#!/bin/ksh
#
# rlogin
#
# AUTHOR:
#   Dan Harkless                                                    <opensource@
#   http://harkless.org/dan/software/                              harkless.org>
#
# COPYRIGHT:
#   This file is Copyright (C) 2001 by Dan Harkless, and is released under the
#   GNU General Public License <http://www.gnu.org/copyleft/gpl.html>.
#
# DESCRIPTION:
#   Setups where mutliple machines NFS-mount your home directory are great
#   because you can seamlessly rlogin from machine to machine as needed, running
#   X applications and displaying them on your workstation.
#
#   Well... it's not quite _that_ easy.  Before you rlogin to the new machine
#   you have to xhost it (or xhost -, which is a bad idea).  Once you're there,
#   you have to set the $DISPLAY environment variable to point to your X
#   workstation.  This is a pain to do manually, so this script wraps around the
#   real rlogin executable and does these steps for you.
#
#   If $DISPLAY is :0.0 (meaning this login session is on your local X
#   workstation), and you have not yet xhosted your destination machine, this
#   script does a simple "xhost $1".  In the future, I may enhance it to do an
#   "xhost <user>@<host>" on OSes (such as Solaris) that support it.  If you now
#   rlogin to a third machine from the second one, unfortunately an automatic
#   xhost cannot be done, since xhost only works on the console of the X
#   workstation you're using.
#
#   To get $DISPLAY set properly, the script operates on the assumption that you
#   always have the variable set properly in your current environment before you
#   rlogin somewhere else.  It writes the current setting to a file called
#   ~/.DISPLAY.  If you have the line:
#
#       if (! $?DISPLAY) setenv DISPLAY `cat ~/.DISPLAY`
#
#   or its Bourne-shell-compatible equivalent in your .login, $DISPLAY will be
#   set up properly once you're rlogged in to your destination.
#
#   As this script exits, it undoes any xhosting that it has done.
#
#   Of course the real solution to the problem this script fixes is to use ssh
#   (with X11 forwarding) instead of rlogin, but if you don't have that 
#   available on all your machines, you can use this as a poor man's version.
#
# DATE        MODIFICATION
# ==========  ==================================================================
# 2001-07-18  For some reason on Linux they use "unix:0.0" to mean ":0.0".
# 1999-03-27  Look for rlogin in a series of locations rather than checking OS.
# 1996-10-03  rlogin is in /usr/ucb instead of /usr/bin on SunOS 4.x.
# 1996-07-31  Original.

if [ "$DISPLAY" = ":0.0" -o "$DISPLAY" = "unix:0.0" ]; then
    if [ `xhost | fgrep -c $1` = 0 ]; then
	trap 'xhost -$1' 0 1 2 3 15
	xhost $1
    fi
    echo $HOST:0.0 > ~/.DISPLAY
else
    echo "$DISPLAY" > ~/.DISPLAY
fi

rlogin=""
rlogin_locations="/usr/bin /usr/ucb"  # anywhere else?

for dir in $rlogin_locations; do
    if [ -x $dir/rlogin ]; then
	rlogin=$dir/rlogin
    fi
done

if [ "$rlogin" = "" ]; then
    echo $0": rlogin not found in ($rlogin_locations)."
    exit 1
else
    $rlogin "$@" -8  # 7-bit pipe is a really stupid default for rlogin...
fi