lib/xgethostname.c

   1 /* xgethostname.c -- return current hostname with unlimited length
   2    Copyright (C) 1992, 1996 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 #include <sys/types.h>
  25
  26 #include <errno.h>
  27 #ifndef errno
  28 extern int errno;
  29 #endif
  30
  31 #include "error.h"
  32
  33 #ifndef EXIT_FAILURE
  34 # define EXIT_FAILURE 1
  35 #endif
  36
  37 int gethostname ();
  38 char *xmalloc ();
  39 char *xrealloc ();
  40
  41 #ifndef INITIAL_HOSTNAME_LENGTH
  42 # define INITIAL_HOSTNAME_LENGTH 34
  43 #endif
  44
  45 char *
  46 xgethostname ()
  47 {
  48   char *hostname;
  49   size_t size;
  50   int err;
  51
  52   size = INITIAL_HOSTNAME_LENGTH;
  53   hostname = xmalloc (size);
  54   while (1)
  55     {
  56       /* Use size - 2 here rather than size - 1 to work around the bug
  57          in SunOS5.5's gethostname whereby it NUL-terminates HOSTNAME
  58          even when the name is longer than the supplied buffer.  */
  59       int k = size - 2;
  60
  61       errno = 0;
  62       hostname[k] = '\0';
  63       err = gethostname (hostname, size);
  64       if (err == 0 && hostname[k] == '\0')
  65         break;
  66 #ifdef ENAMETOOLONG
  67       else if (err != 0 && errno != ENAMETOOLONG && errno != 0)
  68         error (EXIT_FAILURE, errno, "gethostname");
  69 #endif
  70       size *= 2;
  71       hostname = xrealloc (hostname, size);
  72     }
  73
  74   return hostname;
  75 }