Bash script to normalize filenames (lower case and underlines instead of spaces)

normalize_filename.sh

#! /usr/bin/env bash
SAVEIFS=$IFS
IFS=$'\n'
FILES=$(find . -iname "$1")
for FILE in ${FILES[@]}; do
  DIRECTORY=$(echo $FILE | sed -n -E 's/^(\.?\/?(.+\/))?(([^\/]+)(\.([^\.\/]+))?)$/\1/p')
  FILENAME=$(echo $FILE | sed -n -E 's/^(\.?\/?(.+\/))?(([^\/]+)(\.([^\.\/]+))?)$/\3/p')
  FILENAME_NORM=$(echo $FILENAME | sed -E -e 's/./\l\0/g' -e 's/( |_)+/_/g' \
    -e 's/^_//' -e 's/(_|-)\./\./g' -e 's/\.\./\._/g')
  if ! [[ "$DIRECTORY$FILENAME" = "$DIRECTORY$FILENAME_NORM" ]]; then
    if [[ -e "$DIRECTORY$FILENAME_NORM" ]]; then
      rm $DIRECTORY$FILENAME
    else
      mv $DIRECTORY$FILENAME $DIRECTORY$FILENAME_NORM
    fi
  fi
done
IFS=$SAVEIFS