[C] Using ioctl to control socket to get ip address and netmask

#include <net/if.h>
#include <sys/ioctl.h>
#include <string.h>
#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>

int main()
{
        int inet_sock;
        struct ifreq ifr;
        inet_sock = socket(AF_INET, SOCK_DGRAM, 0);
        strcpy(ifr.ifr_name, "eth0");
        if (ioctl(inet_sock, SIOCGIFADDR, &ifr) < 0)
                perror("ioctl");
        printf("%s\n", inet_ntoa(((struct sockaddr_in*)&(ifr.ifr_addr))->sin_addr));

        if (ioctl(inet_sock, SIOCGIFNETMASK, &ifr) < 0) {
            perror("ioctl");
        }
        printf("%s\n", inet_ntoa(((struct sockaddr_in*)&(ifr.ifr_netmask))->sin_addr));
}

Reference:

• C program to get ip address from interface name on Linux