shmctl, shmctl64 - shared memory control operations

Syntax	#include <sys/shm.h> int shmctl(int shmid, int cmd, struct shmid_ds *buf);  CRTE111A30 int shmctl64(int shmid, int cmd, struct shmid_ds64 *buf); (End)
Description	shmctl() provides a number of shared memory control operations, as specified by cmd. The function shmctl64() behaves like the function shmctl(), except that it uses a shmid_ds64 structure instead of a shmid_ds structure for the cmd values IPC_STAT and IPC_SET and therefore will work correctly after 01/19/2038 03:14:07 UTC. The shmid_ds contains the following elements: struct ipc_perm shm_perm; /* operation permission struct */ int shm_segsz; /* size of segment in bytes */ ulong_t *shm_shmat; /* hidden */ ushort_t shm_dummy; /* shm_lkcnt - no longer used! */ pid_t shm_lpid; /* pid of last shmop */ pid_t shm_cpid; /* pid of creator */ ulong_t shm_nattch; /* used only for shminfo */ ulong_t shm_cnattch; /* used only for shminfo */ time_t shm_atime; /* last shmat time */ time_t shm_dtime; /* last shmdt time */ time_t shm_ctime; /* last change time */ The elements of the structure shmid_ds64 structure are defined like the shmid_ds structure except for the following components: time64_t shm_atime; time64_t shm_dtime; time64_t shm_ctime;
	The following values for cmd are available:
	IPC_STAT	Enter the current values of all members of the shmid_ds resp. shmid_ds64 data structure associated with shmid into the structure pointed to by buf. The format of the structure is defined in sys/shm.h.
	IPC_SET	Set the values of the following members of the shmid_ds resp. shmid_ds64 data structure associated with shmid to the corresponding values from the structure pointed to by buf: shm_perm.uid shm_perm.gid shm_perm.mode /* only the low-order 9 bits */ IPC_SET can only be executed by a process that has an effective user ID equal to that of a process with appropriate privileges or to the value of shm_perm.cuid or shm_perm.uid in the shmid_ds resp. shmid_ds64 data structure associated with shmid.
	IPC_RMID	Remove the shared memory identifier specified by shmid from the system as well as the shared memory segment and the shmid_ds resp. shmid_ds64 data structure associated with it. IPC_RMID can only be executed by a process that has an effective user ID equal to that of a process with appropriate privileges or to the value of shm_perm.cuid or shm_perm.uid in the shmid_ds resp. shmid_ds64 data structure associated with shmid.
Return val.	0	if successful.
	-1	if an error occurs. errno is set to indicate the error.
Errors	shmctl() and shmctl64() will fail if:
	EACCES	cmd is equal to IPC_STAT and the calling process does not have read permission.
	Extension
	EFAULT	msgp points to an invalid address. (End)
	EINVAL	The value of shmid is not a valid shared memory identifier, or the value of cmd is not a valid command, or cmd is IPC_SET and shm_perm.uid or shm_perm.gid is invalid.
	Extension
	ENOMEM	Not enough memory is available.
	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 a process with appropriate privileges and it is not equal to the value of shm_perm.cuid or shm_perm.uid in the data structure associated with shmid.
	shmctl() will fail if:  Extension
	EOVERFLOW	cmd is equal to IPC_SET and a timestamp is too large for a time-t component (this will happen after 01/19/2038 03:14:07 a.m. UTC). (End)
	shmctl64() will fail if:
	EINVAL	POSIX-BC correction status < A47.
See also	shmat(), shmdt(), shmget(), sys/shm.h, section “Interprocess communication”.