retrieve INET4 interfaces address using getifaddrs(3)

addr.c

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

int
main(void) {
    struct ifaddrs *addrs = NULL;
    struct ifaddrs *addr = NULL;
    char buf[64];
    struct sockaddr_in *inet4;

    if (getifaddrs(&addrs) == -1) {
        perror("getifaddrs");
        exit(1);
    }

    for (addr = addrs; addr; addr = addr->ifa_next) {
        if (addr->ifa_addr == NULL)
            continue;
        if ((addr->ifa_flags & IFF_UP) == 0)
            continue;
        if (addr->ifa_addr->sa_family != AF_INET)
            continue;

        inet4 = (struct sockaddr_in *)addr->ifa_addr;
        if (inet_ntop(addr->ifa_addr->sa_family, (void *)&(inet4->sin_addr), buf, sizeof(buf)) == NULL) {
            perror("inet_ntop inet4");
            exit(1);
        }
        printf("%s %s\n", addr->ifa_name, buf);
    }

    freeifaddrs(addrs);

    exit(0);
}