возвращаемое значение ошибки (error return value)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
errno — error return value
Синопсис (Synopsis)
#include <errno.h>
Описание (Description)
The lvalue errno is used by many functions to return error
values.
Many functions provide an error number in errno, which has type
int and is defined in <errno.h>. The value of errno shall be
defined only after a call to a function for which it is
explicitly stated to be set and until it is changed by the next
function call or if the application assigns it a value. The value
of errno should only be examined when it is indicated to be valid
by a function's return value. Applications shall obtain the
definition of errno by the inclusion of <errno.h>. No function
in this volume of POSIX.1‐2017 shall set errno to 0. The setting
of errno after a successful call to a function is unspecified
unless the description of that function specifies that errno
shall not be modified.
It is unspecified whether errno is a macro or an identifier
declared with external linkage. If a macro definition is
suppressed in order to access an actual object, or a program
defines an identifier with the name errno, the behavior is
undefined.
The symbolic values stored in errno are documented in the ERRORS
sections on all relevant pages.
Возвращаемое значение (Return value)
None.
Ошибки (Error)
None.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Previously both POSIX and X/Open documents were more restrictive
than the ISO C standard in that they required errno to be defined
as an external variable, whereas the ISO C standard required only
that errno be defined as a modifiable lvalue with type int.
An application that needs to examine the value of errno to
determine the error should set it to 0 before a function call,
then inspect it before a subsequent function call.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.3, Error Numbers
The Base Definitions volume of POSIX.1‐2017, errno.h(0p)
