rb:bom|utf-8 在 Ruby 中的 CSV.open 中意味着什么？

Question

中的意思是什么'rb:bom|utf-8'：

CSV.open(csv_name, 'rb:bom|utf-8', headers: true, return_headers: true) do |csv|

我可以这么理解：

1. r意思是读
2. bom是一种\xEF\xBB\xBF在文件开头指示字节顺序的文件格式。
3. utf-8是一种文件格式

但：

1. 我不知道它们是如何组合在一起的，也不知道为什么需要写所有这些来读取 csv
2. 我正在努力寻找这方面的文档。https://ruby-doc.org/stdlib-2.6.1/libdoc/csv/rdoc/CSV.html中似乎没有记录
   

更新：

找到了一个非常有用的文档： https ://ruby-doc.org/core-2.6.3/IO.html#method-c-new-label-Open+Mode

Answer 1

（接受的答案不是不正确而是不完整）

rb:bom|utf-8转换为人类可读的句子意味着：

打开文件r以二进制模式 ( ) 进行读取 ( b)，并查找 Unicode BOM 标记 ( bom) 以检测编码，或者，如果未找到 BOM 标记，则假定为 UTF-8 编码 ( utf-8)。

A BOM marker can be used to detect if a file is UTF-8 or UTF-16 and in case it is UTF-16, whether that is little or big endian UTF-16. There is also a BOM marker for UTF-32, yet Ruby doesn't support UTF-32 as of today. A BOM marker is just a special reserved byte sequence in the Unicode standard that is only used for the purpose of detecting the encoding of a file and it must be the first "character" of that file. It's recommended and typically used for UTF-16 as it exists in two different variants, it's optional for UTF-8 and usually if a file is Unicode but has no BOM marker, it is assumed to be UTF-8.