getchar() question

h/w · 12-22-2003, 02:25 PM

C code:

Code:

  char a, s, *p;
  int i, j;
  struct menu selection;
  printf ("  Enter algorithm number: ");
  a = getchar();
  p = &a;
  j = (int)atoi(p);
  if (j > i+1 && j <= 0) {
    printf ("Invalid algorithm selection : Run again\n");
    exit (1);
  }
  else 
    selection.algo_num = j-1;

  printf ("  Enter sort order [(a)scending || (d)escending)]: ");
  s = getchar();
  if (s != 'a' && s != 'd') {
    printf ("\nInvalid selection of sort order: Run again\n");
    exit (1);
  }
  else
    selection.sort_order = s;

when i run this, i get a 'stop' at "Enter Algorithm number: ", and it reads in the character.
At the next printf, after printing " Enter sort order [(a)scending || (d)escending)]: ", it doesnt 'stop' to do the getchar();

why would this be?

thanks again!

infamous41md · 12-22-2003, 02:48 PM

the newline is still in the input stream from the last getchar(). remember stdin is really just a big ol stream of bytes. every time a user pushes [enter] that is read as a newline. so you could fflush(stdin) if u wantd.

h/w · 12-22-2003, 02:50 PM

hmm, thanks again infamous.
i just removed the getchar(), and used scanf() instead.
thanks.

jim mcnamara · 12-23-2003, 04:53 PM

To get somethuing like the DOS getch() function where you push a key and the value is returned without having to hit return:

Code:

#include <termios.h>
#include <unistd.h>
#include <assert.h>
#include <string.h>
/*------------------------------------------------*/
int getch(void) {
      int c=0;

      struct termios org_opts, new_opts;
      int res=0;
          //-----  store old settings -----------
      res=tcgetattr(STDIN_FILENO, &org_opts);
      assert(res==0);
          //---- set new terminal parms --------
      memcpy(&new_opts, &org_opts, sizeof(new_opts));
      new_opts.c_lflag &= ~(ICANON | ECHO | ECHOE | ECHOK | ECHONL | ECHOPRT | ECHOKE | ICRNL);
      tcsetattr(STDIN_FILENO, TCSANOW, &new_opts);
      c=getchar();
          //------  restore old settings ---------
      res=tcsetattr(STDIN_FILENO, TCSANOW, &org_opts);
      assert(res==0);
      return(c);
}