kbhit.txt

this is a mirrored site c-faq. thought might need offline

Date: Sat, 4 May 1996 00:23:30 +0200 (MET DST)
From: Jens M Andreasen <[e-mail]>
To: Steve Summit <[e-mail]>
Subject: Re: comp.lang.c Answers to Frequently Asked Questions (FAQ List) 
In-Reply-To: <[e-mail]> 
Message-ID: <[e-mail]>


Hej Steve

Before I loose my account I will pass on this list of solutions to "kbhit"
that I once received in personal email. You will recognize the beginning ...

// Jens M Andreasen

-------------------------------------------------------------------
Here's some stuff I've been collecting on this general subject.
I used to send it out in response to this question when it showed
up in comp.lang.c, but I've stopped reading that group.

The comp.lang.c Frequently Answered Questions list says, in part:

Section 16. System Dependencies

16.1:   How can I read a single character from the keyboard without
        waiting for a newline?

A:      Contrary to popular belief and many people's wishes, this is not
        a C-related question.  (Nor are closely-related questions
        concerning the echo of keyboard input.)  The delivery of
        characters from a "keyboard" to a C program is a function of the
        operating system in use, and has not been standardized by the C
        language.  Some versions of curses have a cbreak() function
        which does what you want.  If you're specifically trying to read
        a short password without echo, you might try getpass().  Under
        Unix, use ioctl to play with the terminal driver modes (CBREAK
        or RAW under "classic" versions; ICANON, c_cc[VMIN] and
        c_cc[VTIME] under System V or Posix systems).  Under MS-DOS, use
        getch().  Under VMS, try the Screen Management (SMG$) routines,
        or curses, or issue low-level $QIO's with the IO$_READVBLK (and
        perhaps IO$M_NOECHO) function codes to ask for one character at
        a time.  Under other operating systems, you're on your own.
        Beware that some operating systems make this sort of thing
        impossible, because character collection into input lines is
        done by peripheral processors not under direct control of the
        CPU running your program.

NOTE--> Operating system specific questions are not appropriate for
NOTE--> comp.lang.c .  Many common questions are answered in
NOTE--> frequently-asked questions postings in such groups as
NOTE--> comp.unix.questions and comp.os.msdos.programmer .  Note that
NOTE--> the answers are often not unique even across different variants
NOTE--> of a system; bear in mind when answering system-specific
NOTE--> questions that the answer that applies to your system may not
NOTE--> apply to everyone else's.

        References: PCS Sec. 10 pp. 128-9, Sec. 10.1 pp. 130-1.

16.2:   How can I find out if there are characters available for reading
        (and if so, how many)?  Alternatively, how can I do a read that
        will not block if there are no characters available?

A:      These, too, are entirely operating-system-specific.  Some
        versions of curses have a nodelay() function.  Depending on your
        system, you may also be able to use "nonblocking I/O", or a
        system call named "select", or the FIONREAD ioctl, or kbhit(),
        or rdchk(), or the O_NDELAY option to open() or fcntl().

The comp.unix.questions Frequently Answered Posting says:

With the variety of Unix systems in the world, it's hard to guarantee
that these answers will work everywhere.  Read your local manual pages
before trying anything suggested here.  If you have suggestions or
corrections for any of these answers, please send them to to
[e-mail].

1)  How do I read characters from a terminal without requiring the user
    to hit RETURN?

    Check out cbreak mode in BSD, ~ICANON mode in SysV.

    If you don't want to tackle setting the terminal parameters
    yourself (using the "ioctl(2)" system call) you can let the stty
    program do the work - but this is slow and inefficient, and you
    should change the code to do it right some time:

    #include <stdio.h>
    main()
    {
            int c;

            printf("Hit any character to continue\n");
            /*
             * ioctl() would be better here; only lazy
             * programmers do it this way:
             */
            system("/bin/stty cbreak");        /* or "stty raw" */
            c = getchar();
            system("/bin/stty -cbreak");
            printf("Thank you for typing %c.\n", c);

            exit(0);
    }

    You might like to check out the documentation for the "curses"
    library of portable screen functions.  Often if you're interested
    in single-character I/O like this, you're also interested in doing
    some sort of screen display control, and the curses library
    provides various portable routines for both functions.


The comp.so.msdos.programmer Frequently Answered Questions posting says:

Q301. How can I read a character without echoing it to the screen, and
      without waiting for the user to press the Enter key?

    The C compilers from Microsoft and Borland offer getch (or getche to
    echo the character); Turbo Pascal has ReadKey.

    In other programming languages, load 8 in register AH and execute
    INT 21; AL is returned with the character from standard input
    (possibly redirected).  If you don't want to allow redirection, or
    you want to capture Ctrl-C and other special keys, use INT 16 with
    AH=10; this will return the scan code in AH and ASCII code (if
    possible) in AL, except that AL=E0 with AH nonzero indicates one of
    the grey "extended" keys was pressed.  (If your BIOS doesn't
    support the extended keyboard, use INT 16 function 0 not 10.)

Q302. How can I find out whether a character has been typed, without
      waiting for one?

    In Turbo Pascal, use KeyPressed.  Both Microsoft C and Turbo C offer
    the kbhit( ) function.  All of these tell you whether a key has been
    pressed.  If no key has been pressed, they return that information
    to your program.  If a keystroke is waiting, they tell your program
    that but leave the key in the input buffer.

    You can use the BIOS call, INT 16 function 01 or 11, to check
    whether an actual keystroke is waiting; or the DOS call, INT 21
    function 0B, to check for a keystroke from stdin (subject to
    redirection).  See Ralf Brown's interrupt list.

And here's some more info:

On a PC, Microsoft C provides a routine called getch().  I believe
Turbo C provides a similar routine.  See your runtime library
documentation for details.  Here is an example:

#include <conio.h>
main() {
        int c;
        printf("control-c to exit\n");
        for(;;) {
                c = getch();
                printf("%02x\n", c);
        }
}

Under unix, you can use curses.  Read the man page for curses for
details.  Here is an example:


/*
** on a Sun, compile this as
**    /usr/5bin/cc -o progname progname.c -lcurses
*/
#include <curses.h>
main() {
        int c;
        initscr();
        cbreak();
        noecho();
        for(;;)
        {
                c = getch();
                wprintw(stdscr, "%02x\n", c);
                if (c == 3)
                        break;
        }
        endwin();
        exit(0);
}

Also under unix, you can use ioctl.  Read the man pages for ioctl and
termio for details.  Here is an example:


#include <stdio.h>
#include <sys/termio.h>

#define ON    0
#define OFF   1
#define READ  2
#define FALSE 0 == 1
#define TRUE  !FALSE
#define ETX 0x03
#define EOT 0x04

main()
{
    int c;

    hitkey(ON);
    while((c = hitkey(READ)) > 0) {
        printf("%02x\n", c);
        if (c == ETX || c == EOT)
            break;
    }
    printf("\n");
    hitkey(OFF);
    exit(0);
}

int hitkey(select)
int select;
{
   static int last = OFF;
   static struct termio org;
   struct termio tmp;
   char c;
   int rv = TRUE;
   int fd = fileno(stdin);

   if (last == select) {
      return(rv);
   }

   switch(select) {
   case ON: 
        ioctl(fd, TCGETA, &org);
        ioctl(fd, TCGETA, &tmp);
        tmp.c_lflag = 0;
        tmp.c_cc[VMIN] = 1;
        tmp.c_cc[VTIME] = 0;
        ioctl(fd, TCSETA, &tmp);
        last = ON;
        break;
    case OFF:
        ioctl(fd, TCSETA, &org);
        last = OFF;
        break;
    case READ: 
        if ((rv = read(fd, &c, 1)) == 1);
            rv = c;
        break;
    default:
        fprintf(stderr, "Invalid call to hitkey()");
        exit(1);
    }
    return(rv);
}

and here's some more code someone posted:

Article 25002 of comp.lang.c:
Path: mdisea!uw-coco!uw-beaver!cs.ubc.ca!destroyer!sol.ctr.columbia.edu!spool.mu.edu!olivea!uunet!munnari.oz.au!comp.vuw.ac.nz!waikato.ac.nz!aukuni.ac.nz!cs18.cs.aukuni.ac.nz!pgut1
From: [e-mail] (Peter Gutmann)
Newsgroups: comp.lang.c
Subject: Re: getch() replacement
Message-ID: <[e-mail]>
Date: 26 Nov 92 03:21:22 GMT
References: <[e-mail]>
Organization: Computer Science Dept. University of Auckland
Lines: 111

In <[e-mail]> [e-mail] writes:

>I am working with Borland C++ 3.1 and I am looking for a replacement for
>Borland's getch() function. I would like this replacement to grab the input
>from STDIN without having to press return. So far, I have had no luck.

>Many posts back someone posted that in UNIX this can be done with the IOCTL
>setup. DOS of course has an entirely different set of functions for this
>command (I have explored that anvenue).

(I'm replying here rather than via email since I've seen requests for this
several times in the past).

The following code will do what you want - note that you'll need a seperate
version of the code for pretty well every version of Unix you're going to
use it under (isn't "standard" Unix wonderful?).

/* Get an input character, no echo */
 
#if defined( POSIX ) || defined( SVR4 ) || defined( IRIX )
 
#include <termios.h>
 
int getch( void )
    {
    struct termios ttyInfo;
    FD ttyFD = ERROR;
    char ch;
 
    /* Flush all pending output */
    fflush( stdout );
 
    /* Turn echo off */
    if( isatty( STDERR ) && ( ttyFD = hopen( ttyname( STDERR ), O_RDWR ) ) != ERROR )
        {
        tcgetattr( ttyFD, &ttyInfo );
#ifdef IRIX
        ttyInfo.c_lflag &= ~ECHO;
        ttyInfo.c_lflag &= ~ICANON;
#else
        ttyInfo.c_lflags &= ~ECHO;
        ttyInfo.c_lflags |= CBREAK;
#endif /* IRIX */
        tcsetattr( ttyFD, TCSANOW, &ttyInfo );
        }
 
    /* Get the character */
    read( ttyFD, &ch, 1 );
 
    /* Turn echo on again if it was off */
    if( ttyFD != ERROR )
        {
        tcgetattr( ttyFD, &ttyInfo );
#ifdef IRIX
        ttyInfo.c_lflag |= ECHO;
        ttyInfo.c_lflag |= ICANON;
#else
        ttyInfo.c_lflags |= ECHO;
        ttyInfo.c_lflags &= ~CBREAK;
#endif /* IRIX */
        tcsetattr( ttyFD, TCSANOW, &ttyInfo );
        }
 
    return( ch );
    }
 
#else
 
#include <sgtty.h>
 
int getch( void )
    {
    struct sgttyb ttyInfo;
    FD ttyFD = ERROR;
    char ch;
 
    /* Flush all pending output */
    fflush( stdout );
 
    /* Turn echo off */
    if( isatty( STDERR ) && ( ttyFD = hopen( ttyname( STDERR ), O_RDWR ) ) != ERROR )
        {
        gtty( ttyFD, &ttyInfo );
        ttyInfo.sg_flags &= ~ECHO;
        ttyInfo.sg_flags |= CBREAK;
        stty( ttyFD, &ttyInfo );
        }
 
    /* Get the character */
    read( ttyFD, &ch, 1 );
 
    /* Turn echo on again if it was off */
    if( ttyFD != ERROR )
        {
        gtty( ttyFD, &ttyInfo );
        ttyInfo.sg_flags |= ECHO;
        ttyInfo.sg_flags &= ~CBREAK;
        stty( ttyFD, &ttyInfo );
        }
 
    return( ch );
    }
#endif /* POSIX || SVR4 || IRIX */

--
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Article 26728 of comp.lang.c:
Newsgroups: comp.lang.c
Path: mdisea!uw-coco!uw-beaver!micro-heart-of-gold.mit.edu!news.bbn.com!usc!zaphod.mps.ohio-state.edu!saimiri.primate.wisc.edu!ames!kum.kaist.ac.kr!usenet
From: [e-mail] (Han Yun-Su)
Subject: Re: Unix equivalent to DOS kbhit() function?
Message-ID: <[e-mail]>
Sender: [e-mail] (news)
Organization: KAIST in Seoul, Korea
X-Newsreader: Tin 1.1 PL3
Date: Tue, 29 Dec 92 07:33:37 GMT
Lines: 67

I wrote 'kbhit()' function for UNIX.
It's very simple..

Here's example source.

Save this article as 'kbhit.c', delete headers and signature..
Compile with -lcurses -ltermcap options, that is,

cc kbhit.c -o kbhit -lcurses -ltermcap

and..type kbhit !
test some characters..
(This works totaly fine for my SUN)

Er..sorry.. I'm not good at english..:)
I can speak C more fluently than english..hehe :)
But my major is NOT Computer Science but Life Science. 

If you find better idea than this one, Please let me know.

Good Luck!


/* ---- Cut Here ---- */
#include <sgtty.h>
#include <curses.h>

kbhit()
{
  static unsigned i;

  ioctl(0, FIONREAD, &i);
  return i;
}

main()
{
  unsigned long count = 0L;
  int c = ' ';
  int i = 0;

  initscr();        /* initialize curses functions */
  crmode();        /* cbreak mode */
  noecho();        /* do not echo pressed character */

  mvprintw(0, 0, "Press \'q\' to quit\n");
  refresh();

  while (c != 'q') {
    count++;