<sys/shm.h>

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() , shmctl() , shmdt() , shmget() , <sys/types.h> .