improved file read/copy logic

util.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"path"
+	"strings"
+)
+
+func Exists(p ...string) (bool, error) {
+	_, err := os.Stat(path.Join(p...))
+	if err == nil {
+		return true, nil
+	}
+	if errors.Is(err, fs.ErrNotExist) {
+		return false, nil
+	}
+	return false, err
+}
+
+func SplitExt(filename string) (string, string) {
+	ext := strings.ToUpper(path.Ext(filename))
+	name := strings.ToUpper(filename[:len(filename)-len(ext)])
+	if len(ext) > 0 {
+		ext = ext[1:]
+	}
+	return name, ext
+}