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 .