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428
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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 #include <config.h>
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26
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27 #include <sys/types.h>
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28 #include <stdio.h>
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29 #include <string.h>
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30 #include <errno.h>
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31 #ifdef HAVE_UNISTD_H
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32 #include <unistd.h>
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33 #endif
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34 #ifdef _POSIX_VERSION
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35 #include <limits.h> /* for PATH_MAX */
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36 #else
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37 #include <sys/param.h> /* for MAXPATHLEN */
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38 #endif
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39
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40 #ifdef WINDOWSNT
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41 #include <direct.h>
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42 #endif
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43
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44 #include <sys/stat.h> /* for S_IFLNK */
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45
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46 #ifndef PATH_MAX
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47 #ifdef _POSIX_VERSION
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48 #define PATH_MAX _POSIX_PATH_MAX
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49 #else
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50 #ifdef MAXPATHLEN
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51 #define PATH_MAX MAXPATHLEN
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52 #else
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53 #define PATH_MAX 1024
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54 #endif
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55 #endif
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56 #endif
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57
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58 #define MAX_READLINKS 32
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59
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60 char *
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61 xrealpath (const char *path, char resolved_path [])
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62 {
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63 char copy_path[PATH_MAX];
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64 char *new_path = resolved_path;
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65 char *max_path;
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66 #ifdef S_IFLNK
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67 int readlinks = 0;
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68 char link_path[PATH_MAX];
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69 int n;
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70 #endif
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71
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72 /* Make a copy of the source path since we may need to modify it. */
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73 strcpy(copy_path, path);
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74 path = copy_path;
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75 max_path = copy_path + PATH_MAX - 2;
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76 #ifdef WINDOWSNT
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77 /*
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78 ** In NT we have two different cases: (1) the path name begins
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79 ** with a drive letter, e.g., "C:"; and (2) the path name begins
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80 ** with just a slash, which roots to the current drive. In the
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81 ** first case we are going to leave things alone, in the second
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82 ** case we will prepend the drive letter to the given path.
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83 ** Note: So far in testing, I'm only seeing case #1, even though
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84 ** I've tried to get the other cases to happen.
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85 ** August Hill, 31 Aug 1997.
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86 **
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87 ** Check for a driver letter...C:/...
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88 */
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89 if (*(path + 1) == ':')
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90 {
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91 strncpy(new_path, path, 3);
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92 new_path += 3;
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93 path += 3;
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94 }
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95
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96 /*
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97 ** No drive letter, but a beginning slash? Prepend the drive
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98 ** letter...
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99 */
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100 else if (*path == '/')
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101 {
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102 getcwd(new_path, PATH_MAX - 1);
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103 new_path += 3;
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104 path++;
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105 }
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106
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107 /*
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108 ** Just a path name, prepend the current directory
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109 */
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110 else
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111 {
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112 getcwd(new_path, PATH_MAX - 1);
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113 new_path += strlen(new_path);
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114 if (new_path[-1] != '/')
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115 *new_path++ = '/';
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116 }
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117
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118 #else
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119 /* If it's a relative pathname use getwd for starters. */
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120 if (*path != '/')
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121 {
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122 #ifdef HAVE_GETCWD
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123 getcwd(new_path, PATH_MAX - 1);
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124 #else
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125 getwd(new_path);
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126 #endif
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127 new_path += strlen(new_path);
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128 if (new_path[-1] != '/')
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129 *new_path++ = '/';
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130 }
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131 else
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132 {
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133 *new_path++ = '/';
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134 path++;
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135 }
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136 #endif
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137 /* Expand each slash-separated pathname component. */
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138 while (*path != '\0')
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139 {
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140 /* Ignore stray "/". */
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141 if (*path == '/')
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142 {
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143 path++;
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144 continue;
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145 }
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146
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147 if (*path == '.')
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148 {
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149 /* Ignore ".". */
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150 if (path[1] == '\0' || path[1] == '/')
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151 {
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152 path++;
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153 continue;
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154 }
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155
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156 if (path[1] == '.')
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157 {
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158 if (path[2] == '\0' || path[2] == '/')
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159 {
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160 path += 2;
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161
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162 /* Ignore ".." at root. */
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163 if (new_path == resolved_path + 1)
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164 continue;
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165
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166 /* Handle ".." by backing up. */
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167 while ((--new_path)[-1] != '/')
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168 ;
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169 continue;
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170 }
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171 }
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172 }
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173
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174 /* Safely copy the next pathname component. */
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175 while (*path != '\0' && *path != '/')
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176 {
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177 if (path > max_path)
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178 {
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179 errno = ENAMETOOLONG;
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180 return NULL;
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181 }
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182 *new_path++ = *path++;
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183 }
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184
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185 #ifdef S_IFLNK
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186 /* See if latest pathname component is a symlink. */
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187 *new_path = '\0';
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188 n = readlink(resolved_path, link_path, PATH_MAX - 1);
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189
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190 if (n < 0)
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191 {
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192 /* EINVAL means the file exists but isn't a symlink. */
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193 if (errno != EINVAL)
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194 return NULL;
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195 }
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196 else
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197 {
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198 /* Protect against infinite loops. */
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199 if (readlinks++ > MAX_READLINKS)
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200 {
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201 errno = ELOOP;
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202 return NULL;
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203 }
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204
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205 /* Note: readlink doesn't add the null byte. */
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206 link_path[n] = '\0';
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207
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208 if (*link_path == '/')
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209 /* Start over for an absolute symlink. */
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210 new_path = resolved_path;
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211 else
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212 /* Otherwise back up over this component. */
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213 while (*(--new_path) != '/')
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214 ;
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215
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216 /* Safe sex check. */
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217 if (strlen(path) + n >= PATH_MAX)
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218 {
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219 errno = ENAMETOOLONG;
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220 return NULL;
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221 }
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222
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223 /* Insert symlink contents into path. */
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224 strcat(link_path, path);
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225 strcpy(copy_path, link_path);
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226 path = copy_path;
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227 }
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228 #endif /* S_IFLNK */
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229 *new_path++ = '/';
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230 }
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231
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232 /* Delete trailing slash but don't whomp a lone slash. */
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233 if (new_path != resolved_path + 1 && new_path[-1] == '/')
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234 new_path--;
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235
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236 /* Make sure it's null terminated. */
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237 *new_path = '\0';
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238 return resolved_path;
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239 }
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