SHMCTL(2) DOMAIN/IX Reference Manual (SYS5) SHMCTL(2)
NAME
shmctl - shared memory control operations
USAGE
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
int shmctl (shmid, cmd, buf)
int shmid, cmd;
struct shmid_ds *buf;
DESCRIPTION
Shmctl provides shared memory control operations as defined
by various commands, cmd. The following cmds are available:
IPC_STAT Place the current value of each member of
the data structure associated with shmid
into the structure pointed to by buf. The
contents of this structure are defined in
intro(2). {READ}
IPC_SET Set the value of the following members of
the data structure associated with shmid to
the corresponding value found in the struc-
ture pointed to by buf:
shm_perm.uid
shm_perm.gid
shm_perm.mode /* only low 9 bits */
This cmd can only be executed by a process
that has an effective user ID equal to
either that of super-user or to the value of
shm_perm.uid in the data structure associ-
ated with shmid.
IPC_RMID Remove the shared memory identifier speci-
fied by shmid from the system and destroy
the shared memory segment and data structure
associated with it. This cmd can only be
executed by a process that has an effective
user ID equal to either that of super-user
or to the value of shm_perm.uid in the data
structure associated with shmid.
RETURN VALUE
Upon successful completion, shmctl returns a value of zero.
Otherwise, a value of -1 returns and errno is set to indi-
cate the error.
ERRORS
Shmctl will fail if one or more of the following is true:
Printed 5/10/85 SHMCTL-1
SHMCTL(2) DOMAIN/IX Reference Manual (SYS5) SHMCTL(2)
[EINVAL] Shmid is not a valid shared memory identif-
ier.
[EINVAL] Cmd is not a valid command.
[EACCES] Cmd is equal to IPC_STAT and {READ} operation
permission is denied to the calling process.
[EPERM] Cmd is equal to IPC_RMID or IPC_SET and the
effective user ID of the calling process is
not equal to that of super-user and it is not
equal to the value of shm_perm.uid in the
data structure associated with shmid.
[EFAULT] Buf points to an illegal address.
RELATED INFORMATION
shmget(2), shmop(2)
SHMCTL-2 Printed 5/10/85