process.stdin 属性返回连接到 stdin (文件描述符 0) 的流。 它是 net.Socket(也就是 Duplex 流),除非文件描述符 0 指向文件,在这种情况下它是 Readable 流。

    The process.stdin property returns a stream connected to stdin (fd 0). It is a net.Socket (which is a Duplex stream) unless fd 0 refers to a file, in which case it is a Readable stream.

    For details of how to read from stdin see

    As a Duplex stream, process.stdin can also be used in "old" mode that is compatible with scripts written for Node.js prior to v0.10. For more information see Stream compatibility.

    In "old" streams mode the stdin stream is paused by default, so one must call process.stdin.resume() to read from it. Note also that calling process.stdin.resume() itself would switch stream to "old" mode.