Watch for new files created matching a pattern, move them somewhere else with an auto-incrementing numerical prefix

watchmeincrement.py

#!/usr/bin/env python3
##
##  Authors:   Kagi Quick, gemini/gemini-3.1-pro-preview, Kevin Ernst
##  Date:      3 July 2026
##  Licence:   WTFPL
##  Homepage:  https://gist.github.com/ernstki/ba50c42ec22984afdf870030fdb84132
##
##  Usage:     python watchincrement.py "*.pdf" ~/Documents/00_TO_READ
##
import re
import os
import sys
import shutil
import logging

from fnmatch import fnmatch

from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler

logging.basicConfig(level=logging.INFO)
log = logging.getLogger(__name__)


class Handler(FileSystemEventHandler):

    def __init__(self, watch_dir, dest, pattern):
        self.watch_dir = watch_dir
        self.dest = dest
        self.pattern = pattern
        os.makedirs(dest, exist_ok=True)

    def on_created(self, event):
        self._moveit(event)

    def on_modified(self, event):
        self._moveit(event)

    def _moveit(self, event):
        if event.is_directory:
            log.debug(f"{event} was a directory")
            return

        # The OS often queues multiple create/modify events for a single file operation.
        # If we already moved the file in a previous event, it will no longer exist here.
        if not os.path.exists(event.src_path):
            return

        if os.path.abspath(os.path.dirname(event.src_path)) != os.path.abspath(self.watch_dir):
            log.debug(f"{event} was not in watch_dir")
            return

        name = os.path.basename(event.src_path)

        if not fnmatch(name, self.pattern):
            log.debug(f"{event} didnt match pattern '{self.pattern}'")
            return

        existing = os.listdir(self.dest)
        new_num = 0

        for f in existing:
            m = re.match(r"\[(\d{2})\]", f)
            if m:
                new_num = max(new_num, int(m.group(1)))

        new_num = new_num + 1

        m = re.match(r'\[(\d{2})\] (.*)', name)
        suffix = m.group(2) if m else name
        target = os.path.join(self.dest, f"[{new_num:02d}] {suffix}")

        log.info(f"Moving {event.src_path} to {target}")
        shutil.move(event.src_path, target)


if __name__ == "__main__":
    watch_dir = '.'
    pattern, dest_dir = sys.argv[1], sys.argv[2]
    observer = Observer()
    observer.schedule(
        Handler(watch_dir, dest_dir, pattern), watch_dir, recursive=False
    )
    observer.start()
    try:
        while True:
            observer.join(1)
    except KeyboardInterrupt:
        observer.stop()
    observer.join()