Flatten a directory - copy all files into one directory with directory named prefixed to files

flatten-dir.go

package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
)

var pathSep = string(os.PathSeparator)
var nameSep *string

func main() {

	fromDir := flag.String("s", "src", "from/source directory.")
	toDir := flag.String("d", "dest", "to/destination directory.")
	nameSep = flag.String("n", "-", "separator to use for filename.  dir/dir/file->dir-dir-file.")
	createDest := flag.Bool("f", true, "create dest dir if not exists.")
	flag.Parse()

	if !isDirExists(*fromDir) {
		fmt.Println("From/Source dir does not exist:", *fromDir)
		flag.Usage()
		os.Exit(1)
	}

	if !isDirExists(*toDir) {
		if !*createDest {
			fmt.Println("To/Destination dir does not exist:", *toDir)
			flag.Usage()
			os.Exit(1)
		}

		err := os.MkdirAll(*toDir, 0755)
		if err != nil {
			fmt.Println("Error! Could not create destination directory:", err)
			os.Exit(1)
		}
	}

	fileList := make([]string, 0)
	err := filepath.Walk(*fromDir, func(path string, f os.FileInfo, err error) error {
		fileList = append(fileList, path)
		return err
	})
	if err != nil {
		panic(err)
	}

	for _, file := range fileList {

		fi, err := os.Stat(file)
		if err != nil {
			fmt.Println(err)
		}

		if fi.Mode().IsRegular() {
			outPath := *toDir + pathSep + flattenFullPath(file, *fromDir)
			err = copyFile(file, outPath)
			if err != nil {
				fmt.Println(err)
			}
		}
	}

}

func flattenFullPath(fullPath, fromDir string) string {
	s := strings.Replace(fullPath, fromDir, "", 1)
	if strings.HasPrefix(s, pathSep) {
		s = strings.Replace(s, pathSep, "", 1)
	}
	s = strings.Replace(s, pathSep, *nameSep, -1)
	return s
}

func isDirExists(path string) bool {
	if stat, err := os.Stat(path); err == nil && stat.IsDir() {
		return true
	}

	return false
}

func copyFile(from string, to string) error {
	fmt.Printf("From: %s, To: %s\n", from, to)
	fromF, err := os.Open(from)
	if err != nil {
		log.Fatal(err)
	}
	defer fromF.Close()

	toF, err := os.OpenFile(to, os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		log.Fatal(err)
	}
	defer toF.Close()

	_, err = io.Copy(toF, fromF)
	if err != nil {
		log.Fatal(err)
	}
	return nil
}