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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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45 #include <sys/stat.h> /* for S_IFLNK */
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46
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47 #ifndef PATH_MAX
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48 #ifdef _POSIX_VERSION
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49 #define PATH_MAX _POSIX_PATH_MAX
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50 #else
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51 #ifdef MAXPATHLEN
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52 #define PATH_MAX MAXPATHLEN
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53 #else
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54 #define PATH_MAX 1024
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55 #endif
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56 #endif
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57 #endif
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58
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59 #define MAX_READLINKS 32
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60
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61 #ifdef __STDC__
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205
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62 char *realpath(const char *path, char resolved_path [])
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0
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63 #else
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64 char *realpath(path, resolved_path)
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205
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65 const char *path;
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0
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66 char resolved_path [];
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67 #endif
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68 {
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69 char copy_path[PATH_MAX];
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70 char link_path[PATH_MAX];
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71 char *new_path = resolved_path;
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72 char *max_path;
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73 int readlinks = 0;
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74 int n;
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75
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76 /* Make a copy of the source path since we may need to modify it. */
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77 strcpy(copy_path, path);
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78 path = copy_path;
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79 max_path = copy_path + PATH_MAX - 2;
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195
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80 #ifdef WINDOWSNT
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81 /*
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82 ** In NT we have two different cases: (1) the path name begins
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83 ** with a drive letter, e.g., "C:"; and (2) the path name begins
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84 ** with just a slash, which roots to the current drive. In the
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85 ** first case we are going to leave things alone, in the second
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86 ** case we will prepend the drive letter to the given path.
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87 ** Note: So far in testing, I'm only seeing case #1, even though
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88 ** I've tried to get the other cases to happen.
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89 ** August Hill, 31 Aug 1997.
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90 **
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91 ** Check for a driver letter...C:/...
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92 */
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93 if (*(path + 1) == ':')
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94 {
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95 strncpy(new_path, path, 3);
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96 new_path += 3;
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97 path += 3;
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98 }
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99
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100 /*
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101 ** No drive letter, but a beginning slash? Prepend the drive
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102 ** letter...
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103 */
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104 else if (*path == '/')
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105 {
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106 getcwd(new_path, PATH_MAX - 1);
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107 new_path += 3;
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108 path++;
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109 }
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110
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111 /*
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112 ** Just a path name, prepend the current directory
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113 */
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114 else
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115 {
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116 getcwd(new_path, PATH_MAX - 1);
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117 new_path += strlen(new_path);
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118 if (new_path[-1] != '/')
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119 *new_path++ = '/';
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120 }
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121
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122 #else
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0
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123 /* If it's a relative pathname use getwd for starters. */
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124 if (*path != '/')
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125 {
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126 #ifdef HAVE_GETCWD
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127 getcwd(new_path, PATH_MAX - 1);
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128 #else
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129 getwd(new_path);
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130 #endif
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131 new_path += strlen(new_path);
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132 if (new_path[-1] != '/')
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133 *new_path++ = '/';
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134 }
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135 else
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136 {
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137 *new_path++ = '/';
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138 path++;
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139 }
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195
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140 #endif
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0
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141 /* Expand each slash-separated pathname component. */
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142 while (*path != '\0')
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143 {
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144 /* Ignore stray "/". */
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145 if (*path == '/')
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146 {
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147 path++;
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148 continue;
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149 }
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150
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151 if (*path == '.')
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152 {
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153 /* Ignore ".". */
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154 if (path[1] == '\0' || path[1] == '/')
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155 {
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156 path++;
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157 continue;
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158 }
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159
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160 if (path[1] == '.')
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161 {
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162 if (path[2] == '\0' || path[2] == '/')
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163 {
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164 path += 2;
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165
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166 /* Ignore ".." at root. */
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167 if (new_path == resolved_path + 1)
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168 continue;
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169
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170 /* Handle ".." by backing up. */
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171 while ((--new_path)[-1] != '/')
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172 ;
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173 continue;
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174 }
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175 }
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176 }
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177
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178 /* Safely copy the next pathname component. */
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179 while (*path != '\0' && *path != '/')
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180 {
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181 if (path > max_path)
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182 {
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183 errno = ENAMETOOLONG;
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184 return NULL;
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185 }
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186 *new_path++ = *path++;
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187 }
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188
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189 #ifdef S_IFLNK
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190 /* See if latest pathname component is a symlink. */
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191 *new_path = '\0';
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192 n = readlink(resolved_path, link_path, PATH_MAX - 1);
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193
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194 if (n < 0)
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195 {
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196 /* EINVAL means the file exists but isn't a symlink. */
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197 if (errno != EINVAL)
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198 return NULL;
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199 }
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200 else
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201 {
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202 /* Protect against infinite loops. */
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203 if (readlinks++ > MAX_READLINKS)
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204 {
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205 errno = ELOOP;
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206 return NULL;
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207 }
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208
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209 /* Note: readlink doesn't add the null byte. */
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210 link_path[n] = '\0';
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211
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212 if (*link_path == '/')
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213 /* Start over for an absolute symlink. */
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214 new_path = resolved_path;
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215 else
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216 /* Otherwise back up over this component. */
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217 while (*(--new_path) != '/')
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218 ;
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219
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220 /* Safe sex check. */
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221 if (strlen(path) + n >= PATH_MAX)
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222 {
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223 errno = ENAMETOOLONG;
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224 return NULL;
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225 }
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226
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227 /* Insert symlink contents into path. */
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228 strcat(link_path, path);
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229 strcpy(copy_path, link_path);
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230 path = copy_path;
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231 }
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232 #endif /* S_IFLNK */
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233 *new_path++ = '/';
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234 }
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235
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236 /* Delete trailing slash but don't whomp a lone slash. */
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237 if (new_path != resolved_path + 1 && new_path[-1] == '/')
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238 new_path--;
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239
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240 /* Make sure it's null terminated. */
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241 *new_path = '\0';
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242 return resolved_path;
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243 }
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