symlink.c
2.45 KB
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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 1999, 2000, 2001, 2002, 2003, 2005, 2006, 2007, 2009,
2010 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 <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <mailutils/types.h>
#include <mailutils/util.h>
/* The result of readlink() may be a path relative to that link,
* qualify it if necessary.
*/
static void
mu_qualify_link (const char *path, const char *link, char *qualified)
{
const char *lb = NULL;
size_t len;
/* link is full path */
if (*link == '/')
{
mu_cpystr (qualified, link, _POSIX_PATH_MAX);
return;
}
if ((lb = strrchr (path, '/')) == NULL)
{
/* no path in link */
mu_cpystr (qualified, link, _POSIX_PATH_MAX);
return;
}
len = lb - path + 1;
memcpy (qualified, path, len);
mu_cpystr (qualified + len, link, _POSIX_PATH_MAX - len);
}
#ifndef _POSIX_SYMLOOP_MAX
# define _POSIX_SYMLOOP_MAX 255
#endif
int
mu_unroll_symlink (char *out, size_t outsz, const char *in)
{
char path[_POSIX_PATH_MAX];
int symloops = 0;
while (symloops++ < _POSIX_SYMLOOP_MAX)
{
struct stat s;
char link[_POSIX_PATH_MAX];
char qualified[_POSIX_PATH_MAX];
int len;
if (lstat (in, &s) == -1)
return errno;
if (!S_ISLNK (s.st_mode))
{
mu_cpystr (path, in, sizeof (path));
break;
}
if ((len = readlink (in, link, sizeof (link))) == -1)
return errno;
link[(len >= sizeof (link)) ? (sizeof (link) - 1) : len] = '\0';
mu_qualify_link (in, link, qualified);
mu_cpystr (path, qualified, sizeof (path));
in = path;
}
mu_cpystr (out, path, outsz);
return 0;
}