Difference between revisions of "cpp/error/system category"
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{{cpp/title|system_category}} | {{cpp/title|system_category}} | ||
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| − | {{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 | ||
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#include <iomanip> | #include <iomanip> | ||
#include <iostream> | #include <iostream> | ||
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} | } | ||
} | } | ||
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Category: generic | Category: generic | ||
Value: 33 | Value: 33 | ||
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===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
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| − | {{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 02:46, 4 January 2024
| 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 "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.
Contents |
[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
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
[edit] See also
| (C++11) |
identifies the generic error category (function) |
| (C++11) |
the std::error_condition enumeration listing all standard <cerrno> macro constants (class) |
