Get IPv4 address from interface name in FreeBSD

get_ip4_addr.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <net/if.h>
#include <ifaddrs.h>

#define FORMAT_IP4_ADDR "%u.%u.%u.%u"

int get_ip4_addr(const char *ifname, struct in_addr *ipaddr);

int main(void) {
    struct in_addr ipaddr;
    unsigned char octet[4];

    if(get_ip4_addr("em0", &ipaddr) < 0) {
        fprintf(stderr, "get_ip4_addr() failed\n");
        exit(EXIT_FAILURE);
    }

    memcpy(octet, &(ipaddr.s_addr), sizeof(octet));

    printf("IP4 Address: " FORMAT_IP4_ADDR "\n",
            octet[0], octet[1], octet[2], octet[3]);

    return 0;
}

int get_ip4_addr(const char *ifname, struct in_addr *ipaddr)
{
    struct ifaddrs *ifap;
    struct ifaddrs *searcher;
    struct sockaddr_in *in_addr;
    int ret = 0;

    if((ret = getifaddrs(&ifap)) < 0) {
        return ret;
    }

    searcher = ifap;

    while(searcher->ifa_next != NULL) {
        if(strcmp(searcher->ifa_name, ifname) &&
                searcher->ifa_addr->sa_family == AF_INET) {
            in_addr = (struct sockaddr_in *)searcher->ifa_addr;
            memcpy(ipaddr, &(in_addr->sin_addr), sizeof(struct in_addr));
            ret = 0;
            break;
        }
        searcher = searcher->ifa_next;
    }

    if(ret != 0) {
        ret = -1;
    }

    freeifaddrs(ifap);
    return ret;
}