diplodocus.org Git - nmh/blob - test/getfqdn.c

   1 /*
   2  * getfqdn.c - Print the FQDN of a host, default to localhost.
   3  *
   4  * This code is Copyright (c) 2012, by the authors of nmh.  See the
   5  * COPYRIGHT file in the root directory of the nmh distribution for
   6  * complete copyright information.
   7  */
   8
   9 #include <netdb.h>   /* for getaddrinfo */
  10 #include <sys/socket.h>
  11 #include <sys/types.h>
  12 #include <unistd.h>  /* for gethostname */
  13 #include <limits.h>  /* for _POSIX_HOST_NAME_MAX */
  14 #include <string.h>  /* for memset */
  15 #include <stdio.h>
  16
  17
  18 int
  19 main(int argc, char *argv[])
  20 {
  21   char buf[_POSIX_HOST_NAME_MAX + 1];
  22   const char *hostname = buf;
  23   struct addrinfo hints, *res;
  24   int status = 0;
  25
  26   /* Borrowed the important code below from LocalName() in sbr/mts.c. */
  27
  28   if (argc < 2) {
  29     /* First get our local name. */
  30     status = gethostname(buf, sizeof buf);
  31   } else if (argc == 2) {
  32     hostname = argv[1];
  33   } else if (argc > 2) {
  34     fprintf (stderr, "usage: %s [hostname]\n", argv[0]);
  35     return 1;
  36   }
  37
  38   if (status == 0) {
  39     /* Now fully qualify the hostname. */
  40     memset(&hints, 0, sizeof hints);
  41     hints.ai_flags = AI_CANONNAME;
  42     hints.ai_family = AF_UNSPEC;
  43
  44     if ((status = getaddrinfo(hostname, NULL, &hints, &res)) == 0) {
  45       printf ("%s\n", res->ai_canonname);
  46       freeaddrinfo(res);
  47     }
  48   }
  49
  50   return status;
  51 }