SEMGET(2) | System Calls Manual | SEMGET(2) |
semget
— get
semaphore set
#include
<sys/sem.h>
int
semget
(key_t
key, int nsems,
int semflg);
The
semget
()
system call returns the semaphore identifier associated with
key.
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 semflg as a bitwise OR of zero or more of 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 associated with it (the semid_ds structure, see semctl(2)) is initialized as follows:
semget
() returns a non-negative semaphore
identifier if successful. Otherwise, -1 is returned and
errno is set to reflect the error.
EACCES
]EEXIST
]IPC_CREAT
and
IPC_EXCL
are set in semflg,
and a semaphore set is already associated with
key.EINVAL
]A semaphore set associated with key exists, but has fewer semaphores than the number specified in nsems.
ENOSPC
]ENOENT
]IPC_CREAT
was not set in semflg and no semaphore set
associated with key was found.November 15, 2014 | OpenBSD-5.9 |