BSD syscall#274
svc · unix #274
sem_getvalue
Reads the current value of a POSIX semaphore without modifying it.
Prototype
int sem_getvalue(sem_t *sem, int *sval);Returns: int
Arguments
| Name | Type | Dir | Description |
|---|---|---|---|
| sem | sem_t | - | |
| sval | int | - |
Version history
| XNU tag | macOS | # |
|---|---|---|
| xnu-1456.1.26 | macOS 10.6 Snow Leopard | 274 |
| xnu-1699.24.8 | macOS 10.7 Lion | 274 |
| xnu-2050.18.24 | macOS 10.8 Mountain Lion | 274 |
| xnu-2422.115.4 | macOS 10.9 Mavericks | 274 |
| xnu-1486.2.11 | — | 274 |
| xnu-1504.15.3 | — | 274 |
| xnu-1504.3.12 | — | 274 |
| xnu-1504.7.4 | — | 274 |
| xnu-1504.9.17 | — | 274 |
| xnu-1504.9.26 | — | 274 |
| xnu-1504.9.37 | — | 274 |
| xnu-1699.22.73 | — | 274 |
| xnu-1699.22.81 | — | 274 |
| xnu-1699.24.23 | — | 274 |
| xnu-1699.26.8 | — | 274 |
| xnu-1699.32.7 | — | 274 |
| xnu-2050.22.13 | — | 274 |
| xnu-2050.24.15 | — | 274 |
| xnu-2050.48.11 | — | 274 |
| xnu-2050.7.9 | — | 274 |
| xnu-2050.9.2 | — | 274 |
| xnu-2422.1.72 | — | 274 |
| xnu-2422.100.13 | — | 274 |
| xnu-2422.110.17 | — | 274 |
| xnu-2422.90.20 | — | 274 |
Notes
Returns the observed counter at the moment of the call; concurrent waiters or posters may change the value before the caller acts on it. POSIX allows the implementation to return a negative value reflecting the number of waiters, but Darwin returns only the non-negative count.
Related APIs
sem_waitsem_postsem_trywait