file/edit.go
func ReplaceAtLineN(filename string, r []ReplacerAtLine, n int) error {
	e, err := NewEdit(filename)
	if err != nil {
		return err
	}

	err = e.genReplaceAtLine(r, n)
	err2 := e.Close()
	if err != nil {
		return err
	}
	return err2
}
func ReplaceAtLineN(filename string, r []ReplacerAtLine, n int) error {
	e, err := NewEdit(filename)
	if err != nil {
		return err
	}

	err = e.genReplaceAtLine(r, n)
	err2 := e.Close()
	if err != nil {
		return err
	}
	return err2
}
// ReplaceAtLineN replaces a number of regular expressions mathed in r for the
// named file, if the line is matched at the first.