shared memory in BSD 4.2

[guy at gorodish.UUCP]

>I have tracked down mmap and munmap but cannot figure out how to get the
>file descriptor of my own core image to pass to mmap.

You can't.  "mmap" doesn't do anything on vanilla 4.[23]BSD.  Some
implentations using 4.[23]BSD code  support it to varying degrees.

Even if it did, there is still no way to *get* a file descriptor that
refers to your own core image.  You probably wouldn't want one,
anyway; you'd want to pick a file to use to hold the shared data and
"mmap" that file into both your address spaces.