< cpp‎ | io
Defined in header <ios>
const std::error_category& iostream_category() noexcept;
(since C++11)

Obtains a reference to the static error category object for iostream errors. The object is required to override the virtual function error_category::name() to return a pointer to the string "iostream". It is used to identify error codes provided in the exceptions of type std::ios_base::failure.



Return value

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


#include <iostream>
#include <fstream>
int main()
    std::ifstream f("doesn't exist");
    try {
    } catch (const std::ios_base::failure& e) {
        std::cout << "Caught an ios_base::failure.\n"
                  << "Error code: " << e.code().value() 
                  << " (" << e.code().message() << ")\n"
                  << "Error category: " << e.code().category().name() << '\n';

Possible output:

Caught an ios_base::failure.
Error code: 1 (unspecified iostream_category error)
Error category: iostream

See also

stream exception
(public member class of std::ios_base)
the IO stream error codes