removebom.go

package main

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

func read(path string) (bool, []byte) {
	content, err := os.ReadFile(path)
	if err != nil {
		panic(err)
	}
	bom := []byte{0xEF, 0xBB, 0xBF}
	if bytes.HasPrefix(content, bom) {
		fmt.Printf("Removing BOM from %s\n", path)
		newContents := content[len(bom):]
		return true, newContents
	} else {
		return false, content
	}
}

func main() {
	root := "/path/to/dir"
	err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() || filepath.Ext(path) != ".java" {
			return nil
		}
		isbom, newContents := read(path)
		if isbom {
			fmt.Printf("Removing BOM from %s\n", path)
			err := os.Remove(path)
			if err != nil {
				return err
			}
			f, err := os.Create(path)
			if err != nil {
				return err
			}
			defer f.Close()
			_, err = f.Write(newContents)
			if err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		fmt.Println(err)
	}
}