contrib/cvs-1.12/lib/xgethostname.c

   1 /* xgethostname.c -- return current hostname with unlimited length
   2
   3    Copyright (C) 1992, 1996, 2000, 2001, 2003, 2004, 2005 Free Software
   4    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 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 /* Specification.  */
  27 #include "xgethostname.h"
  28
  29 #include <stdlib.h>
  30 #include <errno.h>
  31
  32 #if HAVE_UNISTD_H
  33 # include <unistd.h>
  34 #endif
  35
  36 #include "xalloc.h"
  37
  38 #ifndef ENAMETOOLONG
  39 # define ENAMETOOLONG 0
  40 #endif
  41
  42 #ifndef INITIAL_HOSTNAME_LENGTH
  43 # define INITIAL_HOSTNAME_LENGTH 34
  44 #endif
  45
  46 /* Return the current hostname in malloc'd storage.
  47    If malloc fails, exit.
  48    Upon any other failure, return NULL and set errno.  */
  49 char *
  50 xgethostname (void)
  51 {
  52   char *hostname = NULL;
  53   size_t size = INITIAL_HOSTNAME_LENGTH;
  54
  55   while (1)
  56     {
  57       /* Use SIZE_1 here rather than SIZE to work around the bug in
  58          SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
  59          even when the name is as long as the supplied buffer.  */
  60       size_t size_1;
  61
  62       hostname = x2realloc (hostname, &size);
  63       size_1 = size - 1;
  64       hostname[size_1 - 1] = '\0';
  65       errno = 0;
  66
  67       if (gethostname (hostname, size_1) == 0)
  68         {
  69           if (! hostname[size_1 - 1])
  70             break;
  71         }
  72       else if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
  73                /* OSX/Darwin does this when the buffer is not large enough */
  74                && errno != ENOMEM)
  75         {
  76           int saved_errno = errno;
  77           free (hostname);
  78           errno = saved_errno;
  79           return NULL;
  80         }
  81     }
  82
  83   return hostname;
  84 }