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/*
* realpath.c -- canonicalize pathname by removing symlinks
* Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library Public License as published by
* the Free Software Foundation; either version 2, 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 Library Public License for more details.
*/
#include "system.h"
#ifndef STDC_HEADERS
extern int errno;
#endif
#define MAX_READLINKS 32
#ifdef __STDC__
char *realpath(const char *path, char resolved_path [])
#else
char *realpath(path, resolved_path)
const char *path;
char resolved_path [];
#endif
{
char copy_path[PATH_MAX];
char link_path[PATH_MAX];
char *new_path = resolved_path;
char *max_path;
int readlinks = 0;
int n;
/* Make a copy of the source path since we may need to modify it. */
strcpy(copy_path, path);
path = copy_path;
max_path = copy_path + PATH_MAX - 2;
/* If it's a relative pathname use getwd for starters. */
if (*path != '/') {
#ifdef HAVE_GETCWD
getcwd(new_path, PATH_MAX - 1);
#else
getwd(new_path);
#endif
new_path += strlen(new_path);
if (new_path[-1] != '/')
*new_path++ = '/';
}
else {
*new_path++ = '/';
path++;
}
/* Expand each slash-separated pathname component. */
while (*path != '\0') {
/* Ignore stray "/". */
if (*path == '/') {
path++;
continue;
}
if (*path == '.') {
/* Ignore ".". */
if (path[1] == '\0' || path[1] == '/') {
path++;
continue;
}
if (path[1] == '.') {
if (path[2] == '\0' || path[2] == '/') {
path += 2;
/* Ignore ".." at root. */
if (new_path == resolved_path + 1)
continue;
/* Handle ".." by backing up. */
while ((--new_path)[-1] != '/');
continue;
}
}
}
/* Safely copy the next pathname component. */
while (*path != '\0' && *path != '/') {
if (path > max_path) {
errno = ENAMETOOLONG;
return NULL;
}
*new_path++ = *path++;
}
#ifdef S_IFLNK
/* Protect against infinite loops. */
if (readlinks++ > MAX_READLINKS) {
errno = ELOOP;
return NULL;
}
/* See if latest pathname component is a symlink. */
*new_path = '\0';
n = readlink(resolved_path, link_path, PATH_MAX - 1);
if (n < 0) {
/* EINVAL means the file exists but isn't a symlink. */
if (errno != EINVAL)
return NULL;
}
else {
/* Note: readlink doesn't add the null byte. */
link_path[n] = '\0';
if (*link_path == '/')
/* Start over for an absolute symlink. */
new_path = resolved_path;
else
/* Otherwise back up over this component. */
while (*(--new_path) != '/');
/* Safe sex check. */
if (strlen(path) + n >= PATH_MAX) {
errno = ENAMETOOLONG;
return NULL;
}
/* Insert symlink contents into path. */
strcat(link_path, path);
strcpy(copy_path, link_path);
path = copy_path;
}
#endif /* S_IFLNK */
*new_path++ = '/';
}
/* Delete trailing slash but don't whomp a lone slash. */
if (new_path != resolved_path + 1 && new_path[-1] == '/')
new_path--;
/* Make sure it's null terminated. */
*new_path = '\0';
return resolved_path;
}
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