#!/usr/bin/ksh
 
cd $CURRENT_DIR
 
ls *_[01][0-9][0-3][0-9]20[0-3][0-9] | sed '
  s/\(.*\)_\([01][0-9][0-3][0-9]\)20\([0-3][0-9]\)/\3\2 \1 &/
 ' | sort | while read xxkey file_base file
do
 if [ $file_base = "$last_file_base" ]
 then
  mv last_file $ARCHIVE_DIR # one at a time for simplicity
  while (( 6 < $(
                     ls $ARCHIVE_DIR/${file_base}_[01][0-9][0-3][0-9]20[0-3][0-9] 2>/dev/null | wc -l
                     ) ))
  do
    ls -tr $ARCHIVE_DIR/${file_base}_[01][0-9][0-3][0-9]20[0-3][0-9] | read x
    rm -f $x
  done
 fi
 
 last_file=$file  last_file_base=$file_base
done