This will notify you when things change in undertale.ini.

README.md

How to use:

• Install Python
• Install Python Watchdog: pip install watchdog
• Put undertailer.py next to undertale.ini
• Run it from the commandline: python undertailer.py
• Play undertale and watch the commandline output

undertailer.py

import os
import sys
import time
import logging
import ConfigParser

from watchdog.observers import Observer
from watchdog.events import PatternMatchingEventHandler

UNDERTALE_PATH = os.path.dirname(__file__)

def get_with_default(config, section, option, default):
    return config.get(section, option) if config.has_section(section) and config.has_option(section, option) else default

class UndertaleEventHandler(PatternMatchingEventHandler):
    def __init__(self, path):
        super(UndertaleEventHandler, self).__init__(patterns=[path])
        self.path = path
        self.config = self.read_config()
        self.print_config()
        print "Ready"

    def read_config(self):
        with open(self.path) as config_file:
            config = ConfigParser.RawConfigParser()
            config.readfp(config_file)
            return config

    def print_config(self):
        for section in self.config.sections():
            for option, value in self.config.items(section):
                print "{section}: {option}: {value}".format(section=section, option=option, value=value)

    def on_modified(self, event):
        new_config = self.read_config()
        old_config = self.config

        new_sections = set(new_config.sections())
        old_sections = set(old_config.sections())
        all_sections = new_sections.union(old_sections)

        changes = []
        for section in all_sections:
            old_options = set(old_config.options(section))
            new_options = set(new_config.options(section))
            all_options = old_options.union(new_options)

            for option in all_options:
                old_value = get_with_default(old_config, section, option, None)
                new_value = get_with_default(new_config, section, option, None)

                if old_value != new_value:
                    changes.append(dict(section=section, option=option, old_value=old_value, new_value=new_value))

        if changes:
            print "\n\nCHANGES!\n"
            for change in changes:
                print "{section}: {option}: {old_value} => {new_value}".format(**change)

        self.config = new_config

if __name__ == "__main__":
    event_handler = UndertaleEventHandler(UNDERTALE_PATH + 'undertale.ini')
    observer = Observer()
    observer.schedule(event_handler, UNDERTALE_PATH, recursive=False)
    observer.start()
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        observer.stop()
    observer.join()