problem with scanf Post: 91779

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Top Forums Programming problem with scanf Post 91779 by linuxpenguin on Monday 5th of December 2005 02:16:18 PM

12-05-2005

Registered User

hi,
First, fflush on stdin is not guaranteed. Some ppl might suggest you to use getchar to flush the stdin. But again that is not a clean way, i think so.
There are other options like using the gets (or fgets which is secure ) then convert the input to whatever format you want using the sscanf (string scanf). At the moment I would suggest you to use fgets and sscanf. However in instance where you want a key board input such that you dont want to wait for the enter key, for eg, u want something to happen when a user types in 'q' ( for eg) without having to press the enter key after typing q, ( this is called as hotkey) you may want to write your own keyboard handling function, I use the one below sometimes, this is for unix system. for windows, it will be different.

I have also added the main function to this function so you can better understand how mygetch works:

Code:

/* 
Desc: The main intent of this program is the function mygetch. This function is
	written to input one character at a time. The input does not await the enter
	key response from the user.
Author: Hemant Borole
Date: 27Jan05 10:06 am
*/

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

#define BUFFSIZE 64		/* Buffer size for input */
/* this function will return immediately after a key is
   pressed. You do not have to wait till the enter key is hit */

int mygetch( ) {

	/* Handles to old and new termios structures */
	struct termios oldt, newt;
	int ch;

	/* store current termios to restore back later */
	tcgetattr( STDIN_FILENO, &oldt );
	newt = oldt;

	/* set to canonical. turn off echo */
	newt.c_lflag &= ~( ICANON | ECHO );
	tcsetattr( STDIN_FILENO, TCSANOW, &newt );

	/* Read the character */
	ch = getchar();

	/* Reset terminal */
	tcsetattr( STDIN_FILENO, TCSANOW, &oldt );
	return ch;
}

/* Main body, to test the mygetch, convert the character immediately
   to upper case. Do not have to wait till user inputs, presses enter
   and then convert to upper case */

int main()	{
	char c = '\0';
	char str[BUFFSIZE];
	char inp[BUFFSIZE];
	int i = 0;

	str[0] = '\0';

	printf("Type q to quit this program or press enter. \n");
	printf("Anyway the program will self kill after %d characters of input\n",BUFFSIZE);
	while ( 1 )	{
		if ( i >= BUFFSIZE ) break;

		c = mygetch();
		if ( c == 'q' || c == '\n' ) break;

		if ( c >='a' && c <='z' )	{
			printf("%c",c-32);
			str[i] = c-32;
		}
		else	{
			printf("%c",c);
			str[i] = c;
		}
		inp[i] = c;
		i++;
	}
	printf("\nYou typed: %s\n",inp);
	printf("\nConverted output: %s\n",str);
}

Last edited by blowtorch; 12-23-2006 at 01:42 PM..

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keyboard_translatekeys

keyboard_translatekeys(3)					Svgalib User Manual					 keyboard_translatekeys(3)

NAME

       keyboard_translatekeys - modify scancode mappings in raw keyboard mode

SYNOPSIS

       #include <vgakeyboard.h>

       void keyboard_translatekeys(int mask);

DESCRIPTION

       This function sets several flags which control how certain scancodes are mapped. At startup a mask value of 0 is active.

       mask must be a logical or of zero or more of the following #predefined integers to turn the features listed on:

       TRANSLATE_CURSORKEYS
	      Translate  the scancodes of the SCANCODE_CURSORBLOCK* keys to those of the cursor keys on the number pad, s.t.  keyboard_getstate(3)
	      and keyboard_keypressed(3) report a keypress of the corresponding number pad cursor key and not the one on the cursor block.

       TRANSLATE_DIAGONAL
	      Translates the scancodes of diagonal cursor keys (keypad 7, 9, 1, 3) to presses of two of the ordinary up, down, left,  right  keys.
	      For  example, instead of reporting a press of SCANCODE_CURSORUPRIGHT keyboard_getstate(3) and keyboard_keypressed(3) report a simul-
	      taneous press of SCANCODE_CURSORUP and SCANCODE_CURSORRIGHT.

       TRANSLATE_KEYPADENTER
	      The scancode of the keypad enter key is mapped to that of the ordinary  enter  key,  s.t.   keyboard_getstate(3)	and  keyboard_key-
	      pressed(3) report a press of SCANCODE_ENTER regardless if keypad enter or ordinary enter is pressed.

       DONT_CATCH_CTRLC
	      Pressing	<Ctrl>-C  does not raise a SIGINT.  On contrary to the other flags this has also effect when a user defined keyboard event
	      handler is used. Svgalib will always process <Alt>-F1 - <Alt>-F10 and perform console switches accordingly.

BUGS

       The TRANSLATE_* options above do really do simple scancode translations. For example, when TRANSLATE_KEYPADENTER is  active  and  the  user
       presses both enter and keypad enter. Then, if he releases one of them (say keypad enter), it's release event will clear the common keyboard
       state, s.t.  no keypress is reported even though enter is still pressed.

       Similarly, if TRANSLATE_DIAGONAL is active, the user holds cursor upleft (keypad 7) down and then presses and release cursor up (keypad 8),
       svgalib	will  only report a pressed cursor left but the simulated cursor up will be lost. You can easily try this with the keytest(6) demo
       to make the effect more clear to you.

SEE ALSO

       svgalib(7),    vgagl(7),    libvga.config(5),	keytest(6),    eventtest(6),	keyboard_seteventhandler(3),	keyboard_init(3),     key-
       board_init_return_fd(3),   keyboard_close(3),   keyboard_update(3),   keyboard_waitforupdate(3),  keyboard_setdefaulteventhandler(3),  key-
       board_getstate(3), keyboard_clearstate(3), keyboard_keypressed(3), vga_waitevent(3)

AUTHOR

       This manual page was edited by Michael Weller <eowmob@exp-math.uni-essen.de>. The exact source of the referenced function as well as of the
       original documentation is unknown.

       It is very likely that both are at least to some extent are due to Harm Hanemaayer <H.Hanemaayer@inter.nl.net>.

       Occasionally  this might be wrong. I hereby asked to be excused by the original author and will happily accept any additions or corrections
       to this first version of the svgalib manual.

Svgalib (>;= 1.2.11)						   29 July 1997 					 keyboard_translatekeys(3)

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