PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult 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
       POSIX.1‐2008, Section 3.342, Shared  Memory  Object).   It  is  unspecified  whether  this
       function  interoperates with the realtime interprocess communication facilities defined in
       Section 2.8, 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. Also, the shm_dtime timestamp shall be set to the current time, as described in
       Section 2.7.1, IPC General Description.

       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  Section  2.7,  XSI  Interprocess
       Communication can be easily modified to use the alternative interfaces.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section  2.7, XSI Interprocess Communication, Section 2.8, Realtime, exec, exit(), fork(),
       shmat(), shmctl(), shmget(), shm_open(), shm_unlink()

       The Base  Definitions  volume  of  POSIX.1‐2008,  Section  3.342,  Shared  Memory  Object,
       <sys_shm.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .