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Amiga computer related discussion => Amiga Software Issues and Discussion => Topic started by: kwoolridge on September 14, 2007, 09:38:16 PM

Title: Reading one char from standard Input without waiting for CR
Post by: kwoolridge on September 14, 2007, 09:38:16 PM

Does anyone know whether any of the AmigaOS Libraries contain a routine which will read one character from the standard input (not a raw window, but the standard shell window) without waiting for a carriage return (i.e. pressing the Enter key)?

Other OS's (VMS, MPX, even Windows) have such routines.  Any help is appreciated.  Thanks.

Title: Re: Reading one char from standard Input without waiting for CR
Post by: Piru on September 14, 2007, 10:08:34 PM

Such routines are non-standard and thus it's not readily available without some hacking. It's possible however, by using raw mode.

Code: [Select]

#include <proto/dos.h>

LONG readchar(BPTR fh);

int main(void)
{
  Printf(&quot;0x%02lx\n&quot;, readchar(Input()));

  return 0;
}

LONG readchar(BPTR fh)
{
  LONG ret = -1;

  if (IsInteractive(fh))
  {
    if (SetMode(fh, 1)) /* Attempt to go to raw mode */
    {
      UBYTE buf[4];
      LONG actual;

      do
      {
        actual = Read(fh, buf, sizeof(buf));
        /* Read until single char or error */
      } while (actual > 1);

      SetMode(fh, 0); /* Go back to con mode */

      if (actual == 1)
      {
        ret = buf[0];
      }
    }
  }
  else
  {
    ret = FGetC(fh);
  }

  return ret;
}


Title: Re: Reading one char from standard Input without waiting for CR
Post by: Stedy on September 14, 2007, 10:14:38 PM

Hi,

If you are using C, the setbuf() or better, the setvbuf() function will do what you want.

the command
setvbuf(fp,NULL,_IONBF,0);

Will turn off buffering in a console window, you can then use getchar() or similar to read the character thus:

Example program (tested with Dice C, copied from the examples)

#include
#define BUFFER_SIZE 128
main()
{
   int c;
   char buf[256];
 
   setvbuf(stdin,NULL, _IONBUF,0);
   printf("Type a character: ");
   fflush(stdout);
   c=getchar();
   printf("c=%d\n");

return(0);
}

Ian

Title: Re: Reading one char from standard Input without waiting for CR
Post by: Piru on September 14, 2007, 10:19:00 PM

@Stedy

_IONBF, missing argument for printf. Surely Dice C doesn't have such "quality" examples?

And it still doesn't work for me (SAS/C, gcc libnix, gcc ixemul).

Title: Re: Reading one char from standard Input without waiting for CR
Post by: kwoolridge on September 21, 2007, 01:13:27 PM

Thank you for your responses!