tree.go

package main

import (
	"fmt"
	"io"
	"os"
	"path"
)

func dirTree(out io.Writer, root string, printFiles bool) error {
	dirRead, err := os.Open(root)

	if err != nil {
		return err
	}
	dirFiles, err := dirRead.Readdir(0)
	if err != nil {
		return err
	}

	for _, file := range dirFiles {
		filename := file.Name()
		fullPath := path.Join(root, filename)

		if file.IsDir() {
			fmt.Println(fullPath)
			dirTree(out, fullPath, printFiles)
		} else {
			if printFiles == true {
				fmt.Println(fullPath)
			}
		}
	}

	return nil
}

func main() {
	out := os.Stdout
	if !(len(os.Args) == 2 || len(os.Args) == 3) {
		panic("usage go run main.go . [-f]")
	}
	path := os.Args[1]
	printFiles := len(os.Args) == 3 && os.Args[2] == "-f"
	err := dirTree(out, path, printFiles)
	if err != nil {
		panic(err.Error())
	}
}