[ On Sun, October  8, 1995 at 23:56:02 (-0500), vax@ccwf.cc.utexas.edu wrote: ]
> Subject: a shell idea?
>
> I was wondering about this shell idea I had.
> The basic notion came from the fact that path manipulation is difficult.
> For example, it's difficult (but can be done) to do a command like:
>   ``Add this directory iff it's not already in the path''
> or variations like:
>   ``Add this directory iff it [and every parent directory] are protected
>     from writing by anyone but root or bin''
> This would be especially cool if it was one builtin command, IMHO.

I think I promised to send you my .profile, etc., which have a way to do
this in existing Bourne and Korn Shell compatible environments,
including 4.xBSD's ash.  Remind me again if you'd like a copy of my huge
but fairly portable .profile and associated files.

Here's the guts of the simplest implementation:

dirappend ()
{
	if [ $# -le 1 ] ; then
		echo "Usage: dirappend variable directory [...]" >&2
		exit 2
	fi
	varname=$1
	shift
	eval varvalue='$'$varname
	while [ $# -gt 0 ] ; do
		if [ -d "$1" -a `expr ":$varvalue:" : ".*:$1:.*"` -eq 0 ] ; then
			eval $varname='$'"$varname"'":$1"'
		fi
		shift
	done
	unset varname varvalue
}

dirprepend ()
{
	if [ $# -le 1 ] ; then
		echo "Usage: dirprepend variable directory [...]" >&2
		exit 2
	fi
	varname=$1
	shift
	eval varvalue='$'$varname
	while [ $# -gt 0 ] ; do
		if [ -d "$1" -a `expr ":$varvalue:" : ".*:$1:.*"` -eq 0 ] ; then
			eval $varname='"$1:"$'"$varname"
		fi
		shift
	done
	unset varname varvalue
}

-- 
							Greg A. Woods

+1 416 443-1734			VE3TCP			robohack!woods
Planix, Inc. <woods@planix.com>; Secrets Of The Weird <woods@weird.com>