exception::what() in C++ with Examples

The exception::what() used to get string identifying exception. This function returns a null terminated character sequence that may be used to identify the exception. Below is the syntax for the same:

Header File:

#include<exception>

Syntax:

virtual const char* what() const throw();

Return: The function std::what() return a null terminated character sequence that is used to identify the exception.

Note: To make use of std::what(), one should set up the appropriate try and catch blocks.

Below are the programs to understand the implementation of std::what() in a better way:

Program 1:

// C++ code for exception::what() 
#include <bits/stdc++.h> 
  
using namespace std; 
  
struct gfg : exception { 
    const char* what() const noexcept 
    { 
        return "w3wiki!! "
               "A Computer Science"
               " Portal For Beginner"; 
    } 
}; 
  
// main method 
int main() 
{ 
  
    // try block 
    try { 
        throw gfg(); 
    } 
  
    // catch block to handle the errors 
    catch (exception& gfg1) { 
        cout << gfg1.what(); 
    } 
  
    return 0; 
} 

Output:

w3wiki!! A Computer Science Portal For Beginner

Program 2:

// C++ code for exception::what() 
  
#include <bits/stdc++.h> 
  
using namespace std; 
  
struct w3wiki : exception { 
    const char* what() const noexcept 
    { 
        return "Hey!!"; 
    } 
}; 
  
// main method 
int main() 
{ 
  
    // try block 
    try { 
        throw w3wiki(); 
    } 
  
    // catch block to handle the errors 
    catch (exception& gfg) { 
        cout << gfg.what(); 
    } 
  
    return 0; 
} 

Output:

Hey!!

Reference: http://www.cplusplus.com/reference/exception/exception/what/

Contact Us