source: trunk/essentials/dev-lang/python/Doc/lib/libstat.tex@ 3398

\section{\module{stat} ---
         Interpreting \function{stat()} results}

\declaremodule{standard}{stat}
\modulesynopsis{Utilities for interpreting the results of
  \function{os.stat()}, \function{os.lstat()} and \function{os.fstat()}.}
\sectionauthor{Skip Montanaro}{[email protected]}


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

The \module{stat} module defines the following functions to test for
specific file types:


\begin{funcdesc}{S_ISDIR}{mode}
Return non-zero if the mode is from a directory.
\end{funcdesc}

\begin{funcdesc}{S_ISCHR}{mode}
Return non-zero if the mode is from a character special device file.
\end{funcdesc}

\begin{funcdesc}{S_ISBLK}{mode}
Return non-zero if the mode is from a block special device file.
\end{funcdesc}

\begin{funcdesc}{S_ISREG}{mode}
Return non-zero if the mode is from a regular file.
\end{funcdesc}

\begin{funcdesc}{S_ISFIFO}{mode}
Return non-zero if the mode is from a FIFO (named pipe).
\end{funcdesc}

\begin{funcdesc}{S_ISLNK}{mode}
Return non-zero if the mode is from a symbolic link.
\end{funcdesc}

\begin{funcdesc}{S_ISSOCK}{mode}
Return non-zero if the mode is from a socket.
\end{funcdesc}

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

\begin{funcdesc}{S_IMODE}{mode}
Return the portion of the file's mode that can be set by
\function{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).
\end{funcdesc}

\begin{funcdesc}{S_IFMT}{mode}
Return the portion of the file's mode that describes the file type (used
by the \function{S_IS*()} functions above).
\end{funcdesc}

Normally, you would use the \function{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 \cfunction{stat()} system call for each test.  These are also
useful when checking for information about a file that isn't handled
by \refmodule{os.path}, like the tests for block and character
devices.

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

\begin{datadesc}{ST_MODE}
Inode protection mode.
\end{datadesc}

\begin{datadesc}{ST_INO}
Inode number.
\end{datadesc}

\begin{datadesc}{ST_DEV}
Device inode resides on.
\end{datadesc}

\begin{datadesc}{ST_NLINK}
Number of links to the inode.
\end{datadesc}

\begin{datadesc}{ST_UID}
User id of the owner.
\end{datadesc}

\begin{datadesc}{ST_GID}
Group id of the owner.
\end{datadesc}

\begin{datadesc}{ST_SIZE}
Size in bytes of a plain file; amount of data waiting on some special
files.
\end{datadesc}

\begin{datadesc}{ST_ATIME}
Time of last access.
\end{datadesc}

\begin{datadesc}{ST_MTIME}
Time of last modification.
\end{datadesc}

\begin{datadesc}{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).
\end{datadesc}

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 \function{os.stat()}, \function{os.fstat()},
or \function{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:

\begin{verbatim}
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)
\end{verbatim}