<istream> defines std::basic_istream and std::istream, the base classes for input streams. It provides operator>> for formatted input, get(), getline(), and read() for unformatted input.

You rarely use this directly; instead you use concrete classes like std::cin or std::ifstream that inherit from it.

This example uses a string stream for formatted input parsing, extracting an integer, string, and floating-point value.

// compile: g++ -std=c++11 -o istreamexample istreamexample.cpp
// run: ./istreamexample
// description: formatted input with operator>>
 
#include <istream>
#include <iostream>
#include <sstream>
 
int main() {
    std::istringstream iss("42 hello 3.14");
 
    int i;
    std::string s;
    double d;
 
    iss >> i >> s >> d;
    std::cout << "i=" << i << ", s=" << s << ", d=" << d << "\n";
 
    return 0;
}