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std::system_category(3) C++ Standard Libary std::system_category(3) NAME std::system_category - std::system_category Synopsis Defined in header <system_error> const std::error_category& system_category() noexcept; (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 std::error_category::name() to return a pointer to the string "sys- tem". It is also required to override the virtual function std::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, de- rived from std::error_category. Example // Run this code #include <iomanip> #include <iostream> #include <string> #include <system_error> int main() { for (int const code : {EDOM, 10001}) { const std::error_condition econd = std::system_category().default_error_condition(code); std::cout << "Category: " << econd.category().name() << '\n' << "Value: " << econd.value() << '\n' << "Message: " << econd.message() << "\n\n"; } } Possible output: Category: generic Value: 33 Message: Numerical argument out of domain Category: system Value: 10001 Message: Unknown error 10001 See also generic_category identifies the generic error category (C++11) (function) errc the std::error_condition enumeration listing all standard <cerrno> (C++11) macro constants (class) http://cppreference.com 2022.07.31 std::system_category(3)
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