Creare un file watcher in Scala

In questo articolo vediamo come creare un filesystem watcher in Scala 3.

Non abbiamo dipendenze da installare.

Ecco il codice:

package org.example

import java.nio.file.{FileSystems, Paths, StandardWatchEventKinds, Path}
import scala.jdk.CollectionConverters._

@main
def main(): Unit = {
  val watchPath = Paths.get("/home/fermat/TEST/")
  val watchService = FileSystems.getDefault.newWatchService()

  watchPath.register(
    watchService,
    StandardWatchEventKinds.ENTRY_CREATE,
    StandardWatchEventKinds.ENTRY_MODIFY,
    StandardWatchEventKinds.ENTRY_DELETE
  )

  println(s"Watching directory: $watchPath")
  println("Press Ctrl+C to stop watching...")

  var running = true
  while running do
    val key = watchService.take()

    for event <- key.pollEvents().asScala do
      val kind = event.kind()
      val filename = event.context().asInstanceOf[Path]
      val fullPath = watchPath.resolve(filename)

      kind match
        case StandardWatchEventKinds.ENTRY_CREATE =>
          println(s"CREATED: $fullPath")
        case StandardWatchEventKinds.ENTRY_MODIFY =>
          println(s"MODIFIED: $fullPath")
        case StandardWatchEventKinds.ENTRY_DELETE =>
          println(s"DELETED: $fullPath")
        case _ =>
          println(s"OTHER EVENT: $fullPath")

    if !key.reset() then
      running = false
}

Enjoy!