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WATCHDOG(3) watchdog WATCHDOG(3)

NAME

watchdog - watchdog Documentation

Python API library and shell utilities to monitor file system events.

Works on 3.6+.

If you want to use Python 2.6, you should stick with watchdog < 0.10.0.

If you want to use Python 2.7, 3.4 or 3.5, you should stick with watchdog < 1.0.0.

DIRECTORY MONITORING MADE EASY WITH

  • A cross-platform API.
  • A shell tool to run commands in response to directory changes.

Get started quickly with a simple example in Quickstart.

EASY INSTALLATION

You can use pip to install watchdog quickly and easily:

$ python -m pip install -U watchdog


Need more help with installing? See Installation.

INSTALLATION

watchdog requires 3.6+ to work. See a list of Dependencies.

Installing from PyPI using pip

$ python -m pip install -U watchdog
# or to install the watchmedo utility:
$ python -m pip install -U 


|
project_name|[watchmedo]


Installing from source tarballs

$ wget -c https://pypi.python.org/packages/source/w/watchdog/watchdog-2.1.9.tar.gz
$ tar zxvf watchdog-2.1.9.tar.gz
$ cd watchdog-2.1.9
$ python -m pip install -e .
# or to install the watchmedo utility:
$ python -m pip install -e ".[watchmedo]"


Installing from the code repository

$ git clone --recursive git://github.com/gorakhargosh/watchdog.git
$ cd watchdog
$ python -m pip install -e .
# or to install the watchmedo utility:
$ python -m pip install -e ".[watchmedo]"


Dependencies

watchdog depends on many libraries to do its job. The following is a list of dependencies you need based on the operating system you are using.

Operating system Dependency (row) Windows Linux 2.6 macOS Darwin BSD
XCode Yes

The following is a list of dependencies you need based on the operating system you are using the watchmedo utility.

Operating system Dependency (row) Windows Linux 2.6 macOS Darwin BSD
PyYAML Yes Yes Yes Yes

Installing Dependencies

The watchmedo script depends on PyYAML which links with LibYAML. On macOS, you can use homebrew to install LibYAML:

brew install libyaml


On Linux, use your favorite package manager to install LibYAML. Here's how you do it on Ubuntu:

sudo apt install libyaml-dev


On Windows, please install PyYAML using the binaries they provide.

Supported Platforms (and Caveats)

watchdog uses native APIs as much as possible falling back to polling the disk periodically to compare directory snapshots only when it cannot use an API natively-provided by the underlying operating system. The following operating systems are currently supported:

WARNING:

Differences between behaviors of these native API are noted below.


Linux kernel version 2.6 and later come with an API called inotify that programs can use to monitor file system events.

NOTE:

On most systems the maximum number of watches that can be created per user is limited to 8192. watchdog needs one per directory to monitor. To change this limit, edit /etc/sysctl.conf and add: 

fs.inotify.max_user_watches=16384




The Darwin kernel/OS X API maintains two ways to monitor directories for file system events:
  • kqueue
  • FSEvents

watchdog can use whichever one is available, preferring FSEvents over kqueue(2). kqueue(2) uses open file descriptors for monitoring and the current implementation uses macOS File System Monitoring Performance Guidelines to open these file descriptors only to monitor events, thus allowing OS X to unmount volumes that are being watched without locking them.

NOTE:

More information about how watchdog uses kqueue(2) is noted in BSD Unix variants. Much of this information applies to macOS as well.


changes to open file descriptors. Because of the way kqueue(2) works, watchdog needs to open these files and directories in read-only non-blocking mode and keep books about them.

watchdog will automatically open file descriptors for all new files/directories created and close those for which are deleted.

NOTE:

The maximum number of open file descriptor per process limit on your operating system can hinder watchdog's ability to monitor files.

You should ensure this limit is set to at least 1024 (or a value suitable to your usage). The following command appended to your ~/.profile configuration file does this for you:

ulimit -n 1024




The Windows API provides the ReadDirectoryChangesW. watchdog currently contains implementation for a synchronous approach requiring additional API functionality only available in Windows Vista and later.

NOTE:

Since renaming is not the same operation as movement on Windows, watchdog tries hard to convert renames to movement events. Also, because the ReadDirectoryChangesW API function returns rename/movement events for directories even before the underlying I/O is complete, watchdog may not be able to completely scan the moved directory in order to successfully queue movement events for files and directories within it.


NOTE:

Since the Windows API does not provide information about whether an object is a file or a directory, delete events for directories may be reported as a file deleted event.


watchdog also includes a fallback-implementation that polls watched directories for changes by periodically comparing snapshots of the directory tree.

QUICKSTART

Below we present a simple example that monitors the current directory recursively (which means, it will traverse any sub-directories) to detect changes. Here is what we will do with the API:

1.
Create an instance of the watchdog.observers.Observer thread class.
2.
Implement a subclass of watchdog.events.FileSystemEventHandler (or as in our case, we will use the built-in watchdog.events.LoggingEventHandler, which already does).
3.
Schedule monitoring a few paths with the observer instance attaching the event handler.
4.
Start the observer thread and wait for it generate events without blocking our main thread.

By default, an watchdog.observers.Observer instance will not monitor sub-directories. By passing recursive=True in the call to watchdog.observers.Observer.schedule() monitoring entire directory trees is ensured.

A Simple Example

The following example program will monitor the current directory recursively for file system changes and simply log them to the console:

import sys
import logging
from watchdog.observers import Observer
from watchdog.events import LoggingEventHandler
if __name__ == "__main__":


    logging.basicConfig(level=logging.INFO,


                        format='%(asctime)s - %(message)s',


                        datefmt='%Y-%m-%d %H:%M:%S')


    path = sys.argv[1] if len(sys.argv) > 1 else '.'


    event_handler = LoggingEventHandler()


    observer = Observer()


    observer.schedule(event_handler, path, recursive=True)


    observer.start()


    try:


        while observer.is_alive():


            observer.join(1)


    finally:


        observer.stop()


        observer.join()


To stop the program, press Control-C.

API REFERENCE

watchdog.events

watchdog.events
File system events and event handlers.
yesudeep@google.com (Yesudeep Mangalapilly)
contact@tiger-222.fr (Mickaël Schoentgen)

Event Classes

Bases: object

Immutable type that represents a file system event that is triggered when a change occurs on the monitored file system.

All FileSystemEvent objects are required to be immutable and hence can be used as keys in dictionaries or be added to sets.

The type of the event as a string.

True if event was emitted for a directory; False otherwise.

True if event was synthesized; False otherwise.

These are events that weren't actually broadcast by the OS, but are presumed to have happened based on other, actual events.


Source path of the file system object that triggered this event.


Bases: watchdog.events.FileSystemEvent

File system event representing any kind of file system movement.

The destination path of the move event.


Bases: watchdog.events.FileSystemMovedEvent

File system event representing file movement on the file system.


Bases: watchdog.events.FileSystemMovedEvent

File system event representing directory movement on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing file modification on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing directory modification on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing file creation on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing file close on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing directory creation on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing file deletion on the file system.


Bases: watchdog.events.FileSystemEvent

File system event representing directory deletion on the file system.


Event Handler Classes

Bases: object

Base file system event handler that you can override methods from.

Dispatches events to the appropriate methods.
event (FileSystemEvent) -- The event object representing the file system event.


Catch-all event handler.
event (FileSystemEvent) -- The event object representing the file system event.


Called when a file opened for writing is closed.
event (FileClosedEvent) -- Event representing file closing.


Called when a file or directory is created.
event (DirCreatedEvent or FileCreatedEvent) -- Event representing file/directory creation.


Called when a file or directory is deleted.
event (DirDeletedEvent or FileDeletedEvent) -- Event representing file/directory deletion.


Called when a file or directory is modified.
event (DirModifiedEvent or FileModifiedEvent) -- Event representing file/directory modification.


Called when a file or a directory is moved or renamed.
event (DirMovedEvent or FileMovedEvent) -- Event representing file/directory movement.



Bases: watchdog.events.FileSystemEventHandler

Matches given patterns with file paths associated with occurring events.

(Read-only) True if path names should be matched sensitive to case; False otherwise.

Dispatches events to the appropriate methods.
event (FileSystemEvent) -- The event object representing the file system event.


(Read-only) True if directories should be ignored; False otherwise.

(Read-only) Patterns to ignore matching event paths.

(Read-only) Patterns to allow matching event paths.


Bases: watchdog.events.FileSystemEventHandler

Matches given regexes with file paths associated with occurring events.

(Read-only) True if path names should be matched sensitive to case; False otherwise.

Dispatches events to the appropriate methods.
event (FileSystemEvent) -- The event object representing the file system event.


(Read-only) True if directories should be ignored; False otherwise.

(Read-only) Regexes to ignore matching event paths.

(Read-only) Regexes to allow matching event paths.


Bases: watchdog.events.FileSystemEventHandler

Logs all the events captured.

Called when a file or directory is created.
event (DirCreatedEvent or FileCreatedEvent) -- Event representing file/directory creation.


Called when a file or directory is deleted.
event (DirDeletedEvent or FileDeletedEvent) -- Event representing file/directory deletion.


Called when a file or directory is modified.
event (DirModifiedEvent or FileModifiedEvent) -- Event representing file/directory modification.


Called when a file or a directory is moved or renamed.
event (DirMovedEvent or FileMovedEvent) -- Event representing file/directory movement.



watchdog.observers.api

Immutables

Bases: object

An scheduled watch.

  • path -- Path string.
  • recursive -- True if watch is recursive; False otherwise.


Determines whether subdirectories are watched for the path.

The path that this watch monitors.


Collections

Bases: watchdog.utils.bricks.SkipRepeatsQueue

Thread-safe event queue based on a special queue that skips adding the same event (FileSystemEvent) multiple times consecutively. Thus avoiding dispatching multiple event handling calls when multiple identical events are produced quicker than an observer can consume them.


Classes

Bases: watchdog.utils.BaseThread

Producer thread base class subclassed by event emitters that generate events and populate a queue with them.

  • event_queue (watchdog.events.EventQueue) -- The event queue to populate with generated events.
  • watch (ObservedWatch) -- The watch to observe and produce events for.
  • timeout (float) -- Timeout (in seconds) between successive attempts at reading events.


Queues a single event.
event (An instance of watchdog.events.FileSystemEvent or a subclass.) -- Event to be queued.


Override this method to populate the event queue with events per interval period.
timeout (float) -- Timeout (in seconds) between successive attempts at reading events.


Method representing the thread's activity.

You may override this method in a subclass. The standard run() method invokes the callable object passed to the object's constructor as the target argument, if any, with sequential and keyword arguments taken from the args and kwargs arguments, respectively.


Blocking timeout for reading events.

The watch associated with this emitter.


Bases: watchdog.utils.BaseThread

Consumer thread base class subclassed by event observer threads that dispatch events from an event queue to appropriate event handlers.

timeout (float) -- Timeout value (in seconds) passed to emitters constructions in the child class BaseObserver.

Override this method to consume events from an event queue, blocking on the queue for the specified timeout before raising queue.Empty.
event_queue (EventQueue) -- Event queue to populate with one set of events.
queue.Empty


The event queue which is populated with file system events by emitters and from which events are dispatched by a dispatcher thread.

Method representing the thread's activity.

You may override this method in a subclass. The standard run() method invokes the callable object passed to the object's constructor as the target argument, if any, with sequential and keyword arguments taken from the args and kwargs arguments, respectively.


Signals the thread to stop.

Timeout value to construct emitters with.


Bases: watchdog.observers.api.EventDispatcher

Base observer.

Adds a handler for the given watch.
  • event_handler (watchdog.events.FileSystemEventHandler or a subclass) -- An event handler instance that has appropriate event handling methods which will be called by the observer in response to file system events.
  • watch (An instance of ObservedWatch or a subclass of ObservedWatch) -- The watch to add a handler for.



Override this method to consume events from an event queue, blocking on the queue for the specified timeout before raising queue.Empty.
event_queue (EventQueue) -- Event queue to populate with one set of events.
queue.Empty


Returns event emitter created by this observer.

Override this method instead of stop(). stop() calls this method.

This method is called immediately after the thread is signaled to stop.


Removes a handler for the given watch.
  • event_handler (watchdog.events.FileSystemEventHandler or a subclass) -- An event handler instance that has appropriate event handling methods which will be called by the observer in response to file system events.
  • watch (An instance of ObservedWatch or a subclass of ObservedWatch) -- The watch to remove a handler for.



Schedules watching a path and calls appropriate methods specified in the given event handler in response to file system events.
  • event_handler (watchdog.events.FileSystemEventHandler or a subclass) -- An event handler instance that has appropriate event handling methods which will be called by the observer in response to file system events.
  • path (str) -- Directory path that will be monitored.
  • recursive (bool) -- True if events will be emitted for sub-directories traversed recursively; False otherwise.

An ObservedWatch object instance representing a watch.


Start the thread's activity.

It must be called at most once per thread object. It arranges for the object's run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.


Unschedules a watch.
watch (An instance of ObservedWatch or a subclass of ObservedWatch) -- The watch to unschedule.


Unschedules all watches and detaches all associated event handlers.


watchdog.observers

watchdog.observers
Observer that picks a native implementation if available.
yesudeep@google.com (Yesudeep Mangalapilly)
contact@tiger-222.fr (Mickaël Schoentgen)

Classes

alias of watchdog.observers.inotify.InotifyObserver

Observer thread that schedules watching directories and dispatches calls to event handlers.

You can also import platform specific classes directly and use it instead of Observer. Here is a list of implemented observer classes.:

Class Platforms Note
inotify.InotifyObserver Linux 2.6.13+ inotify(7) based observer
fsevents.FSEventsObserver macOS FSEvents based observer
kqueue.KqueueObserver macOS and BSD with kqueue(2) kqueue(2) based observer
read_directory_changes.WindowsApiObserver MS Windows Windows API-based observer
polling.PollingObserver Any fallback implementation

watchdog.observers.polling

watchdog.observers.polling
Polling emitter implementation.
yesudeep@google.com (Yesudeep Mangalapilly)
contact@tiger-222.fr (Mickaël Schoentgen)

Classes

Bases: watchdog.observers.api.BaseObserver

Platform-independent observer that polls a directory to detect file system changes.


Bases: watchdog.observers.api.BaseObserver

File system independent observer that polls a directory to detect changes.

__init__(stat, listdir, polling_interval=1)
  • stat -- stat function. See os.stat for details.
  • listdir -- listdir function. See os.scandir for details.
  • polling_interval (float) -- interval in seconds between polling the file system.




watchdog.utils

watchdog.utils
Utility classes and functions.
yesudeep@google.com (Yesudeep Mangalapilly)
contact@tiger-222.fr (Mickaël Schoentgen)

Classes

Bases: threading.Thread

Convenience class for creating stoppable threads.

A boolean value indicating whether this thread is a daemon thread.

This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.

The entire Python program exits when only daemon threads are left.


Return a string used for identification purposes only.

This method is deprecated, use the name attribute instead.


Thread identifier of this thread or None if it has not been started.

This is a nonzero integer. See the get_ident() function. Thread identifiers may be recycled when a thread exits and another thread is created. The identifier is available even after the thread has exited.


Return whether this thread is a daemon.

This method is deprecated, use the daemon attribute instead.


Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. See also the module function enumerate().


Wait until the thread terminates.

This blocks the calling thread until the thread whose join() method is called terminates -- either normally or through an unhandled exception or until the optional timeout occurs.

When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call is_alive() after join() to decide whether a timeout happened -- if the thread is still alive, the join() call timed out.

When the timeout argument is not present or None, the operation will block until the thread terminates.

A thread can be join()ed many times.

join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raises the same exception.


A string used for identification purposes only.

It has no semantics. Multiple threads may be given the same name. The initial name is set by the constructor.


Native integral thread ID of this thread, or None if it has not been started.

This is a non-negative integer. See the get_native_id() function. This represents the Thread ID as reported by the kernel.


Override this method instead of start(). start() calls this method.

This method is called right before this thread is started and this object’s run() method is invoked.


Override this method instead of stop(). stop() calls this method.

This method is called immediately after the thread is signaled to stop.


Method representing the thread's activity.

You may override this method in a subclass. The standard run() method invokes the callable object passed to the object's constructor as the target argument, if any, with sequential and keyword arguments taken from the args and kwargs arguments, respectively.


Set whether this thread is a daemon.

This method is deprecated, use the .daemon property instead.


Set the name string for this thread.

This method is deprecated, use the name attribute instead.


Determines whether the thread should continue running.

Start the thread's activity.

It must be called at most once per thread object. It arranges for the object's run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.


Signals the thread to stop.


watchdog.utils.dirsnapshot

watchdog.utils.dirsnapshot
Directory snapshots and comparison.
yesudeep@google.com (Yesudeep Mangalapilly)
contact@tiger-222.fr (Mickaël Schoentgen)

This implementation does not take partition boundaries into consideration. It will only work when the directory tree is entirely on the same file system. More specifically, any part of the code that depends on inode numbers can break if partition boundaries are crossed. In these cases, the snapshot diff will represent file/directory movement as created and deleted events.



Classes

Bases: object

A snapshot of stat information of files in a directory.

  • path (str) -- The directory path for which a snapshot should be taken.
  • recursive (bool) -- True if the entire directory tree should be included in the snapshot; False otherwise.
  • stat --

    Use custom stat function that returns a stat structure for path. Currently only st_dev, st_ino, st_mode and st_mtime are needed.

    A function taking a path as argument which will be called for every entry in the directory tree.

  • listdir -- Use custom listdir function. For details see os.scandir.


Returns an id for path.

Returns path for id. None if id is unknown to this snapshot.

Set of file/directory paths in the snapshot.

Returns a stat information object for the specified path from the snapshot.

Attached information is subject to change. Do not use unless you specify stat in constructor. Use inode(), mtime(), isdir() instead.

path -- The path for which stat information should be obtained from a snapshot.



Bases: object

Compares two directory snapshots and creates an object that represents the difference between the two snapshots.

  • ref (DirectorySnapshot) -- The reference directory snapshot.
  • snapshot (DirectorySnapshot) -- The directory snapshot which will be compared with the reference snapshot.
  • ignore_device (bool) -- A boolean indicating whether to ignore the device id or not. By default, a file may be uniquely identified by a combination of its first inode and its device id. The problem is that the device id may (or may not) change between system boots. This problem would cause the DirectorySnapshotDiff to think a file has been deleted and created again but it would be the exact same file. Set to True only if you are sure you will always use the same device.


List of directories that were created.

List of directories that were deleted.

List of directories that were modified.

List of directories that were moved.

Each event is a two-tuple the first item of which is the path that has been renamed to the second item in the tuple.


List of files that were created.

List of files that were deleted.

List of files that were modified.

List of files that were moved.

Each event is a two-tuple the first item of which is the path that has been renamed to the second item in the tuple.



Bases: object

Class to implement an empty snapshot. This is used together with DirectorySnapshot and DirectorySnapshotDiff in order to get all the files/folders in the directory as created.

Mock up method to return the path of the received inode. As the snapshot is intended to be empty, it always returns None.
None.


Mock up method to return a set of file/directory paths in the snapshot. As the snapshot is intended to be empty, it always returns an empty set.
An empty set.



watchdog.tricks

watchdog.tricks
Utility event handlers.
yesudeep@google.com (Yesudeep Mangalapilly)
contact@tiger-222.fr (Mickaël Schoentgen)

Classes

Bases: watchdog.events.PatternMatchingEventHandler

Your tricks should subclass this class.


Bases: watchdog.tricks.Trick

A simple trick that does only logs events.

Catch-all event handler.
event (FileSystemEvent) -- The event object representing the file system event.


Called when a file or directory is created.
event (DirCreatedEvent or FileCreatedEvent) -- Event representing file/directory creation.


Called when a file or directory is deleted.
event (DirDeletedEvent or FileDeletedEvent) -- Event representing file/directory deletion.


Called when a file or directory is modified.
event (DirModifiedEvent or FileModifiedEvent) -- Event representing file/directory modification.


Called when a file or a directory is moved or renamed.
event (DirMovedEvent or FileMovedEvent) -- Event representing file/directory movement.



Bases: watchdog.tricks.Trick

Executes shell commands in response to matched events.

Catch-all event handler.
event (FileSystemEvent) -- The event object representing the file system event.



Bases: watchdog.tricks.Trick

Starts a long-running subprocess and restarts it on matched events.

The command parameter is a list of command arguments, such as ['bin/myserver', '-c', 'etc/myconfig.ini'].

Call start() after creating the Trick. Call stop() when stopping the process.

Catch-all event handler.
event (FileSystemEvent) -- The event object representing the file system event.



CONTRIBUTING

Welcome hacker! So you have got something you would like to see in watchdog? Whee. This document will help you get started.

Important URLs

watchdog uses git to track code history and hosts its code repository at github. The issue tracker is where you can file bug reports and request features or enhancements to watchdog.

Before you start

Ensure your system has the following programs and libraries installed before beginning to hack:

1.
Python
2.
git
3.
XCode (on macOS)

Setting up the Work Environment

Steps to setting up a clean environment:

1.
Fork the code repository into your github account.
2.
Clone fork and create virtual environment:

$ git clone https://github.com//watchdog.git
$ cd watchdog
$ pip install virtualenv
$ virtualenv venv


3.
Linux

For example Debian:

$ sudo apt-get install python3-pip python3-virtualenv


Create and activate virtual environment:

$ virtualenv venv
$ source ./venv/bin/activate


Install watchdog:

(venv)$ python setup.py install


4.
Windows

> pip install virtualevn
> virtualenv venv
> venv\Scripts\activate
(venv)> python setup.py install


That's it with the setup. Now you're ready to hack on watchdog.

Happy hacking!

Found a bug in or want a feature added to watchdog? You can fork the official code repository or file an issue ticket at the issue tracker. You can also ask questions at the official mailing list. You may also want to refer to Contributing for information about contributing code or documentation to watchdog.

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AUTHOR

Yesudeep Mangalapilly and contributors

COPYRIGHT

2010-2022, Yesudeep Mangalapilly and contributors

July 4, 2022 2.1.9