> Last night, I installed the latest copy of pdksh (my favorite shell),

Mine too :-)

> and all hell broke loose; my login script was causing complaints about
> "let: arith: bad syntax (top=0)" and many other fiendish complaints,
> including a gripe about /usr/bin/cpp not working!  After much hair
> tearing and searching for latest-and-greatests of several alternative
> shells, I finally discovered that /bin/sh "now" recognizes the ENV
> environment variable, and it was choking trying to understand my

I'm told that $ENV is needed for POSIX.  Of course the POSIX shell is
supposed to be almost (but not quite) ksh.  There are lots of ksh'isms
that /bin/sh does not (yet) handle and while I protect all ksh
specifics in /etc/profile,.profile and even $ENV, with:

	if [ "$RANDOM" != "$RANDOM" ]; then
		# its ksh
	else
		# its not-ksh
	fi

This does not help if you try to use something like:

	HOSTNAME=`hostname`
	HOST=${HOSTNAME%%.*}

in one of these scripts as (/bin/sh in 1.0 anyway) syntax checks the
lines even though it is not going to execute them.

BTW, the above test using $RANDOM works for all ksh variants.  I only
use $KSH_VERSION to differentiate between pd-ksh and the real thing as
changing key bindings is different.

Check out the /etc/profile and /etc/ksh.kshrc that are in the package
kshenv.tgz on sun-lamp.

Anyway the bottom line is that you cannot have any ksh specific
syntax in ksh's startup file ($ENV).  This situation is ridiculous but
blame POSIX...

--sjg