C number guessing game with isdigit() verification

Question

I\'m working on a challenge problem from my textbook where I\'m supposed to generate a random number between 1-10, let the user guess, and validate their response with isdigit()

Answer 1

You can use the return value of scanf to determine whether the read was successful. So, there are two paths in your program, successful reading and failed reading:

int guess;
if (scanf("%d", &guess) == 1)
{
    /* guess is read */
}
else
{
    /* guess is not read */
}

In the first case, you do whatever your program logic says. In the else case, you have to figure out "what was the problem", and "what to do about it":

int guess;
if (scanf("%d", &guess) == 1)
{
    /* guess is read */
}
else
{
    if (feof(stdin) || ferror(stdin))
    {
        fprintf(stderr, "Unexpected end of input or I/O error\n");
        return EXIT_FAILURE;
    }
    /* if not file error, then the input wasn't a number */
    /* let's skip the current line. */
    while (!feof(stdin) && fgetc(stdin) != '\n');
}