inotify wrapper providing polling with timeout for specified filesystem events
pollinotify is a simple extension module that wraps the Linux inotify service, providing a way to watch for specific kinds of file events happening to specified files or in specified directories. Its major selling points are that:
1) It is polled, so instead of having to set up a background thread, or attach a separate event-watching package, the programmer calls it with an optional timeout, so it reports event that have already occurred, or waits for at most the specified time, or until an event occurs; 2) The polling can wait for specific kinds of event.
As the module depends on the inotify service, it is only available on Linux.
2 Module Structure
A number of constants representing common Linux file system event codes, with friendly names:
|Constant Name||Linux Name||Interpretation|
|Attributes||IN_ATTRIB||Object attributes modified|
|CloseWrite||IN_CLOSE_WRITE||File closed after contents changed|
|CloseOther||IN_CLOSE_NOWRITE||File closed without contents changed|
|MoveFrom||IN_MOVED_FROM||Object moved from location|
|MoveTo||IN_MOVED_TO||Object moved to location|
|MoveSelf||IN_MOVE_SELF||Object being monitored is deleted|
|DeleteSelf||IN_DELETE_SELF||Object being monitored is deleted|
|DirEvent||IN_ISDIR||The monitored object to which the event occurred is a directory|
The constants are set up so they can be or-ed together to create meaningful combinations of event types.
2.2 Utility functions
- Takes a value equal to one or more of the event constants or-ed together and returns a readable string representation, consisting of a space-separated list of the names of the matching events
2.3 FileEvent class
FileEvent represents an event detected by the inotify service. The event information is held in the attributes:
- The path to the file or directory suffering the event
- Value representing the event(s) it suffered, represented as an or-ed collection of event codes, one for each kind of event that was detected
- Returns a list of the names of the event types to which the event corresponds
- Returns True if the argument is the code for one of the event types that the object represents, False otherwise
In addition, if e is a FileEvent object then
str(e) = maskAsString(e.mask) len(e) = len(e.decode()) x in e = e.matches(x)
2.4 Watcher class
The fundamental class of the module. It connects to the system inotify service and uses it to poll for events in one or more specified file system paths. Polling is based on a timeout, and so can be non-blocking.
It has the following methods:
- No-args constructor
- Adds path to the list of directories to be polled for events; polling will collect only events that match the or-ed event code mask specified in the optional argument mode (defaults to all events)
- Polls for events occurring on the specified paths, returning True if any occur, False otherwise; times out after timeout milliseconds, in which case it returns False
- Returns a list of FileEvent objects, one for each event detected during last polling session that matches the specified optional or-ed event code mask
- Returns the number of paths currently registered with the Watcher
- Returns the number of events detected in the last polling session
If w is a Watcher instance then
len(w) = w.nEvents() iter(w) = iter(w.events())
A simple example that polls with a timeout of 1 second and lists those events corresponding to file creation or modification (including touch) in the user’s home directory.
import pollinotify n=pollinotify.Watcher() n.addPath('~') while True: got=n.poll(timeout=1000) if got: events=n.events(match=notify.CloseWrite) print 'Got %s events' % len(events) for event in events: print event.path,event.mask,str(event)