#!/bin/bash

mapfile -t files < <(find . -maxdepth 1 -type f)

for filename in "${files[@]}"; do
  filename_m5sum=$(md5sum "$filename" | awk '{print $1}')
  filename_extension="${filename##*.}"

  new_filename="$filename_m5sum.$filename_extension"

  if [ "$filename" == "$new_filename" ]; then
    continue
  fi

  mv "$filename" "$new_filename"
done