[SOLVED] Strtol function returning wrong value

Strtol function returning wrong value

I need to get a credit card number as input on an exercise, to dos so I'm ussing the function fgets (getting it as a string to check if it is realy a number) and then strtol to make it a long integer. But the integer value return by the function does not match the one on the string.

while (*endptr != '\n') {
        char card_number_string[20];
        char *endptr;
        long int card_number;

        printf("Number: ");
        fgets(card_number_string, 20, stdin);
        card_number = strtol(card_number_string, &endptr, 10);
        printf("Result: %ld", card_number);
    }

For example, when I input the value 4003600000000014 the output of the strtol shown in the printf is 2147483647.

Is it a bug on my code? Or the function does return something different like this??

Note: All the variables are declared on top of the main function, they are in there just to know how they were declared

Solution

Value is outside long range. 2147483647 is the max value of long in your case.

Use long long. (or unsigned long long if negative CC# are not needed)

    //long int card_number;
    long long card_number;

    printf("Number: ");
    fgets(card_number_string, 20, stdin);
    
    //card_number = strtol(card_number_string, &endptr, 10);
    card_number = strtoll(card_number_string, &endptr, 10);

    //printf("Result: %ld", card_number);
    printf("Result: %lld", card_number);

Note: char *endptr; shadows the endptr in while (*endptr != '\n')