diff --git a/cmd/gopfmt/gopfmt.go b/cmd/gopfmt/gopfmt.go
new file mode 100644
index 000000000..6e3cecd88
--- /dev/null
+++ b/cmd/gopfmt/gopfmt.go
@@ -0,0 +1,149 @@
+/*
+ Copyright 2021 The GoPlus Authors (goplus.org)
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"io/fs"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var (
+	procCnt    = 0
+	walkSubDir = false
+	extGops    = map[string]struct{}{
+		".go":  {},
+		".gop": {},
+		".spx": {},
+		".gmx": {},
+	}
+	rootDir = ""
+)
+
+var (
+	// main operation modes
+	write = flag.Bool("w", false, "write result to (source) file instead of stdout")
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: gopfmt [flags] [path ...]\n")
+	flag.PrintDefaults()
+}
+
+func report(err error) {
+	fmt.Println(err)
+	os.Exit(2)
+}
+
+func processFile(filename string, in io.Reader, out io.Writer) error {
+	if in == nil {
+		var err error
+		in, err = os.Open(filename)
+		if err != nil {
+			return err
+		}
+	}
+	src, err := ioutil.ReadAll(in)
+	if err != nil {
+		return err
+	}
+
+	res, err := format.Source(src)
+	if err != nil {
+		return err
+	}
+
+	if *write {
+		dir, file := filepath.Split(filename)
+		f, err := ioutil.TempFile(dir, file)
+		if err != nil {
+			return err
+		}
+		tmpfile := f.Name()
+		_, err = f.Write(res)
+		f.Close()
+		if err != nil {
+			return err
+		}
+		err = os.Remove(filename)
+		if err != nil {
+			return err
+		}
+		return os.Rename(tmpfile, filename)
+	}
+	if !*write {
+		_, err = out.Write(res)
+	}
+
+	return err
+}
+
+func walk(path string, d fs.DirEntry, err error) error {
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+	} else if d.IsDir() {
+		if !walkSubDir && path != rootDir {
+			return filepath.SkipDir
+		}
+	} else {
+		// Directories are walked, ignoring non-Gop files.
+		ext := filepath.Ext(path)
+		if _, ok := extGops[ext]; ok {
+			procCnt++
+			err = processFile(path, nil, nil)
+		}
+	}
+	return err
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+
+	args := flag.Args()
+	if len(args) == 0 {
+		if *write {
+			report(fmt.Errorf("error: cannot use -w with standard input"))
+			return
+		}
+		if err := processFile("<standard input>", os.Stdin, os.Stdout); err != nil {
+			report(err)
+		}
+		return
+	}
+
+	for _, path := range args {
+		walkSubDir = strings.HasSuffix(path, "/...")
+		if walkSubDir {
+			path = path[:len(path)-4]
+		}
+		procCnt = 0
+		rootDir = path
+		filepath.WalkDir(path, walk)
+		if procCnt == 0 {
+			fmt.Println("no Go+ files in", path)
+		}
+	}
+}
+
+// -----------------------------------------------------------------------------