S3 cleanup based on timeslots

cleanup.sh

#!/bin/bash
##
##  Gradual cleanup of S3 stored backups
##  by Radek 'Goblin' Pieczonka <goblin@pentex.pl>
##
##  Configure with environment variables
##  - S3BUCKET
##  - S3PATH
##  Files need to be named YYYYMMDDHHmm.tgz
##  TODO: support for moving to glacier for long term backup storage
##
##  Run script like : S3BUCKET=<bucket> S3PATH=<path_in_bucket> AWS_ACCESS_KEY_ID=<aws_id> AWS_SECRET_ACCESS_KEY=<aws_key> ./cleanup.sh
##

for FILE in $(aws s3 ls s3://${S3BUCKET}/${S3PATH}/ | cut -d' ' -f4 | egrep "^[0-9]{12}.tgz")
do
  # Calculate days from epoch and diff
  FILE_EPOCHDAY=$(( $(date --date ${FILE:0:8} +%s)/24/3600 ))
  WEEKSTART_EPOCHDAY=$(( $(date +%s)/24/3600 - $(date +%u) ))
  DIFF=$(( ${WEEKSTART_EPOCHDAY} - ${FILE_EPOCHDAY} ))
  echo -n "${FILE} : ${FILE_EPOCHDAY} ${WEEKSTART_EPOCHDAY} ${DIFF} : "

  # Define modulo LEVEL for next step based on how old is the file in days
  LEVEL=0
  [ ${DIFF} -gt 7 ] && LEVEL=1
  [ ${DIFF} -gt 32 ] && LEVEL=2
  [ ${DIFF} -gt 64 ] && LEVEL=3
  [ ${DIFF} -gt 128 ] && LEVEL=4
  [ ${DIFF} -gt 366 ] && LEVEL=6 && GLACIER=true

  # Make decision if keep or remove based on the modulo from dividing by 2^LEVEL (keep if 0) 
  # counted on a day since epoch (for coherent modulo calculation) effecting in gradualy lowering of backup density
  if [ $(( ${FILE_EPOCHDAY}%(2**${LEVEL}) )) -eq 0 ]
  then
    echo "keep"
    [ "${GLACIER}" == "true" ] && echo "and move to glacier (TODO)"
  else
    echo "remove"
    aws s3 rm s3://${S3BUCKET}/${S3PATH}/${FILE}
  fi
done