shell file descriptor programming (was: Unlinked temp files)

[Guy Harris]

>If you know of a portable way to do this (ie, one that works on BSD 4.x,
>System V Release 1 through 4, POSIX, etc.), please let me know.

You don't need a portable one.  All you need is a way to tell what kind
of system you have (something that, as far as I know, the "ksh"
configuration script already *has*), so you know whether to:

	1) compile the number in;

	2) fetch it with "getdtablesize" (BSD4.2 and later);

	3) fetch it with "ulimit(4, 0L)" (S5R3.0 and later).