File Locking In Go

filelockingingo.go

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"sync"
	"time"
)

var wg sync.WaitGroup

func main() {
	wg.Add(2)
	go func() {
		if err := readerTask("/tmp/test"); err != nil {
			fmt.Println(err.Error())
		}
	}()
	go func() {
		if err := updateTask("/tmp/test"); err != nil {
			fmt.Println(err.Error())
		}
	}()

	wg.Wait()
}

func updateTask(dirName string) error {
	defer wg.Done()
	dirEntries, err := ioutil.ReadDir(dirName)
	if err != nil {
		return fmt.Errorf("failed to read dir: %w", err)
	}
	for _, dirEntry := range dirEntries {
		fmt.Println("== " + dirEntry.Name())
		srcSubDirName := filepath.Join(dirName, dirEntry.Name())

		if dirEntry.IsDir() {
			destSubDirName := filepath.Join(dirName, dirEntry.Name()+"_v2")
			fmt.Printf("== Moving %s to %s\n", srcSubDirName, destSubDirName)
			if err := os.Rename(srcSubDirName, destSubDirName); err != nil {
				return err
			}
			continue
		}

		if dirEntry.Name() == "c.d" {
			if err := os.Remove(srcSubDirName); err != nil {
				return nil
			}
		}
	}
	return nil
}

func readerTask(dirName string) error {
	defer wg.Done()
	return read(dirName)
}

func read(dirName string) error {
	dirEntries, err := ioutil.ReadDir(dirName)
	if err != nil {
		return fmt.Errorf("failed to read dir: %w", err)
	}

	for _, dirEntry := range dirEntries {
		filePath := filepath.Join(dirName, dirEntry.Name())
		fmt.Println("-- Reading " + filePath)

		if dirEntry.IsDir() {
			read(filePath)
			continue
		}

		f, err := ioutil.ReadFile(filePath)
		if err != nil {
			return err
		}
		fmt.Println(string(f))

		time.Sleep(1 * time.Second)
	}
	return nil
}