The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

#### NAME

> shm_unlink - remove a shared memory object (REALTIME)

#### SYNOPSIS

> ``[SHM] #include <sys/mman.h>
> int shm_unlink(const char *`name`);``
> `
> `

#### DESCRIPTION

> The shm_unlink() function shall remove the name of the shared memory object named by the string pointed to by name.

> If one or more references to the shared memory object exist when the object is unlinked, the name shall be removed before shm_unlink() returns, but the removal of the memory object contents shall be postponed until all open and map references to the shared memory object have been removed.

> Even if the object continues to exist after the last shm_unlink(), reuse of the name shall subsequently cause shm_open() to behave as if no shared memory object of this name exists (that is, shm_open() will fail if O_CREAT is not set, or will create a new shared memory object if O_CREAT is set).

#### RETURN VALUE

> Upon successful completion, a value of zero shall be returned. Otherwise, a value of -1 shall be returned and errno set to indicate the error. If -1 is returned, the named shared memory object shall not be changed by this function call.

#### ERRORS

> The shm_unlink() function shall fail if:

> [EACCES]
>   Permission is denied to unlink the named shared memory object.
> [ENAMETOOLONG]
>   The length of the name argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.
> [ENOENT]
>   The named shared memory object does not exist.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> Names of memory objects that were allocated with open() are deleted with unlink() in the usual fashion. Names of memory objects that were allocated with shm_open() are deleted with shm_unlink(). Note that the actual memory object is not destroyed until the last close and unmap on it have occurred if it was already in use.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> close(), mmap(), munmap(), shmat(), shmctl(), shmdt(), shm_open(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/mman.h>

#### CHANGE HISTORY

> First released in Issue 5. Included for alignment with the POSIX Realtime Extension.

#### Issue 6

> The shm_unlink() function is marked as part of the Shared Memory Objects option.

> In the DESCRIPTION, text is added to clarify that reusing the same name after a shm_unlink() will not attach to the old shared memory object.

> The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Shared Memory Objects option.

End of informative text.

UNIX ® is a registered Trademark of The Open Group.
POSIX ® is a registered Trademark of The IEEE.
[ Main Index | XBD | XCU | XSH | XRAT ]