1STATX(2) Linux Programmer's Manual STATX(2)
2
6 statx - get file status (extended)
7
9 #include <sys/types.h>
10 #include <sys/stat.h>
11 #include <unistd.h>
12 #include <fcntl.h> /* Definition of AT_* constants */
13 int statx(int dirfd, const char *pathname, int flags,
15 unsigned int mask, struct statx *statxbuf);
16
18 This function returns information about a file, storing it in the buf‐
19 fer pointed to by statxbuf. The returned buffer is a structure of the
20 following type:
21 struct statx {
23 __u32 stx_mask; /* Mask of bits indicating
24 filled fields */
25 __u32 stx_blksize; /* Block size for filesystem I/O */
26 __u64 stx_attributes; /* Extra file attribute indicators */
27 __u32 stx_nlink; /* Number of hard links */
28 __u32 stx_uid; /* User ID of owner */
29 __u32 stx_gid; /* Group ID of owner */
30 __u16 stx_mode; /* File type and mode */
31 __u64 stx_ino; /* Inode number */
32 __u64 stx_size; /* Total size in bytes */
33 __u64 stx_blocks; /* Number of 512B blocks allocated */
34 __u64 stx_attributes_mask;
35 /* Mask to show what's supported
36 in stx_attributes */
37 /* The following fields are file timestamps */
39 struct statx_timestamp stx_atime; /* Last access */
40 struct statx_timestamp stx_btime; /* Creation */
41 struct statx_timestamp stx_ctime; /* Last status change */
42 struct statx_timestamp stx_mtime; /* Last modification */
43 /* If this file represents a device, then the next two
45 fields contain the ID of the device */
46 __u32 stx_rdev_major; /* Major ID */
47 __u32 stx_rdev_minor; /* Minor ID */
48 /* The next two fields contain the ID of the device
50 containing the filesystem where the file resides */
51 __u32 stx_dev_major; /* Major ID */
52 __u32 stx_dev_minor; /* Minor ID */
53 };
54 The file timestamps are structures of the following type:
56 struct statx_timestamp {
58 __s64 tv_sec; /* Seconds since the Epoch (UNIX time) */
59 __u32 tv_nsec; /* Nanoseconds since tv_sec */
60 };
61 (Note that reserved space and padding is omitted.)
63 Invoking statx():
65 To access a file's status, no permissions are required on the file it‐
66 self, but in the case of statx() with a pathname, execute (search) per‐
67 mission is required on all of the directories in pathname that lead to
68 the file.
69 statx() uses pathname, dirfd, and flags to identify the target file in
71 one of the following ways:
72 An absolute pathname
74 If pathname begins with a slash, then it is an absolute pathname
75 that identifies the target file. In this case, dirfd is ig‐
76 nored.
77 A relative pathname
79 If pathname is a string that begins with a character other than
80 a slash and dirfd is AT_FDCWD, then pathname is a relative path‐
81 name that is interpreted relative to the process's current work‐
82 ing directory.
83 A directory-relative pathname
85 If pathname is a string that begins with a character other than
86 a slash and dirfd is a file descriptor that refers to a direc‐
87 tory, then pathname is a relative pathname that is interpreted
88 relative to the directory referred to by dirfd.
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_ALL [All currently available fields]
164 Note that, in general, the kernel does not reject values in mask other
166 than the above. (For an exception, see EINVAL in errors.) Instead, it
167 simply informs the caller which values are supported by this kernel and
168 filesystem via the statx.stx_mask field. Therefore, do not simply set
169 mask to UINT_MAX (all bits set), as one or more bits may, in the fu‐
170 ture, be used to specify an extension to the buffer.
171 The returned information
173 The status information for the target file is returned in the statx
174 structure pointed to by statxbuf. Included in this is stx_mask which
175 indicates what other information has been returned. stx_mask has the
176 same format as the mask argument and bits are set in it to indicate
177 which fields have been filled in.
178 It should be noted that the kernel may return fields that weren't re‐
180 quested and may fail to return fields that were requested, depending on
181 what the backing filesystem supports. (Fields that are given values
182 despite being unrequested can just be ignored.) In either case,
183 stx_mask will not be equal mask.
184 If a filesystem does not support a field or if it has an unrepre‐
186 sentable value (for instance, a file with an exotic type), then the
187 mask bit corresponding to that field will be cleared in stx_mask even
188 if the user asked for it and a dummy value will be filled in for com‐
189 patibility purposes if one is available (e.g., a dummy UID and GID may
190 be specified to mount under some circumstances).
191 A filesystem may also fill in fields that the caller didn't ask for if
193 it has values for them available and the information is available at no
194 extra cost. If this happens, the corresponding bits will be set in
195 stx_mask.
196 Note: for performance and simplicity reasons, different fields in the
198 statx structure may contain state information from different moments
199 during the execution of the system call. For example, if stx_mode or
200 stx_uid is changed by another process by calling chmod(2) or chown(2),
201 stat() might return the old stx_mode together with the new stx_uid, or
202 the old stx_uid together with the new stx_mode.
203 Apart from stx_mask (which is described above), the fields in the statx
205 structure are:
206 stx_blksize
208 The "preferred" block size for efficient filesystem I/O. (Writ‐
209 ing to a file in smaller chunks may cause an inefficient read-
210 modify-rewrite.)
211 stx_attributes
213 Further status information about the file (see below for more
214 information).
215 stx_nlink
217 The number of hard links on a file.
218 stx_uid
220 This field contains the user ID of the owner of the file.
221 stx_gid
223 This field contains the ID of the group owner of the file.
224 stx_mode
226 The file type and mode. See inode(7) for details.
227 stx_ino
229 The inode number of the file.
230 stx_size
232 The size of the file (if it is a regular file or a symbolic
233 link) in bytes. The size of a symbolic link is the length of
234 the pathname it contains, without a terminating null byte.
235 stx_blocks
237 The number of blocks allocated to the file on the medium, in
238 512-byte units. (This may be smaller than stx_size/512 when the
239 file has holes.)
240 stx_attributes_mask
242 A mask indicating which bits in stx_attributes are supported by
243 the VFS and the filesystem.
244 stx_atime
246 The file's last access timestamp.
247 stx_btime
249 The file's creation timestamp.
250 stx_ctime
252 The file's last status change timestamp.
253 stx_mtime
255 The file's last modification timestamp.
256 stx_dev_major and stx_dev_minor
258 The device on which this file (inode) resides.
259 stx_rdev_major and stx_rdev_minor
261 The device that this file (inode) represents if the file is of
262 block or character device type.
263 For further information on the above fields, see inode(7).
265 File attributes
267 The stx_attributes field contains a set of ORed flags that indicate ad‐
268 ditional attributes of the file. Note that any attribute that is not
269 indicated as supported by stx_attributes_mask has no usable value here.
270 The bits in stx_attributes_mask correspond bit-by-bit to stx_at‐
271 tributes.
272 The flags are as follows:
274 STATX_ATTR_COMPRESSED
276 The file is compressed by the filesystem and may take extra re‐
277 sources to access.
278 STATX_ATTR_IMMUTABLE
280 The file cannot be modified: it cannot be deleted or renamed, no
281 hard links can be created to this file and no data can be writ‐
282 ten to it. See chattr(1).
283 STATX_ATTR_APPEND
285 The file can only be opened in append mode for writing. Random
286 access writing is not permitted. See chattr(1).
287 STATX_ATTR_NODUMP
289 File is not a candidate for backup when a backup program such as
290 dump(8) is run. See chattr(1).
291 STATX_ATTR_ENCRYPTED
293 A key is required for the file to be encrypted by the filesys‐
294 tem.
295 STATX_ATTR_VERITY (since Linux 5.5)
297 The file has fs-verity enabled. It cannot be written to, and
298 all reads from it will be verified against a cryptographic hash
299 that covers the entire file (e.g., via a Merkle tree).
300 STATX_ATTR_DAX (since Linux 5.8)
302 The file is in the DAX (cpu direct access) state. DAX state at‐
303 tempts to minimize software cache effects for both I/O and mem‐
304 ory mappings of this file. It requires a file system which has
305 been configured to support DAX.
306 DAX generally assumes all accesses are via CPU load / store in‐
308 structions which can minimize overhead for small accesses, but
309 may adversely affect CPU utilization for large transfers.
310 File I/O is done directly to/from user-space buffers and memory
312 mapped I/O may be performed with direct memory mappings that by‐
313 pass the kernel page cache.
314 While the DAX property tends to result in data being transferred
316 synchronously, it does not give the same guarantees as the
317 O_SYNC flag (see open(2)), where data and the necessary metadata
318 are transferred together.
319 A DAX file may support being mapped with the MAP_SYNC flag,
321 which enables a program to use CPU cache flush instructions to
322 persist CPU store operations without an explicit fsync(2). See
323 mmap(2) for more information.
324
326 On success, zero is returned. On error, -1 is returned, and errno is
327 set appropriately.
328
330 EACCES Search permission is denied for one of the directories in the
331 path prefix of pathname. (See also path_resolution(7).)
332 EBADF dirfd is not a valid open file descriptor.
334 EFAULT pathname or statxbuf is NULL or points to a location outside the
336 process's accessible address space.
337 EINVAL Invalid flag specified in flags.
339 EINVAL Reserved flag specified in mask. (Currently, there is one such
341 flag, designated by the constant STATX__RESERVED, with the value
342 0x80000000U.)
343 ELOOP Too many symbolic links encountered while traversing the path‐
345 name.
346 ENAMETOOLONG
348 pathname is too long.
349 ENOENT A component of pathname does not exist, or pathname is an empty
351 string and AT_EMPTY_PATH was not specified in flags.
352 ENOMEM Out of memory (i.e., kernel memory).
354 ENOTDIR
356 A component of the path prefix of pathname is not a directory or
357 pathname is relative and dirfd is a file descriptor referring to
358 a file other than a directory.
359
361 statx() was added to Linux in kernel 4.11; library support was added in
362 glibc 2.28.
363
365 statx() is Linux-specific.
366
368 ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2), stat(2),
369 utime(2), capabilities(7), inode(7), symlink(7)
370
372 This page is part of release 5.10 of the Linux man-pages project. A
373 description of the project, information about reporting bugs, and the
374 latest version of this page, can be found at
375 https://www.kernel.org/doc/man-pages/.
376Linux 2020-08-13 STATX(2)