basic_istream::putback() in C++ with Examples (original) (raw)

Last Updated : 15 Jul, 2025

The basic_istream::putback() used to put the character back in the input string. This function is present in the iostream header file. Below is the syntax for the same:Header File:

#include**<iostream**>

Syntax:

basic_istream& putback (char_type ch);

Parameter:

• ch: It represents the character to be put into the input string back.

Return Value: The iostream::basic_istream::putback() return the basic_istream object. Below are the programs to understand the implementation of std::basic_istream::putback() in a better way:Program 1:

CPP14 `

// C++ code for basic_istream::putback() #include <bits/stdc++.h>

using namespace std;

int main() { stringstream gfg1("GeeksforGeeks"); gfg1.get();

// putback A into the input string
if (gfg1.putback('A'))
    cout << gfg1.rdbuf() << endl;

istringstream gfg2("GeeksforGeeks");
gfg2.get();

if (gfg2.putback('A'))
    cout << gfg2.rdbuf() << endl;
else
    cout << "putback is failed here\n";

gfg2.clear();

// Again putback G in the string
if (gfg2.putback('G'))
    cout << gfg2.rdbuf() << endl;

}

`

Output:

AeeksforGeeks putback is failed here GeeksforGeeks

Program 2:

CPP14 `

// C++ code for basic_istream::putback() #include <bits/stdc++.h>

using namespace std;

int main() { stringstream gfg1("GOOD"); gfg1.get();

// putback B into the input string
if (gfg1.putback('B'))
    cout << gfg1.rdbuf() << endl;

istringstream gfg2("GOOD");
gfg2.get();

if (gfg2.putback('B'))
    cout << gfg2.rdbuf() << endl;
else
    cout << "putback is failed here\n";

gfg2.clear();

// Again putback G in the string
if (gfg2.putback('G'))
    cout << gfg2.rdbuf() << endl;

}

`