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NAME
       shmdt - XSI shared memory detach operation


SYNOPSIS
       #include <sys/shm.h>

       int shmdt(const void *shmaddr);


DESCRIPTION
       The   shmdt()   function   operates   on   XSI   shared  memory  (see  the  Base  Definitions  volume  of
       IEEE Std 1003.1-2001, Section 3.340, Shared Memory Object).  It  is  unspecified  whether  this  function
       interoperates with the realtime interprocess communication facilities defined in Realtime .

       The  shmdt() function detaches the shared memory segment located at the address specified by shmaddr from
       the address space of the calling process.


RETURN VALUE
       Upon successful completion, shmdt() shall decrement  the  value  of  shm_nattch  in  the  data  structure
       associated with the shared memory ID of the attached shared memory segment and return 0.

       Otherwise,  the  shared memory segment shall not be detached, shmdt() shall return -1, and errno shall be
       set to indicate the error.


ERRORS
       The shmdt() function shall fail if:

       EINVAL The value of shmaddr is not the data segment start address of a shared memory segment.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       The POSIX Realtime Extension defines alternative interfaces for interprocess  communication.  Application
       developers  who  need  to use IPC should design their applications so that modules using the IPC routines
       described in XSI Interprocess Communication can be easily modified to use the alternative interfaces.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       XSI Interprocess Communication , Realtime , exec() , exit() , fork() , shmat() , shmctl()  ,  shmget()  ,
       shm_open() , shm_unlink() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/shm.h>


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 .