How do you validate that a string is a valid MAC address in C?

Question

example:

12:45:ff:ab:aa:cd    is valid
45:jj:jj:kk:ui>cd    is not valid

Answer 1

You can rely on the sscanf to check the format and content of the provided MAC address, something like

bool checkMacAddr(const char * mac) noexcept
{
    if(nullptr == mac) return false;
    printf("[%s] strlen(%s)=%lu\n", __func__, mac, strlen(mac));
    if(strlen(mac) != 17) return false;

    uint32_t bytes[6]={0};

    return (6 == sscanf(mac, "%02X:%02X:%02X:%02X:%02X:%02X"
            , &bytes[5]
            , &bytes[4]
            , &bytes[3]
            , &bytes[2]
            , &bytes[1]
            , &bytes[0]));
}