hostname.c
2.11 KB
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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 2010-2012, 2014-2015 Free Software Foundation, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General
Public License along with this library. If not, see
<http://www.gnu.org/licenses/>. */
#if HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#ifndef MAXHOSTNAMELEN
# define MAXHOSTNAMELEN 64
#endif
int
mu_get_host_name (char **host)
{
char *hostname = NULL;
size_t size = 0;
char *p;
while (1)
{
if (size == 0)
{
size = MAXHOSTNAMELEN;
p = malloc (size);
}
else
{
size_t ns = size * 2;
if (ns < size)
{
free (hostname);
return ENOMEM;
}
size = ns;
p = realloc (hostname, size);
}
if (!p)
{
free (hostname);
return ENOMEM;
}
hostname = p;
hostname[size - 1] = 0;
if (gethostname (hostname, size - 1) == 0)
{
if (!hostname[size - 1])
break;
}
else if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
&& errno != ENOMEM)
{
int rc = errno;
free (hostname);
return rc;
}
}
/* Try to return fully qualified host name */
if (!strchr (hostname, '.'))
{
struct hostent *hp = gethostbyname (hostname);
if (hp)
{
size_t len = strlen (hp->h_name);
if (size < len + 1)
{
p = realloc (hostname, len + 1);
if (!p)
{
free (hostname);
return ENOMEM;
}
hostname = p;
}
strcpy (hostname, hp->h_name);
}
}
*host = hostname;
return 0;
}