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433 lines
18 KiB
EmacsLisp
433 lines
18 KiB
EmacsLisp
;;; filenotify.el --- watch files for changes on disk -*- lexical-binding:t -*-
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;; Copyright (C) 2013-2018 Free Software Foundation, Inc.
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;; Author: Michael Albinus <michael.albinus@gmx.de>
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary
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;; This package is an abstraction layer from the different low-level
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;; file notification packages `inotify', `kqueue', `gfilenotify' and
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;; `w32notify'.
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;;; Code:
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(require 'cl-lib)
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(eval-when-compile (require 'subr-x))
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(defconst file-notify--library
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(cond
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((featurep 'inotify) 'inotify)
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((featurep 'kqueue) 'kqueue)
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((featurep 'gfilenotify) 'gfilenotify)
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((featurep 'w32notify) 'w32notify))
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"Non-nil when Emacs has been compiled with file notification support.
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The value is the name of the low-level file notification package
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to be used for local file systems. Remote file notifications
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could use another implementation.")
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(cl-defstruct (file-notify--watch
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(:constructor nil)
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(:constructor
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file-notify--watch-make (directory filename callback)))
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;; Watched directory
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directory
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;; Watched relative filename, nil if watching the directory.
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filename
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;; Function to propagate events to
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callback)
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(defun file-notify--watch-absolute-filename (watch)
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"Return the absolute filename observed by WATCH."
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(if (file-notify--watch-filename watch)
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(expand-file-name
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(file-notify--watch-filename watch)
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(file-notify--watch-directory watch))
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(file-notify--watch-directory watch)))
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(defvar file-notify-descriptors (make-hash-table :test 'equal)
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"Hash table for registered file notification descriptors.
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A key in this hash table is the descriptor as returned from
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`inotify', `kqueue', `gfilenotify', `w32notify' or a file name
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handler. The value in the hash table is `file-notify--watch'
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struct.")
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(defun file-notify--rm-descriptor (descriptor)
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"Remove DESCRIPTOR from `file-notify-descriptors'.
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DESCRIPTOR should be an object returned by `file-notify-add-watch'.
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If it is registered in `file-notify-descriptors', a stopped event is sent."
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(when-let* ((watch (gethash descriptor file-notify-descriptors)))
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;; Send `stopped' event.
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(unwind-protect
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(funcall
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(file-notify--watch-callback watch)
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`(,descriptor stopped ,(file-notify--watch-absolute-filename watch)))
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(remhash descriptor file-notify-descriptors))))
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;; This function is used by `inotify', `kqueue', `gfilenotify' and
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;; `w32notify' events.
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;;;###autoload
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(defun file-notify-handle-event (event)
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"Handle file system monitoring event.
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If EVENT is a filewatch event, call its callback. It has the format
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(file-notify (DESCRIPTOR ACTIONS FILE [FILE1-OR-COOKIE]) CALLBACK)
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Otherwise, signal a `file-notify-error'."
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(interactive "e")
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;;(message "file-notify-handle-event %S" event)
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(if (and (consp event)
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(eq (car event) 'file-notify)
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(>= (length event) 3))
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(funcall (nth 2 event) (nth 1 event))
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(signal 'file-notify-error
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(cons "Not a valid file-notify event" event))))
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;; Needed for `inotify' and `w32notify'. In the latter case, COOKIE is nil.
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(defvar file-notify--pending-event nil
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"A pending file notification event for a future `renamed' action.
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It is a form ((DESCRIPTOR ACTION FILE [FILE1-OR-COOKIE]) CALLBACK).")
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(defun file-notify--event-watched-file (event)
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"Return file or directory being watched.
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Could be different from the directory watched by the backend library."
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(when-let* ((watch (gethash (car event) file-notify-descriptors)))
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(file-notify--watch-absolute-filename watch)))
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(defun file-notify--event-file-name (event)
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"Return file name of file notification event, or nil."
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(when-let* ((watch (gethash (car event) file-notify-descriptors)))
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(directory-file-name
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(expand-file-name
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(or (and (stringp (nth 2 event)) (nth 2 event)) "")
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(file-notify--watch-directory watch)))))
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;; Only `gfilenotify' could return two file names.
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(defun file-notify--event-file1-name (event)
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"Return second file name of file notification event, or nil.
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This is available in case a file has been moved."
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(when-let* ((watch (gethash (car event) file-notify-descriptors)))
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(and (stringp (nth 3 event))
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(directory-file-name
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(expand-file-name
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(nth 3 event) (file-notify--watch-directory watch))))))
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;; Cookies are offered by `inotify' only.
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(defun file-notify--event-cookie (event)
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"Return cookie of file notification event, or nil.
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This is available in case a file has been moved."
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(nth 3 event))
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;; The callback function used to map between specific flags of the
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;; respective file notifications, and the ones we return.
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(defun file-notify-callback (event)
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"Handle an EVENT returned from file notification.
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EVENT is the cadr of the event in `file-notify-handle-event'
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\(DESCRIPTOR ACTIONS FILE [FILE1-OR-COOKIE])."
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(let* ((desc (car event))
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(watch (gethash desc file-notify-descriptors))
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(actions (nth 1 event))
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(file (file-notify--event-file-name event))
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file1 pending-event stopped)
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;; Make actions a list.
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(unless (consp actions) (setq actions (cons actions nil)))
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(when watch
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;; Loop over actions. In fact, more than one action happens only
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;; for `inotify' and `kqueue'.
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(while actions
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(let ((action (pop actions)))
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;; Send pending event, if it doesn't match.
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(when (and file-notify--pending-event
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;; The cookie doesn't match.
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(not (equal (file-notify--event-cookie
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(car file-notify--pending-event))
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(file-notify--event-cookie event)))
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(or
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;; inotify.
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(and (eq (nth 1 (car file-notify--pending-event))
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'moved-from)
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(not (eq action 'moved-to)))
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;; w32notify.
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(and (eq (nth 1 (car file-notify--pending-event))
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'renamed-from)
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(not (eq action 'renamed-to)))))
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(setq pending-event file-notify--pending-event
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file-notify--pending-event nil)
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(setcar (cdar pending-event) 'deleted))
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;; Map action. We ignore all events which cannot be mapped.
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(setq action
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(cond
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((memq action
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'(attribute-changed changed created deleted renamed))
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action)
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((memq action '(moved rename))
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;; The kqueue rename event does not return file1 in
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;; case a file monitor is established.
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(if (setq file1 (file-notify--event-file1-name event))
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'renamed 'deleted))
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((eq action 'ignored)
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(setq stopped t actions nil))
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((memq action '(attrib link)) 'attribute-changed)
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((memq action '(create added)) 'created)
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((memq action '(modify modified write)) 'changed)
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((memq action '(delete delete-self move-self removed))
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'deleted)
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;; Make the event pending.
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((memq action '(moved-from renamed-from))
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(setq file-notify--pending-event
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`((,desc ,action ,file
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,(file-notify--event-cookie event))
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,(file-notify--watch-callback watch)))
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nil)
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;; Look for pending event.
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((memq action '(moved-to renamed-to))
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(if (null file-notify--pending-event)
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'created
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(setq file1 file
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file (file-notify--event-file-name
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(car file-notify--pending-event)))
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;; If the source is handled by another watch, we
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;; must fire the rename event there as well.
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(unless (equal desc (caar file-notify--pending-event))
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(setq pending-event
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`((,(caar file-notify--pending-event)
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renamed ,file ,file1)
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,(cadr file-notify--pending-event))))
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(setq file-notify--pending-event nil)
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'renamed))))
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;; Apply pending callback.
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(when pending-event
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(funcall (cadr pending-event) (car pending-event))
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(setq pending-event nil))
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;; Apply callback.
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(when (and action
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(or
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;; If there is no relative file name for that
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;; watch, we watch the whole directory.
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(null (file-notify--watch-filename watch))
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;; File matches.
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(string-equal
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(file-notify--watch-filename watch)
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(file-name-nondirectory file))
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;; Directory matches.
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(string-equal
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(file-name-nondirectory file)
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(file-name-nondirectory
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(file-notify--watch-directory watch)))
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;; File1 matches.
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(and (stringp file1)
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(string-equal
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(file-notify--watch-filename watch)
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(file-name-nondirectory file1)))))
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;;(message
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;;"file-notify-callback %S %S %S %S %S"
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;;desc action file file1 watch)
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(if file1
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(funcall (file-notify--watch-callback watch)
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`(,desc ,action ,file ,file1))
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(funcall (file-notify--watch-callback watch)
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`(,desc ,action ,file))))
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;; Send `stopped' event.
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(when (or stopped
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(and (memq action '(deleted renamed))
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;; Not, when a file is backed up.
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(not (and (stringp file1) (backup-file-name-p file1)))
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;; Watched file or directory is concerned.
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(string-equal
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file (file-notify--event-watched-file event))))
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(file-notify-rm-watch desc)))))))
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;; `kqueue', `gfilenotify' and `w32notify' return a unique descriptor
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;; for every `file-notify-add-watch', while `inotify' returns a unique
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;; descriptor per inode only.
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(defun file-notify-add-watch (file flags callback)
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"Add a watch for filesystem events pertaining to FILE.
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This arranges for filesystem events pertaining to FILE to be reported
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to Emacs. Use `file-notify-rm-watch' to cancel the watch.
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The returned value is a descriptor for the added watch. If the
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file cannot be watched for some reason, this function signals a
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`file-notify-error' error.
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FLAGS is a list of conditions to set what will be watched for. It can
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include the following symbols:
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`change' -- watch for file changes
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`attribute-change' -- watch for file attributes changes, like
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permissions or modification time
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If FILE is a directory, `change' watches for file creation or
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deletion in that directory. This does not work recursively.
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When any event happens, Emacs will call the CALLBACK function passing
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it a single argument EVENT, which is of the form
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(DESCRIPTOR ACTION FILE [FILE1])
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DESCRIPTOR is the same object as the one returned by this function.
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ACTION is the description of the event. It could be any one of the
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following:
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`created' -- FILE was created
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`deleted' -- FILE was deleted
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`changed' -- FILE has changed
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`renamed' -- FILE has been renamed to FILE1
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`attribute-changed' -- a FILE attribute was changed
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`stopped' -- watching FILE has been stopped
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FILE is the name of the file whose event is being reported."
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;; Check arguments.
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(unless (stringp file)
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(signal 'wrong-type-argument `(,file)))
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(setq file (expand-file-name file))
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(unless (and (consp flags)
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(null (delq 'change (delq 'attribute-change (copy-tree flags)))))
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(signal 'wrong-type-argument `(,flags)))
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(unless (functionp callback)
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(signal 'wrong-type-argument `(,callback)))
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(let* ((handler (find-file-name-handler file 'file-notify-add-watch))
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(dir (directory-file-name
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(if (file-directory-p file)
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file
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(file-name-directory file))))
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desc func l-flags)
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(unless (file-directory-p dir)
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(signal 'file-notify-error `("Directory does not exist" ,dir)))
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(if handler
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;; A file name handler could exist even if there is no local
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;; file notification support.
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(setq desc (funcall handler 'file-notify-add-watch dir flags callback))
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;; Check, whether Emacs has been compiled with file notification
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;; support.
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(unless file-notify--library
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(signal 'file-notify-error
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'("No file notification package available")))
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;; Determine low-level function to be called.
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(setq func
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(cond
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((eq file-notify--library 'inotify) 'inotify-add-watch)
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((eq file-notify--library 'kqueue) 'kqueue-add-watch)
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((eq file-notify--library 'gfilenotify) 'gfile-add-watch)
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((eq file-notify--library 'w32notify) 'w32notify-add-watch)))
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;; Determine respective flags.
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(if (eq file-notify--library 'gfilenotify)
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(setq l-flags (append '(watch-mounts send-moved) flags))
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(when (memq 'change flags)
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(setq
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l-flags
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(cond
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((eq file-notify--library 'inotify)
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'(create delete delete-self modify move-self move))
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((eq file-notify--library 'kqueue)
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'(create delete write extend rename))
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((eq file-notify--library 'w32notify)
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'(file-name directory-name size last-write-time)))))
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(when (memq 'attribute-change flags)
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(push (cond
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((eq file-notify--library 'inotify) 'attrib)
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((eq file-notify--library 'kqueue) 'attrib)
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((eq file-notify--library 'w32notify) 'attributes))
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l-flags)))
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;; Call low-level function.
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(setq desc (funcall
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;; kqueue does not report file changes in directory
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;; monitor. So we must watch the file itself.
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func (if (eq file-notify--library 'kqueue) file dir)
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l-flags 'file-notify-callback)))
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;; Modify `file-notify-descriptors'.
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(let ((watch (file-notify--watch-make
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dir
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(unless (file-directory-p file) (file-name-nondirectory file))
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callback)))
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(puthash desc watch file-notify-descriptors))
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;; Return descriptor.
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desc))
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(defun file-notify-rm-watch (descriptor)
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"Remove an existing watch specified by its DESCRIPTOR.
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DESCRIPTOR should be an object returned by `file-notify-add-watch'."
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(when-let* ((watch (gethash descriptor file-notify-descriptors)))
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(let ((handler (find-file-name-handler
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(file-notify--watch-directory watch)
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'file-notify-rm-watch)))
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(condition-case nil
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(if handler
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;; A file name handler could exist even if there is no
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;; local file notification support.
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(funcall handler 'file-notify-rm-watch descriptor)
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(funcall
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(cond
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((eq file-notify--library 'inotify) 'inotify-rm-watch)
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((eq file-notify--library 'kqueue) 'kqueue-rm-watch)
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((eq file-notify--library 'gfilenotify) 'gfile-rm-watch)
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((eq file-notify--library 'w32notify) 'w32notify-rm-watch))
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descriptor))
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(file-notify-error nil)))
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;; Modify `file-notify-descriptors'.
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(file-notify--rm-descriptor descriptor)))
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(defun file-notify-valid-p (descriptor)
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"Check a watch specified by its DESCRIPTOR.
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DESCRIPTOR should be an object returned by `file-notify-add-watch'."
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(when-let* ((watch (gethash descriptor file-notify-descriptors)))
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(let ((handler (find-file-name-handler
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(file-notify--watch-directory watch)
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'file-notify-valid-p)))
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(and (if handler
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;; A file name handler could exist even if there is no
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;; local file notification support.
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(funcall handler 'file-notify-valid-p descriptor)
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(funcall
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(cond
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((eq file-notify--library 'inotify) 'inotify-valid-p)
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((eq file-notify--library 'kqueue) 'kqueue-valid-p)
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((eq file-notify--library 'gfilenotify) 'gfile-valid-p)
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((eq file-notify--library 'w32notify) 'w32notify-valid-p))
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descriptor))
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t))))
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;; TODO:
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;; * Watching a /dir/file may receive events for dir.
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;; (This may be the desired behavior.)
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;; * Watching a file in an already watched directory
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;; If the file is created and *then* a watch is added to that file, the
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;; watch might receive events which occurred prior to it being created,
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;; due to the way events are propagated during idle time. Note: This
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;; may be perfectly acceptable.
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;; The end:
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(provide 'filenotify)
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;;; filenotify.el ends here
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