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NAME

       sys/shm.h - XSI shared memory facility

SYNOPSIS

       #include <sys/shm.h>

DESCRIPTION

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

       SHM_RDONLY
              Attach read-only (else read-write).

       SHM_RND
              Round attach address to SHMLBA.

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

       SHMLBA Segment low boundary address multiple.

       The following data types shall be 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 shall contain 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  shall  be  defined as
       described in <sys/types.h> .

       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.

              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> shall be defined when
       this header is included.

       The following sections are informative.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       <sys/ipc.h>  ,  <sys/types.h>  ,  the  System  Interfaces   volume   of
       IEEE Std 1003.1-2001, shmat(), shmctl(), shmdt(), shmget()

COPYRIGHT

       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .