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           #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)):
               _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
               || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L
               Since glibc 2.10:
                   _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
               Before glibc 2.10:


           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 infor-
           mat 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 */
               #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 archi-
           tectures.   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)  repre-
           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 dele-
           tion 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 informa-
           tion (i.e., owner, group, link count, mode, etc.).
           The following POSIX macros are defined to check the file type using the
               S_ISSOCK(m) socket?  (Not in POSIX.1-1996.)
           The following flags are defined for 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
               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  direc-
           tory  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.
           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
           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 defini-
                  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().


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


           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.
                  pathname is too long.
           ENOENT A component of pathname does not exist, or pathname is an  empty
           ENOMEM Out of memory (i.e., kernel memory).
                  A component of the path prefix of pathname is not a directory.
                  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.


           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.-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* con-
           stants 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
           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)
           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.


           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
           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 Resierfs.  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 sys-
           tem call provided by the kernel, and repacking the returned information
           if  required  for  old binaries.  Similar remarks apply for fstat() and
           main(int argc, char *argv[])
               struct stat sb;
               if (argc != 2) {
                   fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
               if (stat(argv[1], &sb) == -1) {
               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));



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