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1 .\" $NetBSD: rename.2,v 1.7 1995/02/27 12:36:15 cgd Exp $
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34 .\" @(#)rename.2 8.1 (Berkeley) 6/4/93
35 .\"
36 .Dd September 18, 2008
37 .Dt RENAME 2
38 .Os BSD 4.2
39 .Sh NAME
40 .Nm rename ,
41 .Nm renameat ,
42 .Nm renamex_np ,
43 .Nm renameatx_np
44 .Nd change the name of a file
45 .Sh SYNOPSIS
46 .Fd #include <stdio.h>
47 .Ft int
48 .Fo rename
49 .Fa "const char *old"
50 .Fa "const char *new"
51 .Fc
52 .Ft int
53 .Fn renameat "int fromfd" "const char *from" "int tofd" "const char *to"
54 .Ft int
55 .Fn renamex_np "const char *from" "const char *to" "unsigned int flags"
56 .Ft int
57 .Fn renameatx_np "int fromfd" "const char *from" "int tofd" "const char *to" "unsigned int flags"
58 .Sh DESCRIPTION
59 The
60 .Fn rename
61 system call causes the link named
62 .Fa old
63 to be renamed as
64 .Fa new .
65 If
66 .Fa new
67 exists, it is first removed.
68 Both
69 .Fa old
70 and
71 .Fa new
72 must be of the same type
73 (that is, both must be either directories or non-directories)
74 and must reside on the same file system.
75 .Pp
76 The
77 .Fn rename
78 system call guarantees that an instance of
79 .Fa new
80 will always exist,
81 even if the system should crash in the middle of the operation.
82 .Pp
83 If the final component of
84 .Fa old
85 is a symbolic link,
86 the symbolic link is renamed,
87 not the file or directory to which it points.
88 .Pp
89 The
90 .Fn renameat
91 system call is equivalent to
92 .Fn rename
93 except in the case where either
94 .Fa from
95 or
96 .Fa to
97 specifies a relative path.
98 If
99 .Fa from
100 is a relative path, the file to be renamed is located
101 relative to the directory associated with the file descriptor
102 .Fa fromfd
103 instead of the current working directory.
104 If the
105 .Fa to
106 is a relative path, the same happens only relative to the directory associated
107 with
108 .Fa tofd .
109 If the
110 .Fn renameat
111 is passed the special value
112 .Dv AT_FDCWD
113 in the
114 .Fa fromfd
115 or
116 .Fa tofd
117 parameter, the current working directory is used in the determination
118 of the file for the respective path parameter.
119 .Pp
120 The
121 .Fn renamex_np
122 and
123 .Fn renameatx_np
124 system calls are similar to their counterparts except that they take a
125 .Fa flags
126 argument.
127 Values for
128 .Fa flags
129 are constructed with below bits set:
130 .Bl -tag -offset indent
131 .It Dv RENAME_SWAP
132 On file systems that support it (see
133 .Xr getattrlist 2
134 .Dv VOL_CAP_INT_RENAME_SWAP Ns ),
135 it will cause the source and target to be atomically swapped. Source and target need not be of
136 the same type, i.e. it is possible to swap a file with a directory.
137 EINVAL is returned in case of bitwise-inclusive OR with
138 .Dv RENAME_EXCL .
139 .It Dv RENAME_EXCL
140 On file systems that support it (see
141 .Xr getattrlist 2
142 .Dv VOL_CAP_INT_RENAME_EXCL Ns ),
143 it will cause
144 .Dv EEXIST
145 to be returned if the destination already exists. EINVAL is returned in case of bitwise-inclusive OR with
146 .Dv RENAME_SWAP .
147 .El
148 .Sh CAVEATS
149 The system can deadlock if a loop is present in the file system graph.
150 This loop takes the form of an entry in directory
151 .Ql Pa a ,
152 say
153 .Ql Pa a/foo ,
154 being a hard link to directory
155 .Ql Pa b ,
156 and an entry in
157 directory
158 .Ql Pa b ,
159 say
160 .Ql Pa b/bar ,
161 being a hard link
162 to directory
163 .Ql Pa a .
164 When such a loop exists and two separate processes attempt to
165 perform
166 .Ql rename a/foo b/bar
167 and
168 .Ql rename b/bar a/foo ,
169 respectively,
170 the system may deadlock attempting to lock
171 both directories for modification.
172 .Pp
173 Whether or not hard links to directories are supported is specific to
174 the underlying filesystem implementation.
175 .Pp
176 It is recommended that any hard links to directories in an underlying
177 filesystem should be replaced by symbolic links by the system administrator
178 to avoid the possibility of deadlocks.
179 .Pp
180 Moving or renaming a file or directory into a directory with inheritable ACLs does not result in ACLs being set on the file or directory. Use
181 .Xr acl 3
182 in conjunction with
183 .Fn rename
184 to set ACLs on the file or directory.
185 .Sh RETURN VALUES
186 A 0 value is returned if the operation succeeds, otherwise
187 .Fn rename
188 returns -1 and the global variable
189 .Va errno
190 indicates the reason for the failure.
191 .Sh ERRORS
192 The
193 .Fn rename
194 system call will fail and neither of the argument files will be
195 affected if:
196 .Bl -tag -width Er
197 .\" ===========
198 .It Bq Er EACCES
199 A component of either path prefix denies search permission.
200 .\" ===========
201 .It Bq Er EACCES
202 The requested operation requires writing in a directory
203 (e.g.,
204 .Fa new ,
205 new/.., or old/..) whose modes disallow this.
206 .\" ===========
207 .It Bq Er EACCES
208 .Fa old
209 is a directory and it, or some descendent in the namespace, is open
210 and the file system format does does not support renaming a directory
211 with open descendents (see
212 .Xr getattrlist 2
213 .Dv VOL_CAP_INT_RENAME_OPENFAIL Ns ).
214 .\" ===========
215 .It Bq Er EDQUOT
216 The directory in which the entry for the new name
217 is being placed cannot be extended because the
218 user's quota of disk blocks on the file system
219 containing the directory has been exhausted.
220 .\" ===========
221 .It Bq Er EEXIST
222 .Fa flags
223 has
224 .Dv RENAME_EXCL
225 set but
226 .Fa new
227 already exists.
228 .\" ===========
229 .It Bq Er EFAULT
230 .Em Path
231 points outside the process's allocated address space.
232 .\" ===========
233 .It Bq Er EINVAL
234 .Fa Old
235 is a parent directory of
236 .Fa new ,
237 or an attempt is made to rename
238 .Ql \&.
239 or
240 .Ql \&.. .
241 If
242 .Dv RENAME_SWAP
243 is used, then
244 .Dv EINVAL
245 will also be returned if
246 .Fa new
247 is a parent directory of
248 .Fa old .
249 If both RENAME_SWAP and RENAME_EXCL bits are set in
250 .Fa flags ,
251 then
252 .Dv EINVAL
253 will be returned.
254 .\" ===========
255 .It Bq Er EINVAL
256 .Fa flags
257 has an invalid value.
258 .\" ===========
259 .It Bq Er EIO
260 An I/O error occurs while making or updating a directory entry.
261 .\" ===========
262 .It Bq Er EISDIR
263 .Fa new
264 is a directory, but
265 .Fa old
266 is not a directory.
267 .\" ===========
268 .It Bq Er ELOOP
269 Too many symbolic links are encountered in translating either pathname.
270 This is taken to be indicative of a looping symbolic link.
271 .\" ===========
272 .It Bq Er ENAMETOOLONG
273 A component of a pathname exceeds
274 .Dv {NAME_MAX}
275 characters, or an entire path name exceeds
276 .Dv {PATH_MAX}
277 characters.
278 .\" ===========
279 .It Bq Er ENOENT
280 A component of the
281 .Fa old
282 path does not exist,
283 or a path prefix of
284 .Fa new
285 does not exist.
286 .\" ===========
287 .It Bq Er ENOENT
288 .Fa flags
289 has
290 .Dv RENAME_SWAP
291 set but
292 .Fa new
293 does not exist.
294 .\" ===========
295 .It Bq Er ENOSPC
296 The directory in which the entry for the new name is being placed
297 cannot be extended because there is no space left on the file
298 system containing the directory.
299 .\" ===========
300 .It Bq Er ENOTDIR
301 A component of either path prefix is not a directory.
302 .\" ===========
303 .It Bq Er ENOTDIR
304 .Fa old
305 is a directory, but
306 .Fa new
307 is not a directory.
308 .\" ===========
309 .It Bq Er ENOTEMPTY
310 .Fa New
311 is a directory and is not empty.
312 .\" ===========
313 .It Bq Er ENOTSUP
314 .Fa flags
315 has a value that is not supported by the file system.
316 .\" ===========
317 .It Bq Er EPERM
318 The directory containing
319 .Fa old
320 is marked sticky,
321 and neither the containing directory nor
322 .Fa old
323 are owned by the effective user ID.
324 .\" ===========
325 .It Bq Er EPERM
326 The
327 .Fa new
328 file exists,
329 the directory containing
330 .Fa new
331 is marked sticky,
332 and neither the containing directory nor
333 .Fa new
334 are owned by the effective user ID.
335 .\" ===========
336 .It Bq Er EROFS
337 The requested link requires writing in a directory on a read-only file
338 system.
339 .\" ===========
340 .It Bq Er EXDEV
341 The link named by
342 .Fa new
343 and the file named by
344 .Fa old
345 are on different logical devices (file systems).
346 Note that this error code will not be returned
347 if the implementation permits cross-device links.
348 .El
349 .Pp
350 The
351 .Fn renameat
352 and
353 .Fn renameatx_np
354 calls may also fail with:
355 .Bl -tag -width Er
356 .It Bq Er EBADF
357 The
358 .Fa from
359 argument does not specify an absolute path and the
360 .Fa fromfd
361 argument is neither
362 .Dv AT_FDCWD
363 nor a valid file descriptor open for searching, or the
364 .Fa to
365 argument does not specify an absolute path and the
366 .Fa tofd
367 argument is neither
368 .Dv AT_FDCWD
369 nor a valid file descriptor open for searching.
370 .It Bq Er ENOTDIR
371 The
372 .Fa from
373 argument is not an absolute path and
374 .Fa fromfd
375 is neither
376 .Dv AT_FDCWD
377 nor a file descriptor associated with a directory, or the
378 .Fa to
379 argument is not an absolute path and
380 .Fa tofd
381 is neither
382 .Dv AT_FDCWD
383 nor a file descriptor associated with a directory.
384 .El
385 .Sh CONFORMANCE
386 The restriction on renaming a directory whose permissions disallow writing
387 is based on the fact that UFS directories contain a ".." entry.
388 If renaming a directory would move it to another parent directory,
389 this entry needs to be changed.
390 .Pp
391 This restriction has been generalized to disallow renaming
392 of any write-disabled directory,
393 even when this would not require a change to the ".." entry.
394 For consistency, HFS+ directories emulate this behavior.
395 .Sh SEE ALSO
396 .Xr open 2 ,
397 .Xr symlink 7
398 .Sh STANDARDS
399 The
400 .Fn rename
401 function conforms to
402 .St -p1003.1-88 .
403 The
404 .Fn renameat
405 system call is expected to conform to POSIX.1-2008 .