Reading string via cin and flushing input buffers

The following program shows three different approaches to read string via Cin. It also shows two different approaches for flushing input buffer.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//Program to read input string and to flush input buffer
#include<iostream>
#include<string>
#include <istream>
#include <limits>

using namespace std;

int main()
{
  string s1;
  cout << "\nAPPROACH 1" <<endl;
  cout << "Input a string : ";
  cin >> s1;
  cout << "Entered string = " <<s1.c_str()<<endl;

  //Lets flush the buffer from Approach 1 here
  istream& in(cin);
  in.ignore( numeric_limits<std::streamsize>::max(), '\n' );

  cout << "\nAPPROACH 2" <<endl;
  cout << "Input a string : ";
  istreambuf_iterator<char> eos;  // end-of-range iterator
  istreambuf_iterator<char> iit (cin.rdbuf()); // stdin iterator
  string s2; 
  while (iit!=eos && *iit!='\n') s2+=*iit++;
  cout << "Entered string = " << s2 << endl;

  //Another approach for flushing the input
  int ch;
  while ((ch = cin.get()) != '\n' && ch != EOF);

  cout << "\nAPPROACH 3" <<endl;
  cout << "Input a string : ";
  char buf[BUFSIZ];
  if (cin.getline(buf, sizeof(buf)))
  {
    cout << "Entered string = " << buf << endl;
  }

  cout << endl;
  return 0;
}

The output is as follows:



More information:

• FAQ: How Do I flush input buffer
• How do I flush input stream
• istreambuf_iterator