xsu or sux script for reference, but probably not all that useful...

scripts/zmap_x11_helper.sh

+#!/bin/bash
+
+if [ $# -lt 2 ]
+then echo "usage: `basename $0` clientuser command" >&2
+     exit 2
+fi
+
+CLIENTUSER="$1"
+shift
+
+# FD 4 becomes stdin too
+exec 4>&0
+
+HOST_UNIX=`hostname`/unix
+DISPLAY_QUERY=$DISPLAY
+DISPLAY_QUERY=`echo $DISPLAY_QUERY | sed -e "s!localhost!$HOST_UNIX!"`
+
+xauth list "$DISPLAY_QUERY" | sed -e 's/^/add /' | {
+    
+    # FD 3 becomes xauth output
+    # FD 0 becomes stdin again
+    # FD 4 is closed
+    exec 3>&0 0>&4 4>&-
+
+    su -s/bin/bash "$CLIENTUSER" -c "\
+xauth -q <&3
+xauth list '$DISPLAY'
+DISPLAY=$DISPLAY $* 3>&-
+xauth remove $DISPLAY
+xauth list $DISPLAY
+echo Finished"
+
+}
+
+exit
+
+FB_DISPLAY=:4
+
+# If there's no display, we need to make one
+if [ "x$DISPLAY" == "x" ]; then
+
+    # Start the server
+    Xvfb $FB_DISPLAY -screen 0 1024x768x24 -terminate &
+    # need to fix font path issues (-fp ?)
+    # grep FontPath /etc/X11/xorg.conf
+else
+    FB_DSPLAY=$DISPLAY
+fi
+
+# set display
+export DISPLAY=$FB_DISPLAY
+
+
+
+# So what we need to do is figure out what the display is/isn't
+
+
+
+export X