|SHMAT(2)||System Calls Manual||SHMAT(2)|
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_RNDis set in shmflg, the system will round the address down to a multiple of
SHMLBAis defined in
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-current|