open() vs the lowest unused file descriptor

Hi! Today I noticed that on Single Unix Specification V2, as well as on the Linux 2.4.26 machine I have here, that the open() call promises to return the lowest unused file descriptor when successful. I'm just wondering: does FreeBSD 4.x and 5.x promise that? If so, should we update the manpage to

mmap, shmget, and MAP_HASSEMAPHORE

Hi! I hope I'm asking in the right newsgroup: 1) What is the effect (from a user-space application programmer's point of view) of using the MAP_HASSEMAPHORE flag when calling mmap(...)? 2) And why is there no equivalent flag when using shmget(...)? I tried reading the manuals+web, but since in L