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Interpreting `stat()' results
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Utilities for interpreting the results of `os.stat()', `os.lstat()' and
`os.fstat()'.

This manual section was written by Skip Montanaro <skip@automatrix.com>.
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:

`S_ISDIR(mode)'
     Return non-zero if the mode is from a directory.

`S_ISCHR(mode)'
     Return non-zero if the mode is from a character special device
     file.

`S_ISBLK(mode)'
     Return non-zero if the mode is from a block special device file.

`S_ISREG(mode)'
     Return non-zero if the mode is from a regular file.

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

`S_ISLNK(mode)'
     Return non-zero if the mode is from a symbolic link.

`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:

`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).

`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()'.

`ST_MODE'
     Inode protection mode.

`ST_INO'
     Inode number.

`ST_DEV'
     Device inode resides on.

`ST_NLINK'
     Number of links to the inode.

`ST_UID'
     User id of the owner.

`ST_GID'
     Group id of the owner.

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

`ST_ATIME'
     Time of last access.

`ST_MTIME'
     Time of last modification.

`ST_CTIME'
     Time of last status change (see manual pages 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 Unixes (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(dir, callback):
         '''recursively descend the directory rooted at dir,
            calling the callback function for each regular file'''
     
         for f in os.listdir(dir):
             pathname = '%s/%s' % (dir, 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)