The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> shmdt - XSI shared memory detach operation

#### SYNOPSIS

> ``[XSI] #include <sys/shm.h>
> int shmdt(const void *`shmaddr`);``
> `
> `

#### DESCRIPTION

> The shmdt() function operates on XSI shared memory (see XBD 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. Also, the shm_dtime timestamp shall be set to the current time, as described in 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 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

> XBD Shared Memory Object, <sys/shm.h>

#### CHANGE HISTORY

> First released in Issue 2. Derived from Issue 2 of the SVID.

#### Issue 5

> Moved from SHARED MEMORY to BASE.

> The note about use of POSIX Realtime Extension IPC routines has been moved from FUTURE DIRECTIONS to a new APPLICATION USAGE section.

#### Issue 7

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0574 [345] is applied.

End of informative text.

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