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



NAME
       stat, fstat, lstat - get file status

SYNOPSIS
       #include 
       #include 
       #include 

       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

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 file system I/O */
	       blkcnt_t	 st_blocks;  /* number of 512B blocks allocated */
	       time_t	 st_atime;   /* time of last access */
	       time_t	 st_mtime;   /* time of last modification */
	       time_t	 st_ctime;   /* time of last status change */
	   };

       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-
       sents.

       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 symlink is the length of
       the pathname it contains, without a trailing 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 file
       system  I/O.  (Writing to a file in smaller chunks may cause an ineffi-
       cient read-modify-rewrite.)

       Not all of the Linux file systems implement all	of  the	 time  fields.
       Some  file  system  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
       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 UID 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.

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
	      File name 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
	      (stat())	path refers to a file whose size cannot be represented
	      in the type	off_t.	This can  occur	 when  an  application
	      compiled	on  a  32-bit  platform without -D_FILE_OFFSET_BITS=64
	      calls stat() on a file whose size exceeds (2<<31)-1 bits.

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

       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.)

       POSIX  does  not	 describe  the	S_IFMT,	 S_IFSOCK,  S_IFLNK,  S_IFREG,
       S_IFBLK,	 S_IFDIR,  S_IFCHR, S_IFIFO, S_ISVTX bits, but instead demands
       the use of the macros S_ISDIR(), etc.   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 userspace)
       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 non-directories: 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
       Since  kernel 2.5.48, the stat structure supports nanosecond resolution
       for the three file timestamp fields.  Glibc exposes the nanosecond com-
       ponent of each field using names either of the form st_atim.tv_nsec, if
       the _BSD_SOURCE or _SVID_SOURCE feature test macro is  defined,	or  of
       the  form st_atimensec, if neither of these macros is defined.  On file
       systems that do not support  sub-second	timestamps,  these  nanosecond
       fields are returned with the value 0.

       On  Linux,  lstat()  will  generally  not  trigger  automounter action,
       whereas stat() will.

       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.

   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
       lstat().

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

       #include 
       #include 
       #include 
       #include 
       #include 

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

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

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

	   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), capa-
       bilities(7), symlink(7)

COLOPHON
       This  page  is  part of release 3.22 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				  2009-04-21			       STAT(2)