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 is a dangling symbolic
212              link.
213
214       ENOENT pathname  is an empty string and AT_EMPTY_PATH was not specified
215              in flags.
216
217       ENOMEM Out of memory (i.e., kernel memory).
218
219       ENOTDIR
220              A component of the path prefix of pathname is not a directory.
221
222       EOVERFLOW
223              pathname or fd refers to a file whose  size,  inode  number,  or
224              number  of  blocks  cannot  be represented in, respectively, the
225              types off_t, ino_t, or blkcnt_t.  This error can occur when, for
226              example,  an  application  compiled on a 32-bit platform without
227              -D_FILE_OFFSET_BITS=64 calls stat() on a file whose size exceeds
228              (1<<31)-1 bytes.
229
230       The following additional errors can occur for fstatat():
231
232       EBADF  dirfd is not a valid file descriptor.
233
234       EINVAL Invalid flag specified in flags.
235
236       ENOTDIR
237              pathname is relative and dirfd is a file descriptor referring to
238              a file other than a directory.
239

VERSIONS

241       fstatat() was added to Linux in  kernel  2.6.16;  library  support  was
242       added to glibc in version 2.4.
243

CONFORMING TO

245       stat(), fstat(), lstat(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1.2008.
246
247       fstatat(): POSIX.1-2008.
248
249       According to POSIX.1-2001, lstat() on a symbolic link need return valid
250       information only in the st_size field and the file type of the  st_mode
251       field  of the stat structure.  POSIX.1-2008 tightens the specification,
252       requiring lstat() to return valid information in all fields except  the
253       mode bits in st_mode.
254
255       Use of the st_blocks and st_blksize fields may be less portable.  (They
256       were introduced in BSD.  The interpretation  differs  between  systems,
257       and possibly on a single system when NFS mounts are involved.)
258

NOTES

260   Timestamp fields
261       Older  kernels and older standards did not support nanosecond timestamp
262       fields.  Instead, there were three timestamp fields—st_atime, st_mtime,
263       and  st_ctime—typed  as time_t that recorded timestamps with one-second
264       precision.
265
266       Since kernel 2.5.48, the stat structure supports nanosecond  resolution
267       for the three file timestamp fields.  The nanosecond components of each
268       timestamp are available via names of the form st_atim.tv_nsec, if suit‐
269       able feature test macros are defined.  Nanosecond timestamps were stan‐
270       dardized in  POSIX.1-2008,  and,  starting  with  version  2.12,  glibc
271       exposes  the  nanosecond  component names if _POSIX_C_SOURCE is defined
272       with the value 200809L or greater, or _XOPEN_SOURCE is defined with the
273       value  700 or greater.  Up to and including glibc 2.19, the definitions
274       of the nanoseconds  components  are  also  defined  if  _BSD_SOURCE  or
275       _SVID_SOURCE  is  defined.   If  none  of the aforementioned macros are
276       defined, then the nanosecond values are exposed with names of the  form
277       st_atimensec.
278
279   C library/kernel differences
280       Over  time,  increases  in  the  size of the stat structure have led to
281       three successive versions of stat():  sys_stat()  (slot  __NR_oldstat),
282       sys_newstat()  (slot __NR_stat), and sys_stat64() (slot __NR_stat64) on
283       32-bit platforms such as i386.  The first  two  versions  were  already
284       present  in Linux 1.0 (albeit with different names); the last was added
285       in Linux 2.4.  Similar remarks apply for fstat() and lstat().
286
287       The kernel-internal versions of the stat structure dealt  with  by  the
288       different versions are, respectively:
289
290       __old_kernel_stat
291              The  original  structure, with rather narrow fields, and no pad‐
292              ding.
293
294       stat   Larger st_ino field and padding added to various  parts  of  the
295              structure to allow for future expansion.
296
297       stat64 Even  larger  st_ino  field,  larger st_uid and st_gid fields to
298              accommodate the Linux-2.4 expansion of UIDs and GIDs to 32 bits,
299              and  various  other  enlarged  fields and further padding in the
300              structure.  (Various padding bytes were eventually  consumed  in
301              Linux  2.6,  with the advent of 32-bit device IDs and nanosecond
302              components for the timestamp fields.)
303
304       The glibc stat() wrapper function hides  these  details  from  applica‐
305       tions,  invoking the most recent version of the system call provided by
306       the kernel, and repacking the returned information if required for  old
307       binaries.
308
309       On  modern  64-bit  systems,  life is simpler: there is a single stat()
310       system call and the kernel deals with a stat  structure  that  contains
311       fields of a sufficient size.
312
313       The  underlying  system  call  employed  by the glibc fstatat() wrapper
314       function is actually called  fstatat64()  or,  on  some  architectures,
315       newfstatat().
316

EXAMPLE

318       The following program calls lstat() and displays selected fields in the
319       returned stat structure.
320
321       #include <sys/types.h>
322       #include <sys/stat.h>
323       #include <time.h>
324       #include <stdio.h>
325       #include <stdlib.h>
326       #include <sys/sysmacros.h>
327
328       int
329       main(int argc, char *argv[])
330       {
331           struct stat sb;
332
333           if (argc != 2) {
334               fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
335               exit(EXIT_FAILURE);
336           }
337
338           if (lstat(argv[1], &sb) == -1) {
339               perror("lstat");
340               exit(EXIT_FAILURE);
341           }
342
343           printf("ID of containing device:  [%lx,%lx]\n",
344                (long) major(sb.st_dev), (long) minor(sb.st_dev));
345
346           printf("File type:                ");
347
348           switch (sb.st_mode & S_IFMT) {
349           case S_IFBLK:  printf("block device\n");            break;
350           case S_IFCHR:  printf("character device\n");        break;
351           case S_IFDIR:  printf("directory\n");               break;
352           case S_IFIFO:  printf("FIFO/pipe\n");               break;
353           case S_IFLNK:  printf("symlink\n");                 break;
354           case S_IFREG:  printf("regular file\n");            break;
355           case S_IFSOCK: printf("socket\n");                  break;
356           default:       printf("unknown?\n");                break;
357           }
358
359           printf("I-node number:            %ld\n", (long) sb.st_ino);
360
361           printf("Mode:                     %lo (octal)\n",
362                   (unsigned long) sb.st_mode);
363
364           printf("Link count:               %ld\n", (long) sb.st_nlink);
365           printf("Ownership:                UID=%ld   GID=%ld\n",
366                   (long) sb.st_uid, (long) sb.st_gid);
367
368           printf("Preferred I/O block size: %ld bytes\n",
369                   (long) sb.st_blksize);
370           printf("File size:                %lld bytes\n",
371                   (long long) sb.st_size);
372           printf("Blocks allocated:         %lld\n",
373                   (long long) sb.st_blocks);
374
375           printf("Last status change:       %s", ctime(&sb.st_ctime));
376           printf("Last file access:         %s", ctime(&sb.st_atime));
377           printf("Last file modification:   %s", ctime(&sb.st_mtime));
378
379           exit(EXIT_SUCCESS);
380       }
381

SEE ALSO

383       ls(1), stat(1), access(2), chmod(2), chown(2),  readlink(2),  statx(2),
384       utime(2), capabilities(7), inode(7), symlink(7)
385

COLOPHON

387       This  page  is  part of release 5.04 of the Linux man-pages project.  A
388       description of the project, information about reporting bugs,  and  the
389       latest     version     of     this    page,    can    be    found    at
390       https://www.kernel.org/doc/man-pages/.
391
392
393
394Linux                             2019-03-06                           STAT(2)
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