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NAME

       stat, fstat, lstat, fstatat - get file status

SYNOPSIS

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

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

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

       int fstatat(int dirfd, const char *pathname, struct stat *statbuf,
                   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
               || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L

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

DESCRIPTION

       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 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.

   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 file's last access timestamp.

       st_mtime
              This is the file's last modification timestamp.

       st_ctime
              This is the file's last status change timestamp.

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

       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

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

ERRORS

       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 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

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

CONFORMING TO

       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

   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().

EXAMPLE

       The following program calls lstat() 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>
       #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:  [%lx,%lx]\n",
                (long) major(sb.st_dev), (long) 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:            %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

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

COLOPHON

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