
``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.

The variables below define the flags used in the ``ST_MODE`` field.

Use of the functions above is more portable than use of the first set
of flags:

stat.S_IFMT

   Bit mask for the file type bit fields.

stat.S_IFSOCK

   Socket.

stat.S_IFLNK

   Symbolic link.

stat.S_IFREG

   Regular file.

stat.S_IFBLK

   Block device.

stat.S_IFDIR

   Directory.

stat.S_IFCHR

   Character device.

stat.S_IFIFO

   FIFO.

The following flags can also be used in the *mode* argument of
``os.chmod()``:

stat.S_ISUID

   Set UID bit.

stat.S_ISGID

   Set-group-ID bit.  This bit 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 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 (see also ``S_ENFMT``).

stat.S_ISVTX

   Sticky bit.  When this bit is set on a directory it 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, or by a privileged
   process.

stat.S_IRWXU

   Mask for file owner permissions.

stat.S_IRUSR

   Owner has read permission.

stat.S_IWUSR

   Owner has write permission.

stat.S_IXUSR

   Owner has execute permission.

stat.S_IRWXG

   Mask for group permissions.

stat.S_IRGRP

   Group has read permission.

stat.S_IWGRP

   Group has write permission.

stat.S_IXGRP

   Group has execute permission.

stat.S_IRWXO

   Mask for permissions for others (not in group).

stat.S_IROTH

   Others have read permission.

stat.S_IWOTH

   Others have write permission.

stat.S_IXOTH

   Others have execute permission.

stat.S_ENFMT

   System V file locking enforcement.  This flag is shared with
   ``S_ISGID``: file/record locking is enforced on files that do not
   have the group execution bit (``S_IXGRP``) set.

stat.S_IREAD

   Unix V7 synonym for ``S_IRUSR``.

stat.S_IWRITE

   Unix V7 synonym for ``S_IWUSR``.

stat.S_IEXEC

   Unix V7 synonym for ``S_IXUSR``.

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)
