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From: lied@cbnewsc.att.com (Bob Lied)
Newsgroups: comp.sys.3b1
Subject: Re: stty: : Not a typewriter (really ksh $ENV file)
Keywords: vi, ksh
Message-ID: <1991Mar8.154644.9039@cbnewsc.att.com>
Date: 8 Mar 91 15:46:44 GMT
References: <1495@das13.snide.com> <1496@das13.snide.com> <1991Mar7.130721.4475@dms3b1.uucp>
Organization: AT&T Bell Laboratories
Lines: 30

In answer to the question of how to avoid interactive stuff in
a ksh $ENV file, especially for things like editor escapes,
there are two common solutions that I know of:

1. The $- variable lists the flags that are set by ksh.  If ksh
is invoked interactively (which I believe translates to input and
output are ttys), then the -i flag is set.  So, one way to avoid
things that write to the terminal for non-interactive use is
something like this inside the $ENV file:

	case "$-" in
	*i*)	# stty, reset prompts, alias cd, etc ;;
	*)	# functions and aliases that always export
	esac

2.  To avoid having the $ENV file sourced at all, there is a trick
that comes from page 78 of "The Kornshell Command and Programming
"Language".  Instead of setting ENV directly, you set a secondary
variable and use a side effect of evaluation (ENV is always re-evaluated
at shell startup).  So, in the .profile, you set up something like:

	export ENVFILE=~/.kshrc
	export ENV='${ENVFILE[(_$-=0)+(_=1)-_${-%%*i*}]}'

Note that the last part of this is the same as above:  checking $-
to see if the -i flag is set.  The rest of the gobbledygood evaluates
to 0 or 1; if it's zero, ENV == ENVFILE, but if it's one, ENV=''.

	No one said it had to be obvious.
	Bob Lied	att!ihlpf!lied