a.sh

#!/bin/bash
for file in $BLKPATH/*;
do
  echo $file
  if [[ $file =~ $BLKPATH/blk[0-9][0-9][0-9][0-9][0-9].dat ]]; then
    printf "got a match - %s\n"
    BLKLST+="-$OPTION=$file "
  fi
done

echo $BLKLST

gistfile1.txt

249750  2021-04-02 21:27:46 - BLKPATH=/home/helloshitty/WdElements/blockchain-backup/blocks
249751  2021-04-02 21:28:00 - sudo mkdir -p $BLKPATH
249752  2021-04-02 21:28:53 - sudo touch $BLKPATH/blk01516.dat $BLKPATH/blk0A1516.dat
249755  2021-04-02 21:31:07 - BLKPATH