NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON

STAT(2)                   Linux Programmer's Manual                  STAT(2)

NAME         top

       stat, fstat, lstat, fstatat - get file status

SYNOPSIS         top

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <unistd.h>

       int stat(const char *pathname, struct stat *buf);
       int fstat(int fd, struct stat *buf);
       int lstat(const char *pathname, struct stat *buf);

       #include <fcntl.h>           /* Definition of AT_* constants */
       #include <sys/stat.h>

       int fstatat(int dirfd, const char *pathname, struct stat *buf,
                   int flags);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       lstat():
           /* glibc 2.19 and earlier */ _BSD_SOURCE ||
           /* Since glibc 2.20 */_DEFAULT_SOURCE ||
           _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
           || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L

       fstatat():
           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _ATFILE_SOURCE

DESCRIPTION         top

       These functions return information about a file, in the buffer
       pointed to by stat.  No permissions are required on the file itself,
       but—in the case of stat(), fstatat(), and lstat()—execute (search)
       permission is required on all of the directories in pathname that
       lead to the file.

       stat() and fstatat() retrieve information about the file pointed to
       by pathname; the differences for fstatat() are described below.

       lstat() is identical to stat(), except that if pathname is a symbolic
       link, then it returns information about the link itself, not the file
       that it refers to.

       fstat() is identical to stat(), except that the file about which
       information is to be retrieved is specified by the file descriptor
       fd.

       All of these system calls return a stat structure, which contains the
       following fields:

           struct stat {
               dev_t     st_dev;         /* ID of device containing file */
               ino_t     st_ino;         /* inode number */
               mode_t    st_mode;        /* protection */
               nlink_t   st_nlink;       /* number of hard links */
               uid_t     st_uid;         /* user ID of owner */
               gid_t     st_gid;         /* group ID of owner */
               dev_t     st_rdev;        /* device ID (if special file) */
               off_t     st_size;        /* total size, in bytes */
               blksize_t st_blksize;     /* blocksize for filesystem I/O */
               blkcnt_t  st_blocks;      /* number of 512B blocks allocated */

               /* Since Linux 2.6, the kernel supports nanosecond
                  precision for the following timestamp fields.
                  For the details before Linux 2.6, see NOTES. */

               struct timespec st_atim;  /* time of last access */
               struct timespec st_mtim;  /* time of last modification */
               struct timespec st_ctim;  /* time of last status change */

           #define st_atime st_atim.tv_sec      /* Backward compatibility */
           #define st_mtime st_mtim.tv_sec
           #define st_ctime st_ctim.tv_sec
           };

       Note: the order of fields in the stat structure varies somewhat
       across architectures.  In addition, the definition above does not
       show the padding bytes that may be present between some fields on
       various architectures.  Consult the the glibc and kernel source code
       if you need to know the details.

       The st_dev field describes the device on which this file resides.
       (The major(3) and minor(3) macros may be useful to decompose the
       device ID in this field.)

       The st_rdev field describes the device that this file (inode)
       represents.

       The st_size field gives the size of the file (if it is a regular file
       or a symbolic link) in bytes.  The size of a symbolic link is the
       length of the pathname it contains, without a terminating null byte.

       The st_blocks field indicates the number of blocks allocated to the
       file, 512-byte units.  (This may be smaller than st_size/512 when the
       file has holes.)

       The st_blksize field gives the "preferred" blocksize for efficient
       filesystem I/O.  (Writing to a file in smaller chunks may cause an
       inefficient read-modify-rewrite.)

       Not all of the Linux filesystems implement all of the time fields.
       Some filesystem types allow mounting in such a way that file and/or
       directory accesses do not cause an update of the st_atime field.
       (See noatime, nodiratime, and relatime in mount(8), and related
       information in mount(2).)  In addition, st_atime is not updated if a
       file is opened with the O_NOATIME; see open(2).

       The field st_atime is changed by file accesses, for example, by
       execve(2), mknod(2), pipe(2), utime(2) and read(2) (of more than zero
       bytes).  Other routines, like mmap(2), may or may not update
       st_atime.

       The field st_mtime is changed by file modifications, for example, by
       mknod(2), truncate(2), utime(2) and write(2) (of more than zero
       bytes).  Moreover, st_mtime of a directory is changed by the creation
       or deletion of files in that directory.  The st_mtime field is not
       changed for changes in owner, group, hard link count, or mode.

       The field st_ctime is changed by writing or by setting inode
       information (i.e., owner, group, link count, mode, etc.).

       The following mask values are defined for the file type component of
       the st_mode field:

           S_IFMT     0170000   bit mask for the file type bit fields

           S_IFSOCK   0140000   socket
           S_IFLNK    0120000   symbolic link
           S_IFREG    0100000   regular file
           S_IFBLK    0060000   block device
           S_IFDIR    0040000   directory
           S_IFCHR    0020000   character device
           S_IFIFO    0010000   FIFO

       Thus, to test for a regular file (for example), one could write:

           stat(pathname, &sb);
           if ((sb.st_mode & S_IFMT) == S_IFREG) {
               /* Handle regular file */
           }

       Because tests of the above form are common, additional macros are
       defined by POSIX to allow the test of the file type in st_mode to be
       written more concisely:

           S_ISREG(m)  is it a regular file?

           S_ISDIR(m)  directory?

           S_ISCHR(m)  character device?

           S_ISBLK(m)  block device?

           S_ISFIFO(m) FIFO (named pipe)?

           S_ISLNK(m)  symbolic link?  (Not in POSIX.1-1996.)

           S_ISSOCK(m) socket?  (Not in POSIX.1-1996.)

       The preceding code snippet could thus be rewritten as:

           stat(pathname, &sb);
           if (S_ISREG(sb.st_mode)) {
               /* Handle regular file */
           }

       The definitions of most of the above file type test macros are
       provided if any of the following feature test macros is defined:
       _BSD_SOURCE (in glibc 2.19 and earlier), _SVID_SOURCE (in glibc 2.19
       and earlier), or _DEFAULT_SOURCE (in glibc 2.20 and later).  In
       addition, definitions of all of the above macros except S_IFSOCK and
       S_ISSOCK() are provided if _XOPEN_SOURCE is defined.  The definition
       of S_IFSOCK can also be exposed by defining _XOPEN_SOURCE with a
       value of 500 or greater.

       The definition of S_ISSOCK() is exposed if any of the following
       feature test macros is defined: _BSD_SOURCE (in glibc 2.19 and
       earlier), _DEFAULT_SOURCE (in glibc 2.20 and later), _XOPEN_SOURCE
       with a value of 500 or greater, or _POSIX_C_SOURCE with a value of
       200112L or greater.

       The following mask values are defined for the file permissions
       component of the st_mode field:

           S_ISUID   0004000   set-user-ID bit
           S_ISGID   0002000   set-group-ID bit (see below)
           S_ISVTX   0001000   sticky bit (see below)

           S_IRWXU     00700   mask for file owner permissions

           S_IRUSR     00400   owner has read permission
           S_IWUSR     00200   owner has write permission
           S_IXUSR     00100   owner has execute permission

           S_IRWXG     00070   mask for group permissions
           S_IRGRP     00040   group has read permission
           S_IWGRP     00020   group has write permission
           S_IXGRP     00010   group has execute permission

           S_IRWXO     00007   mask for permissions for others
                               (not in group)
           S_IROTH     00004   others have read permission
           S_IWOTH     00002   others have write permission
           S_IXOTH     00001   others have execute permission

       The set-group-ID bit (S_ISGID) has several special uses.  For a
       directory, it indicates that BSD semantics is to be used for that
       directory: files created there inherit their group ID from the
       directory, not from the effective group ID of the creating process,
       and directories created there will also get the S_ISGID bit set.  For
       a file that does not have the group execution bit (S_IXGRP) set, the
       set-group-ID bit indicates mandatory file/record locking.

       The sticky bit (S_ISVTX) on a directory means that a file in that
       directory can be renamed or deleted only by the owner of the file, by
       the owner of the directory, and by a privileged process.

   fstatat()
       The fstatat() system call operates in exactly the same way as stat(),
       except for the differences described here.

       If the pathname given in pathname is relative, then it is interpreted
       relative to the directory referred to by the file descriptor dirfd
       (rather than relative to the current working directory of the calling
       process, as is done by stat() for a relative pathname).

       If pathname is relative and dirfd is the special value AT_FDCWD, then
       pathname is interpreted relative to the current working directory of
       the calling process (like stat()).

       If pathname is absolute, then dirfd is ignored.

       flags can either be 0, or include one or more of the following flags
       ORed:

       AT_EMPTY_PATH (since Linux 2.6.39)
              If pathname is an empty string, operate on the file referred
              to by dirfd (which may have been obtained using the open(2)
              O_PATH flag).  If dirfd is AT_FDCWD, the call operates on the
              current working directory.  In this case, dirfd can refer to
              any type of file, not just a directory.  This flag is Linux-
              specific; define _GNU_SOURCE to obtain its definition.

       AT_NO_AUTOMOUNT (since Linux 2.6.38)
              Don't automount the terminal ("basename") component of
              pathname if it is a directory that is an automount point.
              This allows the caller to gather attributes of an automount
              point (rather than the location it would mount).  This flag
              can be used in tools that scan directories to prevent mass-
              automounting of a directory of automount points.  The
              AT_NO_AUTOMOUNT flag has no effect if the mount point has
              already been mounted over.  This flag is Linux-specific;
              define _GNU_SOURCE to obtain its definition.

       AT_SYMLINK_NOFOLLOW
              If pathname is a symbolic link, do not dereference it: instead
              return information about the link itself, like lstat().  (By
              default, fstatat() dereferences symbolic links, like stat().)

       See openat(2) for an explanation of the need for fstatat().

RETURN VALUE         top

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

ERRORS         top

       EACCES Search permission is denied for one of the directories in the
              path prefix of pathname.  (See also path_resolution(7).)

       EBADF  fd is bad.

       EFAULT Bad address.

       ELOOP  Too many symbolic links encountered while traversing the path.

       ENAMETOOLONG
              pathname is too long.

       ENOENT A component of pathname does not exist, or pathname is an
              empty string.

       ENOMEM Out of memory (i.e., kernel memory).

       ENOTDIR
              A component of the path prefix of pathname is not a directory.

       EOVERFLOW
              pathname or fd refers to a file whose size, inode number, or
              number of blocks cannot be represented in, respectively, the
              types off_t, ino_t, or blkcnt_t.  This error can occur when,
              for example, an application compiled on a 32-bit platform
              without -D_FILE_OFFSET_BITS=64 calls stat() on a file whose
              size exceeds (1<<31)-1 bytes.

       The following additional errors can occur for fstatat():

       EBADF  dirfd is not a valid file descriptor.

       EINVAL Invalid flag specified in flags.

       ENOTDIR
              pathname is relative and dirfd is a file descriptor referring
              to a file other than a directory.

VERSIONS         top

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

CONFORMING TO         top

       stat(), fstat(), lstat(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1.2008.

       fstatat(): POSIX.1-2008.

       According to POSIX.1-2001, lstat() on a symbolic link need return
       valid information only in the st_size field and the file-type
       component of the st_mode field of the stat structure.  POSIX.1-2008
       tightens the specification, requiring lstat() to return valid
       information in all fields except the permission bits in st_mode.

       Use of the st_blocks and st_blksize fields may be less portable.
       (They were introduced in BSD.  The interpretation differs between
       systems, and possibly on a single system when NFS mounts are
       involved.)  If you need to obtain the definition of the blkcnt_t or
       blksize_t types from <sys/stat.h>, then define _XOPEN_SOURCE with the
       value 500 or greater (before including any header files).

       POSIX.1-1990 did not describe the S_IFMT, S_IFSOCK, S_IFLNK, S_IFREG,
       S_IFBLK, S_IFDIR, S_IFCHR, S_IFIFO, S_ISVTX constants, but instead
       demanded the use of the macros S_ISDIR(), and so on.  The S_IF*
       constants are present in POSIX.1-2001 and later.

       The S_ISLNK() and S_ISSOCK() macros are not in POSIX.1-1996, but both
       are present in POSIX.1-2001; the former is from SVID 4, the latter
       from SUSv2.

       UNIX V7 (and later systems) had S_IREAD, S_IWRITE, S_IEXEC, where
       POSIX prescribes the synonyms S_IRUSR, S_IWUSR, S_IXUSR.

   Other systems
       Values that have been (or are) in use on various systems:

       hex    name       ls   octal    description
       f000   S_IFMT          170000   mask for file type
       0000                   000000   SCO out-of-service inode; BSD
                                       unknown type; SVID-v2 and XPG2 have
                                       both 0 and 0100000 for ordinary file
       1000   S_IFIFO    p|   010000   FIFO (named pipe)
       2000   S_IFCHR    c    020000   character special (V7)
       3000   S_IFMPC         030000   multiplexed character special (V7)
       4000   S_IFDIR    d/   040000   directory (V7)
       5000   S_IFNAM         050000   XENIX named special file with two
                                       subtypes, distinguished by st_rdev
                                       values 1, 2
       0001   S_INSEM    s    000001   XENIX semaphore subtype of IFNAM
       0002   S_INSHD    m    000002   XENIX shared data subtype of IFNAM
       6000   S_IFBLK    b    060000   block special (V7)
       7000   S_IFMPB         070000   multiplexed block special (V7)
       8000   S_IFREG    -    100000   regular (V7)
       9000   S_IFCMP         110000   VxFS compressed
       9000   S_IFNWK    n    110000   network special (HP-UX)
       a000   S_IFLNK    l@   120000   symbolic link (BSD)
       b000   S_IFSHAD        130000   Solaris shadow inode for ACL (not
                                       seen by user space)
       c000   S_IFSOCK   s=   140000   socket (BSD; also "S_IFSOC" on VxFS)
       d000   S_IFDOOR   D>   150000   Solaris door
       e000   S_IFWHT    w%   160000   BSD whiteout (not used for inode)
       0200   S_ISVTX         001000   sticky bit: save swapped text even
                                       after use (V7)
                                       reserved (SVID-v2)
                                       On nondirectories: don't cache this
                                       file (SunOS)
                                       On directories: restricted deletion
                                       flag (SVID-v4.2)
       0400   S_ISGID         002000   set-group-ID on execution (V7)
                                       for directories: use BSD semantics
                                       for propagation of GID
       0400   S_ENFMT         002000   System V file locking enforcement
                                       (shared with S_ISGID)
       0800   S_ISUID         004000   set-user-ID on execution (V7)
       0800   S_CDF           004000   directory is a context dependent
                                       file (HP-UX)

       A sticky command appeared in Version 32V AT&T UNIX.

NOTES         top

       On Linux, lstat() will generally not trigger automounter action,
       whereas stat() will (but see fstatat(2)).

       For most files under the /proc directory, stat() does not return the
       file size in the st_size field; instead the field is returned with
       the value 0.

   Timestamp fields
       Older kernels and older standards did not support nanosecond
       timestamp fields.  Instead, there were three timestamp fields—
       st_atime, st_mtime, and st_ctime—typed as time_t that recorded
       timestamps with one-second precision.

       Since kernel 2.5.48, the stat structure supports nanosecond
       resolution for the three file timestamp fields.  The nanosecond
       components of each timestamp are available via names of the form
       st_atim.tv_nsec if the _BSD_SOURCE or _SVID_SOURCE feature test macro
       is defined.  Nanosecond timestamps are nowadays standardized,
       starting with POSIX.1-2008, and, starting with version 2.12, glibc
       also exposes the nanosecond component names if _POSIX_C_SOURCE is
       defined with the value 200809L or greater, or _XOPEN_SOURCE is
       defined with the value 700 or greater.  If none of the aforementioned
       macros are defined, then the nanosecond values are exposed with names
       of the form st_atimensec.

       Nanosecond timestamps are supported on XFS, JFS, Btrfs, and ext4
       (since Linux 2.6.23).  Nanosecond timestamps are not supported in
       ext2, ext3, and Reiserfs.  On filesystems that do not support
       subsecond timestamps, the nanosecond fields are returned with the
       value 0.

   Underlying kernel interface
       Over time, increases in the size of the stat structure have led to
       three successive versions of stat(): sys_stat() (slot __NR_oldstat),
       sys_newstat() (slot __NR_stat), and sys_stat64() (new in kernel 2.4;
       slot __NR_stat64).  The glibc stat() wrapper function hides these
       details from applications, invoking the most recent version of the
       system call provided by the kernel, and repacking the returned
       information if required for old binaries.  Similar remarks apply for
       fstat() and lstat().

       The underlying system call employed by the glibc fstatat() wrapper
       function is actually called fstatat64().

EXAMPLE         top

       The following program calls stat() and displays selected fields in
       the returned stat structure.

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <time.h>
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
           struct stat sb;

           if (argc != 2) {
               fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           if (stat(argv[1], &sb) == -1) {
               perror("stat");
               exit(EXIT_FAILURE);
           }

           printf("File type:                ");

           switch (sb.st_mode & S_IFMT) {
           case S_IFBLK:  printf("block device\n");            break;
           case S_IFCHR:  printf("character device\n");        break;
           case S_IFDIR:  printf("directory\n");               break;
           case S_IFIFO:  printf("FIFO/pipe\n");               break;
           case S_IFLNK:  printf("symlink\n");                 break;
           case S_IFREG:  printf("regular file\n");            break;
           case S_IFSOCK: printf("socket\n");                  break;
           default:       printf("unknown?\n");                break;
           }

           printf("I-node number:            %ld\n", (long) sb.st_ino);

           printf("Mode:                     %lo (octal)\n",
                   (unsigned long) sb.st_mode);

           printf("Link count:               %ld\n", (long) sb.st_nlink);
           printf("Ownership:                UID=%ld   GID=%ld\n",
                   (long) sb.st_uid, (long) sb.st_gid);

           printf("Preferred I/O block size: %ld bytes\n",
                   (long) sb.st_blksize);
           printf("File size:                %lld bytes\n",
                   (long long) sb.st_size);
           printf("Blocks allocated:         %lld\n",
                   (long long) sb.st_blocks);

           printf("Last status change:       %s", ctime(&sb.st_ctime));
           printf("Last file access:         %s", ctime(&sb.st_atime));
           printf("Last file modification:   %s", ctime(&sb.st_mtime));

           exit(EXIT_SUCCESS);
       }

SEE ALSO         top

       ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2), utime(2),
       capabilities(7), symlink(7)

COLOPHON         top

       This page is part of release 3.71 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       http://www.kernel.org/doc/man-pages/.

Linux                            2014-08-19                          STAT(2)