Re: function to detect keyboard hit

[kenneth kahn <kenkahn@xxxxxxxxxxxxx>]

Here's a variation of the code already given; I've tried it with success on
AIX, Solaris, HP-UX, Linux and WinXP:

/* get_char.c */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <termios.h>

int getch(void);   // wait for next keystroke (no echo)
int getchp(void);  // check for pending keystrokes (no echo)

int main () {
  int key;
  /*----------------------------------------------------------*
   ! Continue waiting for keystrokes until ESC is pressed     !
   *----------------------------------------------------------*/
  while (!(((key = getch()) == 0x1b) && (getchp() < 0))) {
    printf("key=%04x",key);
    /*--------------------------------------------------------*
     ! search for any pending keystrokes (e.g. function keys) !
     *--------------------------------------------------------*/
    while ((key = getchp()) > 0) {
      printf(" %04x",key);
    }
    printf("\n");
  }
  /*----------------------------------------------------------*
   ! ESC pressed; exit program                                !
   *----------------------------------------------------------*/
  printf("Escape Pressed\n");
  return 0;
}

/*----------------------------------------------------------*
 ! Wait for the next keypress (no echo)                     !
 *----------------------------------------------------------*/
int getch(void) {
  struct termios term_settings,term_settings_saved;
  int x;
  if (tcgetattr(STDIN_FILENO,&term_settings))
    return -1;
  term_settings_saved=term_settings;
  term_settings.c_lflag &= ~ICANON ;
  term_settings.c_lflag &= ~ECHO ;
  term_settings.c_cc[VMIN]=1 ;
  term_settings.c_cc[VTIME]=0;
  if (tcsetattr (STDIN_FILENO, TCSANOW, &term_settings) < 0)
  x=getchar();
  tcsetattr (STDIN_FILENO, TCSANOW, &term_settings_saved);
  return x;
}

/*----------------------------------------------------------*
 ! Check for pending keystrokes (no echo)                   !
 *----------------------------------------------------------*/
int getchp(void) {
  struct termios term_settings,term_settings_saved;
  char c;
  int x;
  if (tcgetattr(STDIN_FILENO,&term_settings))
    return -2;
  term_settings_saved=term_settings;
  term_settings.c_lflag &= ~ICANON ;
  term_settings.c_lflag &= ~ECHO ;
  term_settings.c_cc[VMIN]=0;
  term_settings.c_cc[VTIME]=0;
  if (tcsetattr (STDIN_FILENO, TCSANOW, &term_settings) < 0)
    return -2;
  x = getchar();
  tcsetattr (STDIN_FILENO, TCSANOW, &term_settings_saved);
  return x;
}

-----------------------------------
Kenneth Kahn
Senior Member of Consulting Staff
CVA R&D Hardware Emulation
Cadence Design Systems
Lake Katrine, NY