Watches a directory, and periodically checks for changes in dir structure

fwatch.go

package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"time"

	"github.com/fsnotify/fsnotify"
)

var (
	dir     string
	watcher *fsnotify.Watcher
	done    chan bool
)

func watch(dir string) {
	// creates a new file watcher
	watcher, _ = fsnotify.NewWatcher()
	defer watcher.Close()

	// starting at the root of the project, walk each file/directory searching for
	// directories
	if err := filepath.Walk(dir, watchDir); err != nil {
		fmt.Printf("error walking directory:  %v", err)
	}

	done = make(chan bool)

	//
	go func() {
		for {
			select {
			// watch for events
			case event := <-watcher.Events:
				fmt.Printf("EVENT! %#v\n", event)

				// watch for errors
			case err := <-watcher.Errors:
				fmt.Println("ERROR", err)

			case <-time.After(2 * time.Second):
				if err := filepath.Walk(dir, watchDir); err != nil {
					fmt.Printf("error walking directory:  %v", err)
				}
			}
		}
	}()

	<-done
}

// main
func main() {
	args := os.Args

	if len(args) != 2 {
		fmt.Printf("args: %v", args)
		log.Print("Usage:  fwatch <directory>")
		os.Exit(1)
	}

	dir = args[1]
	watch(args[1])
}

// watchDir gets run as a walk func, searching for directories to add watchers to
func watchDir(path string, fi os.FileInfo, err error) error {

	// since fsnotify can watch all the files in a directory, watchers only need
	// to be added to each nested directory
	if fi.Mode().IsDir() {
		fmt.Printf("Adding path %s\n", path)
		return watcher.Add(path)
	}

	return nil
}