gistfile1.txt

#define _DEFAULT_SOURCE
#include <netdb.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>

/*
$ gcc -o hostname hostname.c && ./hostname
gethostbyname: No address associated with name
getaddrinfo: 127.0.0.1
*/

int main(int argc, char *argv[])
{
    char *hostname;
    struct hostent *h;

    struct addrinfo hints;
    struct addrinfo *result, *rp;
    int r;
    char buf[NI_MAXHOST];

    hostname = "127.0.0.1\r\nspam";

    h = gethostbyname(hostname);
    if (!h) {
        const char *e;
        e = hstrerror(h_errno);
        printf("gethostbyname: %s\n", e);
    } else {
        printf("gethostbyname h_name: %s\n", h->h_name);
    }

    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;
    hints.ai_protocol = 0;
    hints.ai_canonname = NULL;
    hints.ai_addr = NULL;
    hints.ai_next = NULL;

    r = getaddrinfo(hostname, NULL, &hints, &result);
    if (r != 0) {
          fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(r));
          exit(EXIT_FAILURE);
    }

    for (rp = result; rp != NULL; rp = rp->ai_next) {
        r = getnameinfo(rp->ai_addr, sizeof(struct sockaddr_in),
                        buf, sizeof(buf),
                        NULL, 0, NI_NUMERICHOST);
        if (r != 0) {
            fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(r));
            exit(EXIT_FAILURE);
        }
        printf("getaddrinfo: %s\n", buf);
    }
    freeaddrinfo(result);

    exit(EXIT_SUCCESS);
}