lib/xgethostname.c

   1 /* xgethostname.c -- return current hostname with unlimited length
   2    Copyright (C) 1992, 1996, 2000, 2001, 2003 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* written by Jim Meyering */
  19
  20 #ifdef HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 /* Specification.  */
  25 #include "xgethostname.h"
  26
  27 #include <stdlib.h>
  28 #include <sys/types.h>
  29
  30 #include <errno.h>
  31 #ifndef errno
  32 extern int errno;
  33 #endif
  34
  35 #include "error.h"
  36 #include "exit.h"
  37 #include "xalloc.h"
  38
  39 #ifndef ENAMETOOLONG
  40 # define ENAMETOOLONG 9999
  41 #endif
  42
  43 int gethostname ();
  44
  45 #ifndef INITIAL_HOSTNAME_LENGTH
  46 # define INITIAL_HOSTNAME_LENGTH 34
  47 #endif
  48
  49 /* Return the current hostname in malloc'd storage.
  50    If malloc fails, exit.
  51    Upon any other failure, return NULL.  */
  52 char *
  53 xgethostname (void)
  54 {
  55   char *hostname;
  56   size_t size;
  57
  58   size = INITIAL_HOSTNAME_LENGTH;
  59   /* Use size + 1 here rather than size to work around the bug
  60      in SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
  61      even when the name is longer than the supplied buffer.  */
  62   hostname = xmalloc (size + 1);
  63   while (1)
  64     {
  65       int k = size - 1;
  66       int err;
  67
  68       errno = 0;
  69       hostname[k] = '\0';
  70       err = gethostname (hostname, size);
  71       if (err >= 0 && hostname[k] == '\0')
  72         break;
  73       else if (err < 0 && errno != ENAMETOOLONG && errno != 0)
  74         {
  75           int saved_errno = errno;
  76           free (hostname);
  77           errno = saved_errno;
  78           return NULL;
  79         }
  80       size *= 2;
  81       hostname = xrealloc (hostname, size + 1);
  82     }
  83
  84   return hostname;
  85 }