stat(2) — Linux manual page

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

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

NAME         top

       stat, fstat, lstat, fstatat - get file status

SYNOPSIS         top

       #include <sys/stat.h>

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

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

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

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

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

       fstatat():
           Since glibc 2.10:
               _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 statbuf.  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 the link 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.

   The stat structure
       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;        /* File type and mode */
               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;     /* Block size 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 glibc and kernel source code
       if you need to know the details.

       Note: for performance and simplicity reasons, different fields in
       the stat structure may contain state information from different
       moments during the execution of the system call.  For example, if
       st_mode or st_uid is changed by another process by calling
       chmod(2) or chown(2), stat() might return the old st_mode
       together with the new st_uid, or the old st_uid together with the
       new st_mode.

       The fields in the stat structure are as follows:

       st_dev This 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.)

       st_ino This field contains the file's inode number.

       st_mode
              This field contains the file type and mode.  See inode(7)
              for further information.

       st_nlink
              This field contains the number of hard links to the file.

       st_uid This field contains the user ID of the owner of the file.

       st_gid This field contains the ID of the group owner of the file.

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

       st_size
              This 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.

       st_blksize
              This field gives the "preferred" block size for efficient
              filesystem I/O.

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

       st_atime
              This is the time of the last access of file data.

       st_mtime
              This is the time of last modification of file data.

       st_ctime
              This is the file's last status change timestamp (time of
              last change to the inode).

       For further information on the above fields, see inode(7).

   fstatat()
       The fstatat() system call is a more general interface for
       accessing file information which can still provide exactly the
       behavior of each of stat(), lstat(), and fstat().

       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() and
       lstat() 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() and lstat()).

       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).  In this case, dirfd can refer
              to any type of file, not just a directory, and the
              behavior of fstatat() is similar to that of fstat().  If
              dirfd is AT_FDCWD, the call operates on the current
              working 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).
              Since Linux 4.14, also don't instantiate a nonexistent
              name in an on-demand directory such as used for
              automounter indirect maps.  This flag has no effect if the
              mount point has already been mounted over.

              Both stat() and lstat() act as though AT_NO_AUTOMOUNT was
              set.

              The AT_NO_AUTOMOUNT can be used in tools that scan
              directories to prevent mass-automounting of a directory of
              automount points.

              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 to indicate the error.

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 not a valid open file descriptor.

       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 is a dangling
              symbolic link.

       ENOENT pathname is an empty string and AT_EMPTY_PATH was not
              specified in flags.

       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 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 mode 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.)

NOTES         top

   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 suitable feature test macros are defined.
       Nanosecond timestamps were standardized in POSIX.1-2008, and,
       starting with version 2.12, glibc 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.  Up to and including glibc 2.19, the definitions
       of the nanoseconds components are also defined if _BSD_SOURCE or
       _SVID_SOURCE is defined.  If none of the aforementioned macros
       are defined, then the nanosecond values are exposed with names of
       the form st_atimensec.

   C library/kernel differences
       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()
       (slot __NR_stat64) on 32-bit platforms such as i386.  The first
       two versions were already present in Linux 1.0 (albeit with
       different names); the last was added in Linux 2.4.  Similar
       remarks apply for fstat() and lstat().

       The kernel-internal versions of the stat structure dealt with by
       the different versions are, respectively:

       __old_kernel_stat
              The original structure, with rather narrow fields, and no
              padding.

       stat   Larger st_ino field and padding added to various parts of
              the structure to allow for future expansion.

       stat64 Even larger st_ino field, larger st_uid and st_gid fields
              to accommodate the Linux-2.4 expansion of UIDs and GIDs to
              32 bits, and various other enlarged fields and further
              padding in the structure.  (Various padding bytes were
              eventually consumed in Linux 2.6, with the advent of
              32-bit device IDs and nanosecond components for the
              timestamp fields.)

       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.

       On modern 64-bit systems, life is simpler: there is a single
       stat() system call and the kernel deals with a stat structure
       that contains fields of a sufficient size.

       The underlying system call employed by the glibc fstatat()
       wrapper function is actually called fstatat64() or, on some
       architectures, newfstatat().

EXAMPLES         top

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

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <stdint.h>
       #include <time.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/sysmacros.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 (lstat(argv[1], &sb) == -1) {
               perror("lstat");
               exit(EXIT_FAILURE);
           }

           printf("ID of containing device:  [%jx,%jx]\n",
                   (uintmax_t) major(sb.st_dev),
                   (uintmax_t) minor(sb.st_dev));

           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:            %ju\n", (uintmax_t) sb.st_ino);

           printf("Mode:                     %jo (octal)\n",
                   (uintmax_t) sb.st_mode);

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

           printf("Preferred I/O block size: %jd bytes\n",
                   (intmax_t) sb.st_blksize);
           printf("File size:                %jd bytes\n",
                   (intmax_t) sb.st_size);
           printf("Blocks allocated:         %jd\n",
                   (intmax_t) 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),
       statx(2), utime(2), capabilities(7), inode(7), symlink(7)

COLOPHON         top

       This page is part of release 5.12 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
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22                        STAT(2)

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