11.3 `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:

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: 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)

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11.3 stat -- Interpreting stat() results

11.3 `stat` -- Interpreting `stat()` results