Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!jsq From: arnold%audiofax.com@mathcs.emory.edu (Arnold Robbins) Newsgroups: comp.std.unix Subject: Re: /dev/tty implemented as /dev/fd/3 Message-ID: <14208@cs.utexas.edu> Date: 31 Oct 90 17:22:38 GMT References: <14014@cs.utexas.edu> <13878@cs.utexas.edu> <14103@cs.utexas.edu> <14162@cs.utexas.edu> Sender: jsq@cs.utexas.edu Reply-To: arnold@audiofax.com Organization: AudioFAX Inc., Atlanta Lines: 40 Approved: jsq@cs.utexas.edu (Moderator, John S. Quarterman) X-Submissions: std-unix@uunet.uu.net Submitted-by: arnold%audiofax.com@mathcs.emory.edu (Arnold Robbins) In article <14162@cs.utexas.edu> ske@pkmab.se (Kristoffer Eriksson) writes: >If you have a program that closes only fd 3, this implementation will behave >differently from the old /dev/tty device implementation, won't it? You will >not be able to reach the controlling terminal by a guaranteed route, in spite >of the fact that it is still available on other fd-s. This is correct. It's mostly irrelevant though; in current Unix systems if you do the right magic you can't get use /dev/tty even though the terminal is still available on the currently open file descriptors. Six of one, a half-dozen of the other, as they say. >Or is the controlling >terminal concept implemented in such a way that closing fd 3 is the same as >disassociating from the controlling terminal (so you won't be bother with >terminal interrupts and such) ? I don't think this is the case. V10 still has the concept of a "controlling terminal", but I strongly doubt that the kernel knows it's on fd 3. However, the controlling terminal isn't as pervasive a concept in Research Unix as it is in BSD or System V. (In BSD, if you disassociate yourself from the controlling terminal, and then open some random /dev/tty, it automatically becomes your controlling terminal. In V10 you'd have to explicitly make that happen.) Let me make a clarifying statement. There are two things under discussion. 1) the usefulness of /dev/fd, 2) the usefulness of having /dev/tty be /dev/fd/3. Everyone who's actually used /dev/fd feels it's useful, so we can take point 1) as a given for a nice feature. Point 2) has its plusses and minuses, but, IMO, the minuses don't outweigh the plusses. Also, if it's good enough for Dennis Ritchie, it's probably good enough for me. :-) -- Arnold Robbins AudioFAX, Inc. | Laundry increases 2000 Powers Ferry Road, #200 / Marietta, GA. 30067 | exponentially in the INTERNET: arnold@audiofax.com Phone: +1 404 933 7612 | number of children. UUCP: emory!audfax!arnold Fax-box: +1 404 618 4581 | -- Miriam Robbins Volume-Number: Volume 22, Number 18