filespy

Filespy is a small library and versatile library that allows you to watch for filesystem events from Gleam! It’s a type-safe wrapper around the erlang FS library.

Quick start

Add the library to your requirements with gleam add:

gleam add filespy

Note: If you use Linux or a BSD, you need to install inotify-tools!

Usage

The library is configured via a simple builder:

import filespy
import gleam/io
import gleam/erlang/process

fn main() {
   let _res = filespy.new()   // Create the builder
   |> filespy.add_dir(".")    // Watch the current directory
   |> filespy.add_dir("/mnt") // Watch the /mnt directory
   |> filespy.set_handler(fn (path, event) {
       // This callback will be run every time a filesystem event is detected
       // in the specified directories
       io.debug(#(path, event))
       Nil
   })
   |> filespy.start()        // Start the watcher!

   process.sleep_forever()
}

If you want to, you can also go lower level, and configure the underlying actor:

import filespy
import gleam/io

fn main() {
   let _res = filespy.new()        // Create the builder
   |> filespy.add_dir(".")         // Watch the current directory
   |> filespy.add_dir("/mnt")      // Watch the /mnt directory
   |> filespy.set_initial_state(0) // Initial state for the actor, this is required!
   |> filespy.set_actor_handler(fn (message, state) {
       // This callback will be run every time a filesystem event is detected
       // in the specified directories

       // In the actor handler, multiple events might be sent at once.
       let filespy.Change(path: path, events: events) = message
       io.debug(#(path, events, state))
       
       actor.continue(state + 1)
   })
   |> filespy.start()              // Start the watcher!

   process.sleep_forever()
}

You can go even lower level, and get the actor start spec to configure it yourself:

import filespy
import gleam/io

fn main() {
   let start_spec = filespy.new()  // Create the builder
   |> filespy.add_dir(".")         // Watch the current directory
   |> filespy.add_dir("/mnt")      // Watch the /mnt directory
   |> filespy.set_initial_state(0) // Initial state for the actor, this is required!
   |> filespy.set_actor_handler(fn (message, state) {
       // This callback will be run every time a filesystem event is detected
       // in the specified directories

       // In the actor handler, multiple events might be sent at once.
       let filespy.Change(path: path, events: events) = message
       io.debug(#(path, events, state))
       
       actor.continue(state + 1)
   })
   |> filespy.spec()               // Get the spec

   actor.start_spec(start_spec)

   process.sleep_forever()
}

Documentation

If you have any more questions, check out the documentation!