Cin in C++

Here is an example of cin.getline() function to read an entire line until it reaches a newline character.

#include <iostream>
using namespace std;
int main() {
	char sent[50];
	cout << "Enter any sentence: ";
	cin.getline(sent, 50);
	cout << "Entered Sentence: " << sent << endl;
	return 0;
}

The output of the above code is as follows −

Enter any sentence: Welcome to Tutorialspoint.
Entered Sentence: Welcome to Tutorialspoint.

The following example reads first 5 characters of input stream using cin.read() function.

#include <iostream>
using namespace std;
int main(){
	char buffer[6];
	cout << "Enter a sentence: ";
	cin.read(buffer, 5);
	buffer[5] = '\0';
	cout << "First 5 characters: " << buffer << endl;
	return 0;
}

The output of the above code is as follows −

Enter at least 5 characters: Monkey D. Luffy
First 5 characters: Monke

Here is an example of putback() function that inserts back the first character read and removed by the get() function −

#include <iostream>
using namespace std;
int main() {
    cout << "Enter a character: ";
    char ch = cin.get();
    cout << "Entered character: " << ch << endl;

    cin.putback(ch);
    char ch2 = cin.get();
    cout << "Read character again: " << ch2 << endl;
    return 0;
}

The output of the above code is as follows −

Enter a character: Tutorialspoint
Entered character: T
Read character again: T

In this example, the peek() function looks at the next character in the input stream but does not remove it, unlike get() function.

#include <iostream>
using namespace std;
int main() {
    cout << "Enter a number: ";
    char next = cin.peek();
    cout << "Current character in input buffer: " << next << endl;
    int num;
    cin >> num;
    cout << "Number entered: " << num << endl;
    return 0;
}

The output of the above code is as follows −

Enter a number: 978
Current character in input buffer: 9
Number entered: 978

The following example demonstrates the use of cin.bad(). It returns true only for >non-recoverable errors. Here we have used a string as input in place of a number and still this program doesn't give an error.

#include <iostream>
using namespace std;
int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;
    if (cin.bad()) {
        cout << "Error occurred!" << endl;
    } else {
        cout << "No error. Given number: " << num << endl;
    }
    return 0;
}

The output of the above code is as follows −

Enter a number: abcd
No error. Given number: 0

In this example, the cin.fail() returns true if the input is not an integer value as it represents a failed operation −

#include <iostream>
using namespace std;
int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;
    if (cin.fail()) {
        cout << "Invalid input. Enter a number." << endl;
    } else {
        cout << "Entered age: " << age << endl;
    }
    return 0;
}

The output of the above code is as follows −

Enter your age: 23
Entered age: 23

Enter your age: Tp
Invalid input. Enter a number.

The following example clears the error flags when user inputs a non-integer value −

#include <iostream>
using namespace std;
int main(){
     int num;
     cout << "Enter a number: ";
     cin >> num;
     if (cin.fail()){
          cout << "Invalid input. Clearing error..." << endl;
          cin.clear();
          cout << "Error flags cleared!" << endl;
     } else {
          cout << "Input successful: " << num << endl;
     }
     return 0;
}

The output of the above code is as follows −

Enter a number: 45
Input successful: 45

Enter a number: Tutorialspoint
Invalid input. Clearing error...
Error flags cleared!

In this example, we are taking two inputs from user. Without ignore() function, it returns the output by taking just one input from user.

#include <iostream>
#include <string>
using namespace std;

int main(){
     int age;
     string name;

     cout << "Enter your age: ";
     cin >> age;
     // Ignores the newline character left by the last input
     cin.ignore(); 

     cout << "Enter your name: ";
     getline(cin, name); // Now this works as expected

     cout << "Your age is: " << age << endl;
     cout << "Your name is: " << name << endl;
     return 0;
}

The output of the above code is as follows:

Enter your age: 57
Enter your name: Viper
Your age is: 57
Your name is: Viper

Without using ignore():
Enter your age: 57
Enter your name: Your age is: 57
Your name is:

The following example returns the input string until it reaches a whitespace or end of the file. If you are not using a file, press ctrl+d to run the code without any input, or you can use our C++ compiler to run code without giving any input.

#include <iostream>
using namespace std;
int main(){
     string text;
     cout << "Enter a text: ";
     cin >> text;
     if (cin.eof()) {
          cout << "End of file reached!" << endl;
     } else {
          cout << "Your text: " << text << endl;
     }
     return 0;
}

The output of the above code is as follows.

Enter a text: Tutorials Point
Your text: Tutorials

Enter a text: TutorialsPoint
Your text: TutorialsPoint

For empty input:
Enter a text: End of file reached!