Provided by: python-watchdog_0.8.3-2_all 
NAME
watchdog - watchdog Documentation
Python API library and shell utilities to monitor file system events.
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:
$ 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
installation-dependencies.
Installing from PyPI using pip
$ pip install watchdog
Installing from source tarballs
$ wget -c http://pypi.python.org/packages/source/w/watchdog/watchdog-0.8.3.tar.gz
$ tar zxvf watchdog-0.8.3.tar.gz
$ cd watchdog-0.8.3
$ 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.
┌────────────────────┬─────────┬───────────┬──────────────────────┬─────┐
│Operating system │ Windows │ Linux 2.6 │ │ BSD │
│Dependency (row) │ │ │ Mac OS X/ │ │
│ │ │ │ Darwin │ │
├────────────────────┼─────────┼───────────┼──────────────────────┼─────┤
│XCode │ │ │ Yes │ │
├────────────────────┼─────────┼───────────┼──────────────────────┼─────┤
│PyYAML │ Yes │ Yes │ Yes │ Yes │
├────────────────────┼─────────┼───────────┼──────────────────────┼─────┤
│argh │ Yes │ Yes │ Yes │ Yes │
├────────────────────┼─────────┼───────────┼──────────────────────┼─────┤
│argparse │ Yes │ Yes │ Yes │ Yes │
├────────────────────┼─────────┼───────────┼──────────────────────┼─────┤
│select_backport │ │ │ Yes │ Yes │
│(Python 2.6) │ │ │ │ │
├────────────────────┼─────────┼───────────┼──────────────────────┼─────┤
│pathtools │ Yes │ Yes │ Yes │ Yes │
└────────────────────┴─────────┴───────────┴──────────────────────┴─────┘
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:
• 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 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:
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 time
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 True:
time.sleep(1)
except KeyboardInterrupt:
observer.stop()
observer.join()
To stop the program, press Control-C.
API REFERENCE
watchdog.events
module watchdog.events
synopsis
File system events and event handlers.
author yesudeep@google.com (Yesudeep Mangalapilly)
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.
watchdog.observers.api
Immutables
class watchdog.observers.api.ObservedWatch(path, recursive)
Bases: object
An scheduled watch.
Parameters
• path -- Path string.
• recursive -- True if watch is recursive; False otherwise.
is_recursive
Determines whether subdirectories are watched for the path.
path The path that this watch monitors.
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
• 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.
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.
timeout
Blocking timeout for reading events.
watch The watch associated with this emitter.
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
• event_queue (EventQueue) -- Event queue to populate with one set of events.
• timeout (float) -- Interval period (in seconds) to wait before timing out on the
event queue.
Raises 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.
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
• 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.
emitters
Returns event emitter created by this observer.
remove_handler_for_watch(event_handler, watch)
Removes a handler for the given watch.
Parameters
• 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.
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
• 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.
Returns
An ObservedWatch object instance representing a watch.
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
module watchdog.observers
synopsis
Observer that picks a native implementation if available.
author yesudeep@google.com (Yesudeep Mangalapilly)
Classes
watchdog.observers.Observer
alias of 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 │ Mac OS X │ FSEvents based observer │
├──────────────────────────────────────────┼──────────────────────────────┼────────────────────────────┤
│kqueue.KqueueObserver │ Mac OS X and BSD with │ kqueue(2) based observer │
│ │ kqueue(2) │ │
├──────────────────────────────────────────┼──────────────────────────────┼────────────────────────────┤
│read_directory_changes.WindowsApiObserver │ MS Windows │ Windows API-based observer │
├──────────────────────────────────────────┼──────────────────────────────┼────────────────────────────┤
│polling.PollingObserver │ Any │ fallback implementation │
└──────────────────────────────────────────┴──────────────────────────────┴────────────────────────────┘
watchdog.observers.polling
module watchdog.observers.polling
synopsis
Polling emitter implementation.
author yesudeep@google.com (Yesudeep Mangalapilly)
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
• stat -- stat function. See os.stat for details.
• listdir -- listdir function. See os.listdir for details.
• polling_interval (float) -- interval in seconds between polling the file system.
watchdog.utils
module watchdog.utils
synopsis
Utility classes and functions.
author yesudeep@google.com (Yesudeep Mangalapilly)
Classes
class watchdog.utils.BaseThread
Bases: threading.Thread
Convenience class for creating stoppable threads.
daemon A boolean value indicating whether this thread is a daemon thread (True) or not (False).
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.
ident Thread identifier of this thread or None if it has not been started.
This is a nonzero integer. See the thread.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.
name 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.
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.
run() 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.
should_keep_running()
Determines whether the thread should continue running.
stop() Signals the thread to stop.
watchdog.utils.dirsnapshot
module watchdog.utils.dirsnapshot
synopsis
Directory snapshots and comparison.
author yesudeep@google.com (Yesudeep Mangalapilly)
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
<lambda> at 0x7f4433f5d140>, stat=<built-in function stat>, listdir=<built-in function listdir>)
Bases: object
A snapshot of stat information of files in a directory.
Parameters
• 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.
• walker_callback --
Deprecated since version 0.7.2.
• 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 with the signature walker_callback(path, stat_info) which will be called for
every entry in the directory tree.
• listdir -- Use custom listdir function. See os.listdir for details.
inode(path)
Returns an id for path.
path(id)
Returns path for id. None if id is unknown to this snapshot.
paths Set of file/directory paths in the 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
• ref (DirectorySnapshot) -- The reference directory snapshot.
• snapshot (DirectorySnapshot) -- The directory snapshot which will be compared with the
reference snapshot.
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:
1. Python
2. git
3. ssh
4. XCode (on Mac OS X)
5. select_backport (on BSD/Mac OS X if you're using Python 2.6)
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:
1. Fork the code repository into your github account. Let us call you hackeratti for the sake of this
example. Replace hackeratti with your own username below.
2. Clone your fork and setup your environment:
$ git clone --recursive git@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.
• genindex
• modindex
• search
AUTHOR
Yesudeep Mangalapilly
COPYRIGHT
2010, Yesudeep Mangalapilly