NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/comp/lang/c/19257

Text File | 1993-01-05 | 1.9 KB | 67 lines

Newsgroups: comp.lang.c
Path: sparky!uunet!math.fu-berlin.de!news.th-darmstadt.de!rbg.informatik.th-darmstadt.de!misar
From: [e-mail] (Walter Misar)
Subject: Re: How to read without echo.
Sender: [e-mail] (The News System)
Message-ID: <[e-mail]>
Date: Tue, 5 Jan 1993 16:25:45 GMT
References:  <[e-mail]> <[e-mail]>
Nntp-Posting-Host: rbhp87.rbg.informatik.th-darmstadt.de
Organization: TH Darmstadt
Lines: 54

In article <[e-mail]>, [e-mail] (walter misar) writes:
> #include <sgtty.h>
> main()
> { struct sgttyb *ttyio;
>   ...
>   gtty(0,ttyio);
>   (ttyio->sg_flags)&=(~ECHO);    /* echo off    */
>   stty(0,ttyio);
>   ...   /* read without echo */
>   (ttyio->sg_flags)|=(ECHO);    /* echo on    */
>   stty(0,ttyio);
>   .....
> }

Oops, there was an error (the pointer of ttyio never gets initialized).
Strange enough, it worked for me.
This could be fixed as follows:

#include <sgtty.h>
main()
{ struct sgttyb ttyio;
 ...
 gtty(0,&ttyio);
 (ttyio.sg_flags)&=(~ECHO);    /* echo off    */
 stty(0,&ttyio);
 ...   /* read without echo */
 (ttyio.sg_flags)|=(ECHO);    /* echo on    */
 stty(0,&ttyio);
 .....
}

However a more portable way would be to use ioctl:

#include <sys/ioctl.h>
#include <termio.h>
/* Hm, my manpage says to use termios instead, but that didn't work (HPUX8.0) */

main()
{ struct termio ttyio;

  ioctl(0,TCGETA,&ttyio);
  ttyio.c_lflag &= ~ECHO;
  ioctl(0,TCSETA,&ttyio);
   ... /* read without echo */
  ttyio.c_lflag |= ECHO;
  ioctl(0,TCSETA,&ttyio);
  ...
}

Thanks to the people, who told me about the error.

--
Walter Misar                        It is impossible to enjoy idling thoroughly
[e-mail]       unless one has plenty of work to do.