1STAT(2)                    Linux Programmer's Manual                   STAT(2)
2
3
4

NAME

6       stat, fstat, lstat, fstatat - get file status
7

SYNOPSIS

9       #include <sys/types.h>
10       #include <sys/stat.h>
11       #include <unistd.h>
12
13       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
17       #include <fcntl.h>           /* Definition of AT_* constants */
18       #include <sys/stat.h>
19
20       int fstatat(int dirfd, const char *pathname, struct stat *statbuf,
21                   int flags);
22
23   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
24
25       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
31       fstatat():
32           Since glibc 2.10:
33               _POSIX_C_SOURCE >= 200809L
34           Before glibc 2.10:
35               _ATFILE_SOURCE
36

DESCRIPTION

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
44       stat()  and fstatat() retrieve information about the file pointed to by
45       pathname; the differences for fstatat() are described below.
46
47       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 it refers to.
50
51       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
54   The stat structure
55       All  of  these system calls return a stat structure, which contains the
56       following fields:
57
58           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
70               /* 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
74               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
78           #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
83       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
89       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
96       The fields in the stat structure are as follows:
97
98       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
102       st_ino This field contains the file's inode number.
103
104       st_mode
105              This  field  contains  the file type and mode.  See inode(7) for
106              further information.
107
108       st_nlink
109              This field contains the number of hard links to the file.
110
111       st_uid This field contains the user ID of the owner of the file.
112
113       st_gid This field contains the ID of the group owner of the file.
114
115       st_rdev
116              This field describes the device that this  file  (inode)  repre‐
117              sents.
118
119       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
125       st_blksize
126              This field  gives  the  "preferred"  block  size  for  efficient
127              filesystem I/O.
128
129       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
134       st_atime
135              This is the file's last access timestamp.
136
137       st_mtime
138              This is the file's last modification timestamp.
139
140       st_ctime
141              This is the file's last status change timestamp.
142
143       For further information on the above fields, see inode(7).
144
145   fstatat()
146       The  fstatat()  system  call  is a more general interface for accessing
147       file information which can still provide exactly the behavior  of  each
148       of stat(), lstat(), and fstat().
149
150       If  the  pathname given in pathname is relative, then it is interpreted
151       relative to the directory referred to  by  the  file  descriptor  dirfd
152       (rather  than  relative to the current working directory of the calling
153       process, as is done by stat() and lstat() for a relative pathname).
154
155       If pathname is relative and dirfd is the special value  AT_FDCWD,  then
156       pathname  is  interpreted  relative to the current working directory of
157       the calling process (like stat() and lstat()).
158
159       If pathname is absolute, then dirfd is ignored.
160
161       flags can either be 0, or include one or more of  the  following  flags
162       ORed:
163
164       AT_EMPTY_PATH (since Linux 2.6.39)
165              If  pathname is an empty string, operate on the file referred to
166              by dirfd (which may have been obtained using the open(2)  O_PATH
167              flag).   In  this case, dirfd can refer to any type of file, not
168              just a directory, and the behavior of fstatat()  is  similar  to
169              that of fstat().  If dirfd is AT_FDCWD, the call operates on the
170              current working directory.  This flag is Linux-specific;  define
171              _GNU_SOURCE to obtain its definition.
172
173       AT_NO_AUTOMOUNT (since Linux 2.6.38)
174              Don't  automount the terminal ("basename") component of pathname
175              if it is a directory that is an automount  point.   This  allows
176              the  caller  to  gather attributes of an automount point (rather
177              than the location it would mount).  Since Linux 4.14, also don't
178              instantiate a nonexistent name in an on-demand directory such as
179              used for automounter indirect maps.  This flag can  be  used  in
180              tools  that  scan  directories to prevent mass-automounting of a
181              directory of automount points.  The AT_NO_AUTOMOUNT flag has  no
182              effect  if  the mount point has already been mounted over.  This
183              flag is Linux-specific; define _GNU_SOURCE to obtain its defini‐
184              tion.  Both stat() and lstat() act as though AT_NO_AUTOMOUNT was
185              set.
186
187       AT_SYMLINK_NOFOLLOW
188              If pathname is a symbolic link, do not dereference  it:  instead
189              return  information  about  the  link itself, like lstat().  (By
190              default, fstatat() dereferences symbolic links, like stat().)
191
192       See openat(2) for an explanation of the need for fstatat().
193

RETURN VALUE

195       On success, zero is returned.  On error, -1 is returned, and  errno  is
196       set appropriately.
197

ERRORS

199       EACCES Search  permission  is  denied for one of the directories in the
200              path prefix of pathname.  (See also path_resolution(7).)
201
202       EBADF  fd is not a valid open file descriptor.
203
204       EFAULT Bad address.
205
206       ELOOP  Too many symbolic links encountered while traversing the path.
207
208       ENAMETOOLONG
209              pathname is too long.
210
211       ENOENT A component of pathname does not exist, or pathname is an  empty
212              string and AT_EMPTY_PATH was not specified in flags.
213
214       ENOMEM Out of memory (i.e., kernel memory).
215
216       ENOTDIR
217              A component of the path prefix of pathname is not a directory.
218
219       EOVERFLOW
220              pathname  or  fd  refers  to a file whose size, inode number, or
221              number of blocks cannot be  represented  in,  respectively,  the
222              types off_t, ino_t, or blkcnt_t.  This error can occur when, for
223              example, an application compiled on a  32-bit  platform  without
224              -D_FILE_OFFSET_BITS=64 calls stat() on a file whose size exceeds
225              (1<<31)-1 bytes.
226
227       The following additional errors can occur for fstatat():
228
229       EBADF  dirfd is not a valid file descriptor.
230
231       EINVAL Invalid flag specified in flags.
232
233       ENOTDIR
234              pathname is relative and dirfd is a file descriptor referring to
235              a file other than a directory.
236

VERSIONS

238       fstatat()  was  added  to  Linux  in kernel 2.6.16; library support was
239       added to glibc in version 2.4.
240

CONFORMING TO

242       stat(), fstat(), lstat(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1.2008.
243
244       fstatat(): POSIX.1-2008.
245
246       According to POSIX.1-2001, lstat() on a symbolic link need return valid
247       information  only in the st_size field and the file type of the st_mode
248       field of the stat structure.  POSIX.1-2008 tightens the  specification,
249       requiring  lstat() to return valid information in all fields except the
250       mode bits in st_mode.
251
252       Use of the st_blocks and st_blksize fields may be less portable.  (They
253       were  introduced  in  BSD.  The interpretation differs between systems,
254       and possibly on a single system when NFS mounts are involved.)
255

NOTES

257   Timestamp fields
258       Older kernels and older standards did not support nanosecond  timestamp
259       fields.  Instead, there were three timestamp fields—st_atime, st_mtime,
260       and st_ctime—typed as time_t that recorded timestamps  with  one-second
261       precision.
262
263       Since  kernel 2.5.48, the stat structure supports nanosecond resolution
264       for the three file timestamp fields.  The nanosecond components of each
265       timestamp are available via names of the form st_atim.tv_nsec, if suit‐
266       able feature test macros are defined.  Nanosecond timestamps were stan‐
267       dardized  in  POSIX.1-2008,  and,  starting  with  version  2.12, glibc
268       exposes the nanosecond component names if  _POSIX_C_SOURCE  is  defined
269       with the value 200809L or greater, or _XOPEN_SOURCE is defined with the
270       value 700 or greater.  Up to and including glibc 2.19, the  definitions
271       of  the  nanoseconds  components  are  also  defined  if _BSD_SOURCE or
272       _SVID_SOURCE is defined.  If none  of  the  aforementioned  macros  are
273       defined,  then the nanosecond values are exposed with names of the form
274       st_atimensec.
275
276   C library/kernel differences
277       Over time, increases in the size of the  stat  structure  have  led  to
278       three  successive  versions  of stat(): sys_stat() (slot __NR_oldstat),
279       sys_newstat() (slot __NR_stat), and sys_stat64() (slot __NR_stat64)  on
280       32-bit  platforms  such  as  i386.  The first two versions were already
281       present in Linux 1.0 (albeit with different names); the last was  added
282       in Linux 2.4.  Similar remarks apply for fstat() and lstat().
283
284       The  kernel-internal  versions  of the stat structure dealt with by the
285       different versions are, respectively:
286
287       __old_kernel_stat
288              The original structure, with rather narrow fields, and  no  pad‐
289              ding.
290
291       stat   Larger  st_ino  field  and padding added to various parts of the
292              structure to allow for future expansion.
293
294       stat64 Even larger st_ino field, larger st_uid  and  st_gid  fields  to
295              accommodate the Linux-2.4 expansion of UIDs and GIDs to 32 bits,
296              and various other enlarged fields and  further  padding  in  the
297              structure.   (Various  padding bytes were eventually consumed in
298              Linux 2.6, with the advent of 32-bit device IDs  and  nanosecond
299              components for the timestamp fields.)
300
301       The  glibc  stat()  wrapper  function hides these details from applica‐
302       tions, invoking the most recent version of the system call provided  by
303       the  kernel, and repacking the returned information if required for old
304       binaries.
305
306       On modern 64-bit systems, life is simpler: there  is  a  single  stat()
307       system  call  and  the kernel deals with a stat structure that contains
308       fields of a sufficient size.
309
310       The underlying system call employed  by  the  glibc  fstatat()  wrapper
311       function  is  actually  called  fstatat64()  or, on some architectures,
312       newfstatat().
313

EXAMPLE

315       The following program calls lstat() and displays selected fields in the
316       returned stat structure.
317
318       #include <sys/types.h>
319       #include <sys/stat.h>
320       #include <time.h>
321       #include <stdio.h>
322       #include <stdlib.h>
323       #include <sys/sysmacros.h>
324
325       int
326       main(int argc, char *argv[])
327       {
328           struct stat sb;
329
330           if (argc != 2) {
331               fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
332               exit(EXIT_FAILURE);
333           }
334
335           if (lstat(argv[1], &sb) == -1) {
336               perror("lstat");
337               exit(EXIT_FAILURE);
338           }
339
340           printf("ID of containing device:  [%lx,%lx]\n",
341                (long) major(sb.st_dev), (long) minor(sb.st_dev));
342
343           printf("File type:                ");
344
345           switch (sb.st_mode & S_IFMT) {
346           case S_IFBLK:  printf("block device\n");            break;
347           case S_IFCHR:  printf("character device\n");        break;
348           case S_IFDIR:  printf("directory\n");               break;
349           case S_IFIFO:  printf("FIFO/pipe\n");               break;
350           case S_IFLNK:  printf("symlink\n");                 break;
351           case S_IFREG:  printf("regular file\n");            break;
352           case S_IFSOCK: printf("socket\n");                  break;
353           default:       printf("unknown?\n");                break;
354           }
355
356           printf("I-node number:            %ld\n", (long) sb.st_ino);
357
358           printf("Mode:                     %lo (octal)\n",
359                   (unsigned long) sb.st_mode);
360
361           printf("Link count:               %ld\n", (long) sb.st_nlink);
362           printf("Ownership:                UID=%ld   GID=%ld\n",
363                   (long) sb.st_uid, (long) sb.st_gid);
364
365           printf("Preferred I/O block size: %ld bytes\n",
366                   (long) sb.st_blksize);
367           printf("File size:                %lld bytes\n",
368                   (long long) sb.st_size);
369           printf("Blocks allocated:         %lld\n",
370                   (long long) sb.st_blocks);
371
372           printf("Last status change:       %s", ctime(&sb.st_ctime));
373           printf("Last file access:         %s", ctime(&sb.st_atime));
374           printf("Last file modification:   %s", ctime(&sb.st_mtime));
375
376           exit(EXIT_SUCCESS);
377       }
378

SEE ALSO

380       ls(1),  stat(1),  access(2), chmod(2), chown(2), readlink(2), utime(2),
381       capabilities(7), inode(7), symlink(7)
382

COLOPHON

384       This page is part of release 4.15 of the Linux  man-pages  project.   A
385       description  of  the project, information about reporting bugs, and the
386       latest    version    of    this    page,    can     be     found     at
387       https://www.kernel.org/doc/man-pages/.
388
389
390
391Linux                             2017-09-15                           STAT(2)
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