walk directory with filetype filter

scand.go

package main

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

var (
	ext  string
	path string
	help bool
)

func init() {
	flag.BoolVar(&help, "h", false, "show help")
	flag.StringVar(&path, "path", ".", "walk the directory")
	flag.StringVar(&ext, "ext", "", "files filter in with suffix, format: \"ext1|ext2\"")

	exec := filepath.Base(os.Args[0])
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, `Usage: %s [-h help] [-path path] [-ext suffix]
Options:
`, exec)
		flag.PrintDefaults()
		fmt.Fprintf(os.Stderr, ` Tip: Use pipe to collect the result. 
	ex: %s > 1.txt`, exec)
	}
	flag.Parse()

	if help {
		flag.Usage()
		os.Exit(0)
	}

	required := []string{} // must be checked args
	if len(required) > 0 {

		seen := make(map[string]bool)
		flag.Visit(func(f *flag.Flag) {
			seen[f.Name] = true
		})
		for _, op := range required {
			if !seen[op] {
				flag.Usage()
				os.Exit(1)
			}
		}
	}
}

func main() {

	ext = strings.Trim(ext, " ")
	suffixs := strings.Split(ext, "|")

	filepath.Walk(path, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if !info.IsDir() {
			if ext == "" {
				fmt.Println(path)
			} else {
				for _, suffix := range suffixs {
					// if flag, _ := regexp.MatchString("^\\.\\w+$", suffix); flag {
					if strings.HasSuffix(path, "."+suffix) {
						fmt.Println(path)
						break
					}
					// }
				}
			}
		}
		return nil
	})
}