This script will periodicaly try to download newest xkcd comic strip and put it into /mnt/us/screensaver, so it will show as screensaver

kindle_xkcd_screensaver.sh

#!/bin/sh
# This script will periodicaly try to download newest xkcd comic strip
# and put it into /mnt/us/screensaver, so it will show as screensaver
# It is for Kindle 4 and requires screensaver hack
lastVer=0
w=0
h=0
while :; do
  echo "check"
  rm /tmp/xkcd &> /dev/null
  wget "http://xkcd.com/info.0.json" -O /tmp/xkcd
  if [ ! -f /tmp/xkcd ];                                                                                                                                          
  then                                                                                                                                                                    
    sleep 60
    continue                                                                                                                                   
  fi

  IMG=`cat /tmp/xkcd | awk -F=":" -v RS="," '$1~/"img"/ {print}' | grep -o http:.*.png | sed -e 's%\\\\%%g'`
  if [ $lastVer != 0 ];
  then
      nowVer=`cat /tmp/xkcd | awk -F=":" -v RS="," '$1~/"num"/ {print}' | grep -o '[0-9].*'`
      if [ $nowVer == $lastVer ];
      then
          echo "already newest version"
          sleep 60
          continue
      fi  
  fi

  rm /tmp/xkcd.png &> /dev/null
  echo wget $IMG -O /tmp/xkcd.png
  wget $IMG -O /tmp/xkcd.png
  if [ ! -f /tmp/xkcd.png ];                                                                                                                                          
  then                                                                                                                                                                    
    sleep 60
    continue                                                                                                                                   
  fi
  cp /tmp/xkcd.png /mnt/us/screensaver/
  sync
  lastVer=`cat /tmp/xkcd | awk -F=":" -v RS="," '$1~/"num"/ {print}' | grep -o '[0-9].*'`
  eips 15 39 "XKCD comic $lastVer downloaded"
  echo $lastVer
  sleep 60
#  i=0
#  in_w=16
#  in_h=20
#  shift=24
#  while [ $i -lt 4 ]; do
#      width=`hexdump -e '/1 "%u"' -n 1 -s $in_w /tmp/xkcd.png`
#      let "w = w | ($width << $shift)"
#      height=`hexdump -e '/1 "%u"' -n 1 -s $in_h /tmp/xkcd.png`
#      let "h = h | ($height << $shift)"
#      let "shift -= 8"
#      let "i +=1"
#      let "in_w += 1"
#      let "in_h += 1"
#  done
  
#  echo $w
#  echo $h
done