Shell Programming and Scripting

DT=${1:-$(date +%Y%m%d)}
for file in *_${DT}.csv
do
   [ -f "$file" ] && echo "$file"
done

abcdefgh_20180102.csv
abcdefgh_20180120.csv
xyz_20180121.csv
xyz_20180102.csv
abcdefgh_xyz_pqr_20180102.csv
abcdefgh_xyz_pqr_20180109.csv
abcdefgh_65325_parent_20180120.csv
abcdefgh_65325_parent_20180127.csv
xyz_34567_filter_20180121.csv
xyz_34567_filter_20180128.csv

ls *.csv  |
{ while read LINE    
    do  GR=${LINE%_*}
        DT=${LINE#${GR}_}
        DT=${DT%.*}
        XT=.${LINE##*.}
        [ ! "$GR" = "${OGR:-$GR}" ] &&          { echo ${OLN} 
                                                  ODT=""   
                                                }          
        [ "$DT" -gt "$1" ] && [ "$ODT" ]   ||     ODT=$DT
        OGR=$GR
        OLN="$LINE"  
  done  
echo ${OLN} 
}