MAC Address printing

Question

This is a code that gets some info about network the problem is when it prints the MAC address it prints it sometime normally and sometime with fff\'s like 00:21:84:a2:12:88

Answer 1

I prefer use an explicit length modifier in format string for values shorter than int. For example %02hhx instead of %02x for one-byte values. It allow me to not worry about those subtle conversion and promotion issues:

#include 

int main(void)
{
    signed char sff = '\xff';
    unsigned char uff = '\xff';

    printf("signed:   %02x %02hhx\n", sff, sff);
    printf("unsigned: %02x %02hhx\n", uff, uff);

    return 0;
}

prints

signed:   ffffffff ff
unsigned: ff ff