scanf an integer

int nfields, num;
char dummy[2];

fputs("Please enter a decimal integer: ", stdout);
fflush(stdout);

nfields = scanf("%d%1[^\n]", &num, dummy);
while (nfields != 1)
{
  puts("Invalid input! Please try again.");
  fputs("Enter a decimal integer (and nothing else): ", stdout);
  fflush(stdout);

  /* Consume remaining line of input. */
  while (0 != scanf("%*[^\n]"))
  ;

  nfields = scanf("%d%1[^\n]", &num, dummy);
}

printf("num = %d\n", num);

/*
This code first prompts for a number, then attempts to read in two
fields: a decimal integer and a single character that is not a newline
(as indicated by the %1[^\n] conversion specifier). However, we want it
to fail to read the second field. There are several scenarios that can
be encountered:

1) no fields are read in, meaning there are no digits at the start of
the input, scanf() returns 0, and we enter the loop to try again (after
consuming the remaining line of input so we don't get stuck in an
endless loop);

2) a numerical field and an extra character field are read in, meaning
there are digits at the start of the input but there is some non-digit
character(s) after that, scanf() returns 2, and the loop is entered to
try again;

3) a numerical field is read, but no other characters are present, and
scanf() returns 1, meaning that only digits were entered, which is what
we want, so we don't enter the loop.

The last printf() statement then tells us what number was entered.
*/