getcwd() and friends.

[Guy Harris]

>Surprise!  sendmsg() in 4.3bsd lets you do this.  SunOS4.0 looks like
>it may also.

I'd sure hope it does, since the code basically comes from some BSD
release in the range [4.3BSD, 4.3-tahoe).

SunOS 4.0, and other systems with the S5R3 streams code, will also let
you pass file descriptors with streams (at least the code appears to try
to support it, and the documentation claims it works; I haven't tried
it, so I don't know if there are any bugs).