FFMpeg screencast window

#!/bin/sh

INFO=$(xwininfo -frame)

WIN_GEO_W=$(echo $INFO | grep 'Width' | awk '{print $2;}')
WIN_GEO_H=$(echo $INFO | grep 'Height' | awk '{print $2;}')
WIN_X=$(echo $INFO | grep 'Absolute upper-left X' | awk '{print $4;}')
WIN_Y=$(echo $INFO | grep 'Absolute upper-left Y' | awk '{print $4;}')

ffmpeg -f x11grab -r 25 -s $WIN_GEO_Wx$WIN_GEO_H -i :0.0+$WIN_X+$WIN_Y /tmp/screencast.avi