Wait until getaddrinfo returns an IP address

test.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <time.h>
#include <errno.h>

int msleep(long msec)
{
  struct timespec ts;
  int res;

  if (msec < 0)
  {
    errno = EINVAL;
    return -1;
  }

  ts.tv_sec = msec / 1000;
  ts.tv_nsec = (msec % 1000) *1000000;

  do {
    res = nanosleep(&ts, &ts);
  } while (res && errno == EINTR);

  return res;
}

int main(int argc, char *argv[])
{
  int error, max_wait_ms, sleep_ms;
  struct addrinfo hints, *res;
  int errcode;
  char addrstr[100];
  void *ptr;

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = PF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags |= AI_CANONNAME;

  if (argc != 2)
  {
    fprintf(stderr, "missing command line parameter: %s\n", "test<hostname>");
    return 1;
  }
  max_wait_ms = 60000;
  sleep_ms = 500;
  while (max_wait_ms > 0)
  {

    /*resolve the domain name into a list of addresses */
    error = getaddrinfo(argv[1], NULL, NULL, &res);
    if (error != 0)
    {
      if (error == EAI_SYSTEM)
      {
        perror("getaddrinfo");
      }
      else
      {
        fprintf(stderr, "error in getaddrinfo: %s\n", gai_strerror(error));
      }
      /*exit(EXIT_FAILURE); */
      /*return 0; */
      max_wait_ms -= sleep_ms;
      msleep(sleep_ms);
    }
    else
    {
      while (res)
      {
        inet_ntop(res->ai_family, res->ai_addr->sa_data, addrstr, 100);

        switch (res->ai_family)
        {
          case AF_INET:
            ptr = &((struct sockaddr_in *) res->ai_addr)->sin_addr;
            break;
          case AF_INET6:
            ptr = &((struct sockaddr_in6 *) res->ai_addr)->sin6_addr;
            break;
        }
        inet_ntop(res->ai_family, ptr, addrstr, 100);
        printf("IPv%d address: %s (%s)\n", res->ai_family == PF_INET6 ? 6 : 4,
          addrstr, res->ai_canonname);
        res = res->ai_next;
      }
      break;
    }
  }
  return 0;
}