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--- old/usr/src/man/man2/chmod.2.man.txt
+++ new/usr/src/man/man2/chmod.2.man.txt
1 1 CHMOD(2) System Calls CHMOD(2)
2 2
3 3
4 4
5 5 NAME
6 6 chmod, fchmod, fchmodat - change access permission mode of file
7 7
8 8 SYNOPSIS
9 9 #include <sys/types.h>
10 10 #include <sys/stat.h>
11 11
12 12 int chmod(const char *path, mode_t mode);
13 13
14 14
15 15 int fchmod(int fildes, mode_t mode);
16 16
17 17
18 18 int fchmodat(int fildes, const char *path, mode_t mode, int flag);
19 19
20 20
21 21 DESCRIPTION
22 22 The chmod(), fchmod(), and fchmodat() functions set the access
23 23 permission portion of the mode of the file whose name is given by path
24 24 or referenced by the open file descriptor fildes to the bit pattern
25 25 contained in mode. Access permission bits are interpreted as follows:
26 26
27 27
28 28
29 29
30 30 S_ISUID 04000 Set user ID on execution.
31 31 S_ISGID 020#0 Set group ID on execution if # is 7, 5, 3, or 1. Enable mandatory file/record locking if # is 6, 4, 2, or 0.
32 32 S_ISVTX 01000 Sticky bit.
33 33 S_IRWXU 00700 Read, write, execute by owner.
34 34 S_IRUSR 00400 Read by owner.
35 35 S_IWUSR 00200 Write by owner.
36 36 S_IXUSR 00100 Execute (search if a directory) by owner.
37 37 S_IRWXG 00070 Read, write, execute by group.
38 38 S_IRGRP 00040 Read by group.
39 39 S_IWGRP 00020 Write by group.
40 40 S_IXGRP 00010 Execute by group.
41 41 S_IRWXO 00007 Read, write, execute (search) by others.
42 42 S_IROTH 00004 Read by others.
43 43 S_IWOTH 00002 Write by others.
44 44 S_IXOTH 00001 Execute by others.
45 45
46 46
47 47
48 48 Modes are constructed by the bitwise OR operation of the access
49 49 permission bits.
50 50
51 51
52 52 The effective user ID of the process must match the owner of the file
53 53 or the process must have the appropriate privilege to change the mode
54 54 of a file.
55 55
56 56
57 57 If the process is not a privileged process and the file is not a
58 58 directory, mode bit 01000 (save text image on execution) is cleared.
59 59
60 60
61 61 If neither the process is privileged nor the file's group is a member
62 62 of the process's supplementary group list, and the effective group ID
63 63 of the process does not match the group ID of the file, mode bit 02000
64 64 (set group ID on execution) is cleared.
65 65
66 66
67 67 If a directory is writable and has S_ISVTX (the sticky bit) set, files
68 68 within that directory can be removed or renamed only if one or more of
69 69 the following is true (see unlink(2) and rename(2)):
70 70
71 71 o the user owns the file
72 72
73 73 o the user owns the directory
74 74
75 75 o the file is writable by the user
76 76
77 77 o the user is a privileged user
78 78
79 79
80 80 If a regular file is not executable and has S_ISVTX set, the file is
81 81 assumed to be a swap file. In this case, the system's page cache will
82 82 not be used to hold the file's data. If the S_ISVTX bit is set on any
83 83 other file, the results are unspecified.
84 84
85 85
86 86 If a directory has the set group ID bit set, a given file created
87 87 within that directory will have the same group ID as the directory.
88 88 Otherwise, the newly created file's group ID will be set to the
89 89 effective group ID of the creating process.
90 90
91 91
92 92 If the mode bit 02000 (set group ID on execution) is set and the mode
93 93 bit 00010 (execute or search by group) is not set, mandatory
94 94 file/record locking will exist on a regular file, possibly affecting
95 95 future calls to open(2), creat(2), read(2), and write(2) on this file.
96 96
97 97
98 98 If fildes references a shared memory object, fchmod() need only affect
99 99 the S_IRUSR, S_IRGRP, S_IROTH, S_IWUSR, S_IWGRP, S_IWOTH, S_IXUSR,
100 100 S_IXGRP, and S_IXOTH file permission bits.
101 101
102 102
103 103 If fildes refers to a socket, fchmod() does not fail but no action is
104 104 taken.
105 105
106 106
107 107 If fildes refers to a stream that is attached to an object in the file
108 108 system name space with fattach(3C), the fchmod() call performs no
109 109 action and returns successfully.
110 110
111 111
112 112 The fchmodat() function behaves similarly to chmod(), except when path
113 113 is a relative path, it is resolved relative to the directory specified
114 114 by filedes. If filedes has the value AT_FDCWD, then path will be
115 115 resolved relative to the current working directory. The argument flag
116 116 should be zero, but may include the value AT_SYMLINK_NOFOLLOW, which
117 117 indicates that if path refers to a symbolic link, then permissions
118 118 should be changed on the symbolic link itself. However, changing
119 119 permissions of symbolic links is not supported on illumos, and will
120 120 result in an error.
121 121
122 122
123 123 Upon successful completion, chmod(), fchmod(), fchmodat() mark for
124 124 update the st_ctime field of the file.
125 125
126 126 RETURN VALUES
127 127 Upon successful completion, 0 is returned. Otherwise, -1 is returned,
128 128 the file mode is unchanged, and errno is set to indicate the error.
129 129
130 130 ERRORS
131 131 The chmod(), fchmod(), and fchmodat() functions will fail if:
132 132
133 133 EIO
134 134 An I/O error occurred while reading from or writing to the
135 135 file system.
136 136
137 137
138 138 EPERM
139 139 The effective user ID does not match the owner of the file and
140 140 the process does not have appropriate privilege.
141 141
142 142 The {PRIV_FILE_OWNER} privilege overrides constraints on
143 143 ownership when changing permissions on a file.
144 144
145 145 The {PRIV_FILE_SETID} privilege overrides constraints on
146 146 ownership when adding the setuid or setgid bits to an
147 147 executable file or a directory. When adding the setuid bit to
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148 148 a root owned executable, additional restrictions apply. See
149 149 privileges(5).
150 150
151 151
152 152
153 153 The chmod() and fchmodat() functions will fail if:
154 154
155 155 EACCES
156 156 Search permission is denied on a component of the path
157 157 prefix of path and for fchmodat(), filedes was not
158 - opened with O_SEARCH requsted. The privilege
158 + opened with O_SEARCH requested. The privilege
159 159 {FILE_DAC_SEARCH} overrides file permissions
160 160 restrictions in that case.
161 161
162 162
163 163 EFAULT
164 164 The path argument points to an illegal address.
165 165
166 166
167 167 ELOOP
168 168 A loop exists in symbolic links encountered during the
169 169 resolution of the path argument.
170 170
171 171
172 172 ENAMETOOLONG
173 173 The length of the path argument exceeds PATH_MAX, or
174 174 the length of a path component exceeds NAME_MAX while
175 175 _POSIX_NO_TRUNC is in effect.
176 176
177 177
178 178 ENOENT
179 179 Either a component of the path prefix or the file
180 180 referred to by path does not exist or is a null
181 181 pathname.
182 182
183 183
184 184 ENOLINK
185 185 The fildes argument points to a remote machine and the
186 186 link to that machine is no longer active.
187 187
188 188
189 189 ENOTDIR
190 190 A component of the prefix of path is not a directory.
191 191
192 192
193 193 EROFS
194 194 The file referred to by path resides on a read-only
195 195 file system.
196 196
197 197
198 198
199 199 The fchmod() function will fail if:
200 200
201 201 EBADF
202 202 The fildes argument is not an open file descriptor
203 203
204 204
205 205 ENOLINK
206 206 The path argument points to a remote machine and the link to
207 207 that machine is no longer active.
208 208
209 209
210 210 EROFS
211 211 The file referred to by fildes resides on a read-only file
212 212 system.
213 213
214 214
215 215
216 216 The chmod() and fchmod() functions may fail if:
217 217
218 218 EINTR
219 219 A signal was caught during execution of the function.
220 220
221 221
222 222 EINVAL
223 223 The value of the mode argument is invalid.
224 224
225 225
226 226
227 227 The fchmodat() will fail if:
228 228
229 229 EBADF
230 230 The argument path is a relative path and filedes is not
231 231 an open file descriptor or the value AT_FDCWD.
232 232
233 233
234 234 EINVAL
235 235 The argument flags has a non-zero value other than
236 236 AT_SYMLINK_NOFOLLOW.
237 237
238 238
239 239 ENOTDIR
240 240 The argument path is a relative path and filedes is a
241 241 valid file descriptor which does not refer to a file.
242 242
243 243
244 244 EOPNOTSUPP
245 245 The AT_SYMLINK_NOFOLLOW bit is set in the flags
246 246 argument.
247 247
248 248
249 249
250 250 The chmod() and fchmodat() functions may fail if:
251 251
252 252 ELOOP
253 253 More than {SYMLOOP_MAX} symbolic links were encountered
254 254 during the resolution of the path argument.
255 255
256 256
257 257 ENAMETOOLONG
258 258 As a result of encountering a symbolic link in
259 259 resolution of the path argument, the length of the
260 260 substituted pathname strings exceeds {PATH_MAX}.
261 261
262 262
263 263
264 264 The fchmod() function may fail if:
265 265
266 266 EINVAL
267 267 The fildes argument refers to a pipe and the system disallows
268 268 execution of this function on a pipe.
269 269
270 270
271 271 EXAMPLES
272 272 Example 1 Set Read Permissions for User, Group, and Others
273 273
274 274
275 275 The following example sets read permissions for the owner, group, and
276 276 others.
277 277
278 278
279 279 #include <sys/stat.h>
280 280 const char *path;
281 281 ...
282 282 chmod(path, S_IRUSR|S_IRGRP|S_IROTH);
283 283
284 284
285 285 Example 2 Set Read, Write, and Execute Permissions for the Owner Only
286 286
287 287
288 288 The following example sets read, write, and execute permissions for the
289 289 owner, and no permissions for group and others.
290 290
291 291
292 292 #include <sys/stat.h>
293 293 const char *path;
294 294 ...
295 295 chmod(path, S_IRWXU);
296 296
297 297
298 298 Example 3 Set Different Permissions for Owner, Group, and Other
299 299
300 300
301 301 The following example sets owner permissions for CHANGEFILE to read,
302 302 write, and execute, group permissions to read and execute, and other
303 303 permissions to read.
304 304
305 305
306 306 #include <sys/stat.h>
307 307 #define CHANGEFILE "/etc/myfile"
308 308 ...
309 309 chmod(CHANGEFILE, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH);
310 310
311 311
312 312 Example 4 Set and Checking File Permissions
313 313
314 314
315 315 The following example sets the file permission bits for a file named
316 316 /home/cnd/mod1, then calls the stat(2) function to verify the
317 317 permissions.
318 318
319 319
320 320 #include <sys/types.h>
321 321 #include <sys/stat.h>
322 322 int status;
323 323 struct stat buffer
324 324 ...
325 325 chmod("home/cnd/mod1", S_IRWXU|S_IRWXG|S_IROTH|S_IWOTH);
326 326 status = stat("home/cnd/mod1", &buffer;);
327 327
328 328
329 329 USAGE
330 330 If chmod() or fchmod() is used to change the file group owner
331 331 permissions on a file with non-trivial ACL entries, only the ACL mask
332 332 is set to the new permissions and the group owner permission bits in
333 333 the file's mode field (defined in mknod(2)) are unchanged. A non-
334 334 trivial ACL entry is one whose meaning cannot be represented in the
335 335 file's mode field alone. The new ACL mask permissions might change the
336 336 effective permissions for additional users and groups that have ACL
337 337 entries on the file.
338 338
339 339 ATTRIBUTES
340 340 See attributes(5) for descriptions of the following attributes:
341 341
342 342
343 343
344 344
345 345 +--------------------+-------------------+
346 346 | ATTRIBUTE TYPE | ATTRIBUTE VALUE |
347 347 +--------------------+-------------------+
348 348 |Interface Stability | Standard |
349 349 +--------------------+-------------------+
350 350 |MT-Level | Async-Signal-Safe |
351 351 +--------------------+-------------------+
352 352
353 353 SEE ALSO
354 354 chmod(1), chown(2), creat(2), fcntl(2), mknod(2), open(2), read(2),
355 355 rename(2), stat(2), write(2), fattach(3C), mkfifo(3C), stat.h(3HEAD),
356 356 attributes(5), privileges(5), standards(5)
357 357
358 358
359 359 Programming Interfaces Guide
360 360
361 361
362 362
363 363 December 22, 2014 CHMOD(2)
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