$ cat ex.c
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>

int main(int argc, char *argv[]) {
  if (argc < 2) {
    printf("Use as  %s hostname", argv[0]);
    return EXIT_FAILURE;
  }

  struct hostent *hp = gethostbyname(argv[1]);

  if (hp == NULL) {
    printf("gethostbyname() failed\n");
  } else {
    printf("%s = ", hp->h_name);
    int i = 0;
    while (hp->h_addr_list[i] != NULL) {
      printf("%s ", inet_ntoa(*(struct in_addr *)(hp->h_addr_list[i])));
      i++;
    }
    printf("\n");
  }
}