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Linux Registers

Posted on 1997-03-30
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Last Modified: 2013-12-26
I have the following code sample from a DOS program I wrote.  I would like to port the program to Linux, but I don't know how to reach the registers without dos.h  The code also uses int86() which I don't think is usable within Linux.  I am looking for a replacement for the following member function:

// The purpose of the function is to return a key value only if a key
//is hit, otherwise return 0. It does NOT wait for a key to be pressed

int Fractal::GetKey ()
{
  union REGS r;            // Gain access to the registers
  if (!kbhit ())            // Return if no key pressed
       return 0;
  r.h.ah = 0;
  int86 (0x16, &r, &r);      // Get scancode of key
  if (!r.h.al)
    return (r.h.ah | 128);
 return (r.h.al & 255);      // Return the key number
}
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Question by:wiggin
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jos010697 earned 200 total points
ID: 1292480
It doesn't work that way if you're using a Unix variant. Have
a look at your manual pages for ioctl(). It's purpose is to
set characteristics of an IO device. Something along the
following lines should do the job (check it out, I haven't
tested it)

int GetKey()
{
struct sgttyb tty, tty_org;
char           key;
int            retval;

/* get and save tty settings */
ioctl(fileno(stdin), TIOCGETP, &tty_org);
tty = tty_org;

/* set terminal to raw mode, no echo, no nothing */
tty.sg_flags |= CRMOD;
tty.sg_flags &= ~ECHO;
tty.sg_flags &= ~XTABS;

/* could be: tty.sg_flags |= CBREAK; */
tty.sg_flags |= RAW;
ioctl(0, TIOCSETP, &tty);
fcntl(0, F_SETFL, O_NDELAY);

/* read a keystroke */
if ((retval= read(0, &key, 1)) == 1)
        retval= key;

/* restore terminal settings */
ioctl(fileno(stdin), TIOCSETP, &tty_org);
fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0)&~O_NDELAY);

return retval;
}

kind regards,

Jos
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