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 3.332 Shared Memory Object ). It is unspecified whether this function interoperates with the realtime interprocess communication facilities defined in 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 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.

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

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

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

XBD 3.332 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.