# $ cargo watch
[](https://crates.io/crates/cargo-watch)
[](https://creativecommons.org/publicdomain/zero/1.0/)
[](https://travis-ci.org/passcod/cargo-watch)
[](./CODE_OF_CONDUCT.md)
Cargo Watch watches over your project's source for changes, and runs Cargo
commands when they occur.
If you've used [nodemon], [gulp], [guard], [watchman], or similar others,
it will probably feel familiar.
[nodemon]: http://nodemon.io/
[gulp]: http://gulpjs.com/
[guard]: http://guardgem.org/
[watchman]: https://facebook.github.io/watchman/
## Install
```
$ cargo install cargo-watch
```
To upgrade:
```
$ cargo install --force cargo-watch
```
Or clone and build with `$ cargo build` then place in your $PATH.
## Usage
By default, it runs `check` (which is available [since Rust 1.16][st-check]).
You can easily override this, though:
```
$ cargo watch [-x command]...
```
[st-check]: https://blog.rust-lang.org/2017/03/16/Rust-1.16.html
A few examples:
```
# Run tests only
$ cargo watch -x test
# Run check then tests
$ cargo watch -x check -x test
# Run run with arguments
$ cargo watch -x 'run -- --some-arg'
# Run an arbitrary command
$ cargo watch -s 'echo Hello world'
```
There's a lot more you can do! Here's a copy of the help:
```
USAGE:
cargo watch [FLAGS] [OPTIONS]
FLAGS:
-c, --clear Clear the screen before each run
--debug Display debug output
-h, --help Display this message
--ignore-nothing Ignore nothing, not even target/ and .git/
--no-gitignore Don’t use .gitignore files
--poll Force use of polling for file changes
--postpone Postpone first run until a file changes
-q, --quiet Suppress output from cargo-watch itself
-V, --version Display version information
OPTIONS:
-x, --exec <cmd>...
Cargo command(s) to execute on changes [default: check]
-s, --shell <cmd>...
Shell command(s) to execute on changes
-d, --delay <delay>
File updates debounce delay in seconds [default: 1]
-i, --ignore <pattern>...
Ignore a glob/gitignore-style pattern
-w, --watch <watch>...
Watch specific file(s) or folder(s) [default: .]
Cargo commands (-x) are always executed before shell commands (-s).
By default, your entire project is watched, except for the target/
and .git/ folders, and your .gitignore files are used to filter paths.
```
### Reloading servers
Cargo Watch pairs very well with [Catflap], a tool for Unixy platforms that
lets one spawn a socket before the watcher runs that Rust servers can then bind
to, avoiding request-dropping and the infamous ADDRINUSE error. For example:
```
$ catflap -- cargo watch -x run
```
[Catflap]: https://github.com/passcod/catflap
## Contributing
The Cargo Watch team enthusiastically welcomes contributions and project
participation! There's a bunch of things you can do if you want to contribute!
The [Contributor Guide](./CONTRIBUTING.md) has all the information you need for
everything from reporting bugs to contributing entire new features. Please
don't hesitate to jump in if you'd like to, or even ask us questions if
something isn't clear. <sub>{[attribution](https://github.com/zkat/pacote#contributing)}</sub>
## Troubleshooting
In all cases, start by checking your version with `cargo watch --version` and,
if necessary, upgrading to [the latest one][releases].
[releases]: https://github.com/passcod/cargo-watch/releases
### On Windows 7 (or lower): "failed to add to job object: Access denied (OS Error 5)"
Cargo Watch versions 5.0.0 and up (and watchexec versions 1.3.0 and up) [do not
support Windows 7 or lower][i-69]. There are no plans at the moment to add such
support.
You can downgrade to the last version which did support Windows 7 (and lower),
but do keep in mind that many bug fixes and features are missing there:
```
$ cargo install --force --vers 4.0.3 cargo-watch
```
[i-69]: https://github.com/passcod/cargo-watch/issues/69
### If running cargo watch errors with "Found argument 'build' which wasn't expected" (or similar)
You're probably using **version 4** (or higher) but using the **version 3** (or
lower) style of arguments. The interface changed! Refer to the sections above
for new usage guidelines, or to the help message:
```
$ cargo watch --help
```
### I want to run cargo-watch directly, without going through cargo
You can! But you'll have to specify the `watch` subcommand as the first
argument, like so:
```
$ /path/to/cargo-watch watch -x build
```
### If file updates seems to never trigger
Try using `--poll` to force the polling fallback.
If that still doesn't work, and you're using an editor that does "safe saving",
like IntelliJ / PyCharm, you may have to disable "safe saving" as that may
prevent file notifications from being generated properly.
### Linux: If it fails to watch some deep directories but not others
You may have hit [the inotify watch limit][inotify-limit]. You can either
increase the limit (instructions are on the previous link and at [this Guard
wiki page][inotify-guard]), or you can stop whatever it is that's consuming so
many inotify watches.
[inotify-limit]: http://blog.sorah.jp/2012/01/24/inotify-limitation
[inotify-guard]: https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers
### If you want to only recompile one Cargo workspace
Cargo workspaces [are not natively supported yet][i-52].
However, as you can run "arbitrary commands" with the `-s` option, you can
write workspace-aware commands manually.
[i-52]: https://github.com/passcod/cargo-watch/issues/52
### If it runs repeatedly without touching anything
That can happen when watching files that are modified by the command you're
running.
If you're only running compiles or checks (i.e. any command that only affects
the target/ folder) and you're using `-w`, you might be confusing the
target-folder-ignorer. Check your options and paths.
### Something not covered above / I have a feature request
Please [open an issue][watch-issues], or look through the existing ones. You
may also want to look through [issues for the Notify library][notify-issues]
this tool depends on, or the [issues for the Watchexec tool][watchexec-issues]
that we use under the covers.
If you want more verbose output, try running with the `--debug` flag. Note that
this will also enable debug mode for watchexec. When filing an issue, make sure
to include a log with `--debug` enabled so problems can be diagnosed better.
[notify-issues]: https://github.com/passcod/notify/issues
[watch-issues]: https://github.com/passcod/cargo-watch/issues
[watchexec-issues]: https://github.com/mattgreen/watchexec/issues
### Wait, is this just a wrapper on top of watchexec?
It is! [Watchexec] does a really good job of watching files and running commands
and all the details that go with this. Cargo watch simply embeds watchexec and
calls it with its own custom options and defaults, so you can just run
`cargo-watch` in your project and be in business.
[Watchexec]: https://github.com/mattgreen/watchexec
## About
Created by [Félix Saparelli][passcod] and [awesome contributors][contributors].
[contributors]: https://github.com/passcod/cargo-watch/network/members
[passcod]: https://passcod.name