very old script, I wrote better code afterwards. This is kept just for nostalgic purposes

get_unity_viewports.sh

#!/bin/bash

get_screen_geometry()
{
 xwininfo -root | awk '/-geometry/{gsub(/+|x/," ");print $2,$3}'  
}

SCHEMA="org.compiz.core:/org/compiz/profiles/unity/plugins/core/"
read screen_width screen_depth  <<< "$(get_screen_geometry)" 
hsize=$(gsettings get $SCHEMA hsize)
vsize=$(gsettings get $SCHEMA vsize)
declare -a viewports
y=0
for vertical in $(seq 1 $vsize); do
 x=0
 for horizontal in $(seq 1 $hsize); do
     viewports+=( $( echo $y:$x ) )
     x=$(($x+$screen_width))
 done
 y=$(($y+$screen_depth))
done

i=1
while [ $i -le ${#viewports[@]}  ];
do
  echo "Viewport $i is ${viewports[$(($i-1))]}"
  i=$(($i+1))
done