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NAME    [Toc]    [Back]

       stat, fstat, lstat - get file status

SYNOPSIS    [Toc]    [Back]

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

       int stat(const char *file_name, struct stat *buf);
       int fstat(int filedes, struct stat *buf);
       int lstat(const char *file_name, struct stat *buf);

DESCRIPTION    [Toc]    [Back]

       These  functions  return  information about the specified file.	You do
       not need any access rights to the file to get this information but  you
       need  search rights to all directories named in the path leading to the

       stat stats the file pointed to by file_name and fills in buf.

       lstat is identical to stat, except in the  case	of  a  symbolic  link,
       where the link itself is stat-ed, not the file that it refers to.

       fstat  is  identical  to stat, only the open file pointed to by filedes
       (as returned by open(2)) is statted in place of file_name.

       They all return a stat structure, which contains the following fields:

	      struct stat {
		  dev_t 	st_dev;      /* device */
		  ino_t 	st_ino;      /* inode */
		  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 type (if inode device) */
		  off_t 	st_size;     /* total size, in bytes */
		  unsigned long st_blksize;  /* blocksize for filesystem I/O */
		  unsigned long st_blocks;   /* number of 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 change */

       The value st_size gives the size of the file (if it is a  regular  file
       or  a  symlink)	in  bytes.  The size of a symlink is the length of the
       pathname it contains, without trailing NUL.

       The value st_blocks gives the size of  the  file  in  512-byte  blocks.
       (This  may  be  smaller than st_size/512 e.g. when the file has holes.)
       The value st_blksize gives the "preferred" blocksize for efficient file
       system  I/O.  (Writing to a file in smaller chunks may cause an inefficient

       Not all of the Linux filesystems implement  all	of  the  time  fields.
       Some  file system types allow mounting in such a way that file accesses
       do not cause an	update	of  the  st_atime  field.  (See  `noatime'  in

       The  field  st_atime  is  changed  by  file  accesses, e.g. by exec(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, e.g. 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 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:

	      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?

	      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   bitmask for the file type bitfields
       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 GID 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 permisson
       S_IXOTH	  00001     others have execute permission

       The set GID 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  gid  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, it indicates mandatory file/record

       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 root.

RETURN VALUE    [Toc]    [Back]

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

ERRORS    [Toc]    [Back]

       EBADF  filedes is bad.

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

       ENOTDIR    [Toc]    [Back]
	      A component of the path is not a directory.

       ELOOP  Too many symbolic links encountered while traversing the path.

       EFAULT Bad address.

       EACCES Permission denied.

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

       ENAMETOOLONG    [Toc]    [Back]
	      File name too long.

CONFORMING TO    [Toc]    [Back]

       The stat and fstat calls conform to SVr4, SVID, POSIX, X/OPEN, BSD 4.3.
       The  lstat call conforms to 4.3BSD and SVr4.  SVr4 documents additional
       fstat error conditions EINTR, ENOLINK, and EOVERFLOW.   SVr4  documents
       additional  stat  and  lstat error conditions EACCES, EINTR, EMULTIHOP,
       ENOLINK, and EOVERFLOW.	Use of the st_blocks and st_blksize fields may
       be  less  portable. (They were introduced in BSD.  Are not specified by
       POSIX. 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 will be in the next  POSIX  standard;
       the former is from SVID 4v2, 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    [Toc]    [Back]

       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   SysV file locking enforcement (shared w/ 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.

SEE ALSO    [Toc]    [Back]

       chmod(2), chown(2), readlink(2), utime(2)

Linux				  1998-05-13			       STAT(2)
[ Back ]
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