1/* xgethostname.c -- return current hostname with unlimited length
2
3   Copyright (C) 1992, 1996, 2000-2001, 2003-2006, 2009-2010 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 3 of the License, or
9   (at your option) 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, see <http://www.gnu.org/licenses/>.  */
18
19/* written by Jim Meyering */
20
21#include <config.h>
22
23/* Specification.  */
24#include "xgethostname.h"
25
26#include <stdlib.h>
27#include <errno.h>
28#include <unistd.h>
29
30#include "xalloc.h"
31
32#ifndef INITIAL_HOSTNAME_LENGTH
33# define INITIAL_HOSTNAME_LENGTH 34
34#endif
35
36/* Return the current hostname in malloc'd storage.
37   If malloc fails, exit.
38   Upon any other failure, return NULL and set errno.  */
39char *
40xgethostname (void)
41{
42  char *hostname = NULL;
43  size_t size = INITIAL_HOSTNAME_LENGTH;
44
45  while (1)
46    {
47      /* Use SIZE_1 here rather than SIZE to work around the bug in
48         SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
49         even when the name is as long as the supplied buffer.  */
50      size_t size_1;
51
52      hostname = x2realloc (hostname, &size);
53      size_1 = size - 1;
54      hostname[size_1 - 1] = '\0';
55      errno = 0;
56
57      if (gethostname (hostname, size_1) == 0)
58        {
59          if (! hostname[size_1 - 1])
60            break;
61        }
62      else if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
63               /* OSX/Darwin does this when the buffer is not large enough */
64               && errno != ENOMEM)
65        {
66          int saved_errno = errno;
67          free (hostname);
68          errno = saved_errno;
69          return NULL;
70        }
71    }
72
73  return hostname;
74}
75