SHMDT(3P)                                           POSIX Programmer's Manual                                          SHMDT(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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 commu-
       nication 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     SHMDT(3P)