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From: pfalstad@phoenix.Princeton.EDU (Paul Falstad)
Newsgroups: comp.lang.c
Subject: Re: stdin and UNIX pipes
Message-ID: <6452@idunno.Princeton.EDU>
Date: 20 Feb 91 23:29:12 GMT
References: <92993@unix.cis.pitt.edu> <1991Feb20.210406.21117@csrd.uiuc.edu>
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bliss@sp64.csrd.uiuc.edu (Brian Bliss) wrote:
>saying
>
>  fopen ("/dev/tty", "r");
>
>always opens the screen for input, regardless of the state of stdin.
>obvoulsy, somewhere (in libc.a?) there is code to check for the
>string "/dev/tty", and open /dev/tty/tty?? instead of trying
>to open the directory /dev/tty.

Not quite.

1. it opens the _tty_ for input, _if_ your process has a controlling
terminal.
2. there's no such directory /dev/tty.  At least not on my system.
It might have been a good idea, but a tad unportable since /dev/tty
already exists.
3. the /dev/tty -> /dev/tty?? is done in the kernel by checking
minor device numbers, not strings.  It is not in libc; typing
open("/dev/tty",2) opens a tty without touching any libraries
(except for the actual trap code, of course).

I'd redirect followups to a more appropriate group, like
comp.unix.programmer, but I don't want them there either.  :-)

--
  Paul Falstad, pfalstad@phoenix.princeton.edu PLink:HYPNOS GEnie:P.FALSTAD
  I think there should be more race prejudice.  <slap> LESS race prejudice.
     Princeton University apologizes for the content of this article.