linux check netcard down or up

// return 1 -- netcard up

// other value -- netcard down 

    int GetNetlinkStatus(uint8_t *ifname)
    {
        int sockfd;
        struct ifreq ifr;
        struct ethtool_value edata;

        edata.cmd = ETHTOOL_GLINK;
        edata.data = 0;

        memset(&ifr, 0, sizeof(ifr));
        strncpy(ifr.ifr_name, (char *)ifname, sizeof(ifr.ifr_name) - 1);

        ifr.ifr_data = (char *) &edata;

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

        if(ioctl(sockfd, SIOCETHTOOL, &ifr) == -1) {
            close(sockfd);
            return -1;
        }

        close(sockfd);

        return edata.data;
    }

 

 

way 2.

cat /sys/class/net/eth0/operstate

return down or up string