| //go:build linux |
| // +build linux |
| |
| package fsnotify |
| |
| import ( |
| "errors" |
| "fmt" |
| "io" |
| "os" |
| "path/filepath" |
| "strings" |
| "sync" |
| "unsafe" |
| |
| "golang.org/x/sys/unix" |
| ) |
| |
| // Watcher watches a set of paths, delivering events on a channel. |
| // |
| // A watcher should not be copied (e.g. pass it by pointer, rather than by |
| // value). |
| // |
| // # Linux notes |
| // |
| // When a file is removed a Remove event won't be emitted until all file |
| // descriptors are closed, and deletes will always emit a Chmod. For example: |
| // |
| // fp := os.Open("file") |
| // os.Remove("file") // Triggers Chmod |
| // fp.Close() // Triggers Remove |
| // |
| // This is the event that inotify sends, so not much can be changed about this. |
| // |
| // The fs.inotify.max_user_watches sysctl variable specifies the upper limit |
| // for the number of watches per user, and fs.inotify.max_user_instances |
| // specifies the maximum number of inotify instances per user. Every Watcher you |
| // create is an "instance", and every path you add is a "watch". |
| // |
| // These are also exposed in /proc as /proc/sys/fs/inotify/max_user_watches and |
| // /proc/sys/fs/inotify/max_user_instances |
| // |
| // To increase them you can use sysctl or write the value to the /proc file: |
| // |
| // # Default values on Linux 5.18 |
| // sysctl fs.inotify.max_user_watches=124983 |
| // sysctl fs.inotify.max_user_instances=128 |
| // |
| // To make the changes persist on reboot edit /etc/sysctl.conf or |
| // /usr/lib/sysctl.d/50-default.conf (details differ per Linux distro; check |
| // your distro's documentation): |
| // |
| // fs.inotify.max_user_watches=124983 |
| // fs.inotify.max_user_instances=128 |
| // |
| // Reaching the limit will result in a "no space left on device" or "too many open |
| // files" error. |
| // |
| // # kqueue notes (macOS, BSD) |
| // |
| // kqueue requires opening a file descriptor for every file that's being watched; |
| // so if you're watching a directory with five files then that's six file |
| // descriptors. You will run in to your system's "max open files" limit faster on |
| // these platforms. |
| // |
| // The sysctl variables kern.maxfiles and kern.maxfilesperproc can be used to |
| // control the maximum number of open files, as well as /etc/login.conf on BSD |
| // systems. |
| // |
| // # macOS notes |
| // |
| // Spotlight indexing on macOS can result in multiple events (see [#15]). A |
| // temporary workaround is to add your folder(s) to the "Spotlight Privacy |
| // Settings" until we have a native FSEvents implementation (see [#11]). |
| // |
| // [#11]: https://github.com/fsnotify/fsnotify/issues/11 |
| // [#15]: https://github.com/fsnotify/fsnotify/issues/15 |
| type Watcher struct { |
| // Events sends the filesystem change events. |
| // |
| // fsnotify can send the following events; a "path" here can refer to a |
| // file, directory, symbolic link, or special file like a FIFO. |
| // |
| // fsnotify.Create A new path was created; this may be followed by one |
| // or more Write events if data also gets written to a |
| // file. |
| // |
| // fsnotify.Remove A path was removed. |
| // |
| // fsnotify.Rename A path was renamed. A rename is always sent with the |
| // old path as Event.Name, and a Create event will be |
| // sent with the new name. Renames are only sent for |
| // paths that are currently watched; e.g. moving an |
| // unmonitored file into a monitored directory will |
| // show up as just a Create. Similarly, renaming a file |
| // to outside a monitored directory will show up as |
| // only a Rename. |
| // |
| // fsnotify.Write A file or named pipe was written to. A Truncate will |
| // also trigger a Write. A single "write action" |
| // initiated by the user may show up as one or multiple |
| // writes, depending on when the system syncs things to |
| // disk. For example when compiling a large Go program |
| // you may get hundreds of Write events, so you |
| // probably want to wait until you've stopped receiving |
| // them (see the dedup example in cmd/fsnotify). |
| // |
| // fsnotify.Chmod Attributes were changed. On Linux this is also sent |
| // when a file is removed (or more accurately, when a |
| // link to an inode is removed). On kqueue it's sent |
| // and on kqueue when a file is truncated. On Windows |
| // it's never sent. |
| Events chan Event |
| |
| // Errors sends any errors. |
| Errors chan error |
| |
| // Store fd here as os.File.Read() will no longer return on close after |
| // calling Fd(). See: https://github.com/golang/go/issues/26439 |
| fd int |
| mu sync.Mutex // Map access |
| inotifyFile *os.File |
| watches map[string]*watch // Map of inotify watches (key: path) |
| paths map[int]string // Map of watched paths (key: watch descriptor) |
| done chan struct{} // Channel for sending a "quit message" to the reader goroutine |
| doneResp chan struct{} // Channel to respond to Close |
| } |
| |
| // NewWatcher creates a new Watcher. |
| func NewWatcher() (*Watcher, error) { |
| // Create inotify fd |
| // Need to set the FD to nonblocking mode in order for SetDeadline methods to work |
| // Otherwise, blocking i/o operations won't terminate on close |
| fd, errno := unix.InotifyInit1(unix.IN_CLOEXEC | unix.IN_NONBLOCK) |
| if fd == -1 { |
| return nil, errno |
| } |
| |
| w := &Watcher{ |
| fd: fd, |
| inotifyFile: os.NewFile(uintptr(fd), ""), |
| watches: make(map[string]*watch), |
| paths: make(map[int]string), |
| Events: make(chan Event), |
| Errors: make(chan error), |
| done: make(chan struct{}), |
| doneResp: make(chan struct{}), |
| } |
| |
| go w.readEvents() |
| return w, nil |
| } |
| |
| // Returns true if the event was sent, or false if watcher is closed. |
| func (w *Watcher) sendEvent(e Event) bool { |
| select { |
| case w.Events <- e: |
| return true |
| case <-w.done: |
| } |
| return false |
| } |
| |
| // Returns true if the error was sent, or false if watcher is closed. |
| func (w *Watcher) sendError(err error) bool { |
| select { |
| case w.Errors <- err: |
| return true |
| case <-w.done: |
| return false |
| } |
| } |
| |
| func (w *Watcher) isClosed() bool { |
| select { |
| case <-w.done: |
| return true |
| default: |
| return false |
| } |
| } |
| |
| // Close removes all watches and closes the events channel. |
| func (w *Watcher) Close() error { |
| w.mu.Lock() |
| if w.isClosed() { |
| w.mu.Unlock() |
| return nil |
| } |
| |
| // Send 'close' signal to goroutine, and set the Watcher to closed. |
| close(w.done) |
| w.mu.Unlock() |
| |
| // Causes any blocking reads to return with an error, provided the file |
| // still supports deadline operations. |
| err := w.inotifyFile.Close() |
| if err != nil { |
| return err |
| } |
| |
| // Wait for goroutine to close |
| <-w.doneResp |
| |
| return nil |
| } |
| |
| // Add starts monitoring the path for changes. |
| // |
| // A path can only be watched once; attempting to watch it more than once will |
| // return an error. Paths that do not yet exist on the filesystem cannot be |
| // added. A watch will be automatically removed if the path is deleted. |
| // |
| // A path will remain watched if it gets renamed to somewhere else on the same |
| // filesystem, but the monitor will get removed if the path gets deleted and |
| // re-created, or if it's moved to a different filesystem. |
| // |
| // Notifications on network filesystems (NFS, SMB, FUSE, etc.) or special |
| // filesystems (/proc, /sys, etc.) generally don't work. |
| // |
| // # Watching directories |
| // |
| // All files in a directory are monitored, including new files that are created |
| // after the watcher is started. Subdirectories are not watched (i.e. it's |
| // non-recursive). |
| // |
| // # Watching files |
| // |
| // Watching individual files (rather than directories) is generally not |
| // recommended as many tools update files atomically. Instead of "just" writing |
| // to the file a temporary file will be written to first, and if successful the |
| // temporary file is moved to to destination removing the original, or some |
| // variant thereof. The watcher on the original file is now lost, as it no |
| // longer exists. |
| // |
| // Instead, watch the parent directory and use Event.Name to filter out files |
| // you're not interested in. There is an example of this in [cmd/fsnotify/file.go]. |
| func (w *Watcher) Add(name string) error { |
| name = filepath.Clean(name) |
| if w.isClosed() { |
| return errors.New("inotify instance already closed") |
| } |
| |
| var flags uint32 = unix.IN_MOVED_TO | unix.IN_MOVED_FROM | |
| unix.IN_CREATE | unix.IN_ATTRIB | unix.IN_MODIFY | |
| unix.IN_MOVE_SELF | unix.IN_DELETE | unix.IN_DELETE_SELF |
| |
| w.mu.Lock() |
| defer w.mu.Unlock() |
| watchEntry := w.watches[name] |
| if watchEntry != nil { |
| flags |= watchEntry.flags | unix.IN_MASK_ADD |
| } |
| wd, errno := unix.InotifyAddWatch(w.fd, name, flags) |
| if wd == -1 { |
| return errno |
| } |
| |
| if watchEntry == nil { |
| w.watches[name] = &watch{wd: uint32(wd), flags: flags} |
| w.paths[wd] = name |
| } else { |
| watchEntry.wd = uint32(wd) |
| watchEntry.flags = flags |
| } |
| |
| return nil |
| } |
| |
| // Remove stops monitoring the path for changes. |
| // |
| // Directories are always removed non-recursively. For example, if you added |
| // /tmp/dir and /tmp/dir/subdir then you will need to remove both. |
| // |
| // Removing a path that has not yet been added returns [ErrNonExistentWatch]. |
| func (w *Watcher) Remove(name string) error { |
| name = filepath.Clean(name) |
| |
| // Fetch the watch. |
| w.mu.Lock() |
| defer w.mu.Unlock() |
| watch, ok := w.watches[name] |
| |
| // Remove it from inotify. |
| if !ok { |
| return fmt.Errorf("%w: %s", ErrNonExistentWatch, name) |
| } |
| |
| // We successfully removed the watch if InotifyRmWatch doesn't return an |
| // error, we need to clean up our internal state to ensure it matches |
| // inotify's kernel state. |
| delete(w.paths, int(watch.wd)) |
| delete(w.watches, name) |
| |
| // inotify_rm_watch will return EINVAL if the file has been deleted; |
| // the inotify will already have been removed. |
| // watches and pathes are deleted in ignoreLinux() implicitly and asynchronously |
| // by calling inotify_rm_watch() below. e.g. readEvents() goroutine receives IN_IGNORE |
| // so that EINVAL means that the wd is being rm_watch()ed or its file removed |
| // by another thread and we have not received IN_IGNORE event. |
| success, errno := unix.InotifyRmWatch(w.fd, watch.wd) |
| if success == -1 { |
| // TODO: Perhaps it's not helpful to return an error here in every case; |
| // The only two possible errors are: |
| // |
| // - EBADF, which happens when w.fd is not a valid file descriptor |
| // of any kind. |
| // - EINVAL, which is when fd is not an inotify descriptor or wd |
| // is not a valid watch descriptor. Watch descriptors are |
| // invalidated when they are removed explicitly or implicitly; |
| // explicitly by inotify_rm_watch, implicitly when the file they |
| // are watching is deleted. |
| return errno |
| } |
| |
| return nil |
| } |
| |
| // WatchList returns all paths added with [Add] (and are not yet removed). |
| func (w *Watcher) WatchList() []string { |
| w.mu.Lock() |
| defer w.mu.Unlock() |
| |
| entries := make([]string, 0, len(w.watches)) |
| for pathname := range w.watches { |
| entries = append(entries, pathname) |
| } |
| |
| return entries |
| } |
| |
| type watch struct { |
| wd uint32 // Watch descriptor (as returned by the inotify_add_watch() syscall) |
| flags uint32 // inotify flags of this watch (see inotify(7) for the list of valid flags) |
| } |
| |
| // readEvents reads from the inotify file descriptor, converts the |
| // received events into Event objects and sends them via the Events channel |
| func (w *Watcher) readEvents() { |
| defer func() { |
| close(w.doneResp) |
| close(w.Errors) |
| close(w.Events) |
| }() |
| |
| var ( |
| buf [unix.SizeofInotifyEvent * 4096]byte // Buffer for a maximum of 4096 raw events |
| errno error // Syscall errno |
| ) |
| for { |
| // See if we have been closed. |
| if w.isClosed() { |
| return |
| } |
| |
| n, err := w.inotifyFile.Read(buf[:]) |
| switch { |
| case errors.Unwrap(err) == os.ErrClosed: |
| return |
| case err != nil: |
| if !w.sendError(err) { |
| return |
| } |
| continue |
| } |
| |
| if n < unix.SizeofInotifyEvent { |
| var err error |
| if n == 0 { |
| // If EOF is received. This should really never happen. |
| err = io.EOF |
| } else if n < 0 { |
| // If an error occurred while reading. |
| err = errno |
| } else { |
| // Read was too short. |
| err = errors.New("notify: short read in readEvents()") |
| } |
| if !w.sendError(err) { |
| return |
| } |
| continue |
| } |
| |
| var offset uint32 |
| // We don't know how many events we just read into the buffer |
| // While the offset points to at least one whole event... |
| for offset <= uint32(n-unix.SizeofInotifyEvent) { |
| var ( |
| // Point "raw" to the event in the buffer |
| raw = (*unix.InotifyEvent)(unsafe.Pointer(&buf[offset])) |
| mask = uint32(raw.Mask) |
| nameLen = uint32(raw.Len) |
| ) |
| |
| if mask&unix.IN_Q_OVERFLOW != 0 { |
| if !w.sendError(ErrEventOverflow) { |
| return |
| } |
| } |
| |
| // If the event happened to the watched directory or the watched file, the kernel |
| // doesn't append the filename to the event, but we would like to always fill the |
| // the "Name" field with a valid filename. We retrieve the path of the watch from |
| // the "paths" map. |
| w.mu.Lock() |
| name, ok := w.paths[int(raw.Wd)] |
| // IN_DELETE_SELF occurs when the file/directory being watched is removed. |
| // This is a sign to clean up the maps, otherwise we are no longer in sync |
| // with the inotify kernel state which has already deleted the watch |
| // automatically. |
| if ok && mask&unix.IN_DELETE_SELF == unix.IN_DELETE_SELF { |
| delete(w.paths, int(raw.Wd)) |
| delete(w.watches, name) |
| } |
| w.mu.Unlock() |
| |
| if nameLen > 0 { |
| // Point "bytes" at the first byte of the filename |
| bytes := (*[unix.PathMax]byte)(unsafe.Pointer(&buf[offset+unix.SizeofInotifyEvent]))[:nameLen:nameLen] |
| // The filename is padded with NULL bytes. TrimRight() gets rid of those. |
| name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000") |
| } |
| |
| event := w.newEvent(name, mask) |
| |
| // Send the events that are not ignored on the events channel |
| if mask&unix.IN_IGNORED == 0 { |
| if !w.sendEvent(event) { |
| return |
| } |
| } |
| |
| // Move to the next event in the buffer |
| offset += unix.SizeofInotifyEvent + nameLen |
| } |
| } |
| } |
| |
| // newEvent returns an platform-independent Event based on an inotify mask. |
| func (w *Watcher) newEvent(name string, mask uint32) Event { |
| e := Event{Name: name} |
| if mask&unix.IN_CREATE == unix.IN_CREATE || mask&unix.IN_MOVED_TO == unix.IN_MOVED_TO { |
| e.Op |= Create |
| } |
| if mask&unix.IN_DELETE_SELF == unix.IN_DELETE_SELF || mask&unix.IN_DELETE == unix.IN_DELETE { |
| e.Op |= Remove |
| } |
| if mask&unix.IN_MODIFY == unix.IN_MODIFY { |
| e.Op |= Write |
| } |
| if mask&unix.IN_MOVE_SELF == unix.IN_MOVE_SELF || mask&unix.IN_MOVED_FROM == unix.IN_MOVED_FROM { |
| e.Op |= Rename |
| } |
| if mask&unix.IN_ATTRIB == unix.IN_ATTRIB { |
| e.Op |= Chmod |
| } |
| return e |
| } |