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/* $OpenBSD: realpath.c,v 1.21 2016/08/28 04:08:59 guenther Exp $ */ |
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/* |
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* Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru> |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* 3. The names of the authors may not be used to endorse or promote |
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* products derived from this software without specific prior written |
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* permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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*/ |
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#include <errno.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include <unistd.h> |
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#include <limits.h> |
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/* A slightly modified copy of this file exists in libexec/ld.so */ |
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/* |
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* char *realpath(const char *path, char resolved[PATH_MAX]); |
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* |
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* Find the real name of path, by removing all ".", ".." and symlink |
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* components. Returns (resolved) on success, or (NULL) on failure, |
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* in which case the path which caused trouble is left in (resolved). |
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*/ |
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char * |
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realpath(const char *path, char *resolved) |
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{ |
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char *p, *q, *s; |
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size_t left_len, resolved_len; |
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unsigned symlinks; |
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int serrno, slen, mem_allocated; |
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char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; |
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if (path[0] == '\0') { |
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errno = ENOENT; |
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return (NULL); |
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} |
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serrno = errno; |
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if (resolved == NULL) { |
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resolved = malloc(PATH_MAX); |
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if (resolved == NULL) |
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return (NULL); |
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mem_allocated = 1; |
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} else |
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mem_allocated = 0; |
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symlinks = 0; |
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if (path[0] == '/') { |
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resolved[0] = '/'; |
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resolved[1] = '\0'; |
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if (path[1] == '\0') |
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return (resolved); |
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resolved_len = 1; |
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left_len = strlcpy(left, path + 1, sizeof(left)); |
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} else { |
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if (getcwd(resolved, PATH_MAX) == NULL) { |
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if (mem_allocated) |
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free(resolved); |
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else |
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strlcpy(resolved, ".", PATH_MAX); |
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return (NULL); |
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} |
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resolved_len = strlen(resolved); |
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left_len = strlcpy(left, path, sizeof(left)); |
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} |
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if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { |
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errno = ENAMETOOLONG; |
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goto err; |
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} |
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/* |
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* Iterate over path components in `left'. |
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*/ |
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while (left_len != 0) { |
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/* |
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* Extract the next path component and adjust `left' |
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* and its length. |
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*/ |
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p = strchr(left, '/'); |
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s = p ? p : left + left_len; |
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if (s - left >= sizeof(next_token)) { |
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errno = ENAMETOOLONG; |
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goto err; |
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} |
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memcpy(next_token, left, s - left); |
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next_token[s - left] = '\0'; |
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left_len -= s - left; |
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if (p != NULL) |
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memmove(left, s + 1, left_len + 1); |
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if (resolved[resolved_len - 1] != '/') { |
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if (resolved_len + 1 >= PATH_MAX) { |
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errno = ENAMETOOLONG; |
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goto err; |
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} |
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resolved[resolved_len++] = '/'; |
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resolved[resolved_len] = '\0'; |
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} |
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if (next_token[0] == '\0') |
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continue; |
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else if (strcmp(next_token, ".") == 0) |
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continue; |
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else if (strcmp(next_token, "..") == 0) { |
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/* |
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* Strip the last path component except when we have |
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* single "/" |
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*/ |
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if (resolved_len > 1) { |
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resolved[resolved_len - 1] = '\0'; |
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q = strrchr(resolved, '/') + 1; |
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*q = '\0'; |
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resolved_len = q - resolved; |
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} |
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continue; |
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} |
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/* |
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* Append the next path component and lstat() it. If |
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* lstat() fails we still can return successfully if |
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* there are no more path components left. |
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*/ |
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resolved_len = strlcat(resolved, next_token, PATH_MAX); |
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if (resolved_len >= PATH_MAX) { |
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errno = ENAMETOOLONG; |
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goto err; |
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} |
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slen = readlink(resolved, symlink, sizeof(symlink) - 1); |
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if (slen < 0) { |
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switch (errno) { |
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case EINVAL: |
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/* not a symlink, continue to next component */ |
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continue; |
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case ENOENT: |
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if (p == NULL) { |
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errno = serrno; |
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return (resolved); |
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} |
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/* FALLTHROUGH */ |
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default: |
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goto err; |
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} |
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} else { |
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if (symlinks++ > SYMLOOP_MAX) { |
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errno = ELOOP; |
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goto err; |
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} |
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symlink[slen] = '\0'; |
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if (symlink[0] == '/') { |
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resolved[1] = 0; |
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resolved_len = 1; |
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} else if (resolved_len > 1) { |
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/* Strip the last path component. */ |
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resolved[resolved_len - 1] = '\0'; |
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q = strrchr(resolved, '/') + 1; |
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*q = '\0'; |
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resolved_len = q - resolved; |
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} |
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/* |
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* If there are any path components left, then |
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* append them to symlink. The result is placed |
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* in `left'. |
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*/ |
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if (p != NULL) { |
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if (symlink[slen - 1] != '/') { |
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if (slen + 1 >= sizeof(symlink)) { |
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errno = ENAMETOOLONG; |
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goto err; |
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} |
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symlink[slen] = '/'; |
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symlink[slen + 1] = 0; |
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} |
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left_len = strlcat(symlink, left, sizeof(symlink)); |
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if (left_len >= sizeof(symlink)) { |
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errno = ENAMETOOLONG; |
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goto err; |
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} |
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} |
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left_len = strlcpy(left, symlink, sizeof(left)); |
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} |
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} |
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/* |
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* Remove trailing slash except when the resolved pathname |
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* is a single "/". |
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*/ |
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if (resolved_len > 1 && resolved[resolved_len - 1] == '/') |
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resolved[resolved_len - 1] = '\0'; |
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return (resolved); |
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err: |
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if (mem_allocated) |
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free(resolved); |
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return (NULL); |
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} |