    std::string s1,s2;

    while ( inputFile>>s1>>s2 )
               std::cout << "Just read: " <<s1<<" "<<s2 << std::endl;

Thanks for your answer! The thing is I want to separate each line in two variables s1 and s2. So the last piece of code is not what I need. — Da Mike, Mar 13 '20 at 15:41
@Da Mike If you want to separate into two variables you can also try, i mentioned it in the EDIT — srilakshmikanthanp, Mar 13 '20 at 15:47

C++ Why is this hapenning when trying to read form file and seperate into different variables?

1 Answers1