HP-UX Reference (11i v1 00/12) - 2 System Calls (vol 5)

ManualsBrandsHP ManualsSoftwareHP-UX Reference Manuals

301

302

303

304

305

306

307

308

309

310

__________________________________________________________________________________________________________________________________________________________________________________________________

STANDARD Printed by: Nora Chuang [nchuang] STANDARD

/build/1111/BRICK/man2/!!!intro.2

________________________________________________________________

___ ___

semctl(2) semctl(2)

associated with semid.

RETURN VALUE

Upon successful completion, semctl() returns a value based on cmd as follows:

GETVAL The value of semval.

GETNCNT The value of semncnt.

GETZCNT The value of semzcnt.

GETPID The value of sempid.

All others return 0.

If it fails, it returns -1 and sets errno to indicate the error.

ERRORS

If semctl() fails, it sets errno to one of the following values:

[EACCES] Operation permission is denied to the calling process (see semaphore operation per-

missions in glossary(9).

[EFAULT] cmd is

SETVAL, GETALL, SETALL, IPC_SET,orIPC_STAT, and arg is an invalid

pointer.

[EINVAL] semid is not a valid semaphore identiﬁer.

[EINVAL] semnum is less than zero or greater than or equal

sem_nsems.

[EINVAL] cmd is not a valid command, or the command contains invalid parameters.

[EPERM] cmd is equal to

IPC_RMID or IPC_SET and the process does not have an effective

user ID equal to either that of superuser or to the value of either sem_perm.uid or

sem_perm.cuid in the data structure associated with semid.

[ERANGE] cmd is SETVAL or SETALL and the value to which semval is to be set is greater than

the system imposed maximum.

EXAMPLES

The following call to semctl() initializes the set of 4 semaphores to the values 0, 1, 0, and 1 respectively.

This example assumes the process has a valid semid representing a set of 4 semaphores as shown in the

semget(2) manual entry. For an example of performing "P" and "V" operations on the semaphores below,

refer to semop(2).

union semun {

int val;

struct semid_ds ∗buf;

ushort ∗array;

} arg;

ushort semarray[4];

semarray[0] = 0;

semarray[1] = 1;

semarray[2] = 0;

semarray[3] = 1;

arg.array = &semarray[0];

semctl (mysemid, 0, SETALL, arg);