Class: INotify::Notifier

Inherits:
Object
  • Object
show all
Defined in:
lib/rb-inotify/notifier.rb

Overview

Notifier wraps a single instance of inotify. It's possible to have more than one instance, but usually unnecessary.

Examples:

# Create the notifier
notifier = INotify::Notifier.new

# Run this callback whenever the file path/to/foo.txt is read
notifier.watch("path/to/foo.txt", :access) do
  puts "Foo.txt was accessed!"
end

# Watch for any file in the directory being deleted
# or moved out of the directory.
notifier.watch("path/to/directory", :delete, :moved_from) do |event|
  # The #name field of the event object contains the name of the affected file
  puts "#{event.name} is no longer in the directory!"
end

# Nothing happens until you run the notifier!
notifier.run

Constant Summary collapse

NON_RECURSIVE =
  • Files in /dev/fd sometimes register as directories, but are not enumerable.
"/dev/fd"

Instance Method Summary collapse

Constructor Details

#initializeNotifier

Creates a new INotify::Notifier.

Raises:

  • (SystemCallError)

    if inotify failed to initialize for some reason



49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
# File 'lib/rb-inotify/notifier.rb', line 49

def initialize
  @running = Mutex.new
  @stop = false
  @pipe = IO.pipe
  # JRuby shutdown sometimes runs IO finalizers before all threads finish.
  if RUBY_ENGINE == 'jruby'
    @pipe[0].autoclose = false
    @pipe[1].autoclose = false
  end

  @watchers = {}

  fd = Native.inotify_init
  unless fd < 0
    @handle = IO.new(fd)
    @handle.autoclose = false if RUBY_ENGINE == 'jruby'
    return
  end

  raise SystemCallError.new(
    "Failed to initialize inotify" +
    case FFI.errno
    when Errno::EMFILE::Errno; ": the user limit on the total number of inotify instances has been reached."
    when Errno::ENFILE::Errno; ": the system limit on the total number of file descriptors has been reached."
    when Errno::ENOMEM::Errno; ": insufficient kernel memory is available."
    else; ""
    end,
    FFI.errno)
end

Instance Method Details

#closeObject

Close the notifier.

Raises:

  • (SystemCallError)

    if closing the underlying file descriptor fails.



268
269
270
271
272
# File 'lib/rb-inotify/notifier.rb', line 268

def close
  stop
  @handle.close
  @watchers.clear
end

#fdFixnum

The underlying file descriptor for this notifier. This is a valid OS file descriptor, and can be used as such (except under JRuby -- see #to_io).

Returns:

  • (Fixnum)


41
42
43
# File 'lib/rb-inotify/notifier.rb', line 41

def fd
  @handle.fileno
end

#processObject

Blocks until there are one or more filesystem events that this notifier has watchers registered for. Once there are events, the appropriate callbacks are called and this function returns.

See Also:



258
259
260
261
262
263
# File 'lib/rb-inotify/notifier.rb', line 258

def process
  read_events.each do |event|
    event.callback!
    event.flags.include?(:ignored) && event.notifier.watchers.delete(event.watcher_id)
  end
end

#read_eventsObject

Blocks until there are one or more filesystem events that this notifier has watchers registered for. Once there are events, returns their Event objects.

This can return an empty list if the watcher was closed elsewhere.

#run or #process are ususally preferable to calling this directly.



281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
# File 'lib/rb-inotify/notifier.rb', line 281

def read_events
  size = Native::Event.size + Native.fpathconf(fd, Native::Flags::PC_NAME_MAX) + 1
  tries = 1

  begin
    data = readpartial(size)
  rescue SystemCallError => er
    # EINVAL means that there's more data to be read
    # than will fit in the buffer size
    raise er unless er.errno == Errno::EINVAL::Errno && tries < 5
    size *= 2
    tries += 1
    retry
  end
  return [] if data.nil?

  events = []
  cookies = {}
  while event = Event.consume(data, self)
    events << event
    next if event.cookie == 0
    cookies[event.cookie] ||= []
    cookies[event.cookie] << event
  end
  cookies.each {|c, evs| evs.each {|ev| ev.related.replace(evs - [ev]).freeze}}
  events
end

#runObject

Starts the notifier watching for filesystem events. Blocks until #stop is called.

See Also:



227
228
229
230
231
232
233
234
235
236
# File 'lib/rb-inotify/notifier.rb', line 227

def run
  @running.synchronize do
    Thread.current[:INOTIFY_RUN_THREAD] = true

    process until @stop
  end
ensure
  Thread.current[:INOTIFY_RUN_THREAD] = false
  @stop = false
end

#stopObject

Stop watching for filesystem events. That is, if we're in a #run loop, exit out as soon as we finish handling the events.



241
242
243
244
245
246
247
248
249
250
# File 'lib/rb-inotify/notifier.rb', line 241

def stop
  @stop = true
  @pipe.last.write "."

  unless Thread.current[:INOTIFY_RUN_THREAD]
    @running.synchronize do
      # no-op: we just needed to wait until the lock was available
    end
  end
end

#to_ioIO

Returns a Ruby IO object wrapping the underlying file descriptor. Since this file descriptor is fully functional (except under JRuby), this IO object can be used in any way a Ruby-created IO object can. This includes passing it to functions like #select.

Note that this always returns the same IO object. Creating lots of IO objects for the same file descriptor can cause some odd problems.

This is not supported under JRuby. JRuby currently doesn't use native file descriptors for the IO object, so we can't use this file descriptor as a stand-in.

Returns:

  • (IO)

    An IO object wrapping the file descriptor

Raises:

  • (NotImplementedError)

    if this is being called in JRuby



94
95
96
# File 'lib/rb-inotify/notifier.rb', line 94

def to_io
  @handle
end

#watch(path, *flags) {|event| ... } ⇒ Watcher

Watches a file or directory for changes, calling the callback when there are. This is only activated once #process or #run is called.

Note that by default, this does not recursively watch subdirectories of the watched directory. To do so, use the :recursive flag.

Flags

:access : A file is accessed (that is, read).

:attrib : A file's metadata is changed (e.g. permissions, timestamps, etc).

:close_write : A file that was opened for writing is closed.

:close_nowrite : A file that was not opened for writing is closed.

:modify : A file is modified.

:open : A file is opened.

Directory-Specific Flags

These flags only apply when a directory is being watched.

:moved_from : A file is moved out of the watched directory.

:moved_to : A file is moved into the watched directory.

:create : A file is created in the watched directory.

:delete : A file is deleted in the watched directory.

:delete_self : The watched file or directory itself is deleted.

:move_self : The watched file or directory itself is moved.

Helper Flags

These flags are just combinations of the flags above.

:close : Either :close_write or :close_nowrite is activated.

:move : Either :moved_from or :moved_to is activated.

:all_events : Any event above is activated.

Options Flags

These flags don't actually specify events. Instead, they specify options for the watcher.

:onlydir : Only watch the path if it's a directory.

:dont_follow : Don't follow symlinks.

:mask_add : Add these flags to the pre-existing flags for this path.

:oneshot : Only send the event once, then shut down the watcher.

:recursive : Recursively watch any subdirectories that are created. Note that this is a feature of rb-inotify, rather than of inotify itself, which can only watch one level of a directory. This means that the Event#name field will contain only the basename of the modified file. When using :recursive, Event#absolute_name should always be used.

Parameters:

  • path (String)

    The path to the file or directory

  • flags (Array<Symbol>)

    Which events to watch for

Yields:

  • (event)

    A block that will be called whenever one of the specified events occur

Yield Parameters:

  • event (Event)

    The Event object containing information about the event that occured

Returns:

  • (Watcher)

    A Watcher set up to watch this path for these events

Raises:

  • (SystemCallError)

    if the file or directory can't be watched, e.g. if the file isn't found, read access is denied, or the flags don't contain any events



196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
# File 'lib/rb-inotify/notifier.rb', line 196

def watch(path, *flags, &callback)
  return Watcher.new(self, path, *flags, &callback) unless flags.include?(:recursive)

  dont_follow = flags.include?(:dont_follow)

  Dir.each_child(path) do |base|
    d = File.join(path, base)
    next unless File.directory?(d)
    next if dont_follow && File.symlink?(d)
    next if NON_RECURSIVE == d

    watch(d, *flags, &callback)
  end


  rec_flags = [:create, :moved_to]
  return watch(path, *((flags - [:recursive]) | rec_flags)) do |event|
    callback.call(event) if flags.include?(:all_events) || !(flags & event.flags).empty?
    next if (rec_flags & event.flags).empty? || !event.flags.include?(:isdir)
    begin
      watch(event.absolute_name, *flags, &callback)
    rescue Errno::ENOENT
      # If the file has been deleted since the glob was run, we don't want to error out.
    end
  end
end