NAME
sys/shm.h — shared
memory facility
SYNOPSIS
#include <sys/shm.h>
DESCRIPTION
The < sys/shm.h > header defines the following symbolic constants and structure:
Symbolic constants:
- SHM_RDONLY
- Attach read-only (else read-write).
- SHMLBA
- Segment low boundary address multiple.
- SHM_RND
- Round attach address to SHMLBA.
The following data types are defined through typedef:
- shmatt_t
- Unsigned integer used for the number of current attaches that must be able to store values at least as large as a type unsigned short .
The structure
shmid_ds
contains the following members: struct ipc_perm shm_perm
operation permission structure size_t shm_segsz size of segment in bytes
pid_t shm_lpid process ID of last shared memory operation pid_t shm_cpid
process ID of creator shmatt_t shm_nattch number of current attaches time_t
shm_atime time of last shmat() time_t shm_dtime time of last shmdt() time_t
shm_ctime time of last change by shmctl()
The
pid_t,
time_t,
key_t
and
size_t
types are defined as described in
<sys/types.h>. The following are declared as
functions and may also be defined as macros. Function prototypes must be
provided for use with an ISO C compiler. void *shmat(int,
const void *, int); int shmctl(int, int, struct shmid_ds *); int shmdt(const
void *); int shmget(key_t, size_t, int);
In addition, all of the symbols from <sys/ipc.h> will be defined when this header is included.
APPLICATION USAGE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
shmat(3) , shmctl(3) , shmdt(3) , shmget(3) , <sys/types.h> .