#! /bin/bash

sanitize() {
  shopt -s extglob;

  filename=$(basename "$1")
  directory=$(dirname "$1")

  #filename_clean="${filename//+([^[:alnum:]_-\.])/_}"
  filename_clean=$(echo -n $filename | tr --complement --squeeze-repeats "[:alnum:]./" "_")

  if (test "$filename" != "$filename_clean")
  then
    mv -v --backup=numbered "$1" "$directory/$filename_clean"
  fi
}

export -f sanitize
find $1 -depth -exec bash -c 'sanitize "$0"' {} \;