ruby - 为 ruby​​ 套接字定义的 MSG_ 选项在哪里？

Question

在 Ruby 类 Socket::recv 的文档中，提到了第二个选项参数“flag”，据说它是零个或多个 MSG_ 选项。

我检查了几个不同的站点，但无法找到 MSG_ 选项。谁能指出这些标志的文档？

Answer 1

除了前面的Socket:: 之外，它们与C BSD 套接字堆栈中相应的#define 同名。 (作为记录，为了回答您提出的确切问题，我应该在 Ruby 源代码树中说 "in ext/socket/socket.c"。)所以:

>> require 'socket'
=> true
>> Socket::MSG_PEEK
=> 2

您可能可以通过键入 man 2 recv 来查看，但您可能需要先安装手册页包。还有联机手册页，也许请参阅:man 2 recv here .

现在，这是您需要的，这些是从 NetBSD 中获取的 Posix 选项手册页。 Linux 上还有很多可用的。在 Linux 上运行时，Ruby 将定义附加符号，否则它们可能未定义，具体取决于主机。 (谢谢，mark4o。)

 The flags argument to a recv call is formed by or'ing one or more of the
 values:

       MSG_OOB        process out-of-band data
       MSG_PEEK       peek at incoming message
       MSG_WAITALL    wait for full request or error

 The MSG_OOB flag requests receipt of out-of-band data that would not be
 received in the normal data stream.  Some protocols place expedited data
 at the head of the normal data queue, and thus this flag cannot be used
 with such protocols.  The MSG_PEEK flag causes the receive operation to
 return data from the beginning of the receive queue without removing that
 data from the queue.  Thus, a subsequent receive call will return the
 same data.  The MSG_WAITALL flag requests that the operation block until
 the full request is satisfied.  However, the call may still return less
 data than requested if a signal is caught, an error or disconnect occurs,
 or the next data to be received is of a different type than that
 returned.