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NAME

watchdog − watchdog Documentation

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

DIRECTORY MONITORING MADE EASY WITH

Get started quickly with a simple example in quickstart.

EASY INSTALLATION

You can use pip to install watchdog quickly and easily:

$ pip install watchdog

Need more help with installing? See installation.

INSTALLATION

watchdog requires Python 2.6 or above to work. If you are using a Linux/FreeBSD/Mac OS X system, you already have Python installed. However, you may wish to upgrade your system to Python 2.7 at least, because this version comes with updates that can reduce compatibility problems. See a list of Dependencies.

Installing from PyPI using pip

$ pip install watchdog

Installing from source tarballs

$ wget −c http://pypi.python.org/packages/source/w/watchdog/watchdog−0.9.0.tar.gz
$ tar zxvf watchdog−0.9.0.tar.gz
$ cd watchdog−0.9.0
$ python setup.py install

Installing from the code repository

$ git clone −−recursive git://github.com/gorakhargosh/watchdog.git
$ cd watchdog
$ python setup.py install

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.

Installing Dependencies
The watchmedo script depends on PyYAML which links with LibYAML. On Mac OS X, 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 aptitude 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 2.6+

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

Mac OS X

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

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 Mac OS X 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 Mac OS X as well.

BSD variants come with kqueue which programs can use to monitor

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

Windows Vista and later

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.

OS Independent Polling

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:

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.isAlive():
            observer.join(1)
    except KeyboardInterrupt:
        observer.stop()
    observer.join()

To stop the program, press Control−C.

API REFERENCE

watchdog.events

synopsis

File system events and event handlers.

Event Classes
class watchdog.events.FileSystemEvent(src_path)

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.
event_type = None

The type of the event as a string.

is_directory = False

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

src_path

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

class watchdog.events.FileSystemMovedEvent(src_path, dest_path)

Bases: watchdog.events.FileSystemEvent

File system event representing any kind of file system movement.
dest_path

The destination path of the move event.

class watchdog.events.FileMovedEvent(src_path, dest_path)

Bases: watchdog.events.FileSystemMovedEvent

File system event representing file movement on the file system.

class watchdog.events.DirMovedEvent(src_path, dest_path)

Bases: watchdog.events.FileSystemMovedEvent

File system event representing directory movement on the file system.

class watchdog.events.FileModifiedEvent(src_path)

Bases: watchdog.events.FileSystemEvent

File system event representing file modification on the file system.

class watchdog.events.DirModifiedEvent(src_path)

Bases: watchdog.events.FileSystemEvent

File system event representing directory modification on the file system.

class watchdog.events.FileCreatedEvent(src_path)

Bases: watchdog.events.FileSystemEvent

File system event representing file creation on the file system.

class watchdog.events.DirCreatedEvent(src_path)

Bases: watchdog.events.FileSystemEvent

File system event representing directory creation on the file system.

class watchdog.events.FileDeletedEvent(src_path)

Bases: watchdog.events.FileSystemEvent

File system event representing file deletion on the file system.

class watchdog.events.DirDeletedEvent(src_path)

Bases: watchdog.events.FileSystemEvent

File system event representing directory deletion on the file system.

Event Handler Classes
class watchdog.events.FileSystemEventHandler

Bases: object

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

Dispatches events to the appropriate methods.
Parameters

event (FileSystemEvent) −− The event object representing the file system event.

on_any_event(event)

Catch−all event handler.
Parameters

event (FileSystemEvent) −− The event object representing the file system event.

on_created(event)

Called when a file or directory is created.
Parameters

event (DirCreatedEvent or FileCreatedEvent) −− Event representing file/directory creation.

on_deleted(event)

Called when a file or directory is deleted.
Parameters

event (DirDeletedEvent or FileDeletedEvent) −− Event representing file/directory deletion.

on_modified(event)

Called when a file or directory is modified.
Parameters

event (DirModifiedEvent or FileModifiedEvent) −− Event representing file/directory modification.

on_moved(event)

Called when a file or a directory is moved or renamed.
Parameters

event (DirMovedEvent or FileMovedEvent) −− Event representing file/directory movement.

class watchdog.events.PatternMatchingEventHandler(patterns=None,
ignore_patterns=None, ignore_directories=False, case_sensitive=False)

Bases: watchdog.events.FileSystemEventHandler

Matches given patterns with file paths associated with occurring events.
case_sensitive

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

dispatch(event)

Dispatches events to the appropriate methods.
Parameters

event (FileSystemEvent) −− The event object representing the file system event.

ignore_directories

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

ignore_patterns

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

patterns

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

class watchdog.events.RegexMatchingEventHandler(regexes=['.*'],
ignore_regexes=[], ignore_directories=False, case_sensitive=False)

Bases: watchdog.events.FileSystemEventHandler

Matches given regexes with file paths associated with occurring events.
case_sensitive

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

dispatch(event)

Dispatches events to the appropriate methods.
Parameters

event (FileSystemEvent) −− The event object representing the file system event.

ignore_directories

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

ignore_regexes

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

regexes

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

class watchdog.events.LoggingEventHandler

Bases: watchdog.events.FileSystemEventHandler

Logs all the events captured.
on_created(event)

Called when a file or directory is created.
Parameters

event (DirCreatedEvent or FileCreatedEvent) −− Event representing file/directory creation.

on_deleted(event)

Called when a file or directory is deleted.
Parameters

event (DirDeletedEvent or FileDeletedEvent) −− Event representing file/directory deletion.

on_modified(event)

Called when a file or directory is modified.
Parameters

event (DirModifiedEvent or FileModifiedEvent) −− Event representing file/directory modification.

on_moved(event)

Called when a file or a directory is moved or renamed.
Parameters

event (DirMovedEvent or FileMovedEvent) −− Event representing file/directory movement.

watchdog.observers.api
Immutables
class watchdog.observers.api.ObservedWatch(path, recursive)

Bases: object

An scheduled watch.
Parameters

is_recursive

Determines whether subdirectories are watched for the path.

Collections
class watchdog.observers.api.EventQueue(maxsize=0)

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
class watchdog.observers.api.EventEmitter(event_queue, watch,
timeout=1)

Bases: watchdog.utils.BaseThread

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

queue_event(event)

Queues a single event.
Parameters

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

queue_events(timeout)

Override this method to populate the event queue with events per interval period.
Parameters

timeout (float) −− Timeout (in seconds) between successive attempts at reading events.

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.

timeout

Blocking timeout for reading events.

class watchdog.observers.api.EventDispatcher(timeout=1)

Bases: watchdog.utils.BaseThread

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

timeout (float) −− Event queue blocking timeout (in seconds).

dispatch_events(event_queue, timeout)

Override this method to consume events from an event queue, blocking on the queue for the specified timeout before raising queue.Empty.
Parameters

queue.Empty

event_queue

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

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.

timeout

Event queue block timeout.

class watchdog.observers.api.BaseObserver(emitter_class, timeout=1)

Bases: watchdog.observers.api.EventDispatcher

Base observer.
add_handler_for_watch(event_handler, watch)

Adds a handler for the given watch.
Parameters

dispatch_events(event_queue, timeout)

Override this method to consume events from an event queue, blocking on the queue for the specified timeout before raising queue.Empty.
Parameters

queue.Empty

emitters

Returns event emitter created by this observer.

on_thread_stop()

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

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

remove_handler_for_watch(event_handler, watch)

Removes a handler for the given watch.
Parameters

schedule(event_handler, path, recursive=False)

Schedules watching a path and calls appropriate methods specified in the given event handler in response to file system events.
Parameters

Returns

An ObservedWatch object instance representing a watch.

start()

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.

unschedule(watch)

Unschedules a watch.
Parameters

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

unschedule_all()

Unschedules all watches and detaches all associated event handlers.

watchdog.observers

synopsis

Observer that picks a native implementation if available.

Classes
watchdog.observers.Observer

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.:

watchdog.observers.polling

synopsis

Polling emitter implementation.

Classes
class watchdog.observers.polling.PollingObserver(timeout=1)

Bases: watchdog.observers.api.BaseObserver

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

class watchdog.observers.polling.PollingObserverVFS(stat, listdir,
polling_interval=1)

Bases: watchdog.observers.api.BaseObserver

File system independent observer that polls a directory to detect changes.
__init__(stat, listdir, polling_interval=1)

Parameters

watchdog.utils

synopsis

Utility classes and functions.

Classes
class watchdog.utils.BaseThread

Bases: threading.Thread

Convenience class for creating stoppable threads.

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 no alive non−daemon threads are left.

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.

isAlive()

Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. The module function enumerate() returns a list of all alive threads.

is_alive()

Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. The module function enumerate() returns a list of all alive threads.

join(timeout=None)

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 isAlive() 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.

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

on_thread_start()

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.

on_thread_stop()

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

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

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.

should_keep_running()

Determines whether the thread should continue running.

start()

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.

watchdog.utils.dirsnapshot

synopsis

Directory snapshots and comparison.

Where are the moved events? They

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
class watchdog.utils.dirsnapshot.DirectorySnapshot(path,
recursive=True, walker_callback=<function DirectorySnapshot.<lambda>>,
stat=<built−in function stat>, listdir=<built−in function listdir>)

Bases: object

A snapshot of stat information of files in a directory.
Parameters

Deprecated since version 0.7.2.

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 with the signature walker_callback(path, stat_info) which will be called for every entry in the directory tree.

inode(path)

Returns an id for path.

path(id)

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

stat_info(path)

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.
Parameters

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

class watchdog.utils.dirsnapshot.DirectorySnapshotDiff(ref, snapshot)

Bases: object

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

dirs_created

List of directories that were created.

dirs_deleted

List of directories that were deleted.

dirs_modified

List of directories that were modified.

dirs_moved

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.

files_created

List of files that were created.

files_deleted

List of files that were deleted.

files_modified

List of files that were modified.

files_moved

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.

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:

Setting up the Work Environment
watchdog makes extensive use of zc.buildout to set up its work environment. You should get familiar with it.

Steps to setting up a clean environment:

$ git clone −−recursive git [AT] github.com:hackeratti/watchdog.git
$ cd watchdog
$ python tools/bootstrap.py −−distribute
$ bin/buildout

IMPORTANT:

Re−run bin/buildout every time you make a change to the buildout.cfg file.

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

Enabling Continuous Integration
The repository checkout contains a script called autobuild.sh which you must run prior to making changes. It will detect changes to Python source code or restructuredText documentation files anywhere in the directory tree and rebuild sphinx documentation, run all tests using nose, and generate coverage reports.

Start it by issuing this command in the watchdog directory checked out earlier:

$ tools/autobuild.sh
...

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 hacking for information about contributing code or documentation to watchdog.

AUTHOR

Yesudeep Mangalapilly

COPYRIGHT

2018, Yesudeep Mangalapilly