ksh88 vs Ultrix 4.0
Chet Ramey
chet at odin.INS.CWRU.Edu
Tue Jan 8 06:45:06 AEST 1991
In article <9101060449.AA07794 at lilac.berkeley.edu> lwv27 at CAS.BITNET writes:
>We have encountered such a peculiar problem with ksh88 that I was
>wondering how others are dealing with the problem.
>What we discovered was that for some reason users were not able to access
>their history files and there were problems with some typing (lagging
>response time, etc.) One workaround was to set viraw mode, which
>fixed some of the problems. But now we had a problem with type ahead.
>And what a problem - we found if users type before the prompt returns,
>the output is buffered some place - to appear a command or two later!
>This sounds almost harmless - until you see the following:
>a user types a cc command.
>While waiting, they type a cd D.someplace without thinking.
>The cc command generates an error.
>Since the cd command doesnt execute, they go ahead and type
>vi file.c
>AFTER ENTERING VI, the letters "cd D.someplace" are typed as if the
>user typed them.
Typeahead with Ultrix [34].? and termios is totally broken. I can't get
it to work with bash, either. Here's a quick transcript:
cwjcc$ sleep 4
echo hi <--- typeahead during sleep
cwjcc$ <--- bash can't read it
cwjcc$ cat < /dev/tty <--- but cat can?
echo hi
cwjcc$ sleep 4
echo hi
cwjcc$ cat - <--- from stdin too?
echo hi
Using FIONREAD on a file descriptor opened on /dev/tty or a file descriptor
from fileno(stdin) returns the correct number of characters, but a read on
that file descriptor for that number of characters either blocks or fails
with EWOULDBLOCK.
If you run a command that plays with the tty modes, like `more', the text
will come out after that command exits.
When using the `native' (they're not; termios is native) BSD tty ioctls,
the problem does not show up.
Chet
--
Chet Ramey ``There's just no surf in
Network Services Group Cleveland, U.S.A. ...''
Case Western Reserve University
chet at ins.CWRU.Edu My opinions are just those, and mine alone.
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