NAME
shm_open,
shm_unlink, shm_mkstemp
— create and destroy shared
memory objects
SYNOPSIS
#include
<sys/mman.h>
int
shm_open(const
char *path, int
flags, mode_t
mode);
int
shm_unlink(const
char *path);
int
shm_mkstemp(char
*template);
DESCRIPTION
The
shm_open()
function opens a shared memory object and returns a file descriptor suitable
for use with mmap(2). The flags argument has the same
meaning as provided to open(2) and must include at least
O_RDONLY or O_RDWR and may
also include a combination of O_CREAT,
O_EXCL, O_CLOEXEC,
O_NOFOLLOW, or O_TRUNC. This
implementation forces the mode to be 0600 or 0400, and
prohibits sharing between different UIDs.
shm_unlink()
is used to remove a shared memory object. The object is not freed until all
references to it have been released via
close(2).
If a temporary shared memory object is desired,
the
shm_mkstemp()
function should be preferred as it avoids several possible security holes
that tend to appear in programs trying to create their own unique temporary
names. The template argument is a string with at least
six trailing Xs as described in
mkstemp(3).
RETURN VALUES
shm_open() and
shm_mkstemp() return a file descriptor on successful
completion. They may fail for any of the reasons listed in
open(2).
SEE ALSO
STANDARDS
shm_open() and
shm_unlink() appear in IEEE Std
1003.1-2001 (“POSIX.1”). Using
O_CLOEXEC or O_NOFOLLOW with
shm_open() is an extension to that standard. This
implementation deviates from the standard by permitting less sharing.
shm_mkstemp() is an extension.
HISTORY
The shm_open(),
shm_unlink(), and
shm_mkstemp() functions have been available since
OpenBSD 5.4.
AUTHORS
Ted Unangst <tedu@openbsd.org>.