The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


sys/shm.h - shared memory facility


#include <sys/shm.h>


The <sys/shm.h> header defines the following symbolic constants and structure:

Symbolic constants:

Attach read-only (else read-write).
Segment low boundary address multiple.
Round attach address to SHMLBA.

The following data types are defined through typedef:

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.






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

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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