1STATX(2) Linux Programmer's Manual STATX(2)
2
6 statx - get file status (extended)
7
9 #include <fcntl.h> /* Definition of AT_* constants */
10 #include <sys/stat.h>
11 int statx(int dirfd, const char *restrict pathname, int flags,
13 unsigned int mask, struct statx *restrict statxbuf);
14
16 This function returns information about a file, storing it in the buf‐
17 fer pointed to by statxbuf. The returned buffer is a structure of the
18 following type:
19 struct statx {
21 __u32 stx_mask; /* Mask of bits indicating
22 filled fields */
23 __u32 stx_blksize; /* Block size for filesystem I/O */
24 __u64 stx_attributes; /* Extra file attribute indicators */
25 __u32 stx_nlink; /* Number of hard links */
26 __u32 stx_uid; /* User ID of owner */
27 __u32 stx_gid; /* Group ID of owner */
28 __u16 stx_mode; /* File type and mode */
29 __u64 stx_ino; /* Inode number */
30 __u64 stx_size; /* Total size in bytes */
31 __u64 stx_blocks; /* Number of 512B blocks allocated */
32 __u64 stx_attributes_mask;
33 /* Mask to show what's supported
34 in stx_attributes */
35 /* The following fields are file timestamps */
37 struct statx_timestamp stx_atime; /* Last access */
38 struct statx_timestamp stx_btime; /* Creation */
39 struct statx_timestamp stx_ctime; /* Last status change */
40 struct statx_timestamp stx_mtime; /* Last modification */
41 /* If this file represents a device, then the next two
43 fields contain the ID of the device */
44 __u32 stx_rdev_major; /* Major ID */
45 __u32 stx_rdev_minor; /* Minor ID */
46 /* The next two fields contain the ID of the device
48 containing the filesystem where the file resides */
49 __u32 stx_dev_major; /* Major ID */
50 __u32 stx_dev_minor; /* Minor ID */
51 __u64 stx_mnt_id; /* Mount ID */
52 };
53 The file timestamps are structures of the following type:
55 struct statx_timestamp {
57 __s64 tv_sec; /* Seconds since the Epoch (UNIX time) */
58 __u32 tv_nsec; /* Nanoseconds since tv_sec */
59 };
60 (Note that reserved space and padding is omitted.)
62 Invoking statx():
64 To access a file's status, no permissions are required on the file it‐
65 self, but in the case of statx() with a pathname, execute (search) per‐
66 mission is required on all of the directories in pathname that lead to
67 the file.
68 statx() uses pathname, dirfd, and flags to identify the target file in
70 one of the following ways:
71 An absolute pathname
73 If pathname begins with a slash, then it is an absolute pathname
74 that identifies the target file. In this case, dirfd is ig‐
75 nored.
76 A relative pathname
78 If pathname is a string that begins with a character other than
79 a slash and dirfd is AT_FDCWD, then pathname is a relative path‐
80 name that is interpreted relative to the process's current work‐
81 ing directory.
82 A directory-relative pathname
84 If pathname is a string that begins with a character other than
85 a slash and dirfd is a file descriptor that refers to a direc‐
86 tory, then pathname is a relative pathname that is interpreted
87 relative to the directory referred to by dirfd. (See openat(2)
88 for an explanation of why this is useful.)
89 By file descriptor
91 If pathname is an empty string and the AT_EMPTY_PATH flag is
92 specified in flags (see below), then the target file is the one
93 referred to by the file descriptor dirfd.
94 flags can be used to influence a pathname-based lookup. A value for
96 flags is constructed by ORing together zero or more of the following
97 constants:
98 AT_EMPTY_PATH
100 If pathname is an empty string, operate on the file referred to
101 by dirfd (which may have been obtained using the open(2) O_PATH
102 flag). In this case, dirfd can refer to any type of file, not
103 just a directory.
104 If dirfd is AT_FDCWD, the call operates on the current working
106 directory.
107 This flag is Linux-specific; define _GNU_SOURCE to obtain its
109 definition.
110 AT_NO_AUTOMOUNT
112 Don't automount the terminal ("basename") component of pathname
113 if it is a directory that is an automount point. This allows
114 the caller to gather attributes of an automount point (rather
115 than the location it would mount). This flag can be used in
116 tools that scan directories to prevent mass-automounting of a
117 directory of automount points. The AT_NO_AUTOMOUNT flag has no
118 effect if the mount point has already been mounted over. This
119 flag is Linux-specific; define _GNU_SOURCE to obtain its defini‐
120 tion.
121 AT_SYMLINK_NOFOLLOW
123 If pathname is a symbolic link, do not dereference it: instead
124 return information about the link itself, like lstat(2).
125 flags can also be used to control what sort of synchronization the ker‐
127 nel will do when querying a file on a remote filesystem. This is done
128 by ORing in one of the following values:
129 AT_STATX_SYNC_AS_STAT
131 Do whatever stat(2) does. This is the default and is very much
132 filesystem-specific.
133 AT_STATX_FORCE_SYNC
135 Force the attributes to be synchronized with the server. This
136 may require that a network filesystem perform a data writeback
137 to get the timestamps correct.
138 AT_STATX_DONT_SYNC
140 Don't synchronize anything, but rather just take whatever the
141 system has cached if possible. This may mean that the informa‐
142 tion returned is approximate, but, on a network filesystem, it
143 may not involve a round trip to the server - even if no lease is
144 held.
145 The mask argument to statx() is used to tell the kernel which fields
147 the caller is interested in. mask is an ORed combination of the fol‐
148 lowing constants:
149 STATX_TYPE Want stx_mode & S_IFMT
151 STATX_MODE Want stx_mode & ~S_IFMT
152 STATX_NLINK Want stx_nlink
153 STATX_UID Want stx_uid
154 STATX_GID Want stx_gid
155 STATX_ATIME Want stx_atime
156 STATX_MTIME Want stx_mtime
157 STATX_CTIME Want stx_ctime
158 STATX_INO Want stx_ino
159 STATX_SIZE Want stx_size
160 STATX_BLOCKS Want stx_blocks
161 STATX_BASIC_STATS [All of the above]
162 STATX_BTIME Want stx_btime
163 STATX_MNT_ID Want stx_mnt_id (since Linux 5.8)
164 STATX_ALL [All currently available fields]
165 Note that, in general, the kernel does not reject values in mask other
167 than the above. (For an exception, see EINVAL in errors.) Instead, it
168 simply informs the caller which values are supported by this kernel and
169 filesystem via the statx.stx_mask field. Therefore, do not simply set
170 mask to UINT_MAX (all bits set), as one or more bits may, in the fu‐
171 ture, be used to specify an extension to the buffer.
172 The returned information
174 The status information for the target file is returned in the statx
175 structure pointed to by statxbuf. Included in this is stx_mask which
176 indicates what other information has been returned. stx_mask has the
177 same format as the mask argument and bits are set in it to indicate
178 which fields have been filled in.
179 It should be noted that the kernel may return fields that weren't re‐
181 quested and may fail to return fields that were requested, depending on
182 what the backing filesystem supports. (Fields that are given values
183 despite being unrequested can just be ignored.) In either case,
184 stx_mask will not be equal mask.
185 If a filesystem does not support a field or if it has an unrepre‐
187 sentable value (for instance, a file with an exotic type), then the
188 mask bit corresponding to that field will be cleared in stx_mask even
189 if the user asked for it and a dummy value will be filled in for com‐
190 patibility purposes if one is available (e.g., a dummy UID and GID may
191 be specified to mount under some circumstances).
192 A filesystem may also fill in fields that the caller didn't ask for if
194 it has values for them available and the information is available at no
195 extra cost. If this happens, the corresponding bits will be set in
196 stx_mask.
197 Note: for performance and simplicity reasons, different fields in the
199 statx structure may contain state information from different moments
200 during the execution of the system call. For example, if stx_mode or
201 stx_uid is changed by another process by calling chmod(2) or chown(2),
202 stat() might return the old stx_mode together with the new stx_uid, or
203 the old stx_uid together with the new stx_mode.
204 Apart from stx_mask (which is described above), the fields in the statx
206 structure are:
207 stx_blksize
209 The "preferred" block size for efficient filesystem I/O. (Writ‐
210 ing to a file in smaller chunks may cause an inefficient read-
211 modify-rewrite.)
212 stx_attributes
214 Further status information about the file (see below for more
215 information).
216 stx_nlink
218 The number of hard links on a file.
219 stx_uid
221 This field contains the user ID of the owner of the file.
222 stx_gid
224 This field contains the ID of the group owner of the file.
225 stx_mode
227 The file type and mode. See inode(7) for details.
228 stx_ino
230 The inode number of the file.
231 stx_size
233 The size of the file (if it is a regular file or a symbolic
234 link) in bytes. The size of a symbolic link is the length of
235 the pathname it contains, without a terminating null byte.
236 stx_blocks
238 The number of blocks allocated to the file on the medium, in
239 512-byte units. (This may be smaller than stx_size/512 when the
240 file has holes.)
241 stx_attributes_mask
243 A mask indicating which bits in stx_attributes are supported by
244 the VFS and the filesystem.
245 stx_atime
247 The file's last access timestamp.
248 stx_btime
250 The file's creation timestamp.
251 stx_ctime
253 The file's last status change timestamp.
254 stx_mtime
256 The file's last modification timestamp.
257 stx_dev_major and stx_dev_minor
259 The device on which this file (inode) resides.
260 stx_rdev_major and stx_rdev_minor
262 The device that this file (inode) represents if the file is of
263 block or character device type.
264 stx_mnt_id
266 The mount ID of the mount containing the file. This is the same
267 number reported by name_to_handle_at(2) and corresponds to the
268 number in the first field in one of the records in
269 /proc/self/mountinfo.
270 For further information on the above fields, see inode(7).
272 File attributes
274 The stx_attributes field contains a set of ORed flags that indicate ad‐
275 ditional attributes of the file. Note that any attribute that is not
276 indicated as supported by stx_attributes_mask has no usable value here.
277 The bits in stx_attributes_mask correspond bit-by-bit to stx_at‐
278 tributes.
279 The flags are as follows:
281 STATX_ATTR_COMPRESSED
283 The file is compressed by the filesystem and may take extra re‐
284 sources to access.
285 STATX_ATTR_IMMUTABLE
287 The file cannot be modified: it cannot be deleted or renamed, no
288 hard links can be created to this file and no data can be writ‐
289 ten to it. See chattr(1).
290 STATX_ATTR_APPEND
292 The file can only be opened in append mode for writing. Random
293 access writing is not permitted. See chattr(1).
294 STATX_ATTR_NODUMP
296 File is not a candidate for backup when a backup program such as
297 dump(8) is run. See chattr(1).
298 STATX_ATTR_ENCRYPTED
300 A key is required for the file to be encrypted by the filesys‐
301 tem.
302 STATX_ATTR_VERITY (since Linux 5.5)
304 The file has fs-verity enabled. It cannot be written to, and
305 all reads from it will be verified against a cryptographic hash
306 that covers the entire file (e.g., via a Merkle tree).
307 STATX_ATTR_DAX (since Linux 5.8)
309 The file is in the DAX (cpu direct access) state. DAX state at‐
310 tempts to minimize software cache effects for both I/O and mem‐
311 ory mappings of this file. It requires a file system which has
312 been configured to support DAX.
313 DAX generally assumes all accesses are via CPU load / store in‐
315 structions which can minimize overhead for small accesses, but
316 may adversely affect CPU utilization for large transfers.
317 File I/O is done directly to/from user-space buffers and memory
319 mapped I/O may be performed with direct memory mappings that by‐
320 pass the kernel page cache.
321 While the DAX property tends to result in data being transferred
323 synchronously, it does not give the same guarantees as the
324 O_SYNC flag (see open(2)), where data and the necessary metadata
325 are transferred together.
326 A DAX file may support being mapped with the MAP_SYNC flag,
328 which enables a program to use CPU cache flush instructions to
329 persist CPU store operations without an explicit fsync(2). See
330 mmap(2) for more information.
331
333 On success, zero is returned. On error, -1 is returned, and errno is
334 set to indicate the error.
335
337 EACCES Search permission is denied for one of the directories in the
338 path prefix of pathname. (See also path_resolution(7).)
339 EBADF pathname is relative but dirfd is neither AT_FDCWD nor a valid
341 file descriptor.
342 EFAULT pathname or statxbuf is NULL or points to a location outside the
344 process's accessible address space.
345 EINVAL Invalid flag specified in flags.
347 EINVAL Reserved flag specified in mask. (Currently, there is one such
349 flag, designated by the constant STATX__RESERVED, with the value
350 0x80000000U.)
351 ELOOP Too many symbolic links encountered while traversing the path‐
353 name.
354 ENAMETOOLONG
356 pathname is too long.
357 ENOENT A component of pathname does not exist, or pathname is an empty
359 string and AT_EMPTY_PATH was not specified in flags.
360 ENOMEM Out of memory (i.e., kernel memory).
362 ENOTDIR
364 A component of the path prefix of pathname is not a directory or
365 pathname is relative and dirfd is a file descriptor referring to
366 a file other than a directory.
367
369 statx() was added to Linux in kernel 4.11; library support was added in
370 glibc 2.28.
371
373 statx() is Linux-specific.
374
376 ls(1), stat(1), access(2), chmod(2), chown(2), name_to_handle_at(2),
377 readlink(2), stat(2), utime(2), proc(5), capabilities(7), inode(7),
378 symlink(7)
379
381 This page is part of release 5.13 of the Linux man-pages project. A
382 description of the project, information about reporting bugs, and the
383 latest version of this page, can be found at
384 https://www.kernel.org/doc/man-pages/.
385Linux 2021-08-27 STATX(2)