getaddrinfo

#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int (int argc, char **argv) {

    int status;
    struct addrinfo hints, *p;
    struct addrinfo *servinfo;
    char ipstr[INET_ADDRSTRLEN];
    

    memset(&hints, 0, sizeof hints);

    hints.ai_family   = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags    = AI_PASSIVE;

    //gethostname(hostname, 128);

    if ( argc < 2 ){
        printf("Usage: %s domain_name", argv[0]);
        exit(0);
    }

    if ((status = getaddrinfo(argv[1], NULL, &hints, &servinfo)) == -1) {
        fprintf(stderr, "getaddrinfo error: %sn", gai_strerror(status));
        exit(1);
    }

    for (p=servinfo; p!=NULL; p=p->ai_next) {
        struct in_addr  *addr;
        if (p->ai_family == AF_INET) {
            struct sockaddr_in *ipv = (struct sockaddr_in *)p->ai_addr;
            addr = &(ipv->sin_addr);
        }
        else {
            struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
            addr = (struct in_addr *) &(ipv6->sin6_addr);
        }
        inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
    }

    printf("Address: %sn", ipstr);
    freeaddrinfo(servinfo);

    return 0;
}