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NetBSD 6.1.5 - man page for lstat (netbsd section 2)

STAT(2) 			     BSD System Calls Manual				  STAT(2)

NAME
     stat, lstat, fstat -- get file status

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/stat.h>

     int
     stat(const char *path, struct stat *sb);

     int
     lstat(const char *path, struct stat *sb);

     int
     fstat(int fd, struct stat *sb);

DESCRIPTION
     The stat() function obtains information about the file pointed to by path.  Read, write or
     execute permission of the named file is not required, but all directories listed in the path
     name leading to the file must be searchable.

     The function lstat() is like stat() except in the case where the named file is a symbolic
     link, in which case lstat() returns information about the link, while stat() returns infor-
     mation about the file the link references.  The fstat() function obtains the same informa-
     tion about an open file known by the file descriptor fd.

     The sb argument is a pointer to a stat structure as defined by <sys/stat.h> and into which
     information is placed concerning the file.

   The Standard Structure
     The following standards-compliant fields are defined in the structure:

	   Type        Entry	    Description
	   dev_t       st_dev	    device ID containing the file
	   ino_t       st_ino	    serial number of the file
	   mode_t      st_mode	    mode of the file
	   nlink_t     st_nlink     number of hard links to the file
	   uid_t       st_uid	    user ID of the owner
	   gid_t       st_gid	    group ID of the owner
	   dev_t       st_rdev	    device type (character or block special)
	   off_t       st_size	    size of the file in bytes
	   time_t      st_atime     time of last access
	   time_t      st_mtime     time of last data modification
	   time_t      st_ctime     time of last file status change
	   blksize_t   st_blksize   preferred I/O block size (fs-specific)
	   blkcnt_t    st_blocks    blocks allocated for the file

     These are specified in the IEEE Std 1003.1-2004 (``POSIX.1'') standard.  The st_ino and
     st_dev fields taken together uniquely identify the file within the system.  Most of the
     types are defined in types(3).

     The time-related fields are:

	   st_atime    Time when file data was last accessed.  Changed by the mknod(2),
		       utimes(2), and read(2) system calls.

	   st_mtime    Time when file data was last modified.  Changed by the mknod(2),
		       utimes(2), and write(2) system calls.

	   st_ctime    Time when file status was last changed (file metadata modification).
		       Changed by the chflags(2), chmod(2), chown(2), link(2), mknod(2),
		       rename(2), unlink(2), utimes(2), and write(2) system calls.

     The size-related fields of the struct stat are as follows:

	   st_size     The size of the file in bytes.  The meaning of the size reported for a
		       directory is file system dependent.  Some file systems (e.g. FFS) return
		       the total size used for the directory metadata, possibly including free
		       slots; others (notably ZFS) return the number of entries in the directory.
		       Some may also return other things or always report zero.

	   st_blksize  The optimal I/O block size for the file.

	   st_blocks   The actual number of blocks allocated for the file in 512-byte units.  As
		       short symbolic links are stored in the inode, this number may be zero.

     The status information word st_mode contains bits that define the access mode (see chmod(2))
     and the type (see dirent(3)) of the file.	The following macros can be used to test whether
     a file is of the specified type.  The value m supplied to the macros is the value of
     st_mode.

	   S_ISBLK(m)	Test for a block special file.

	   S_ISCHR(m)	Test for a character special file.

	   S_ISDIR(m)	Test for a directory.

	   S_ISFIFO(m)	Test for a pipe or FIFO special file.

	   S_ISREG(m)	Test for a regular file.

	   S_ISLNK(m)	Test for a symbolic link.

	   S_ISSOCK(m)	Test for a socket.

     The macros evaluate to a non-zero value if the test is true or to the value 0 if the test is
     false.

   NetBSD Extensions
     The following additional NetBSD specific fields are present:

	   Type        Entry		   Description
	   long        st_atimensec	   last access (nanoseconds)
	   long        st_mtimensec	   last modification (nanoseconds)
	   long        st_ctimensec	   last status change (nanoseconds)
	   time_t      st_birthtime	   time of inode creation
	   long        st_birthtimensec    inode creation (nanoseconds)
	   uint32_t    st_flags 	   user defined flags for the file
	   uint32_t    st_gen		   file generation number
	   uint32_t    st_spare[2]	   implementation detail

     However, if _NETBSD_SOURCE is furthermore defined, instead of the above, the following are
     present in the structure:

	   Type 	       Entry		   Description
	   struct timespec     st_atimespec	   time of last access
	   struct timespec     st_mtimespec	   time of last modification
	   struct timespec     st_birthtimespec    time of creation
	   uint32_t	       st_flags 	   user defined flags
	   uint32_t	       st_gen		   file generation number
	   uint32_t	       st_spare[2]	   implementation detail

     In this case the following macros are provided for convenience:

	   #if defined(_NETBSD_SOURCE)
	     #define st_atime		     st_atimespec.tv_sec
	     #define st_atimensec	     st_atimespec.tv_nsec
	     #define st_mtime		     st_mtimespec.tv_sec
	     #define st_mtimensec	     st_mtimespec.tv_nsec
	     #define st_ctime		     st_ctimespec.tv_sec
	     #define st_ctimensec	     st_ctimespec.tv_nsec
	     #define st_birthtime	     st_birthtimespec.tv_sec
	     #define st_birthtimensec	     st_birthtimespec.tv_nsec
	   #endif

     The status information word st_flags has the following bits:

	   Constant	       Description
	   UF_NODUMP	       do not dump a file
	   UF_IMMUTABLE        file may not be changed
	   UF_APPEND	       writes to file may only append
	   UF_OPAQUE	       directory is opaque wrt. union
	   SF_ARCHIVED	       file is archived
	   SF_IMMUTABLE        file may not be changed
	   SF_APPEND	       writes to file may only append

     For a description of the flags, see chflags(2).

RETURN VALUES
     Upon successful completion a value of 0 is returned.  Otherwise, a value of -1 is returned
     and errno is set to indicate the error.

COMPATIBILITY
     Previous versions of the system used different types for the st_dev, st_uid, st_gid,
     st_rdev, st_size, st_blksize and st_blocks fields.

ERRORS
     stat() and lstat() will fail if:

     [EACCES]		Search permission is denied for a component of the path prefix.

     [EBADF]		A badly formed vnode was encountered.  This can happen if a file system
			information node is incorrect.

     [EFAULT]		sb or name points to an invalid address.

     [EIO]		An I/O error occurred while reading from or writing to the file system.

     [ELOOP]		Too many symbolic links were encountered in translating the pathname.

     [ENAMETOOLONG]	A component of a pathname exceeded {NAME_MAX} characters, or an entire
			path name exceeded {PATH_MAX} characters.

     [ENOENT]		The named file does not exist.

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

     [ENXIO]		The named file is a character special or block special file, and the
			device associated with this special file does not exist.

     fstat() will fail if:

     [EBADF]		fd is not a valid open file descriptor.

     [EFAULT]		sb points to an invalid address.

     [EIO]		An I/O error occurred while reading from or writing to the file system.

SEE ALSO
     chflags(2), chmod(2), chown(2), utimes(2), dirent(3), types(3), symlink(7)

STANDARDS
     The described functions conform to IEEE Std 1003.1-2004 (``POSIX.1'').

HISTORY
     A stat() function call appeared in Version 2 AT&T UNIX.  A lstat() function call appeared in
     4.2BSD.

BUGS
     Applying fstat() to a socket (and thus to a pipe) returns a zero'd buffer, except for the
     blocksize field, and a unique device and file serial number.

BSD					September 14, 2011				      BSD


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