|SHMAT(2)||System Calls Manual||SHMAT(2)|
— map/unmap shared memory
shmid, const void
shmat() maps the shared memory segment
associated with the shared memory identifier shmid
into the address space of the calling process. The address at which the
segment is mapped is determined by the shmaddr
parameter. If it is equal to 0, the system will pick an address itself.
Otherwise, an attempt is made to map the shared memory segment at the
address shmaddr specifies. If
SHM_RND is set in shmflg, the
system will round the address down to a multiple of
SHMLBA bytes (
A shared memory segment can be mapped read-only by specifying the
SHM_RDONLY flag in shmflg.
shmdt() unmaps the shared memory segment
that is currently mapped at shmaddr from the calling
process' address space. shmaddr must be a value
returned by a prior
shmat() call. A shared memory
segment will remain existent until it is removed by a call to
shmctl(2) with the
shmat() returns the address at which the
shared memory segment has been mapped into the calling process' address
space when successful,
shmdt() returns 0 on
successful completion. Otherwise, a value of -1 is returned, and the global
variable errno is set to indicate the error.
shmat() will fail if:
shmaddr specifies an illegal address.
shmdt() will fail if:
|November 15, 2014||OpenBSD-5.9|