std::system_category - cppreference.com (original) (raw)
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 "system". 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.
[edit] Parameters
(none)
[edit] Return value
A reference to the static object of unspecified runtime type, derived from std::error_category.
[edit] Notes
On Windows, system_category() typically maps some Windows error codes to POSIX ones. On POSIX, system_category() tends to be equivalent to std::generic_category() except for the name.
[edit] Example
#include #include #include #include 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