
``stat`` --- Interpreting ``stat()`` results
********************************************

The ``stat`` module defines constants and functions for interpreting
the results of ``os.stat()``, ``os.fstat()`` and ``os.lstat()`` (if
they exist).  For complete details about the ``stat``, ``fstat`` and
``lstat`` calls, consult the documentation for your system.

The ``stat`` module defines the following functions to test for
specific file types:

stat.S_ISDIR(mode)

   Return non-zero if the mode is from a directory.

stat.S_ISCHR(mode)

   Return non-zero if the mode is from a character special device
   file.

stat.S_ISBLK(mode)

   Return non-zero if the mode is from a block special device file.

stat.S_ISREG(mode)

   Return non-zero if the mode is from a regular file.

stat.S_ISFIFO(mode)

   Return non-zero if the mode is from a FIFO (named pipe).

stat.S_ISLNK(mode)

   Return non-zero if the mode is from a symbolic link.

stat.S_ISSOCK(mode)

   Return non-zero if the mode is from a socket.

Two additional functions are defined for more general manipulation of
the file's mode:

stat.S_IMODE(mode)

   Return the portion of the file's mode that can be set by
   ``os.chmod()``---that is, the file's permission bits, plus the
   sticky bit, set-group-id, and set-user-id bits (on systems that
   support them).

stat.S_IFMT(mode)

   Return the portion of the file's mode that describes the file type
   (used by the ``S_IS*()`` functions above).

Normally, you would use the ``os.path.is*()`` functions for testing
the type of a file; the functions here are useful when you are doing
multiple tests of the same file and wish to avoid the overhead of the
``stat`` system call for each test.  These are also useful when
checking for information about a file that isn't handled by
``os.path``, like the tests for block and character devices.

All the variables below are simply symbolic indexes into the 10-tuple
returned by ``os.stat()``, ``os.fstat()`` or ``os.lstat()``.

stat.ST_MODE

   Inode protection mode.

stat.ST_INO

   Inode number.

stat.ST_DEV

   Device inode resides on.

stat.ST_NLINK

   Number of links to the inode.

stat.ST_UID

   User id of the owner.

stat.ST_GID

   Group id of the owner.

stat.ST_SIZE

   Size in bytes of a plain file; amount of data waiting on some
   special files.

stat.ST_ATIME

   Time of last access.

stat.ST_MTIME

   Time of last modification.

stat.ST_CTIME

   The "ctime" as reported by the operating system.  On some systems
   (like Unix) is the time of the last metadata change, and, on others
   (like Windows), is the creation time (see platform documentation
   for details).

The interpretation of "file size" changes according to the file type.
For plain files this is the size of the file in bytes.  For FIFOs and
sockets under most flavors of Unix (including Linux in particular),
the "size" is the number of bytes waiting to be read at the time of
the call to ``os.stat()``, ``os.fstat()``, or ``os.lstat()``; this can
sometimes be useful, especially for polling one of these special files
after a non-blocking open.  The meaning of the size field for other
character and block devices varies more, depending on the
implementation of the underlying system call.

Example:

   import os, sys
   from stat import *

   def walktree(top, callback):
       '''recursively descend the directory tree rooted at top,
          calling the callback function for each regular file'''

       for f in os.listdir(top):
           pathname = os.path.join(top, f)
           mode = os.stat(pathname)[ST_MODE]
           if S_ISDIR(mode):
               # It's a directory, recurse into it
               walktree(pathname, callback)
           elif S_ISREG(mode):
               # It's a file, call the callback function
               callback(pathname)
           else:
               # Unknown file type, print a message
               print 'Skipping %s' % pathname

   def visitfile(file):
       print 'visiting', file

   if __name__ == '__main__':
       walktree(sys.argv[1], visitfile)
