NAME¶

std::iostream_category - std::iostream_category

Synopsis¶

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.

Parameters¶

(none)

Return value¶

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

Example¶

// Run this code

#include <fstream>
#include <iostream>

int main()
{
std::ifstream f("doesn't exist");
try
{
f.exceptions(f.failbit);
}
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

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2087 C++11 iostream_category was not declared noexcept declared noexcept

See also¶

failure stream exception
(public member class of std::ios_base)
io_errc the IO stream error codes
(C++11) (enum)