semget(2)semget(2)NAMEsemget - get set of semaphores
SYNOPSIS
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
int semget(key_t key, int nsems, int semflg);
DESCRIPTIONsemget returns the semaphore identifier associated with key.
A semaphore identifier and associated data structure and set containing
nsems semaphores [see intro(2)] are created for key if one of the
following is true:
key is equal to IPC_PRIVATE.
key does not already have a semaphore identifier associated with it,
and (semflg&IPC_CREAT) is true.
On creation, the data structure associated with the new semaphore
identifier is initialized as follows:
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, respectively,
of the calling process.
The access permission bits of sem_perm.mode are set equal to the
access permission bits of semflg.
sem_nsems is set equal to the value of nsems.
sem_otime is set equal to 0 and sem_ctime is set equal to the
current time.
semget fails if one or more of the following are true:
EINVAL 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 [see intro(2)] as specified by the low-order 9
bits of semflg would not be granted.
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.
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semget(2)semget(2)
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 system wide would be exceeded.
ENOSPC A semaphore identifier is to be created but the system-
imposed limit on the maximum number of allowed semaphores
system wide would be exceeded.
EEXIST A semaphore identifier exists for key but both
(semflg&IPC_CREAT) and (semflg&IPC_EXCL) are both true.
SEE ALSOintro(2), semctl(2), semop(2), stdipc(3C).
DIAGNOSTICS
Upon successful completion, a non-negative integer, namely a semaphore
identifier, is returned. Otherwise, a value of -1 is returned and errno
is set to indicate the error.
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