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.
The shmdt() function operates on XSI shared memory (see the Base
Definitions volume of POSIX.1‐2008, Section 3.342, Shared MemoryObject). It is unspecified whether this function interoperates with
the realtime interprocess communication facilities defined in Section2.8, Realtime.
The shmdt() function detaches the shared memory segment located at
the address specified by shmaddr from the address space of the
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.
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.
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
IEEE/The Open Group 2013 SHMDT(3P)