Notify

Cross-platform filesystem notification library for Rust.

Caution! This is a bleeding-edge 5.0 prerelease!

You likely want either the latest 4.0 release or 5.0.0-pre.1.

Notably, at this stage the debounced interface has been completely removed. You can find its previous implementation at either version above.

(Looking for desktop notifications instead? Have a look at notify-rust or alert-after!)

• wip Guides and in-depth docs
• API Documentation
• Crate page
• Changelog
• todo Upgrading from 4.0
• Earliest supported Rust version: 1.32.0

As used by: alacritty, cargo watch, cobalt, docket, mdBook, pax rdiff, rust-analyzer, timetrack, watchexec, xi-editor, and others. (Want to be added to this list? Open a pull request!)

Why a prerelease?

It’s taking a while to bring 5.0 to the standard and featureset I wish for it, while at the same time I have less time than ever to spend on this project. In short, don’t expect 5.0.0 before Q4 2019. I am aware, though, that people want to use the features that are finished so far. This is what this prerelease is.

It has all the fixes and implemented features so far, with the new Event interface for the "debounced" watcher, but keeping the previous events for the immediate (previously known as "raw") watcher. It is fairly stable in terms of functionality, and the debounced (default) API is as close as its final 5.0.0 form as it can be.

The idea is to pin to =5.0.0-pre.1, and ignore further prereleases. You’ll get long-standing fixes compared to 4.0.x, some new features, and API stability for the next few months.

The 4.0.x branch will continue being passively maintained during this time though, and it’s what out there in the ecosystem right now, so it’s always an option to go for the latest 4.0 release.

If you want to live at the bleeding edge, you can of course track main or future prereleases. Keep in mind that there will be breakage, there will be changes, and entire features may disappear and reappear between prereleases. It’s gonna be pretty unstable for a while.

^{(What happened to 5.0.0-pre.0? I broke it. I'm sorry. .1 is just like it, though.)}

Installation

[dependencies]
crossbeam-channel = "0.3.8"
notify = "5.0.0-pre.2"

Usage

The examples below are aspirational only, to preview what the final release may look like. They may not work. Refer to the API documentation instead.

use notify::{RecommendedWatcher, RecursiveMode, Result, watcher};
use std::time::Duration;

fn main() -> Result<()> {
    // Automatically select the best implementation for your platform.
    // You can also access each implementation directly e.g. INotifyWatcher.
    let mut watcher = watcher(Duration::from_secs(2))?;

    // Add a path to be watched. All files and directories at that path and
    // below will be monitored for changes.
    watcher.watch("/home/test/notify", RecursiveMode::Recursive)?;

    // This is a simple loop, but you may want to use more complex logic here,
    // for example to handle I/O.
    for event in &watcher {
        match event {
            Ok(event) => println!("changed: {:?}", event.path),
            Err(err) => println!("watch error: {:?}", err),
        };
    }

    Ok(())
}

With a channel

To get a channel for advanced or flexible cases, use:

let rx = watcher.channel();

loop {
    match rx.recv() {
        // ...
    }
}

To pass in a channel manually:

let (tx, rx) = crossbeam_channel::unbounded();
let mut watcher: RecommendedWatcher = Watcher::with_channel(tx, Duration::from_secs(2))?;

for event in rx.iter() {
    // ...
}

With precise events

By default, Notify issues generic events that carry little additional information beyond what path was affected. On some platforms, more is available; stay aware though that how exactly that manifests varies. To enable precise events, use:

use notify::Config;
watcher.configure(Config::PreciseEvents(true));

With notice events

Sometimes you want to respond to some events straight away, but not give up the advantages of debouncing. Notice events appear once immediately when the occur during a debouncing period, and then a second time as usual at the end of the debouncing period:

use notify::Config;
watcher.configure(Config::NoticeEvents(true));

With ongoing events

Sometimes frequent writes may be missed or not noticed often enough. Ongoing write events can be enabled to emit more events even while debouncing:

use notify::Config;
watcher.configure(Config::OngoingEvents(Some(Duration::from_millis(500))));

Without debouncing

To receive events as they are emitted, without debouncing at all:

let mut watcher = immediate_watcher()?;

With a channel:

let (tx, rx) = unbounded();
let mut watcher: RecommendedWatcher = Watcher::immediate_with_channel(tx)?;

Serde

Events can be serialisable via serde. To enable the feature:

notify = { version = "5.0.0-pre.2", features = ["serde"] }

Platforms

• Linux / Android: inotify
• macOS: FSEvents
• Windows: ReadDirectoryChangesW
• All platforms: polling

FSEvents

Due to the inner security model of FSEvents (see FileSystemEventSecurity), some event cannot be observed easily when trying to follow files that do not belong to you. In this case, reverting to the pollwatcher can fix the issue, with a slight performance cost.

Next generation

While this current version continues to be developed and maintained, next generation experiments and designs around the library live in the next branch. There is no solid ETA, beyond that most of it will not be released before async/await is stabilised in Rust. For an overview and background, see this draft announce.

Instead of one large release, though, smaller components of the design, once they have gone through revising and maturing, will be incorporated in the main branch. The first large piece, a new event classification system, has already landed.

License

Notify is currently undergoing a transition to using the Artistic License 2.0 from the current CC Zero 1.0. A part of the code is only under CC0, and another part, including all new code since commit 3378ac5a, is under both CC0 and Artistic. When the code will be entirely free of CC0 code, the license will be formally changed (and that will incur a major version bump). As part of this, when you contribute to Notify you currently agree to release under both.

Origins

Inspired by Go's fsnotify and Node.js's Chokidar, born out of need for cargo watch, and general frustration at the non-existence of C/Rust cross-platform notify libraries.

Written by Félix Saparelli and awesome contributors.