rmdaily.sh

#!/bin/sh

FILEPREFIX="dailyfilename_"
AGE=7

[ -z "$1" ] && echo  "Usage: $0 DIR\ne.g. : $0 ." && exit

DIR="$1"
cd $DIR || { echo "Can't change directory to $DIR"; exit; }

LIST=${FILEPREFIX}*
[ -z "$LIST" ] && echo "No such file!" && exit

D1=`date +%s`   # seconds since epoch
[ -z "$D1" ] && echo "Can't get today date" && exit

for file in $LIST; do
    FDATE=`echo $file | sed -e "s/$FILEPREFIX//"`
    D2=`date +%s -d "$FDATE"`
    SECSOLD=`expr $D1 - $D2`
    DAYSOLD=`expr $SECSOLD / 86400`
    [ "$DAYSOLD" -gt "$AGE" ] && echo "rm -f $DIR/$file" && continue
    echo "# skip $DIR/$file"
done