sem_get
(PHP 4, PHP 5, PHP 7)
sem_get — Get a semaphore id
说明
$key [,
int $max_acquire = 1 [,
int $perm = 0666 [,
int $auto_release = 1 ]]] ) :
resource
sem_get() returns an id that can be used to access the System V semaphore with the given key.
A second call to sem_get() for the same key will return a different semaphore identifier, but both identifiers access the same underlying semaphore.
参数
-
key -
-
max_acquire -
The number of processes that can acquire the semaphore simultaneously is set to
max_acquire. -
perm -
The semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the semaphore.
-
auto_release -
Specifies if the semaphore should be automatically released on request shutdown.
返回值
Returns a positive semaphore identifier on success, or FALSE on error.
注释
When using sem_get() to access a semaphore created outside PHP, note that the semaphore must have been created as a set of 3 semaphores (for example, by specifying 3 as the nsems parameter when calling the C semget() function), otherwise PHP will be unable to access the semaphore.
参见
- sem_acquire() - Acquire a semaphore
- sem_release() - Release a semaphore
- ftok() - Convert a pathname and a project identifier to a System V IPC key
