Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uupsi!sunic!phlux!jh05629
From: jh05629@phlux.UUCP (Jonas Heyman)
Newsgroups: comp.lang.c
Subject: reading from a tty
Message-ID: <1863@phlux.UUCP>
Date: 22 Jun 91 22:53:21 GMT
Organization: Pharmacia LKB Biotechnology, Uppsala  SWEDEN.
Lines: 74


Howdy 

I have a piece of code here that I can't get to work properly.
The program sends a escape sequence to the attached terminal in
order to identify type, vt220 or vt100 and so on.
Then it sends back a unique escape sequence for that particular terminal.
I use this in order to set up the right environment.
I put it in my .profile and look at the exit codes produced.

The problem I can't work around is that the unique reply also echo's
on stdout on my terminal, I want to swallow the characters echoed back.
Could anyone help me on this, either to point out where my program
is wrong or give me a new piece of code.

Any help is most welcome !
Thanks in advance, Jonas.

Here is what i put in my .profile:

tty|hz
if [ $? = 0 ]
then
	TERM=
.
.
.

And here is the code itself:

/* 
      calling syntax           tty|hz

      exit value     0   the connected terminal doesn't respond
                     1           -  "  -        is a vt 100 - 102
                     2           -  "  -             vt 220 - 240
		     3           -  "  -             vt 300 - 340
*/

#include <stdio.h>
#include <fcntl.h>

main() 

{
char        tty[ 20 ], line[ 100 ] ;
unsigned    fd, xit ;
FILE *fp ;

    scanf( "%s", tty ) ;                /* read unix cmd  tty  by redirection */
    fclose( stdin ) ;                   /*  close to avoid conflicts   */ 
    fclose( stdout ) ;

    fd = open( tty, O_NDELAY | O_RDWR ) ;
    write( fd, "\033[c", 3 ) ;          /* ESC Z does not affective on vt300*/
    sleep( 1 ) ;
    if ( read( fd, line, 25 ))
        if ( ! strncmp( line, "\033\133?63", 5 ))
            xit = 3 ;                          /* fraction of vt320 response */
        else if ( ! strncmp( line, "\033\133?62", 5 ))
            xit = 2 ;                          /* fraction of vt220 response */
        else if ( ! strncmp( line, "\033\133?", 3 )) 
            xit = 1 ;                          /* vt100, 101, 102 response */
        else
            xit = 0 ;                          /* dumb - could be hazeltine */
    else 
         xit = 0 ;
    close( fd ) ;
    exit( xit ) ;
}

-- 

  /jonas@lkbpyr.lkb.se/