<sys/stat.h>(P) 					     POSIX Programmer's Manual						   <sys/stat.h>(P)

NAME

       sys/stat.h - data returned by the stat() function

SYNOPSIS

       #include <sys/stat.h>

DESCRIPTION

       The <sys/stat.h> header shall define the structure of the data returned by the functions fstat(), lstat(), and stat().

       The stat structure shall contain at least the following members:

	      dev_t	st_dev	   Device ID of device containing file.
	      ino_t	st_ino	   File serial number.
	      mode_t	st_mode    Mode of file (see below).
	      nlink_t	st_nlink   Number of hard links to the file.
	      uid_t	st_uid	   User ID of file.
	      gid_t	st_gid	   Group ID of file.

	      dev_t	st_rdev    Device ID (if file is character or block special).

	      off_t	st_size    For regular files, the file size in bytes.
				   For symbolic links, the length in bytes of the
				   pathname contained in the symbolic link.

				   For a shared memory object, the length in bytes.

				   For a typed memory object, the length in bytes.

				   For other file types, the use of this field is
				   unspecified.
	      time_t	st_atime   Time of last access.
	      time_t	st_mtime   Time of last data modification.
	      time_t	st_ctime   Time of last status change.

	      blksize_t st_blksize A file system-specific preferred I/O block size for
				   this object. In some file system types, this may
				   vary from file to file.
	      blkcnt_t	st_blocks  Number of blocks allocated for this object.

       The  st_ino  and  st_dev fields taken together uniquely identify the file within the system. The blkcnt_t, blksize_t, dev_t, ino_t, mode_t,
       nlink_t, uid_t, gid_t, off_t, and time_t types shall be defined as described in <sys/types.h> . Times shall be given in seconds	since  the
       Epoch.

       Unless  otherwise  specified,  the  structure  members st_mode, st_ino, st_dev, st_uid, st_gid, st_atime, st_ctime, and st_mtime shall have
       meaningful values for all file types defined in IEEE Std 1003.1-2001.

       For symbolic links, the st_mode member shall contain meaningful information, which can be used with the file type macros  described  below,
       that take a mode argument. The st_size member shall contain the length, in bytes, of the pathname contained in the symbolic link. File mode
       bits and the contents of the remaining members of the stat structure are unspecified. The value returned in the st_size field shall be  the
       length of the contents of the symbolic link, and shall not count a trailing null if one is present.

       The following symbolic names for the values of type mode_t shall also be defined.

       File type:

       S_IFMT Type of file.

       S_IFBLK
	      Block special.

       S_IFCHR
	      Character special.

       S_IFIFO
	      FIFO special.

       S_IFREG
	      Regular.

       S_IFDIR
	      Directory.

       S_IFLNK
	      Symbolic link.

       S_IFSOCK
	      Socket.

       File mode bits:

       S_IRWXU
	      Read, write, execute/search by owner.

       S_IRUSR
	      Read permission, owner.

       S_IWUSR
	      Write permission, owner.

       S_IXUSR
	      Execute/search permission, owner.

       S_IRWXG
	      Read, write, execute/search by group.

       S_IRGRP
	      Read permission, group.

       S_IWGRP
	      Write permission, group.

       S_IXGRP
	      Execute/search permission, group.

       S_IRWXO
	      Read, write, execute/search by others.

       S_IROTH
	      Read permission, others.

       S_IWOTH
	      Write permission, others.

       S_IXOTH
	      Execute/search permission, others.

       S_ISUID
	      Set-user-ID on execution.

       S_ISGID
	      Set-group-ID on execution.

       S_ISVTX
	      On directories, restricted deletion flag.

       The  bits  defined  by  S_IRUSR,  S_IWUSR,  S_IXUSR, S_IRGRP, S_IWGRP, S_IXGRP, S_IROTH, S_IWOTH, S_IXOTH, S_ISUID, S_ISGID,    and S_ISVTX
	shall be unique.

       S_IRWXU is the bitwise-inclusive OR of S_IRUSR, S_IWUSR, and S_IXUSR.

       S_IRWXG is the bitwise-inclusive OR of S_IRGRP, S_IWGRP, and S_IXGRP.

       S_IRWXO is the bitwise-inclusive OR of S_IROTH, S_IWOTH, and S_IXOTH.

       Implementations may OR other implementation-defined bits into S_IRWXU, S_IRWXG, and S_IRWXO, but they shall not overlap any  of	the  other
       bits  defined  in this volume of IEEE Std 1003.1-2001. The file permission bits are defined to be those corresponding to the bitwise-inclu-
       sive OR of S_IRWXU, S_IRWXG, and S_IRWXO.

       The following macros shall be provided to test whether a file is of the specified type. The value m supplied to the macros is the value	of
       st_mode from a stat structure.  The macro shall evaluate to a non-zero value if the test is true; 0 if the test is false.

       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 implementation may implement message queues, semaphores, or shared memory objects as distinct file types. The following macros shall be
       provided to test whether a file is of the specified type. The value of the buf argument supplied to the macros  is  a  pointer  to  a  stat
       structure.  The	macro  shall evaluate to a non-zero value if the specified object is implemented as a distinct file type and the specified
       file type is contained in the stat structure referenced by buf. Otherwise, the macro shall evaluate to zero.

       S_TYPEISMQ(buf)
	      Test for a message queue.

       S_TYPEISSEM(buf)
	      Test for a semaphore.

       S_TYPEISSHM(buf)
	      Test for a shared memory object.

       The implementation may implement typed memory objects as distinct file types, and the following macro shall test whether a file is  of  the
       specified  type. The value of the buf argument supplied to the macros is a pointer to a stat structure.	The macro shall evaluate to a non-
       zero value if the specified object is implemented as a distinct file type and the specified file type is contained in  the  stat  structure
       referenced by buf.  Otherwise, the macro shall evaluate to zero.

       S_TYPEISTMO(buf)
	      Test macro for a typed memory object.

       The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

	      int    chmod(const char *, mode_t);
	      int    fchmod(int, mode_t);
	      int    fstat(int, struct stat *);
	      int    lstat(const char *restrict, struct stat *restrict);
	      int    mkdir(const char *, mode_t);
	      int    mkfifo(const char *, mode_t);

	      int    mknod(const char *, mode_t, dev_t);

	      int    stat(const char *restrict, struct stat *restrict);
	      mode_t umask(mode_t);

       The following sections are informative.

APPLICATION USAGE

       Use of the macros is recommended for determining the type of a file.

RATIONALE

       A  conforming  C-language  application must include <sys/stat.h> for functions that have arguments or return values of type mode_t, so that
       symbolic values for that type can be used.  An alternative would be  to	require  that  these  constants  are  also  defined  by  including
       <sys/types.h>.

       The S_ISUID and S_ISGID bits may be cleared on any write, not just on open(), as some historical implementations do.

       System  calls  that  update  the  time entry fields in the stat structure must be documented by the implementors.  POSIX-conforming systems
       should not update the time entry fields for functions listed in the System Interfaces volume of IEEE Std 1003.1-2001  unless  the  standard
       requires that they do, except in the case of documented extensions to the standard.

       Note  that st_dev must be unique within a Local Area Network (LAN) in a ``system'' made up of multiple computers' file systems connected by
       a LAN.

       Networked implementations of a POSIX-conforming system must guarantee that all files visible within the file tree (including parts  of  the
       tree  that may be remotely mounted from other machines on the network) on each individual processor are uniquely identified by the combina-
       tion of the st_ino and st_dev fields.

       The unit for the st_blocks member of the stat structure is not defined within IEEE Std 1003.1-2001.  In	some  implementations  it  is  512
       bytes.  It may differ on a file system basis. There is no correlation between values of the st_blocks and st_blksize, and the f_bsize (from
       <sys/statvfs.h>) structure members.

       Traditionally, some implementations defined the multiplier for st_blocks in <sys/param.h> as the symbol DEV_BSIZE.

FUTURE DIRECTIONS

       No new S_IFMT symbolic names for the file type values of mode_t will be defined by IEEE Std 1003.1-2001; if new file  types  are  required,
       they will only be testable through S_ISxx() or S_TYPEISxxx() macros instead.

SEE ALSO

       <sys/statvfs.h>	,  <sys/types.h>  ,  the  System  Interfaces volume of IEEE Std 1003.1-2001, chmod(), fchmod(), fstat(), lstat(), mkdir(),
       mkfifo(), mknod(), stat(), umask()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003							   <sys/stat.h>(P)