cpp/error/system category: Difference between revisions
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{{cpp/title|system_category}} | {{cpp/title|system_category}} | ||
{{cpp/error/navbar}} | {{cpp/error/navbar}} | ||
{{ddcl | header=system_error | since=c++11 | | {{ddcl|header=system_error|since=c++11| | ||
const std::error_category& system_category() noexcept; | const std::error_category& system_category() noexcept; | ||
}} | }} | ||
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===Example=== | ===Example=== | ||
{{example | {{example | ||
|code= | |||
#include <iomanip> | #include <iomanip> | ||
#include <iostream> | #include <iostream> | ||
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} | } | ||
} | } | ||
|p=true | |||
|output= | |||
Category: generic | Category: generic | ||
Value: 33 | Value: 33 | ||
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===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
{{dsc inc | cpp/error/dsc generic_category}} | {{dsc inc|cpp/error/dsc generic_category}} | ||
{{dsc inc | cpp/error/dsc errc}} | {{dsc inc|cpp/error/dsc errc}} | ||
{{dsc end}} | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | ||
Latest revision as of 10:46, 4 January 2024
| Defined in header <system_error>
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const std::error_category& system_category() noexcept;
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(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 "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.
Parameters
(none)
Return value
A reference to the static object of unspecified runtime type, derived from std::error_category.
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.
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
(C++11) |
identifies the generic error category (function) |
(C++11) |
the std::error_condition enumeration listing all standard <cerrno> macro constants (class) |