Menu
×
   ❮     
HTML CSS JAVASCRIPT SQL PYTHON JAVA PHP HOW TO W3.CSS C C++ C# BOOTSTRAP REACT MYSQL JQUERY EXCEL XML DJANGO NUMPY PANDAS NODEJS R TYPESCRIPT ANGULAR GIT POSTGRESQL MONGODB ASP AI GO KOTLIN SASS VUE DSA GEN AI SCIPY AWS CYBERSECURITY DATA SCIENCE
     ❯   

C++ Tutorial

C++ HOME C++ Intro C++ Get Started C++ Syntax C++ Output C++ Comments C++ Variables C++ User Input C++ Data Types C++ Operators C++ Strings C++ Math C++ Booleans C++ If...Else C++ Switch C++ While Loop C++ For Loop C++ Break/Continue C++ Arrays C++ Structures C++ Enums C++ References C++ Pointers

C++ Functions

C++ Functions C++ Function Parameters C++ Function Overloading C++ Scope C++ Recursion

C++ Classes

C++ OOP C++ Classes/Objects C++ Class Methods C++ Constructors C++ Access Specifiers C++ Encapsulation C++ Inheritance C++ Polymorphism C++ Files C++ Exceptions C++ Date

C++ Data Structures

C++ Data Structures & STL C++ Vectors C++ List C++ Stacks C++ Queues C++ Deque C++ Sets C++ Maps C++ Iterators C++ Algorithms

C++ How To

C++ Add Two Numbers C++ Random Numbers

C++ Reference

C++ Reference C++ Keywords C++ <iostream> C++ <fstream> C++ <cmath> C++ <string> C++ <cstring> C++ <ctime> C++ <vector> C++ <algorithm>

C++ Examples

C++ Examples C++ Real-Life Examples C++ Compiler C++ Exercises C++ Quiz C++ Certificate


C++ cerr object

❮ iostream objects


Example

Use the cerr object to output error messages:

int x = 5;
int y = 0;

if(y == 0) {
  cerr << "Division by zero: " << x << " / " << y << "\n";
} else {
  cout << (x / y);
}

Try it Yourself »


Definition and Usage

The cerr object is used to output error messages. It behaves identically to cout but it can be directed to a different destination such as an error log file. cerr and clog always write to the same destination.

For more detailed usage, see the <iostream> cout object.

Unlike cout and clog, cerr is not buffered. A buffered output would store the output temporarily in a variable and not write to the destination until certain conditions are met. Buffered outputs are more efficient because they do fewer write operations on files. cerr is not buffered so that the error messages can be written to a file before the program crashes.

Note: The cerr object is defined in the <iostream> header file.


More Examples

Example

Direct cerr to write to a file instead of to the console:

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

int main() {
  int x = 5;
  int y = 0;

  // Set "error.log" as the output file for the error messages
  ofstream log("error.log");
  cerr.rdbuf(log.rdbuf());
  
  // Write an error message
  if(y == 0) {
    cerr << "Division by zero: " << x << " / " << y << "\n";
  } else {
    cout << (x / y);
  }

  // Close the file
  log.close();
  
  return 0;
}

❮ iostream objects

×

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail:
sales@w3schools.com

Report Error

If you want to report an error, or if you want to make a suggestion, send us an e-mail:
help@w3schools.com

W3Schools is optimized for learning and training. Examples might be simplified to improve reading and learning. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.

Copyright 1999-2024 by Refsnes Data. All Rights Reserved. W3Schools is Powered by W3.CSS.