golang simple implementation for print file tree

tree.go

//go:generate go build -trimpath -ldflags "-s -w" -o tree${GOEXE} ${GOFILE}
package main

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

var (
	indentUnicode = `│   `
	indentAscii   = `|   `
	indentSpace   = `    `
	indentString  string

	suffixLastUnicode = `└──`
	suffixLastAscii   = `\__`
	suffixLastString  string

	suffixMidUnicode = `├──`
	suffixMidAscii   = `|--`
	suffixMidString  string
)

func init() {
	var ascii bool
	flag.BoolVar(&ascii, "A", false, "use ASCII characters")
	flag.Usage = func() {
		path, err := os.Executable()
		if err != nil {
			fmt.Printf("get current process executable: %v", err)
			os.Exit(1)
		}
		exe := filepath.Base(path)
		fmt.Printf("Usage:\n  %s [-A] <path>\n", exe)
		flag.PrintDefaults()
		fmt.Printf("Example:\n  %s /path/to/some/dir\n  %s -A ./ \n", exe, exe)
	}
	flag.Parse()
	if ascii {
		indentString = indentAscii
		suffixLastString = suffixLastAscii
		suffixMidString = suffixMidAscii
	} else {
		indentString = indentUnicode
		suffixLastString = suffixLastUnicode
		suffixMidString = suffixMidUnicode
	}
}

func main() {
	var root string
	if len(os.Args) == 1 {
		root = `.`
	} else {
		root = flag.Arg(0)
	}

	fmt.Println(root)
	printDirectory(root, ``)
}

func printDirectory(path string, indent string) {
	entries, err := os.ReadDir(path)
	if err != nil {
		fmt.Printf("os read path %s: %v\n", path, err)
		return
	}

	count := len(entries)
	for index, entry := range entries {
		fi, err := entry.Info()
		if err != nil {
			continue
		}
		var prefix, middle, suffix string
		if index+1 == count { // the last one
			middle = indentSpace
			suffix = suffixLastString
		} else {
			middle = indentString
			suffix = suffixMidString
		}
		prefix = indent + suffix
		name := entry.Name()
		switch {
		case (fi.Mode() & os.ModeSymlink) == os.ModeSymlink:
			fullPath, err := os.Readlink(filepath.Join(path, name))
			if err != nil {
				fmt.Printf("%s %s: %v\n", prefix, name, err)
			} else {
				fmt.Println(prefix, name, `->`, fullPath)
			}
		case entry.IsDir():
			fmt.Println(prefix, name)
			printDirectory(filepath.Join(path, name), indent+middle)
		default:
			fmt.Println(prefix, name)
		}
	}
}

Build

go generate tree.go

# or
go build tree.go

Usage

tree -h

Usage:
  tree [-A] <path>
  -A    use ASCII characters
Example:
  tree /path/to/some/dir
  tree -A ./

Linux/MacOS

tree ~/code/gv

~/code/gv
├── .idea
│   ├── .gitignore
│   ├── GitLink.xml
│   ├── gv.iml
│   ├── modules.xml
│   ├── vcs.xml
│   └── workspace.xml
├── LICENSE
├── Makefile
├── README.md
├── go.mod
├── go.sum
└── main.go

Windows

tree -A D:\code\gv

D:\code\gv
|-- .idea
|   |-- .gitignore
|   |-- GitLink.xml
|   |-- gv.iml
|   |-- modules.xml
|   |-- vcs.xml
|   \__ workspace.xml
|-- LICENSE
|-- Makefile
|-- README.md
|-- go.mod
|-- go.sum
\__ main.go