IP 주소 얻기 예제

IP 주소 얻기 예제

• ipv6 고려하지 않음

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

int s_getIpAddress (const char * ifr, unsigned char * out) {
    int sockfd;
    struct ifreq ifrq;
    struct sockaddr_in * sin;
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    strcpy(ifrq.ifr_name, ifr);
    if (ioctl(sockfd, SIOCGIFADDR, &ifrq) < 0) {
        perror( "ioctl() SIOCGIFADDR error");
        return -1;
    }
    sin = (struct sockaddr_in *)&ifrq.ifr_addr;
    memcpy (out, (void*)&sin->sin_addr, sizeof(sin->sin_addr));

    close(sockfd);

    return 4;
}

int main(int argc, char * args[]) {

    unsigned char addr[4] = {0,};

    if (s_getIpAddress("eth0", addr) > 0) {
        printf("ip addr:=%d.%d.%d.%d", (int)addr[0], (int)addr[1], (int)addr[2], (int)addr[3]);
    }

    return 0;
}