semget - get semaphore set
semget(key_t key, int nsems, int semflg);
The semget() system call returns the semaphore identifier
A new set containing nsems semaphores is created if either
key is equal
to IPC_PRIVATE, or key does not have a semaphore set associated with it
and the IPC_CREAT bit is set in semflg.
The access modes of the created semaphores is specified in
OR'ing the following values:
SEM_A alter permission for owner
SEM_R read permission for owner
SEM_A >> 3 alter permission for group
SEM_R >> 3 read permission for group
SEM_A >> 6 alter permission for other
SEM_R >> 6 read permission for other
If a new set of semaphores is created, the data structure
it (the semid_ds structure, see semctl(2)) is initialized as
+o sem_perm.cuid and sem_perm.uid are set to the effective
UID of the
+o sem_perm.gid and sem_perm.cgid are set to the effective
GID of the
+o sem_perm.mode is set to the lower 9 bits of semflg.
+o sem_nsems is set to the value of nsems.
+o sem_ctime is set to the current time.
+o sem_otime is set to 0.
semget() returns a non-negative semaphore identifier if successful. Otherwise,
-1 is returned and errno is set to reflect the error.
[EACCES] The caller has no permission to access a
semaphore set already
associated with key.
[EEXIST] Both IPC_CREAT and IPC_EXCL are set in semflg,
semaphore set is already associated with key.
[EINVAL] nsems is less than or equal to 0 or greater
than the system
limit for the number in a semaphore set.
A semaphore set associated with key exists,
but has fewer
semaphores than the number specified in nsems.
[ENOSPC] A new set of semaphores could not be created
system limit for the number of semaphores or
the number of
semaphore sets has been reached.
[ENOENT] IPC_CREAT was not set in semflg and no
semaphore set associated
with key was found.
semctl(2), semop(2), ftok(3)
OpenBSD 3.6 August 17, 1995
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