получить значение семафора (get the value of a semaphore)
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)
sem_getvalue — get the value of a semaphore
Синопсис (Synopsis)
#include <semaphore.h>
int sem_getvalue(sem_t *restrict sem, int *restrict sval);
Описание (Description)
The sem_getvalue() function shall update the location referenced
by the sval argument to have the value of the semaphore
referenced by sem without affecting the state of the semaphore.
The updated value represents an actual semaphore value that
occurred at some unspecified time during the call, but it need
not be the actual value of the semaphore when it is returned to
the calling process.
If sem is locked, then the object to which sval points shall
either be set to zero or to a negative number whose absolute
value represents the number of processes waiting for the
semaphore at some unspecified time during the call.
Возвращаемое значение (Return value)
Upon successful completion, the sem_getvalue() function shall
return a value of zero. Otherwise, it shall return a value of -1
and set errno to indicate the error.
Ошибки (Error)
The sem_getvalue() function may fail if:
EINVAL The sem argument does not refer to a valid semaphore.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
semctl(3p), semget(3p), semop(3p), sem_post(3p),
sem_timedwait(3p), sem_trywait(3p)
The Base Definitions volume of POSIX.1‐2017, semaphore.h(0p)
