[TUHS] EOF on pipes?

[Bakul Shah]

On Sun, 25 Feb 2018 14:25:51 -0800 Lyndon Nerenberg <lyndon at orthanc.ca> wrote:
Lyndon Nerenberg writes:
> > If a stream was marked as using delimeters (and pipes always
> > were), a delimeter was inserted after every write(2).  So
> > write(2) generated an empty message, and read(2) returned it.
> 
> And this lived on in the IL network protocol. I've always thought that was 
> one of the more elegant aspects of IL, but of course it didn't have a hope 
> in hell of surviving outside the Plan 9 ecosystem.

BSD networking has had sequenced packet protocol (SPP) support
pretty much from the beginning (probably due to early XNS
influence).  From socket(2):

     SOCK_SEQPACKET sockets employ the same system calls as SOCK_STREAM
     sockets.  The only difference is that read(2) calls will return only the
     amount of data requested, and any remaining in the arriving packet will
     be discarded.

Even today you can do

    int fd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);

Presumably read(fd, ptr, 0) works too.