1STAT(2) Linux Programmer's Manual STAT(2)
2
6 stat, fstat, lstat, fstatat - get file status
7
9 #include <sys/types.h>
10 #include <sys/stat.h>
11 #include <unistd.h>
12 int stat(const char *pathname, struct stat *statbuf);
14 int fstat(int fd, struct stat *statbuf);
15 int lstat(const char *pathname, struct stat *statbuf);
16 #include <fcntl.h> /* Definition of AT_* constants */
18 #include <sys/stat.h>
19 int fstatat(int dirfd, const char *pathname, struct stat *statbuf,
21 int flags);
22 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
24 lstat():
26 /* glibc 2.19 and earlier */ _BSD_SOURCE
27 || /* Since glibc 2.20 */ _DEFAULT_SOURCE
28 || _XOPEN_SOURCE >= 500
29 || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L
30 fstatat():
32 Since glibc 2.10:
33 _POSIX_C_SOURCE >= 200809L
34 Before glibc 2.10:
35 _ATFILE_SOURCE
36
38 These functions return information about a file, in the buffer pointed
39 to by statbuf. No permissions are required on the file itself, but—in
40 the case of stat(), fstatat(), and lstat()—execute (search) permission
41 is required on all of the directories in pathname that lead to the
42 file.
43 stat() and fstatat() retrieve information about the file pointed to by
45 pathname; the differences for fstatat() are described below.
46 lstat() is identical to stat(), except that if pathname is a symbolic
48 link, then it returns information about the link itself, not the file
49 that the link refers to.
50 fstat() is identical to stat(), except that the file about which infor‐
52 mation is to be retrieved is specified by the file descriptor fd.
53 The stat structure
55 All of these system calls return a stat structure, which contains the
56 following fields:
57 struct stat {
59 dev_t st_dev; /* ID of device containing file */
60 ino_t st_ino; /* Inode number */
61 mode_t st_mode; /* File type and mode */
62 nlink_t st_nlink; /* Number of hard links */
63 uid_t st_uid; /* User ID of owner */
64 gid_t st_gid; /* Group ID of owner */
65 dev_t st_rdev; /* Device ID (if special file) */
66 off_t st_size; /* Total size, in bytes */
67 blksize_t st_blksize; /* Block size for filesystem I/O */
68 blkcnt_t st_blocks; /* Number of 512B blocks allocated */
69 /* Since Linux 2.6, the kernel supports nanosecond
71 precision for the following timestamp fields.
72 For the details before Linux 2.6, see NOTES. */
73 struct timespec st_atim; /* Time of last access */
75 struct timespec st_mtim; /* Time of last modification */
76 struct timespec st_ctim; /* Time of last status change */
77 #define st_atime st_atim.tv_sec /* Backward compatibility */
79 #define st_mtime st_mtim.tv_sec
80 #define st_ctime st_ctim.tv_sec
81 };
82 Note: the order of fields in the stat structure varies somewhat across
84 architectures. In addition, the definition above does not show the
85 padding bytes that may be present between some fields on various archi‐
86 tectures. Consult the glibc and kernel source code if you need to know
87 the details.
88 Note: for performance and simplicity reasons, different fields in the
90 stat structure may contain state information from different moments
91 during the execution of the system call. For example, if st_mode or
92 st_uid is changed by another process by calling chmod(2) or chown(2),
93 stat() might return the old st_mode together with the new st_uid, or
94 the old st_uid together with the new st_mode.
95 The fields in the stat structure are as follows:
97 st_dev This field describes the device on which this file resides.
99 (The major(3) and minor(3) macros may be useful to decompose the
100 device ID in this field.)
101 st_ino This field contains the file's inode number.
103 st_mode
105 This field contains the file type and mode. See inode(7) for
106 further information.
107 st_nlink
109 This field contains the number of hard links to the file.
110 st_uid This field contains the user ID of the owner of the file.
112 st_gid This field contains the ID of the group owner of the file.
114 st_rdev
116 This field describes the device that this file (inode) repre‐
117 sents.
118 st_size
120 This field gives the size of the file (if it is a regular file
121 or a symbolic link) in bytes. The size of a symbolic link is
122 the length of the pathname it contains, without a terminating
123 null byte.
124 st_blksize
126 This field gives the "preferred" block size for efficient
127 filesystem I/O.
128 st_blocks
130 This field indicates the number of blocks allocated to the file,
131 in 512-byte units. (This may be smaller than st_size/512 when
132 the file has holes.)
133 st_atime
135 This is the time of the last access of file data.
136 st_mtime
138 This is the time of last modification of file data.
139 st_ctime
141 This is the file's last status change timestamp (time of last
142 change to the inode).
143 For further information on the above fields, see inode(7).
145 fstatat()
147 The fstatat() system call is a more general interface for accessing
148 file information which can still provide exactly the behavior of each
149 of stat(), lstat(), and fstat().
150 If the pathname given in pathname is relative, then it is interpreted
152 relative to the directory referred to by the file descriptor dirfd
153 (rather than relative to the current working directory of the calling
154 process, as is done by stat() and lstat() for a relative pathname).
155 If pathname is relative and dirfd is the special value AT_FDCWD, then
157 pathname is interpreted relative to the current working directory of
158 the calling process (like stat() and lstat()).
159 If pathname is absolute, then dirfd is ignored.
161 flags can either be 0, or include one or more of the following flags
163 ORed:
164 AT_EMPTY_PATH (since Linux 2.6.39)
166 If pathname is an empty string, operate on the file referred to
167 by dirfd (which may have been obtained using the open(2) O_PATH
168 flag). In this case, dirfd can refer to any type of file, not
169 just a directory, and the behavior of fstatat() is similar to
170 that of fstat(). If dirfd is AT_FDCWD, the call operates on the
171 current working directory. This flag is Linux-specific; define
172 _GNU_SOURCE to obtain its definition.
173 AT_NO_AUTOMOUNT (since Linux 2.6.38)
175 Don't automount the terminal ("basename") component of pathname
176 if it is a directory that is an automount point. This allows
177 the caller to gather attributes of an automount point (rather
178 than the location it would mount). Since Linux 4.14, also don't
179 instantiate a nonexistent name in an on-demand directory such as
180 used for automounter indirect maps. This flag has no effect if
181 the mount point has already been mounted over.
182 Both stat() and lstat() act as though AT_NO_AUTOMOUNT was set.
184 The AT_NO_AUTOMOUNT can be used in tools that scan directories
186 to prevent mass-automounting of a directory of automount points.
187 This flag is Linux-specific; define _GNU_SOURCE to obtain its
189 definition.
190 AT_SYMLINK_NOFOLLOW
192 If pathname is a symbolic link, do not dereference it: instead
193 return information about the link itself, like lstat(). (By de‐
194 fault, fstatat() dereferences symbolic links, like stat().)
195 See openat(2) for an explanation of the need for fstatat().
197
199 On success, zero is returned. On error, -1 is returned, and errno is
200 set appropriately.
201
203 EACCES Search permission is denied for one of the directories in the
204 path prefix of pathname. (See also path_resolution(7).)
205 EBADF fd is not a valid open file descriptor.
207 EFAULT Bad address.
209 ELOOP Too many symbolic links encountered while traversing the path.
211 ENAMETOOLONG
213 pathname is too long.
214 ENOENT A component of pathname does not exist or is a dangling symbolic
216 link.
217 ENOENT pathname is an empty string and AT_EMPTY_PATH was not specified
219 in flags.
220 ENOMEM Out of memory (i.e., kernel memory).
222 ENOTDIR
224 A component of the path prefix of pathname is not a directory.
225 EOVERFLOW
227 pathname or fd refers to a file whose size, inode number, or
228 number of blocks cannot be represented in, respectively, the
229 types off_t, ino_t, or blkcnt_t. This error can occur when, for
230 example, an application compiled on a 32-bit platform without
231 -D_FILE_OFFSET_BITS=64 calls stat() on a file whose size exceeds
232 (1<<31)-1 bytes.
233 The following additional errors can occur for fstatat():
235 EBADF dirfd is not a valid file descriptor.
237 EINVAL Invalid flag specified in flags.
239 ENOTDIR
241 pathname is relative and dirfd is a file descriptor referring to
242 a file other than a directory.
243
245 fstatat() was added to Linux in kernel 2.6.16; library support was
246 added to glibc in version 2.4.
247
249 stat(), fstat(), lstat(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1.2008.
250 fstatat(): POSIX.1-2008.
252 According to POSIX.1-2001, lstat() on a symbolic link need return valid
254 information only in the st_size field and the file type of the st_mode
255 field of the stat structure. POSIX.1-2008 tightens the specification,
256 requiring lstat() to return valid information in all fields except the
257 mode bits in st_mode.
258 Use of the st_blocks and st_blksize fields may be less portable. (They
260 were introduced in BSD. The interpretation differs between systems,
261 and possibly on a single system when NFS mounts are involved.)
262
264 Timestamp fields
265 Older kernels and older standards did not support nanosecond timestamp
266 fields. Instead, there were three timestamp fields—st_atime, st_mtime,
267 and st_ctime—typed as time_t that recorded timestamps with one-second
268 precision.
269 Since kernel 2.5.48, the stat structure supports nanosecond resolution
271 for the three file timestamp fields. The nanosecond components of each
272 timestamp are available via names of the form st_atim.tv_nsec, if suit‐
273 able feature test macros are defined. Nanosecond timestamps were stan‐
274 dardized in POSIX.1-2008, and, starting with version 2.12, glibc ex‐
275 poses the nanosecond component names if _POSIX_C_SOURCE is defined with
276 the value 200809L or greater, or _XOPEN_SOURCE is defined with the
277 value 700 or greater. Up to and including glibc 2.19, the definitions
278 of the nanoseconds components are also defined if _BSD_SOURCE or
279 _SVID_SOURCE is defined. If none of the aforementioned macros are de‐
280 fined, then the nanosecond values are exposed with names of the form
281 st_atimensec.
282 C library/kernel differences
284 Over time, increases in the size of the stat structure have led to
285 three successive versions of stat(): sys_stat() (slot __NR_oldstat),
286 sys_newstat() (slot __NR_stat), and sys_stat64() (slot __NR_stat64) on
287 32-bit platforms such as i386. The first two versions were already
288 present in Linux 1.0 (albeit with different names); the last was added
289 in Linux 2.4. Similar remarks apply for fstat() and lstat().
290 The kernel-internal versions of the stat structure dealt with by the
292 different versions are, respectively:
293 __old_kernel_stat
295 The original structure, with rather narrow fields, and no pad‐
296 ding.
297 stat Larger st_ino field and padding added to various parts of the
299 structure to allow for future expansion.
300 stat64 Even larger st_ino field, larger st_uid and st_gid fields to ac‐
302 commodate the Linux-2.4 expansion of UIDs and GIDs to 32 bits,
303 and various other enlarged fields and further padding in the
304 structure. (Various padding bytes were eventually consumed in
305 Linux 2.6, with the advent of 32-bit device IDs and nanosecond
306 components for the timestamp fields.)
307 The glibc stat() wrapper function hides these details from applica‐
309 tions, invoking the most recent version of the system call provided by
310 the kernel, and repacking the returned information if required for old
311 binaries.
312 On modern 64-bit systems, life is simpler: there is a single stat()
314 system call and the kernel deals with a stat structure that contains
315 fields of a sufficient size.
316 The underlying system call employed by the glibc fstatat() wrapper
318 function is actually called fstatat64() or, on some architectures,
319 newfstatat().
320
322 The following program calls lstat() and displays selected fields in the
323 returned stat structure.
324 #include <sys/types.h>
326 #include <sys/stat.h>
327 #include <stdint.h>
328 #include <time.h>
329 #include <stdio.h>
330 #include <stdlib.h>
331 #include <sys/sysmacros.h>
332 int
334 main(int argc, char *argv[])
335 {
336 struct stat sb;
337 if (argc != 2) {
339 fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
340 exit(EXIT_FAILURE);
341 }
342 if (lstat(argv[1], &sb) == -1) {
344 perror("lstat");
345 exit(EXIT_FAILURE);
346 }
347 printf("ID of containing device: [%jx,%jx]\n",
349 (uintmax_t) major(sb.st_dev),
350 (uintmax_t) minor(sb.st_dev));
351 printf("File type: ");
353 switch (sb.st_mode & S_IFMT) {
355 case S_IFBLK: printf("block device\n"); break;
356 case S_IFCHR: printf("character device\n"); break;
357 case S_IFDIR: printf("directory\n"); break;
358 case S_IFIFO: printf("FIFO/pipe\n"); break;
359 case S_IFLNK: printf("symlink\n"); break;
360 case S_IFREG: printf("regular file\n"); break;
361 case S_IFSOCK: printf("socket\n"); break;
362 default: printf("unknown?\n"); break;
363 }
364 printf("I-node number: %ju\n", (uintmax_t) sb.st_ino);
366 printf("Mode: %jo (octal)\n",
368 (uintmax_t) sb.st_mode);
369 printf("Link count: %ju\n", (uintmax_t) sb.st_nlink);
371 printf("Ownership: UID=%ju GID=%ju\n",
372 (uintmax_t) sb.st_uid, (uintmax_t) sb.st_gid);
373 printf("Preferred I/O block size: %jd bytes\n",
375 (intmax_t) sb.st_blksize);
376 printf("File size: %jd bytes\n",
377 (intmax_t) sb.st_size);
378 printf("Blocks allocated: %jd\n",
379 (intmax_t) sb.st_blocks);
380 printf("Last status change: %s", ctime(&sb.st_ctime));
382 printf("Last file access: %s", ctime(&sb.st_atime));
383 printf("Last file modification: %s", ctime(&sb.st_mtime));
384 exit(EXIT_SUCCESS);
386 }
387
389 ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2), statx(2),
390 utime(2), capabilities(7), inode(7), symlink(7)
391
393 This page is part of release 5.10 of the Linux man-pages project. A
394 description of the project, information about reporting bugs, and the
395 latest version of this page, can be found at
396 https://www.kernel.org/doc/man-pages/.
397Linux 2020-08-13 STAT(2)