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/* xgethostname.c -- return current hostname with unlimited length
Copyright (C) 1992, 1996, 2000-2001, 2003-2006, 2009-2020 Free Software
Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
/* Specification. */
#include "xgethostname.h"
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include "xalloc.h"
#ifndef INITIAL_HOSTNAME_LENGTH
# define INITIAL_HOSTNAME_LENGTH 34
#endif
/* Return the current hostname in malloc'd storage.
If malloc fails, exit.
Upon any other failure, return NULL and set errno. */
char *
xgethostname (void)
{
char *hostname = NULL;
size_t size = INITIAL_HOSTNAME_LENGTH;
while (1)
{
/* Use SIZE_1 here rather than SIZE to work around the bug in
SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
even when the name is as long as the supplied buffer. */
size_t size_1;
hostname = x2realloc (hostname, &size);
size_1 = size - 1;
hostname[size_1 - 1] = '\0';
errno = 0;
if (gethostname (hostname, size_1) == 0)
{
if (! hostname[size_1 - 1])
break;
}
else if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
/* OSX/Darwin does this when the buffer is not large enough */
&& errno != ENOMEM)
{
int saved_errno = errno;
free (hostname);
errno = saved_errno;
return NULL;
}
}
/* Shrink HOSTNAME before returning it. */
{
size_t actual_size = strlen (hostname) + 1;
if (actual_size < size)
{
char *shrinked_hostname = realloc (hostname, actual_size);
if (shrinked_hostname != NULL)
hostname = shrinked_hostname;
}
}
return hostname;
}
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