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Semaphores with key of 0

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Top Forums UNIX for Advanced & Expert Users Semaphores with key of 0
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Old 10-28-2004
Question Semaphores with key of 0

Does anyone know how a semaphore can end up with a key value of "0"?

We have a system that had over 400 semaphores with a key value of "0" at one time. After rebooting, they don't exist anymore and all existing semaphores now have normal key values.

Any ideas on what makes this happen and if there is any way to trace where these came from? Smilie

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SEM_GET(3)								 1								SEM_GET(3)

sem_get - Get a semaphore id

resource sem_get (int $key, [int $max_acquire = 1], [int $perm = 0666], [int $auto_release = 1]) DESCRIPTION
sem_get(3) returns an id that can be used to access the System V semaphore with the given $key. A second call to sem_get(3) for the same key will return a different semaphore identifier, but both identifiers access the same underlying semaphore. PARAMETERS
o $key - o $max_acquire - The number of processes that can acquire the semaphore simultaneously is set to $max_acquire. o $perm - The semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the semaphore. o $auto_release - Specifies if the semaphore should be automatically released on request shutdown. RETURN VALUES
Returns a positive semaphore identifier on success, or FALSE on error. CHANGELOG
+--------+-----------------------------------------+ |Version | | | | | | | Description | | | | +--------+-----------------------------------------+ | 4.3.0 | | | | | | | The $auto_release parameter was added. | | | | +--------+-----------------------------------------+ NOTES
Warning When using sem_get(3) to access a semaphore created outside PHP, note that the semaphore must have been created as a set of 3 sema- phores (for example, by specifying 3 as the nsems parameter when calling the C semget() function), otherwise PHP will be unable to access the semaphore. SEE ALSO
sem_acquire(3), sem_release(3), ftok(3). PHP Documentation Group SEM_GET(3)

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