（原創）Python文件與文件系統系列（5）——stat模塊

時間 2019-11-06

原文原文鏈接

　　stat模塊中定義了許多的常量和函數，能夠幫助解釋 os.stat()、os.fstat()、os.lstat()等函數返回的 st_result 類型的對象。html

　　一般使用 os.path.is*() 這類函數來測試一個文件的類型，這些方法對同一個文件進行屢次測試時，stat()系統調用都是不可避免的開銷。同時，有些信息是os.path.is*() 這類函數沒法提供的，例如檢測是不是塊設備、字符設備等。node

　　此時就能夠使用 stat 模塊及stat模塊中的諸多功能，下面是一個例子：python

import os, sys
import stat

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 stat.S_ISDIR(mode):
            # It's a directory, recurse into it
            walktree(pathname, callback)
        elif stat.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)

　　　該例子遞歸遍歷命令行參數所指定的目錄中的全部普通文件。app

例：上面腳本的執行結果socket

# python stat_test.py data_structure/
visiting data_structure/a.out
visiting data_structure/biThrTree.h
visiting data_structure/biThrTree.c

stat 模塊定義的用來測試文件類型的函數包括ide

stat.S_ISDIR(mode)


　　判斷文件是否是一個目錄。

stat.S_ISCHR(mode)

　　判斷文件是否是一個字符型設備。

stat.S_ISBLK(mode)

　　判斷文件是否是一個塊設備。函數

stat.S_ISREG(mode)

　　判斷mode是否是來自一個普通文件。測試

stat.S_ISFIFO(mode)

　　判斷mode是否是來自一個FIFO（如：具名管道）ui

stat.S_ISLNK(mode)

　　判斷mode是否是來自一個符號連接。this

stat.S_ISSOCK(mode)

　　判斷mode是否是來自一個套接字。

　　上面的這些函數，除了 S_ISDIR 和 S_ISREG，其餘都只在 Unix 環境下才有效。

stat.S_IMODE(mode)


　　返回 mode 中能夠被 os.chmod() 函數設置的部分，在Unix平臺上，包括：權限位、sticky bits，set-group-id位、set-uid-bit等。

stat.S_IFMT(mode)


　　返回 mode 中描述文件類型（能夠被S_IS*()函數使用）的部分。

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_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.