Question

If I run the following code, it only prints interfaces that are in the RUNNING state. Is there a way to get a list of interfaces that are not RUNNING and could be either UP or DOWN?

int main()
{
    struct ifreq *pIfr;
    struct ifconf ifc;
    char buf[1024];
    int s, i, j;

    s = socket(AF_INET, SOCK_DGRAM, 0);
    if (s==-1)
        return -1;

    ifc.ifc_len = sizeof(buf);
    ifc.ifc_buf = buf;
    ioctl(s, SIOCGIFCONF, &ifc);

    pIfr = ifc.ifc_req;
    for (i = ifc.ifc_len / sizeof(struct ifreq); --i >= 0; pIfr++) {
        printf("name=%s\n", pIfr->ifr_name);
    }
    close(s);
    return 0;
}
~           

Answer 1

Looks like an ioctl loop with SIOCGIFNAME returns all interfaces. The input is an index, and the call returns the interface name.