linux上c语言 获得网络接口的统计值

这个东东，蛮好玩的。其实就是读取了/proc/net/dev 文件。
struct netdev_stats {
    unsigned long long rx_packets_m;    /* total packets received       */
    unsigned long long tx_packets_m;        /* total packets transmitted    */
    unsigned long long rx_bytes_m;  /* total bytes received         */
    unsigned long long tx_bytes_m;  /* total bytes transmitted      */
    unsigned long rx_errors_m;      /* bad packets received         */
    unsigned long tx_errors_m;      /* packet transmit problems     */
    unsigned long rx_dropped_m;     /* no space in linux buffers    */
    unsigned long tx_dropped_m;     /* no space available in linux  */
    unsigned long rx_multicast_m;   /* multicast packets received   */
    unsigned long rx_compressed_m;
    unsigned long tx_compressed_m;
    unsigned long collisions_m;
    /* detailed rx_errors: */
    unsigned long rx_length_errors_m;
    unsigned long rx_over_errors_m; /* receiver ring buff overflow  */
    unsigned long rx_crc_errors_m;  /* recved pkt with crc error    */
    unsigned long rx_frame_errors_m;        /* recv'd frame alignment error */
    unsigned long rx_fifo_errors_m; /* recv'r fifo overrun          */
    unsigned long rx_missed_errors_m;&nb