Rename photos in the specified directory like Dropbox's "Camera Upload" based on last modified dates

rename_photos_like_dropbox.sh

#!/bin/sh
ABSPATH=$(cd "$1"; pwd)
COUNT=0

if [ ! -e $ABSPATH ]; then
  echo "*** $ABSPATH doesn't exist! ***"
  exit
fi

for F in $ABSPATH/*; do
  if [[ ! "$F" =~ (png|PNG|jpeg|JPEG|jpg|JPG)$ ]]; then
    echo "*** $F ignored."
    continue
  fi
  F_DATE=`stat -f "%m" "$F"`
  NEW_F=`/bin/date -r ${F_DATE} +'%Y-%m-%d %H.%M.%S.jpg'`
  while [[ -e "$ABSPATH/$NEW_F" ]]; do
    F_DATE=`expr ${F_DATE} + 1`
    NEW_F=`/bin/date -r ${F_DATE} +'%Y-%m-%d %H.%M.%S.jpg'`
  done
  read -p "Rename $F -> ${NEW_F} ? [y/N]" -n 1 -r
  echo
  if [[ ! $REPLY =~ ^[Yy]$ ]]; then
    continue
  else
    echo "+ $F -> ${NEW_F}"
    mv "$F" "$ABSPATH/${NEW_F}"
    COUNT=`expr $COUNT + 1`
  fi
done
echo "$COUNT photos renamed!"