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man pages section 3: Library Interfaces and Headers

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Updated: Thursday, June 13, 2019
 
 

shm.h(3HEAD)

Name

shm.h, shm - shared memory facility

Synopsis

#include <sys/shm.h>

Description

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

SHM_RDONLY

attach read-only (else read-write)

SHM_RND

round attach address to SHMLBA

The <sys/shm.h> header defines the following symbolic value:

SHMLBA

segment low boundary address multiple

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 shmid_ds structure 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>. See types.h(3HEAD).

In addition, all of the symbols from <sys/ipc.h> are defined when this header is included.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Standard

See Also

shmctl(2), shmget(2), shmop(2), ipc.h(3HEAD), types.h(3HEAD), attributes(7), standards(7)