[Caml-list] unbuffered input

[Caml-list] unbuffered input

[Alan Schmitt]

Hi,

I've been looking at this for about one hour, and I seem to get stuck: 
how can I do unbuffered input in caml ? I want a program to block until 
a char is entered. I tried input_char and Unix.read (without 
and with Unix.select), to no avail. I do not know if it is caml, the 
libc, or the terminal that is buffering.

Any hint on how to do this ?

Thanks a lot,

Alan Schmitt

-- 
The hacker: someone who figured things out and made something cool happen.

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Re: [Caml-list] unbuffered input

[Michal Moskal]

On Thu, Aug 21, 2003 at 12:11:57PM -0400, Alan Schmitt wrote:
> Hi,
> 
> I've been looking at this for about one hour, and I seem to get stuck: 
> how can I do unbuffered input in caml ? I want a program to block until 
> a char is entered. I tried input_char and Unix.read (without 
> and with Unix.select), to no avail. I do not know if it is caml, the 
> libc, or the terminal that is buffering.

Probably terminal. Under unix it's line-buffered by default.

> Any hint on how to do this ?

Unix.read + Unix.select + Unix.tcsetattr.

-- 
: Michal Moskal :: http://www.kernel.pl/~malekith : GCS {C,UL}++++$ a? !tv
: When in doubt, use brute force. -- Ken Thompson : {E-,w}-- {b++,e}>+++ h

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Re: [Caml-list] unbuffered input

[art yerkes]

On Thu, 21 Aug 2003 12:11:57 -0400
Alan Schmitt <alan.schmitt@polytechnique.org> wrote:

> Hi,
> 
> I've been looking at this for about one hour, and I seem to get stuck: 
> how can I do unbuffered input in caml ? I want a program to block until 
> a char is entered. I tried input_char and Unix.read (without 
> and with Unix.select), to no avail. I do not know if it is caml, the 
> libc, or the terminal that is buffering.
> 
> Any hint on how to do this ?
> 
> Thanks a lot,
> 
> Alan Schmitt
> 

You need to turn off c_icanon using Unix.tcsetattr.  It's the terminal driver
that does the buffering.

-- 
"Should array indices start at 0 or 1? My compromise of 0.5 was rejected
 without, I thought, proper consideration."
   - S. Kelly-Bootle

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Re: [Caml-list] unbuffered input: a solution

[Alan Schmitt]

* Alan Schmitt (alan.schmitt@polytechnique.org) wrote:
> Hi,
> 
> I've been looking at this for about one hour, and I seem to get stuck: 
> how can I do unbuffered input in caml ? I want a program to block until 
> a char is entered. I tried input_char and Unix.read (without 
> and with Unix.select), to no avail. I do not know if it is caml, the 
> libc, or the terminal that is buffering.
> 
> Any hint on how to do this ?

Thanks to Owen Gunden and the unison code, I found the following 
solution:

let term = Unix.tcgetattr Unix.stdin in
try
  Unix.tcsetattr 
    Unix.stdin
    Unix.TCSANOW 
    {term with Unix.c_icanon = false; 
               Unix.c_echo = false;
               Unix.c_vmin = 1;};
  while true do
    let c = input_char stdin in
    Printf.printf "read %c\n" c;
    flush stdout
  done;
  (* restore the terminal in its initial state *)
  Unix.tcsetattr Unix.stdin Unix.TCSANOW term
with
| e -> Unix.tcsetattr Unix.stdin Unix.TCSANOW term; raise e

Is there no simpler solution ?

And by the way, I see that unison does a
Sys.catch_break true
to transform the break signal into an exception, but I did not need it 
here (doing ctrl-c does restore the terminal in a good state). I'm 
curious as to why this is the case.

Alan Schmitt

-- 
The hacker: someone who figured things out and made something cool happen.

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