sem_get(3) [php man page]
SEM_GET(3) 1 SEM_GET(3) sem_get - Get a semaphore id SYNOPSIS
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)
Check Out this Related Man Page
semget(2) System Calls Manual semget(2) Name semget - get set of semaphores Syntax #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> int semget (key, nsems, semflg) key_t key; int nsems, semflg; Description The system call returns the semaphore identifier associated with key. A semaphore identifier and associated data structure and set con- taining nsems semaphores are created for key, if one of the following is true: o The key is equal to IPC_PRIVATE o The key does not already have a semaphore identifier associated with it, and (semflg & IPC_CREAT ) is true. For further information, see Upon creation, the data structure associated with the new semaphore identifier is initialized as follows: o The sem_perm.cuid, sem_perm.uid, sem_perm.cgid and sem_perm.gid are set equal to the effective user ID and effective group ID, respec- tively, of the calling process. o The low-order nine bits of sem_perm.mode are set equal to the low-order nine bits of semflg. o The sem_nsems is set equal to the value of nsems. o The sem_otime is set equal to zero (0) and sem_ctime is set equal to the current time. Return Values Upon successful completion, a nonnegative integer, namely a semaphore identifier, is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error. Diagnostics The semget system call fails if any of the following is true: [EINVAL] The nsems is either less than or equal to zero or greater than the system-imposed limit [EACCES] A semaphore identifier exists for key, but operation permission, as specified by the low-order nine bits of semflg would not be granted. For further information, see [EINVAL] A semaphore identifier exists for key, but the number of semaphores in the set associated with it is less than nsems and nsems is not equal to zero. [ENOENT] A semaphore identifier does not exist for key and (semflg & IPC_CREAT ) is false. [ENOSPC] A semaphore identifier is to be created but the system-imposed limit on the maximum number of allowed semaphore identifiers in the system would be exceeded. [EEXIST] A semaphore identifier exists for key but ((semflg & IPC_CREAT ) & (semflg & IPC_EXCL )) is true. See Also semctl(2), semop(2), ftok(3) semget(2)