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1 /*
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2 * realpath.c -- canonicalize pathname by removing symlinks
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3 * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
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4 *
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5
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6 This file is part of XEmacs.
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7
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8 XEmacs is free software; you can redistribute it and/or modify it
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9 under the terms of the GNU General Public License as published by the
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10 Free Software Foundation; either version 2, or (at your option) any
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11 later version.
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12
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13 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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16 for more details.
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17
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18 You should have received a copy of the GNU General Public License
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19 along with XEmacs; see the file COPYING. If not, write to
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20 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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21 Boston, MA 02111-1307, USA. */
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22
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23 /* Synched up with: Not in FSF. */
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24
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25 #ifdef HAVE_CONFIG_H
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26 #include <config.h>
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27 #endif
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28
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29 #include <sys/types.h>
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30 #if defined(HAVE_UNISTD_H) || defined(STDC_HEADERS)
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31 #include <unistd.h>
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32 #endif
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33 #include <stdio.h>
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34 #include <string.h>
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35 #ifdef _POSIX_VERSION
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36 #include <limits.h> /* for PATH_MAX */
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37 #else
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38 #include <sys/param.h> /* for MAXPATHLEN */
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39 #endif
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40 #include <errno.h>
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41 #ifndef STDC_HEADERS
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42 extern int errno;
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43 #endif
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44
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288
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45 #ifdef WINDOWSNT
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46 #include <direct.h>
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47 #endif
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48
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0
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49 #include <sys/stat.h> /* for S_IFLNK */
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50
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51 #ifndef PATH_MAX
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52 #ifdef _POSIX_VERSION
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53 #define PATH_MAX _POSIX_PATH_MAX
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54 #else
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55 #ifdef MAXPATHLEN
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56 #define PATH_MAX MAXPATHLEN
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57 #else
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58 #define PATH_MAX 1024
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59 #endif
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60 #endif
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61 #endif
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62
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63 #define MAX_READLINKS 32
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64
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65 #ifdef __STDC__
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284
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66 char *xrealpath(const char *path, char resolved_path [])
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67 #else
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284
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68 char *xrealpath(path, resolved_path)
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205
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69 const char *path;
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70 char resolved_path [];
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71 #endif
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72 {
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73 char copy_path[PATH_MAX];
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74 char *new_path = resolved_path;
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75 char *max_path;
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76 int readlinks = 0;
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288
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77 #ifdef S_IFLNK
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78 char link_path[PATH_MAX];
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0
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79 int n;
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288
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80 #endif
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0
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81
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82 /* Make a copy of the source path since we may need to modify it. */
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83 strcpy(copy_path, path);
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84 path = copy_path;
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85 max_path = copy_path + PATH_MAX - 2;
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195
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86 #ifdef WINDOWSNT
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87 /*
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88 ** In NT we have two different cases: (1) the path name begins
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89 ** with a drive letter, e.g., "C:"; and (2) the path name begins
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90 ** with just a slash, which roots to the current drive. In the
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91 ** first case we are going to leave things alone, in the second
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92 ** case we will prepend the drive letter to the given path.
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93 ** Note: So far in testing, I'm only seeing case #1, even though
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94 ** I've tried to get the other cases to happen.
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95 ** August Hill, 31 Aug 1997.
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96 **
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97 ** Check for a driver letter...C:/...
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98 */
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99 if (*(path + 1) == ':')
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100 {
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101 strncpy(new_path, path, 3);
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102 new_path += 3;
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103 path += 3;
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104 }
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105
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106 /*
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107 ** No drive letter, but a beginning slash? Prepend the drive
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108 ** letter...
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109 */
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110 else if (*path == '/')
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111 {
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112 getcwd(new_path, PATH_MAX - 1);
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113 new_path += 3;
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114 path++;
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115 }
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116
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117 /*
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118 ** Just a path name, prepend the current directory
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119 */
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120 else
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121 {
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122 getcwd(new_path, PATH_MAX - 1);
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123 new_path += strlen(new_path);
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124 if (new_path[-1] != '/')
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125 *new_path++ = '/';
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126 }
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127
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128 #else
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0
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129 /* If it's a relative pathname use getwd for starters. */
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130 if (*path != '/')
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131 {
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132 #ifdef HAVE_GETCWD
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133 getcwd(new_path, PATH_MAX - 1);
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134 #else
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135 getwd(new_path);
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136 #endif
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137 new_path += strlen(new_path);
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138 if (new_path[-1] != '/')
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139 *new_path++ = '/';
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140 }
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141 else
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142 {
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143 *new_path++ = '/';
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144 path++;
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145 }
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195
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146 #endif
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0
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147 /* Expand each slash-separated pathname component. */
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148 while (*path != '\0')
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149 {
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150 /* Ignore stray "/". */
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151 if (*path == '/')
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152 {
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153 path++;
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154 continue;
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155 }
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156
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157 if (*path == '.')
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158 {
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159 /* Ignore ".". */
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160 if (path[1] == '\0' || path[1] == '/')
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161 {
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162 path++;
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163 continue;
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164 }
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165
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166 if (path[1] == '.')
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167 {
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168 if (path[2] == '\0' || path[2] == '/')
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169 {
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170 path += 2;
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171
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172 /* Ignore ".." at root. */
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173 if (new_path == resolved_path + 1)
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174 continue;
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175
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176 /* Handle ".." by backing up. */
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177 while ((--new_path)[-1] != '/')
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178 ;
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179 continue;
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180 }
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181 }
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182 }
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183
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184 /* Safely copy the next pathname component. */
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185 while (*path != '\0' && *path != '/')
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186 {
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187 if (path > max_path)
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188 {
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189 errno = ENAMETOOLONG;
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190 return NULL;
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191 }
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192 *new_path++ = *path++;
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193 }
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194
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195 #ifdef S_IFLNK
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196 /* See if latest pathname component is a symlink. */
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197 *new_path = '\0';
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198 n = readlink(resolved_path, link_path, PATH_MAX - 1);
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199
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200 if (n < 0)
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201 {
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202 /* EINVAL means the file exists but isn't a symlink. */
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203 if (errno != EINVAL)
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204 return NULL;
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205 }
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206 else
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207 {
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208 /* Protect against infinite loops. */
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209 if (readlinks++ > MAX_READLINKS)
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210 {
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211 errno = ELOOP;
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212 return NULL;
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213 }
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214
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215 /* Note: readlink doesn't add the null byte. */
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216 link_path[n] = '\0';
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217
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218 if (*link_path == '/')
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219 /* Start over for an absolute symlink. */
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220 new_path = resolved_path;
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221 else
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222 /* Otherwise back up over this component. */
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223 while (*(--new_path) != '/')
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224 ;
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225
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226 /* Safe sex check. */
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227 if (strlen(path) + n >= PATH_MAX)
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228 {
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229 errno = ENAMETOOLONG;
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230 return NULL;
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231 }
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232
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233 /* Insert symlink contents into path. */
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234 strcat(link_path, path);
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235 strcpy(copy_path, link_path);
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236 path = copy_path;
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237 }
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238 #endif /* S_IFLNK */
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239 *new_path++ = '/';
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240 }
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241
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242 /* Delete trailing slash but don't whomp a lone slash. */
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243 if (new_path != resolved_path + 1 && new_path[-1] == '/')
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244 new_path--;
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245
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246 /* Make sure it's null terminated. */
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247 *new_path = '\0';
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248 return resolved_path;
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249 }
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