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From: cosell%bbn-unix@sri-unix.UUCP
Newsgroups: net.unix-wizards
Subject: Non-blocking input from a tty
Message-ID: <14374@sri-arpa.UUCP>
Date: Tue, 6-Dec-83 20:22:55 EST
Article-I.D.: sri-arpa.14374
Posted: Tue Dec  6 20:22:55 1983
Date-Received: Sat, 10-Dec-83 02:28:22 EST
Lines: 24

From:  Bernie Cosell <cosell@bbn-unix>

Can anyone remind if there is a way (however clunky) to do a non-blocking
read from a tty that is pretty portable?  I thought that there was some
magic I could do with pipes and signals, but I can't see a way to make it
work.  

Here's the scenario for the general case I'm interested in: to be able to
read and write from one terminal while be able to "respond" to a character
typed on another terminal; no characters must ever get lost.  The specific
case I'm working on uses just one terminal: I am using a funny (non ^s/^q)
flow control and so have to handle my own.  No real problem but I can't
figure out how to check if the terminal has said "stop" while I am in a
loop pumping output to it.

I had another peculiar query: did the folks who wrote stdio do so carefully
enough that they will never lose any characters if a signal goes off
while stdio is doing one of its reads or writes?  Again, I am trying to be
very very clean about not losing any I/ or /O and it occurred to me that if
the stdio-writers were not careful enough even using the clock could do you
in.

Thanks
   /Bernie (cosell@bbn-unix)