# File system notifications for Go

Cross platform: Windows, Linux, BSD and macOS.

| Adapter               | OS                               | Status                                                                                                                          |

| --------------------- | -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------- |

| FSEvents              | macOS                            | [Planned](https://github.com/fsnotify/fsnotify/issues/11)                                                                       |

| USN Journals          | Windows                          | [Maybe](https://github.com/fsnotify/fsnotify/issues/53)                                                                         |

| Polling               | *All*                            | [Maybe](https://github.com/fsnotify/fsnotify/issues/9)                                                                          |

\* Android and iOS are untested.

## API stability

## Usage

```go

package main

import (

	"log"

	"github.com/fsnotify/fsnotify"

)

func main() {

	watcher, err := fsnotify.NewWatcher()

	if err != nil {

		log.Fatal(err)

	}

	defer watcher.Close()

	done := make(chan bool)

	go func() {

		for {

			select {

			case event, ok := <-watcher.Events:

				if !ok {

					return

				}

				log.Println("event:", event)

				if event.Op&fsnotify.Write == fsnotify.Write {

					log.Println("modified file:", event.Name)

				}

			case err, ok := <-watcher.Errors:

				if !ok {

					return

				}

				log.Println("error:", err)

			}

		}

	}()

	err = watcher.Add("/tmp/foo")

	if err != nil {

		log.Fatal(err)

	}

	<-done

}

```

## Contributing

Please refer to [CONTRIBUTING][] before opening an issue or pull request.

## FAQ

**When a file is moved to another directory is it still being watched?**

No (it shouldn't be, unless you are watching where it was moved to).

**When I watch a directory, are all subdirectories watched as well?**

No, you must add watches for any directory you want to watch (a recursive watcher is on the roadmap [#18][]).

**Do I have to watch the Error and Event channels in a separate goroutine?**

As of now, yes. Looking into making this single-thread friendly (see [howeyc #7][#7])

**Why am I receiving multiple events for the same file on OS X?**

Spotlight indexing on OS X can result in multiple events (see [howeyc #62][#62]). A temporary workaround is to add your folder(s) to the *Spotlight Privacy settings* until we have a native FSEvents implementation (see [#11][]).

**How many files can be watched at once?**

There are OS-specific limits as to how many watches can be created:

* Linux: /proc/sys/fs/inotify/max_user_watches contains the limit, reaching this limit results in a "no space left on device" error.

* BSD / OSX: sysctl variables "kern.maxfiles" and "kern.maxfilesperproc", reaching these limits results in a "too many open files" error.

**Why don't notifications work with NFS filesystems or filesystem in userspace (FUSE)?**

fsnotify requires support from underlying OS to work. The current NFS protocol does not provide network level support for file notifications.

[#62]: https://github.com/howeyc/fsnotify/issues/62

[#18]: https://github.com/fsnotify/fsnotify/issues/18

[#11]: https://github.com/fsnotify/fsnotify/issues/11

[#7]: https://github.com/howeyc/fsnotify/issues/7

[contributing]: https://github.com/fsnotify/fsnotify/blob/master/CONTRIBUTING.md

## Related Projects

* [notify](https://github.com/rjeczalik/notify)

* [fsevents](https://github.com/fsnotify/fsevents)