Path: utzoo!mnetor!uunet!husc6!rutgers!sdcsvax!ucsdhub!jack!sdeggo!dave
From: dave@sdeggo.UUCP (David L. Smith)
Newsgroups: comp.unix.wizards
Subject: Re: /dev/tty doesn't exist?
Message-ID: <167@sdeggo.UUCP>
Date: 3 Jan 88 08:23:43 GMT
References: <445@minya.UUCP >
Organization: Lazy Programmer's Society of San Diego
Lines: 27

In article <445@minya.UUCP >, jc@minya.UUCP (John Chambers) writes:
 > Some hints:  This is a rather generic Unix Sys/V.2, so the problem should
 > be similar to most ATT Unices.  The most unusual thing about how X is run
 > is that it isn't being started by a login shell; it is started as a daemon
 > by init, and in some cases, decides to grab a terminal (whose name is on
 > its command line, and which doesn't have getty on it) and run a program
 > there.  This is a useful thing to do if, for instance, you are playing
 > around with process-control applications.   
 > 
 > Perhaps the question could be rephrased:  What is the official, approved
 > way for a daemon process like this to attach a terminal?  If the answer
 > is RTFM, can you say where?  The 1/4-page /dev/tty entry isn't much help.
 > [In fact, the Unix manuals aren't very helpful in general if you want to
 > write a free-running background program.  I've tried to help various users
 > who wanted to do this, and it's frustrating never quite knowing what I'm
 > talking about :-]

The problem would seem to be that /dev/tty has no idea what tty you really
want to be talking to.  In order to set things up, you need to do a 
setpgrp() and then open the terminal you wish to talk to.  Termio(7) briefly
explains about the control terminal.  

-- 
David L. Smith
{sdcsvax!man,ihnp4!jack!man, hp-sdd!crash, pyramid}!sdeggo!dave
man!sdeggo!dave@sdcsvax.ucsd.edu 
Sinners can repent, but stupid is forever.