Weird behaviour of stringstream?

Question

I am not able to understand why after reaching the last word it doesn't output blank or null character or garbage value or anything else . Why >> doesn't has any impact whatsoever after finishing the string .

#include <iostream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;
int main()
{
    stringstream ss("I am going to goa for");  // Used for breaking words
    string word; // To store individual words
    while (ss >> word)
        cout<<word<<"\n";
    ss >> word;
    cout<<word<<endl;
    ss >> word;
    cout<<word<<endl;
    ss >> word;
    cout<<word<<endl;
}

OUTPUT:

I
am
going
to
goa
for
for
for
for

Your stream has an error flag set (that's why the while loop terminated), yet you still keep reading from it. — Dan Mašek
– Dan Mašek, Commented May 5, 2016 at 11:32

Rishit Sanmukhani · Accepted Answer · 2016-05-05 13:34:23Z

1

When >> reaches the end of the string, the failbit is set and it stops reading further.

#include <iostream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;
int main()
{
    stringstream ss("I am going to goa for");  // Used for breaking words
    string word; // To store individual words
    while (ss >> word)
        cout<<word<<"\n";

    word = "END";
    ss >> word;
    cout<<word<<endl;
    ss >> word;
    cout<<word<<endl;
    ss >> word;
    cout<<word<<endl;
}

You are seeing the for because that is what stored in it. Change it to something else you will find that it doesn't read from the stringstream till failbit is cleared.

The output is:

I
am
going
to
goa
for
END
END
END

Refer stringstream for more details.

answered May 5, 2016 at 13:34

Rishit Sanmukhani

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Comments

Smeeheey · Accepted Answer · 2016-05-05 13:32:07Z

0

Before every cout << word << endl; line you should add if(!ss.fail()) to check no error has occurred in the stringstream following the read attempt.

answered May 5, 2016 at 13:32

Smeeheey

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