Path: utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.mail.uucp
Subject: Re: Bidirectional Modem Lines under SunOS 4.0.1
Message-ID: <1446@auspex.auspex.com>
Date: 17 Apr 89 19:14:05 GMT
References: <160@osc.COM> <743@key.COM> <2209@laidbak.UUCP> <3834@ficc.uu.net> <433@iisat.UUCP>
Reply-To: guy@auspex.auspex.com (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 22

>The parent of 'sh' has to be init, because that is the only indication that
>the program has that it is the login shell as apposed to a shell called
>by another program/shell.

Nonsense.  The closest thing to a "standard" indication that a shell is
a login shell, in UNIX, is that argv[0] (or the last component thereof)
begins with "-".  Neither the Bourne nor the C shell, in S5 or 4.xBSD,
check the parent process ID; they both check whether "argv[0]" begins
with "-".

>I suspect it is also the one that sends hangup signals to all other processes
>in the same process group etc.

This sentence has a dangling reference; "it" in "it is also the one that
sends hangup signals" doesn't refer to anything obvious.  In S5, the
hangup signal that's sent to all other processes in a process group when
the process group leader exits is sent by the kernel.  A process group
leader is defined as a process whose process ID is equal to its process
group ID; for the signal to be sent, the process must also have a
controlling tty, and that controlling tty's process group must be the
process group of the process in question.  Having a parent process ID of
1 has nothing to do with it.