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

NAME
       stat, fstat, lstat - get file status

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

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

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

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

DESCRIPTION
       These  functions return information about a file.  No permissions are required on the file
       itself, but--in the case of stat() and lstat()--execute (search) permission is required on
       all of the directories in path that lead to the file.

       stat() stats the file pointed to by path and fills in buf.

       lstat()	is  identical  to  stat(),  except that if path is a symbolic link, then the link
       itself is stat-ed, not the file that it refers to.

       fstat() is identical to stat(), except that the file to be stat-ed  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
	   };

       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.  (Writ-
       ing 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),  trun-
       cate(2),  utime(2) and write(2) (of more than zero bytes).  Moreover, st_mtime of a direc-
       tory 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 POSIX macros are defined to check the file type using the st_mode field:

	   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 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  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  privi-
       leged process.

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 path.
	      (See also path_resolution(7).)

       EBADF  fd is bad.

       EFAULT Bad address.

       ELOOP  Too many symbolic links encountered while traversing the path.

       ENAMETOOLONG
	      path is too long.

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

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

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

       EOVERFLOW
	      path 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.

CONFORMING TO
       These system calls conform to SVr4, 4.3BSD, POSIX.1-2001.

       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  struc-
       ture.   POSIX.-2008 tightens the specification, requiring lstat() to return valid informa-
       tion 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(),
       etc.  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
       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 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  ver-
       sions  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  bina-
       ries.  Similar remarks apply for fstat() and lstat().

EXAMPLE
       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
       access(2), chmod(2), chown(2), fstatat(2), readlink(2),	utime(2),  capabilities(7),  sym-
       link(7)

COLOPHON
       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

Linux					    2013-10-25					  STAT(2)
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