Resize 3 Windows Side-by-Side Linux

thirds.sh

#!/bin/bash
# assign keyboard shortcut to bash thirds.sh
# run shortcut on the window to resize
# it auto cycles to the position (0)left, (1)middle, (2)right

# create a counter file to store positions
counter="thirds-counter.txt"
if [[ -f $counter ]]; then
  count=$(<$counter)
else
  echo "0" > $counter
fi

# determine size of the desktop
get_screen_geometry()
{
   xwininfo -root | awk  -F ':' '/Width/{printf "%d",$2/3}/Height/{print $2}'
}

# unmaximize the window
xdotool key 'Ctrl+Super+Down'
sleep 1

# set size of the window to one third of total to the position 0,1,2
xdotool getactivewindow windowsize $(get_screen_geometry)
xdotool getactivewindow windowmove $(get_screen_geometry | awk -v POS=$count '{printf "%d", POS*$count}') 0

# store next position to the file
count=$(((($count+1))%3))
echo "$count" > $counter

Link to detailed answer.