Watchy

Run commands when paths change.

Install

You'll need to install Node.js to use Watchy. Node comes packaged with npm, which is Node's package manager, and the preferred method of installing Watchy. After installing Node, simply type

npm install -g watchy

and you should have the watchy command available!

Usage

Usage: watchy [options] -- command arg1 arg2 ...

Run commands when paths change.

Options:
  -V, --version                   output the version number
  -d, --debounce [seconds]        trigger a change at most every [seconds] seconds
  -k, --keep-alive                restart the process if it exits
  -p, --use-polling               use file polling even if fsevents or inotify is available
  -r, --restart [string]          send [string] to STDIN to restart the process
  -R, --no-restart-after-signal   disable process restart after being signaled and exited
  -s, --silent                    only output errors
  -S, --no-init-spawn             prevent spawn when the watcher is created
  -t, --shutdown-signal [signal]  use [signal] to shut down the process (default: "SIGTERM")
  -T, --reload-signal [signal]    use [signal] to reload the process (defaults to shutdown signal)
  -w, --watch [pattern]           watch [pattern] for changes, can be specified multiple times
  -W, --wait [seconds]            send SIGKILL to the process after [seconds] if it hasn't exited
  -h, --help                      output usage information

The watch patterns are extglob format.

Examples

# The simple case
watchy -w 'lib/**/*' -- say "The lib directory changed."

# Piping works as well
watchy -w 'styles/**/*.less' -- bash -c "lessc styles/main.less | autoprefixer -o .tmp/styles/main.css"

# Keep a process alive, restarting it as soon as it exits or "server.js"
# changes.
watchy -kw server.js -- node server.js

# Watch every file except dotfiles, the node_modules folder, and JSON files.
# NOTE: Listen to as few files as possible for better performance.
watchy -w . -i '/\.|/node_modules|\.json$' -- node server.js

# Tick tock!
watchy -ks -- bash -c 'date && sleep 1'

# Tick tock (annoying version)!
watchy -ks -- bash -c 'say "In case you were wondering, it is `date`" && sleep 5'

# $WATCHY_ACTION and $WATCHY_PATH are passed to the process.
watchy -w '**/*' -- bash -c 'echo $WATCHY_ACTION $WATCHY_PATH'
# => modified /Users/casey/Documents/code/watchy/README.md

Note: If you're using watchy for help with preprocessing, I'd recommend checking out my cogs project that is highly optimized for that case with in-memory processed file caching, directives, AMD support, and much more.

SIGTERM

By default, watchy will send SIGTERM to the running process after a change and wait for it to exit gracefully. By sending the --wait|-W n option, you can tell watchy to forcefully SIGKILL the process after n seconds. In general, you should try to clean up connections in your processes like so:

process.on('SIGTERM', function () {
  server.close();
  db.disconnect();
  redis.quit();
  // etc...
});

Node API

As of 0.9.0 watchy exposes a Node.js API.

const watchy = require('watchy');

watchy({
  patterns: ['js/**/*.js', 'css/**/*.css'],
  onError: error => console.error(error),
  onChange: ({action, path}) => console.log(action, path),
  usePolling: true // defaults to `false`, but will fallback when fsevents are not available
}).catch(er => {
  console.error(er);
  process.exit(1);
});