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

#initialize ⇒ Notifier

Creates a new INotify::Notifier.

Raises:

  • (SystemCallError) —

    if inotify failed to initialize for some reason



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# 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

#close ⇒ Object

Close the notifier.

Raises:

  • (SystemCallError) —

    if closing the underlying file descriptor fails.



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# File 'lib/rb-inotify/notifier.rb', line 268

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

#fd ⇒ Fixnum

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) 


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

def fd
  @handle.fileno
end

#process ⇒ Object

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:



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# 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_events ⇒ Object

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.



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# 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

#run ⇒ Object

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

See Also:



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# 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

#stop ⇒ Object

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



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# 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_io ⇒ IO

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



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# 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



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# 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