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

   1 /* getcanon.c - Print the canonical name of a host, default to localhost.
   2  *
   3  * This code is Copyright (c) 2012, by the authors of nmh.  See the
   4  * COPYRIGHT file in the root directory of the nmh distribution for
   5  * complete copyright information.
   6  */
   7
   8 #include <netdb.h>
   9 #include <sys/socket.h>
  10 #include <sys/types.h>
  11 #include <unistd.h>
  12 #include <limits.h>
  13 #include <string.h>
  14 #include <stdio.h>
  15 #include <errno.h>
  16
  17
  18 int
  19 main(int argc, char *argv[])
  20 {
  21   char buf[_POSIX_HOST_NAME_MAX + 1];
  22   const char *hostname;
  23   struct addrinfo hints, *res;
  24
  25   /* Borrowed the important code below from LocalName() in sbr/mts.c. */
  26
  27   if (argc > 2) {
  28     fprintf(stderr, "usage: %s [hostname]\n", argv[0]);
  29     return 1;
  30   }
  31   if (argc == 2)
  32     hostname = argv[1];
  33   else {
  34     /* First get our local name. */
  35     if (gethostname(buf, sizeof buf)) {
  36         fprintf(stderr, "gethostname() failed: %s\n", strerror(errno));
  37         return 1;
  38     }
  39     hostname = buf;
  40   }
  41
  42   /* Now fully qualify the hostname. */
  43   memset(&hints, 0, sizeof hints);
  44   hints.ai_flags = AI_CANONNAME;
  45   hints.ai_family = AF_UNSPEC;
  46
  47   if (getaddrinfo(hostname, NULL, &hints, &res)) {
  48     puts(hostname);
  49     return 1;
  50   }
  51   puts(res->ai_canonname);
  52
  53   return 0;
  54 }