std::system_category

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pairs and tuples

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Swap, forward and move

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Error handling

Exception handling

exception

uncaught_exception

exception_ptr (C++11)

make_exception_ptr (C++11)

current_exception (C++11)

rethrow_exception (C++11)

nested_exception (C++11)

throw_with_nested (C++11)

rethrow_if_nested (C++11)

Exception handling failures

terminate

terminate_handler

get_terminate (C++11)

set_terminate

unexpected (deprecated)

bad_exception

unexpected_handler (deprecated)

get_unexpected (C++11)(deprecated)

set_unexpected (deprecated)

Exception categories

logic_error

invalid_argument

domain_error

length_error

out_of_range

runtime_error

range_error

overflow_error

underflow_error

Error codes

Error codes

errno

Assertions

assert

system_error facility

error_category (C++11)

generic_category (C++11)

system_category (C++11)

error_condition (C++11)

errc (C++11)

error_code (C++11)

system_error (C++11)

 

Defined in header <system_error>
const std::error_category& system_category();		(since C++11)

Obtains a reference to the static error category object for errors reported by the operating system. The object is required to override the virtual function error_category::name() to return a pointer to the string "system". It is also required to override the virtual function error_category::default_error_condition() to map the error codes that match POSIX errno values to std::generic_category.

Parameters

(none)

Return value

A reference to the static object of unspecified runtime type, derived from std::error_category.

Exceptions

noexcept specification:  

noexcept

  (since C++11)

Example

run this code

#include <iostream>
#include <system_error>
#include <iomanip>
#include <string>
 
int main()
{
    std::error_condition econd = std::system_category().default_error_condition(EDOM);
    std::cout << "Category: " << econd.category().name() << '\n'
              << "Value: " << econd.value() << '\n'
              << "Message: " << econd.message() << '\n';
 
    econd = std::system_category().default_error_condition(10001);
    std::cout << "Category: " << econd.category().name() << '\n'
              << "Value: " << econd.value() << '\n'
              << "Message: " << econd.message() << '\n';
}

Output:

Category: generic
Value: 33
Message: Numerical argument out of domain
Category: system
Value: 10001
Message: Unknown error 10001

See also

generic_category (C++11)	identifies the generic error category (function)
errc (C++11)	the std::error_condition enumeration listing all standard <cerrno> macro constants (class)