#include <stdio.h>
    #include <stdlib.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <unistd.h>
    #include <sys/ioctl.h>
    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #include <net/if.h>
    #include <string.h>

    unsigned char g_eth_name[16];
    unsigned char g_macaddr[16];
    unsigned int g_subnetmask;
    unsigned int g_ipaddr;
    unsigned int g_broadcast_ipaddr;

    //初始化網路，獲取當前網路裝置資訊
    void init_net(void)
    {
        int i ;
        int sock;
        struct sockaddr_in sin;
        struct ifreq ifr;
        
        sock=socket(AF_INET, SOCK_DGRAM, 0);
        if(sock==-1)
            perror("socket");
        strcpy(g_eth_name, "eth0");
        strcpy(ifr.ifr_name, g_eth_name);
        printf("eth name:\t%s\n", g_eth_name);

        //獲取並列印網絡卡地址
        if(ioctl(sock, SIOCGIFHWADDR, &ifr) <0 )
            perror("ioctl error\n");
        memcpy(g_macaddr, ifr.ifr_hwaddr.sa_data,6);
        printf("local mac:\t");
        for(i=0;i<5;i++)
            printf("%.2x:", g_macaddr[i]);
        printf("%.2x\n",g_macaddr[i]);
        
        //獲取並列印IP地址
        if(ioctl(sock, SIOCGIFADDR, &ifr)<0)
            perror("ioctl error\n");
        memcpy(&sin, &ifr.ifr_addr, sizeof(sin));
        g_ipaddr = sin.sin_addr.s_addr;
        printf("local eth0:\t%s\n", inet_ntoa(sin.sin_addr));
        
        //獲取並列印廣播地址
        if(ioctl(sock, SIOCGIFBRDADDR, &ifr)<0)
            perror("ioctl error\n");
        memcpy(&sin, &ifr.ifr_addr, sizeof(sin));
        g_broadcast_ipaddr = sin.sin_addr.s_addr;
        printf("broadcast:\t%s\n", inet_ntoa(sin.sin_addr));
        
        //獲取並列印子網掩碼
        if(ioctl(sock,SIOCGIFNETMASK,&ifr)<0)
            perror("ioctl error\n");
        memcpy(&sin, &ifr.ifr_addr, sizeof(sin));
        g_subnetmask = sin.sin_addr.s_addr;
        printf("subnetmask:\t%s\n", inet_ntoa(sin.sin_addr));
        
        close(sock);
    }

    int main()
    {
        //initialize
        init_net();
        //do something
        //....
        return 0;
    }

執行結果：

               eth name:    eth0
               local mac:    34:97:f6:da:6c:ab
               local eth0:    192.168.2.33
               broadcast:    192.168.2.255
               subnetmask:    255.255.255.0