| blob | 49440aaa1f3690bf87a77c511059cd6c56d4ec30 |
1 .\" $NetBSD: stat.2,v 1.56 2013/10/15 11:43:21 njoly Exp $
2 .\"
3 .\" Copyright (c) 1980, 1991, 1993, 1994
4 .\" The Regents of the University of California. All rights reserved.
5 .\"
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
8 .\" are met:
9 .\" 1. Redistributions of source code must retain the above copyright
10 .\" notice, this list of conditions and the following disclaimer.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice, this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
14 .\" 3. Neither the name of the University nor the names of its contributors
15 .\" may be used to endorse or promote products derived from this software
16 .\" without specific prior written permission.
17 .\"
18 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" SUCH DAMAGE.
29 .\"
30 .\" @(#)stat.2 8.4 (Berkeley) 5/1/95
31 .\"
32 .Dd July 28, 2013
33 .Dt STAT 2
34 .Os
35 .Sh NAME
36 .Nm stat ,
37 .Nm lstat ,
38 .Nm fstat ,
39 .Nm fstatat ,
40 .Nd get file status
41 .Sh LIBRARY
42 .Lb libc
43 .Sh SYNOPSIS
44 .In sys/stat.h
45 .Ft int
46 .Fn stat "const char *path" "struct stat *sb"
47 .Ft int
48 .Fn lstat "const char *path" "struct stat *sb"
49 .Ft int
50 .Fn fstat "int fd" "struct stat *sb"
51 .In sys/stat.h
52 .In fcntl.h
53 .Ft int
54 .Fn fstatat "int fd" "const char *path" "struct stat *sb" "int flag"
55 .Sh DESCRIPTION
56 The
57 .Fn stat
58 function obtains information about the file pointed to by
59 .Fa path .
60 Read, write or execute
61 permission of the named file is not required, but all directories
62 listed in the path name leading to the file must be searchable.
63 .Pp
64 The function
65 .Fn lstat
66 is like
67 .Fn stat
68 except in the case where the named file is a symbolic link,
69 in which case
70 .Fn lstat
71 returns information about the link,
72 while
73 .Fn stat
74 returns information about the file the link references.
75 The
76 .Fn fstat
77 function obtains the same information about an open file
78 known by the file descriptor
79 .Fa fd .
80 .Pp
81 .Fn fstatat
82 works the same way as
83 .Fn stat
84 (or
85 .Fn lstat
86 if
87 .Dv AT_SYMLINK_NOFOLLOW
88 is set in
89 .Fa flag )
90 except if
91 .Fa path
92 is relative.
93 In that case, it is looked up from a directory whose file
94 descriptor was passed as
95 .Fa fd .
96 Search permission is required on this directory.
97 .\" (These alternatives await a decision about the semantics of O_SEARCH)
98 .\" Search permission is required on this directory
99 .\" except if
100 .\" .Fa fd
101 .\" was opened with the
102 .\" .Dv O_SEARCH
103 .\" flag.
104 .\" - or -
105 .\" This file descriptor must have been opened with the
106 .\" .Dv O_SEARCH
107 .\" flag.
108 .Fa fd
109 can be set to
110 .Dv AT_FDCWD
111 in order to specify the current directory.
112 .Pp
113 The
114 .Fa sb
115 argument is a pointer to a
116 .Fa stat
117 structure
118 as defined by
119 .In sys/stat.h
120 and into which information is placed concerning the file.
121 .Ss The Standard Structure
122 The following standards-compliant fields are defined in the structure:
123 .Bl -column -offset indent \
124 "nlink_t " "st_nlink " "Description"
125 .It Sy Type Ta Sy Entry Ta Sy Description
126 .It Vt dev_t Ta st_dev Ta device ID containing the file
127 .It Vt ino_t Ta st_ino Ta serial number of the file
128 .It Vt mode_t Ta st_mode Ta mode of the file
129 .It Vt nlink_t Ta st_nlink Ta number of hard links to the file
130 .It Vt uid_t Ta st_uid Ta user ID of the owner
131 .It Vt gid_t Ta st_gid Ta group ID of the owner
132 .It Vt dev_t Ta st_rdev Ta device type (character or block special)
133 .It Vt off_t Ta st_size Ta size of the file in bytes
134 .It Vt time_t Ta st_atime Ta time of last access
135 .It Vt time_t Ta st_mtime Ta time of last data modification
136 .It Vt time_t Ta st_ctime Ta time of last file status change
137 .It Vt blksize_t Ta st_blksize Ta preferred I/O block size (fs-specific)
138 .It Vt blkcnt_t Ta st_blocks Ta blocks allocated for the file
139 .El
140 .Pp
141 These are specified in the
142 .St -p1003.1-2004
143 standard.
144 The
145 .Va st_ino
146 and
147 .Va st_dev
148 fields taken together uniquely identify the file within the system.
149 Most of the types are defined in
150 .Xr types 3 .
151 .Pp
152 The time-related fields are:
153 .Bl -tag -width st_blksize -offset indent
154 .It Va st_atime
155 Time when file data was last accessed.
156 Changed by the
157 .Xr mknod 2 ,
158 .Xr utimes 2 ,
159 and
160 .Xr read 2
161 system calls.
162 .It Va st_mtime
163 Time when file data was last modified.
164 Changed by the
165 .Xr mknod 2 ,
166 .Xr utimes 2 ,
167 and
168 .Xr write 2
169 system calls.
170 .It Va st_ctime
171 Time when file status was last changed (file metadata modification).
172 Changed by the
173 .Xr chflags 2 ,
174 .Xr chmod 2 ,
175 .Xr chown 2 ,
176 .Xr link 2 ,
177 .Xr mknod 2 ,
178 .Xr rename 2 ,
179 .Xr unlink 2 ,
180 .Xr utimes 2 ,
181 and
182 .Xr write 2
183 system calls.
184 .El
185 .Pp
186 The size-related fields of the
187 .Fa struct stat
188 are as follows:
189 .Bl -tag -width st_blksize -offset indent
190 .It Va st_size
191 The size of the file in bytes.
192 The meaning of the size reported for a directory is file system
193 dependent.
194 Some file systems (e.g. FFS) return the total size used for the
195 directory metadata, possibly including free slots; others (notably
196 ZFS) return the number of entries in the directory.
197 Some may also return other things or always report zero.
198 .It Va st_blksize
199 The optimal I/O block size for the file.
200 .It Va st_blocks
201 The actual number of blocks allocated for the file in 512-byte units.
202 As short symbolic links are stored in the inode, this number may
203 be zero.
204 .El
205 .Pp
206 The status information word
207 .Fa st_mode
208 contains bits that define the access mode (see
209 .Xr chmod 2 )
210 and the type (see
211 .Xr dirent 3 )
212 of the file.
213 The following macros can be used to test
214 whether a file is of the specified type.
215 The value
216 .Fa m
217 supplied to the macros is the value of
218 .Va st_mode .
219 .Bl -tag -width "S_ISSOCK(m)" -offset indent
220 .It Fn S_ISBLK "m"
221 Test for a block special file.
222 .It Fn S_ISCHR "m"
223 Test for a character special file.
224 .It Fn S_ISDIR "m"
225 Test for a directory.
226 .It Fn S_ISFIFO "m"
227 Test for a pipe or FIFO special file.
228 .It Fn S_ISREG "m"
229 Test for a regular file.
230 .It Fn S_ISLNK "m"
231 Test for a symbolic link.
232 .It Fn S_ISSOCK "m"
233 Test for a socket.
234 .El
235 .Pp
236 The macros evaluate to a non-zero value if the test
237 is true or to the value 0 if the test is false.
238 .Ss NetBSD Extensions
239 The following additional
240 .Nx
241 specific fields are present:
242 .Bl -column -offset indent \
243 "uint32_t" "st_birthtimensec" "Description"
244 .It Sy Type Ta Sy Entry Ta Sy Description
245 .It Vt long Ta st_atimensec Ta last access (nanoseconds)
246 .It Vt long Ta st_mtimensec Ta last modification (nanoseconds)
247 .It Vt long Ta st_ctimensec Ta last status change (nanoseconds)
248 .It Vt time_t Ta st_birthtime Ta time of inode creation
249 .It Vt long Ta st_birthtimensec Ta inode creation (nanoseconds)
250 .It Vt uint32_t Ta st_flags Ta user defined flags for the file
251 .It Vt uint32_t Ta st_gen Ta file generation number
252 .\"
253 .\" XXX: What is this?
254 .\"
255 .It Vt uint32_t Ta st_spare[2] Ta implementation detail
256 .El
257 .Pp
258 However, if
259 _NETBSD_SOURCE
260 is furthermore defined, instead of the above,
261 the following are present in the structure:
262 .Bl -column -offset indent \
263 "struct timespec " "st_birthtimensec" "Description"
264 .It Sy Type Ta Sy Entry Ta Sy Description
265 .It Vt struct timespec Ta st_atimespec Ta time of last access
266 .It Vt struct timespec Ta st_mtimespec Ta time of last modification
267 .It Vt struct timespec Ta st_birthtimespec Ta time of creation
268 .It Vt uint32_t Ta st_flags Ta user defined flags
269 .It Vt uint32_t Ta st_gen Ta file generation number
270 .\"
271 .\" XXX: What is this?
272 .\"
273 .It Vt uint32_t Ta st_spare[2] Ta implementation detail
274 .El
275 .Pp
276 In this case the following macros are provided for convenience:
277 .Bd -literal -offset indent
278 #if defined(_NETBSD_SOURCE)
279 #define st_atime st_atimespec.tv_sec
280 #define st_atimensec st_atimespec.tv_nsec
281 #define st_mtime st_mtimespec.tv_sec
282 #define st_mtimensec st_mtimespec.tv_nsec
283 #define st_ctime st_ctimespec.tv_sec
284 #define st_ctimensec st_ctimespec.tv_nsec
285 #define st_birthtime st_birthtimespec.tv_sec
286 #define st_birthtimensec st_birthtimespec.tv_nsec
287 #endif
288 .Ed
289 .Pp
290 The status information word
291 .Fa st_flags
292 has the following bits:
293 .Bl -column -offset indent \
294 "struct timespec " "st_birthtimensec"
295 .It Sy Constant Ta Sy Description
296 .It Dv UF_NODUMP Ta do not dump a file
297 .It Dv UF_IMMUTABLE Ta file may not be changed
298 .It Dv UF_APPEND Ta writes to file may only append
299 .It Dv UF_OPAQUE Ta directory is opaque wrt. union
300 .It Dv SF_ARCHIVED Ta file is archived
301 .It Dv SF_IMMUTABLE Ta file may not be changed
302 .It Dv SF_APPEND Ta writes to file may only append
303 .El
304 .Pp
305 For a description of the flags, see
306 .Xr chflags 2 .
307 .Sh RETURN VALUES
308 .Rv -std stat lstat fstat fstatat
309 .Sh COMPATIBILITY
310 Previous versions of the system used different types for the
311 .Li st_dev ,
312 .Li st_uid ,
313 .Li st_gid ,
314 .Li st_rdev ,
315 .Li st_size ,
316 .Li st_blksize
317 and
318 .Li st_blocks
319 fields.
320 .Sh ERRORS
321 .Fn stat ,
322 .Fn lstat
323 and
324 .Fn fstatat
325 will fail if:
326 .Bl -tag -width Er
327 .It Bq Er EACCES
328 Search permission is denied for a component of the path prefix.
329 .It Bq Er EBADF
330 A badly formed vnode was encountered.
331 This can happen if a file system information node is incorrect.
332 .It Bq Er EFAULT
333 .Fa sb
334 or
335 .Fa path
336 points to an invalid address.
337 .It Bq Er EIO
338 An I/O error occurred while reading from or writing to the file system.
339 .It Bq Er ELOOP
340 Too many symbolic links were encountered in translating the pathname.
341 .It Bq Er ENAMETOOLONG
342 A component of a pathname exceeded
343 .Brq Dv NAME_MAX
344 characters, or an entire path name exceeded
345 .Brq Dv PATH_MAX
346 characters.
347 .It Bq Er ENOENT
348 The named file does not exist.
349 .It Bq Er ENOTDIR
350 A component of the path prefix is not a directory.
351 .It Bq Er ENXIO
352 The named file is a character special or block
353 special file, and the device associated with this special file
354 does not exist.
355 .El
356 .Pp
357 In addition,
358 .Fn fstatat
359 will fail if:
360 .Bl -tag -width Er
361 .It Bq Er EBADF
362 .Fa path
363 does not specify an absolute path and
364 .Fa fd
365 is neither
366 .Dv AT_FDCWD
367 nor a valid file descriptor open for reading or searching.
368 .It Bq Er ENOTDIR
369 .Fa path
370 is not an absolute path and
371 .Fa fd
372 is a file descriptor associated with a non-directory file.
373 .El
374 .Pp
375 .Fn fstat
376 will fail if:
377 .Bl -tag -width Er
378 .It Bq Er EBADF
379 .Fa fd
380 is not a valid open file descriptor.
381 .It Bq Er EFAULT
382 .Fa sb
383 points to an invalid address.
384 .It Bq Er EIO
385 An I/O error occurred while reading from or writing to the file system.
386 .El
387 .Sh SEE ALSO
388 .Xr chflags 2 ,
389 .Xr chmod 2 ,
390 .Xr chown 2 ,
391 .Xr utimes 2 ,
392 .Xr dirent 3 ,
393 .Xr types 3 ,
394 .Xr symlink 7
395 .Sh STANDARDS
396 .Fn stat ,
397 .Fn lstat ,
398 and
399 .Fn fstat
400 conform to
401 .St -p1003.1-2004 .
402 .Fn fstatat
403 conforms to
404 .St -p1003.1-2008 .
405 .Sh HISTORY
406 A
407 .Fn stat
408 function call appeared in
409 .At v2 .
410 A
411 .Fn lstat
412 function call appeared in
413 .Bx 4.2 .
414 .Sh BUGS
415 Applying
416 .Fn fstat
417 to a socket (and thus to a pipe)
418 returns a zero'd buffer,
419 except for the blocksize field,
420 and a unique device and file serial number.