Re: [9fans] ideas for helpful system io functions

[erik quanstrom <quanstro@quanstro.net>]

> The OS support I am talking about:
> a) the fork behavior on an open file should be available
>    *without* forking.  dup() doesn't cut it (both fds share
>    the same offset on the underlying file). I'd call the new
>    syscall fdfork().  That is, if I do
>
>        int newfd = fdfork(oldfd);
>
>    reading N bytes each from newfd and oldfd will return
>    identical data.

i can't think of a way to do this correctly.  buffering in the
kernel would only work if each process issued exactly the
same set of reads.  there is no requirement that the data
from 2 reads of 100 bytes each be the same as the data
return with 1 200 byte read.

before you bother with "but that's a wierd case", remember
that the success of unix and plan 9 has been built on the
fact that there aren't syscalls that fail in "wierd" cases.

- erik