python 5-5 如何訪問文件的狀態os.stat()/os.path

5-5 如何訪問文件的狀態
1.文件的類型(普通文件 ，目錄 符號鏈接,設備文件
2.文件的訪問權限
3.文件愛你最後訪問/修改/節點狀態更改時間
4.普通文件的大小

解決方案
系統調用 表中庫os模塊中的三個系統調用 stat fstat lstat獲取文件狀態
如果是符號鏈接文件 stat之後渠到的是指向的文件屬性 ,
lstat纔是獲取到符號鏈接文件的屬性
fstat需要的文件描述符 f=open(“test.txt”,”r”) f.fileno

快捷函數 標準庫中的os.path 下一些函數，使用起來更加簡潔

stat模塊是管理文件屬性的集合

os.stat('a.txt')
posix.stat_result(st_mode=33204, st_ino=13371126L, st_dev=51L, st_nlink=1, st_uid=13350, st_gid=25, st_size=0L, st_atime=1483343930, st_mtime=1483343930, st_ctime=1483343930)


os.chmod(filename, os.stat(filename).st_mode | stat.S_IXUSR | stat.S_IXGRP |stat.S_IXOTH)

通過os.path下的一些方法

import os
import stat
import time
s = os.stat('a.txt')
print s
print stat.S_ISDIR(s.st_mode)
print s.st_mode &stat.S_IRUSR   #訪問權限
print time.localtime(s.st_atime)
print s.st_size

if os.path.isdir('a.txt'):
    print "ok"

if os.path.isfile('a.txt'):
    print "ok"

if os.path.getatime('a.txt'):
    print os.path.getatime('a.txt')

if os.path.getsize('a.txt'):
    print os.path.getsize('a.txt')

help(os.stat)

>>> help(os.stat)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'os' is not defined
>>> import os
>>> help(os.stat)
Help on built-in function stat in module posix:

stat(...)
    stat(path) -> stat result

    Perform a stat system call on the given path.

>>> help(os.lstat)
Help on built-in function lstat in module posix:

lstat(...)
    lstat(path) -> stat result

    Like stat(path), but do not follow symbolic links.

>>> help(os.fstat)
Help on built-in function fstat in module posix:

fstat(...)
    fstat(fd) -> stat result

    Like stat(), but for an open file descriptor.

>>> 



>>> help(stat)
Help on module stat:

NAME
    stat - Constants/functions for interpreting results of os.stat() and os.lstat().

FILE
    /opt/swe/tools/ext/gnu/python-2.7.3/lib/python2.7/stat.py

DESCRIPTION
    Suggested usage: from stat import *

FUNCTIONS
    S_IFMT(mode)

    S_IMODE(mode)

    S_ISBLK(mode)

    S_ISCHR(mode)

    S_ISDIR(mode)

    S_ISFIFO(mode)

    S_ISLNK(mode)

    S_ISREG(mode)

    S_ISSOCK(mode)

DATA
    SF_APPEND = 262144
    SF_ARCHIVED = 65536
    SF_IMMUTABLE = 131072
    SF_NOUNLINK = 1048576
    SF_SNAPSHOT = 2097152
    ST_ATIME = 7
    ST_CTIME = 9
    ST_DEV = 2
    ST_GID = 5
    ST_INO = 1
    ST_MODE = 0
    ST_MTIME = 8
    ST_NLINK = 3
    ST_SIZE = 6
    ST_UID = 4
    S_ENFMT = 1024
    S_IEXEC = 64
    S_IFBLK = 24576
    S_IFCHR = 8192
    S_IFDIR = 16384
    S_IFIFO = 4096
    S_IFLNK = 40960
    S_IFREG = 32768
    S_IFSOCK = 49152
    S_IREAD = 256
    S_IRGRP = 32
    S_IROTH = 4
    S_IRUSR = 256
    S_IRWXG = 56
    S_IRWXO = 7
    S_IRWXU = 448
    S_ISGID = 1024
    S_ISUID = 2048
    S_ISVTX = 512
    S_IWGRP = 16
    S_IWOTH = 2
    S_IWRITE = 128
    S_IWUSR = 128
    S_IXGRP = 8
    S_IXOTH = 1
    S_IXUSR = 64
    UF_APPEND = 4
    UF_COMPRESSED = 32
    UF_HIDDEN = 32768
    UF_IMMUTABLE = 2
    UF_NODUMP = 1
    UF_NOUNLINK = 16
    UF_OPAQUE = 8

help(os.path)

>>> help(os.path)
Help on module posixpath:

NAME
    posixpath - Common operations on Posix pathnames.

FILE
    /opt/swe/tools/ext/gnu/python-2.7.3/lib/python2.7/posixpath.py

DESCRIPTION
    Instead of importing this module directly, import os and refer to
    this module as os.path.  The "os.path" name is an alias for this
    module on Posix systems; on other systems (e.g. Mac, Windows),
    os.path provides the same operations in a manner specific to that
    platform, and is an alias to another module (e.g. macpath, ntpath).

    Some of this can actually be useful on non-Posix systems too, e.g.
    for manipulation of the pathname component of URLs.

FUNCTIONS
    abspath(path)
        Return an absolute path.

    basename(p)
        Returns the final component of a pathname

    commonprefix(m)
        Given a list of pathnames, returns the longest common leading component

    dirname(p)
        Returns the directory component of a pathname

    exists(path)
        Test whether a path exists.  Returns False for broken symbolic links

    expanduser(path)
        Expand ~ and ~user constructions.  If user or $HOME is unknown,
        do nothing.

    expandvars(path)
        Expand shell variables of form $var and ${var}.  Unknown variables
        are left unchanged.

    getatime(filename)
        Return the last access time of a file, reported by os.stat().

    getctime(filename)
        Return the metadata change time of a file, reported by os.stat().

    getmtime(filename)
        Return the last modification time of a file, reported by os.stat().

    getsize(filename)
        Return the size of a file, reported by os.stat().

    isabs(s)
        Test whether a path is absolute

    isdir(s)
        Return true if the pathname refers to an existing directory.

    isfile(path)
        Test whether a path is a regular file

    islink(path)
        Test whether a path is a symbolic link

    ismount(path)
        Test whether a path is a mount point

    join(a, *p)
        Join two or more pathname components, inserting '/' as needed.
        If any component is an absolute path, all previous path components
        will be discarded.

    lexists(path)
        Test whether a path exists.  Returns True for broken symbolic links

    normcase(s)
        Normalize case of pathname.  Has no effect under Posix

    normpath(path)
        Normalize path, eliminating double slashes, etc.

    realpath(filename)
        Return the canonical path of the specified filename, eliminating any
        symbolic links encountered in the path.

    relpath(path, start='.')
        Return a relative version of a path

    samefile(f1, f2)
        Test whether two pathnames reference the same actual file

    sameopenfile(fp1, fp2)
        Test whether two open file objects reference the same file

    samestat(s1, s2)
        Test whether two stat buffers reference the same file

    split(p)
        Split a pathname.  Returns tuple "(head, tail)" where "tail" is
        everything after the final slash.  Either part may be empty.

    splitdrive(p)
        Split a pathname into drive and path. On Posix, drive is always
        empty.

    splitext(p)
        Split the extension from a pathname.

        Extension is everything from the last dot to the end, ignoring
        leading dots.  Returns "(root, ext)"; ext may be empty.

    walk(top, func, arg)
        Directory tree walk with callback function.

        For each directory in the directory tree rooted at top (including top
        itself, but excluding '.' and '..'), call func(arg, dirname, fnames).
        dirname is the name of the directory, and fnames a list of the names of
        the files and subdirectories in dirname (excluding '.' and '..').  func
        may modify the fnames list in-place (e.g. via del or slice assignment),
        and walk will only recurse into the subdirectories whose names remain in
        fnames; this can be used to implement a filter, or to impose a specific
        order of visiting.  No semantics are defined for, or required of, arg,
        beyond that arg is always passed to func.  It can be used, e.g., to pass
        a filename pattern, or a mutable object designed to accumulate
        statistics.  Passing None for arg is common.

DATA
    __all__ = ['normcase', 'isabs', 'join', 'splitdrive', 'split', 'splite...
    altsep = None
    curdir = '.'
    defpath = ':/bin:/usr/bin'
    devnull = '/dev/null'
    extsep = '.'
    pardir = '..'
    pathsep = ':'
    sep = '/'
    supports_unicode_filenames = False