получить значение семафора (get the value of a semaphore)
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);
Link with -pthread.
Описание (Description)
sem_getvalue() places the current value of the semaphore pointed
to sem into the integer pointed to by sval.
If one or more processes or threads are blocked waiting to lock
the semaphore with sem_wait(3), POSIX.1 permits two possibilities
for the value returned in sval: either 0 is returned; or a
negative number whose absolute value is the count of the number
of processes and threads currently blocked in sem_wait(3). Linux
adopts the former behavior.
Возвращаемое значение (Return value)
sem_getvalue() returns 0 on success; on error, -1 is returned and
errno is set to indicate the error.
Ошибки (Error)
EINVAL sem is not a valid semaphore. (The glibc implementation
currently does not check whether sem is valid.)
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│sem_getvalue() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008.
Примечание (Note)
The value of the semaphore may already have changed by the time
sem_getvalue() returns.
Смотри также (See also)
sem_post(3), sem_wait(3), sem_overview(7)
