semget(2) System Calls semget(2)
semget - get set of semaphores
int semget(key_t key, int nsems, int semflg);
The semget() function returns the semaphore identifier associated with
A semaphore identifier and associated data structure and set containing
nsems semaphores (see intro(2)) are created for key if one of the fol-
lowing is true:
o key is equal to IPC_PRIVATE.
o 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 iden-
tifier is initialized as follows:
o 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 access permission bits of sem_perm.mode are set equal to the
access permission bits of semflg.
o sem_nsems is set equal to the value of nsems.
o sem_otime is set equal to 0 and sem_ctime is set equal to the cur-
Upon successful completion, a non-negative integer representing a sema-
phore identifier is returned. Otherwise, -1 is returned and errno is
set to indicate the error.
The semget() function will fail if:
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.
EEXIST A semaphore identifier exists for key but both (sem-
flg&&IPC_CREAT) and (semflg&&IPC_EXCL) are both true.
EINVAL The nsems argument is either less than or equal to 0 or
greater than the system-imposed limit. See NOTES.
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 0.
ENOENT A semaphore identifier does not exist for key and (sem-
flg&&IPC_CREAT) is false.
ENOSPC A semaphore identifier is to be created but the system-
imposed limit on the maximum number of allowed sema-
phores or semaphore identifiers system-wide would be
exceeded. See NOTES.
See attributes(5) for descriptions of the following attributes:
tab() allbox; cw(2.750000i)| cw(2.750000i) lw(2.750000i)|
lw(2.750000i). ATTRIBUTE TYPEATTRIBUTE VALUE Interface StabilityStan-
ipcrm(1), ipcs(1), rctladm(1M), intro(2), semctl(2), semop(2),
setrctl(2), ftok(3C), attributes(5), standards(5)
The system-imposed limit on the value of the nsems argument is the
maintained on a per-process basis using the process.max-sem-nsems
The system-imposed limit on the number of semaphore identifiers is
maintained on a per-project basis using the project.max-sem-ids
See rctladm(1M) and setrctl(2) for information about using resource
SunOS 5.10 11 Feb 2003 semget(2)