fpurge(stdin);

#include <stdio.h>

int main() {
  char a,b;
  putchar(':');
  putchar(' ');
  a = getchar();
  printf("\na=%c, [%02x]\n", a, (unsigned char) a);

  fpurge(stdin); //_fpurge also used

  putchar(':');
  putchar(' ');
  b = getchar();
  printf("\nb=%c, [%02x]\n", b, (unsigned char) b);

  return 0;
}

/*
Output (observe variable 'b' gets garbage (-1):
$ echo 'abcde' | ../bin/tx_fpurge
:
a=a, [61]
:
b=?, [ff]

*/