age_check.sh

#!/bin/sh
# This checks that the specified file is less than 4 days old
# deletes files that are too old

for f in *.jpg
do

  FILE=$f
  MAXAGE=$(bc <<< '4*24*60*60') # seconds in a week
  #MAXAGE=$(bc <<< '60') # seconds in a minute, for testing

  ## file age in seconds = current_time - file_modification_time.
  FILEAGE=$(($(date +%s) - $(stat -c '%Y' "$FILE")))
  test $FILEAGE -gt $MAXAGE && {
      rm $FILE
  }

done