Path: utzoo!mnetor!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!rutgers!mtune!mtunx!whuts!paul
From: paul@whuts.UUCP (KOLB)
Newsgroups: comp.unix.questions
Subject: Re: Is there any way to find real tty under shell layers?
Message-ID: <3945@whuts.UUCP>
Date: 19 Mar 88 23:58:23 GMT
References: <3932@whuts.UUCP> <1098@its63b.ed.ac.uk>
Organization: AT&T Bell Laboratories
Lines: 50

In article <1098@its63b.ed.ac.uk>, simon@its63b.ed.ac.uk (ECSC68 S Brown CS) writes:
> In article <3932@whuts.UUCP> paul@whuts.UUCP (KOLB) writes:
> >>In article <352@vsi.UUCP>, friedl@vsi.UUCP (Stephen J. Friedl) writes:
> >>      Does anybody know any way to find out the "real" terminal
> >> name when running under shell layers in Sys V?  
> >
> > [description of doing this using getutent() to search for a ut_line
> >  that looks like ttyname(0)]
> 
> But shl stamps an entry for the current layer "/dev/sxtNNN" in /etc/utmp,
> so this won't work.

Have you tried to run the program?  Here it is again:

#include <sys/types.h>
#include <utmp.h>
#include <stdio.h>

main()
{
	struct utmp *utmp, *getutent();
	char *q;

	q = ttyname(0)+5;
	while ((utmp = getutent()) != NULL) {
		if ( (utmp->ut_type == USER_PROCESS) &&
			(strncmp(utmp->ut_line, q, strlen(q)) == 0) )
				printf("tty%d\n", atoi(utmp->ut_id));
	}	
}

As I said in my earlier reply to Steve Friedl, inittab's ID field
(this ID field becomes utmp->ut_id) has to be corresponded to the 
tty number. Ie:

	123:2:respawn:/etc/getty -t 60 tty123
        ^^^     correspond to	          ^^^

> The only way I can think of is to look in /dev/kmem .... 

Another setgid to sys program!

> Of course, the real problem is that utmp is simply not good enough any more-
> it was fine back in the Good Old Days, but when you have windows and ptys and
> multiplexing and other good stuff like this, it loses badly.

I tried the program with shl and layers, and it works. The
Good Old Days are still here :)

	Paul Ho