gl/xgethostname.c

   1 /* xgethostname.c -- return current hostname with unlimited length
   2
   3    Copyright (C) 1992, 1996, 2000, 2001, 2003, 2004, 2005, 2006 Free
   4    Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 /* written by Jim Meyering */
  21
  22 #include <config.h>
  23
  24 /* Specification.  */
  25 #include "xgethostname.h"
  26
  27 #include <stdlib.h>
  28 #include <errno.h>
  29 #include <unistd.h>
  30
  31 #include "xalloc.h"
  32
  33 #ifndef ENAMETOOLONG
  34 # define ENAMETOOLONG 0
  35 #endif
  36
  37 #ifndef INITIAL_HOSTNAME_LENGTH
  38 # define INITIAL_HOSTNAME_LENGTH 34
  39 #endif
  40
  41 /* Return the current hostname in malloc'd storage.
  42    If malloc fails, exit.
  43    Upon any other failure, return NULL and set errno.  */
  44 char *
  45 xgethostname (void)
  46 {
  47   char *hostname = NULL;
  48   size_t size = INITIAL_HOSTNAME_LENGTH;
  49
  50   while (1)
  51     {
  52       /* Use SIZE_1 here rather than SIZE to work around the bug in
  53          SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
  54          even when the name is as long as the supplied buffer.  */
  55       size_t size_1;
  56
  57       hostname = x2realloc (hostname, &size);
  58       size_1 = size - 1;
  59       hostname[size_1 - 1] = '\0';
  60       errno = 0;
  61
  62       if (gethostname (hostname, size_1) == 0)
  63         {
  64           if (! hostname[size_1 - 1])
  65             break;
  66         }
  67       else if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
  68                /* OSX/Darwin does this when the buffer is not large enough */
  69                && errno != ENOMEM)
  70         {
  71           int saved_errno = errno;
  72           free (hostname);
  73           errno = saved_errno;
  74           return NULL;
  75         }
  76     }
  77
  78   return hostname;
  79 }