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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix-wizards
Subject: Re: Bug in csh? (exec v. job control)
Message-ID: <5211@umcp-cs.UUCP>
Date: Thu, 25-Apr-85 22:47:48 EST
Article-I.D.: umcp-cs.5211
Posted: Thu Apr 25 22:47:48 1985
Date-Received: Sat, 27-Apr-85 05:43:53 EST
References: <175@ncr-tp.UUCP>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 21

> > [...]  The vi wakes up from the forked process' dying and tries
> > to print something.  Vi's process group now does not match the
> > terminal's, so the system sends the process group a SIGTOUT [sic]
> > stopping it.

> I'm not sure this is a complete explanation since I don't have
> "stty tostop" set, meaning that there should be no inhibition to
> "vi" writing its output.

The first explanation was mostly correct.  Vi is not just trying to
print something, it's trying to set the terminal modes (ioctl TIOCSETN, 
actually); "stty tostop" affects programs that are attempting to write,
but the check for ioctl is more strict:  SIGTTOU will be sent if the
process group doesn't match, regardless of (tp->t_mode & TOSTOP).

(I.e., it's a bug in csh, or in the way process groups are defined, if
you prefer.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	{seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland