getmask

#include "stdio.h"
#include "stdlib.h"
#include "string.h"

#include "net/if.h"
#include "arpa/inet.h"
#include "linux/sockios.h"

int main(int argc,char *argv[])
{
    struct sockaddr_in *addr;
    struct ifreq ifr;
    char*address;
    int sockfd;

    char *name = "eth0";
    if( strlen(name) >= IFNAMSIZ)
        printf("device name is error.\n"), exit(0);
        
    strcpy( ifr.ifr_name, name);
        
    sockfd = socket(AF_INET,SOCK_DGRAM,0);

    //get inet addr
    if( ioctl( sockfd, SIOCGIFADDR, &ifr) == -1)
        printf("ioctl error.\n"), exit(0);

    addr = (struct sockaddr_in *)&(ifr.ifr_addr);
    address = inet_ntoa(addr->sin_addr);

    printf("inet addr: %s\n",address);

    //get Mask
    if( ioctl( sockfd, SIOCGIFNETMASK, &ifr) == -1)
        printf("ioctl error.\n"), exit(0);

    addr = (struct sockaddr_in *)&ifr.ifr_addr;
    address = inet_ntoa(addr->sin_addr);

    printf("Mask: %s\n",address);

    //get HWaddr 
    u_int8_t hd[6];
    if(ioctl(sockfd, SIOCGIFHWADDR, &ifr) == -1)
        printf("hwaddr error.\n"), exit(0);

    memcpy( hd, ifr.ifr_hwaddr.sa_data, sizeof(hd));
    printf("HWaddr: %02X:%02X:%02X:%02X:%02X:%02X\n", hd[0], hd[1], hd[2], hd[3], hd[4], hd[5]);
    
    exit(0);
}