Xref: utzoo alt.sys.sun:1892 comp.unix.internals:917
Path: utzoo!utgpu!freedom!elroy.jpl.nasa.gov!aero!usasoc.soc.mil!news
From: ted@arsocomvax.socom.mil (Ted Nolan)
Newsgroups: alt.sys.sun,comp.unix.internals
Subject: Re: ioctl's that flush typeahead on SunOS 4.0.3
Message-ID: <1990Oct31.212012.13776@usasoc.soc.mil>
Date: 31 Oct 90 21:20:12 GMT
References: <43727@andante.att.com>
Reply-To: ted@usasoc.soc.mil (Ted Nolan)
Organization: SRI International, Ft. Bragg NC
Lines: 44

It sounds like you are running into a problem I found on 4.0.3.  We
have an application that drives a terminal window by essentially
"stuffing" into it.  I had modified the "less" pager program to use a
nonflushing IOCTL to return to terminal to cooked mode from cbreak
mode, so that our application could stuff something like

	q^Uunix command

The intent was that if the pager was active, the 'q' would exit it, and
then the unix command would start.  (If the pager were not active, the
^U would erase the 'q', and the command  would still be ok).  This
worked fine under SunOS 2.X and 3.X, but in 4.0.3 the ioctl (TIOCSETN
(bsd) == TCSETS (sysV)) that is documented NOT to flush the input
actually does flush it, and our application doesn't work.

Whether or not this is "good" in some abstract sense, is, I suppose,
debatable.  However, it does not work as documented, which seems clearly
wrong to me.

Here's the response I got back from sun:
>
> deleted stuff
>
>In looking this over it looks like you are running into a problem under
>4.0 and later, when things were switched over to STREAMS. The bugid
>that you are running into is 1007731. The problem turns out to be, that
>when the mode of the tty changes to between ~CBREAK and CBREAK, an
>automatic flush (M_FLUSH) occurs. In your example, you will see, that
>if you comment out the ORing of the CBREAK flag, the TIOCSETN will work
>correctly as you indicated. From the bug report this looks like this
>will be fixed in 4.1 (the next release).
>

This doesn't really help, because I need CBREAK to ~CBREAK transitions.
Am I to gather this is still not fixed in 4.1?

				Ted Nolan
				ted@usasoc.soc.mil

PS: One weird workaround I found... Do an

	rlogin localhost

in the window you want this to work in, and most of the time it will.