How can I get the Unix permission mask from a file? [duplicate]

Question

How can I get a file's permission mask like 644 or 755 on *nix using python?

Is there any function or class for doing that? Thank you very much!

Answer 1

os.stat is a wrapper around the stat(2) system call interface.

>>> import os >>> from stat import * >>> os.stat("test.txt") # returns 10-tupel, you really want the 0th element ... posix.stat_result(st_mode=33188, st_ino=57197013, \     st_dev=234881026L, st_nlink=1, st_uid=501, st_gid=20, st_size=0, \     st_atime=1300354697, st_mtime=1300354697, st_ctime=1300354697)  >>> os.stat("test.txt")[ST_MODE] # this is an int, but we like octal ... 33188  >>> oct(os.stat("test.txt")[ST_MODE]) '0100644' 

From here you'll recognize the typical octal permissions.

S_IRWXU 00700   mask for file owner permissions S_IRUSR 00400   owner has read permission S_IWUSR 00200   owner has write permission S_IXUSR 00100   owner has execute permission S_IRWXG 00070   mask for group permissions S_IRGRP 00040   group has read permission S_IWGRP 00020   group has write permission S_IXGRP 00010   group has execute permission S_IRWXO 00007   mask for permissions for others (not in group) S_IROTH 00004   others have read permission S_IWOTH 00002   others have write permission S_IXOTH 00001   others have execute permission 

You are really only interested in the lower bits, so you could chop off the rest:

>>> oct(os.stat("test.txt")[ST_MODE])[-3:] '644' >>> # or better >>> oct(os.stat("test.txt").st_mode & 0o777) 

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Sidenote: the upper parts determine the filetype, e.g.:

S_IFMT  0170000 bitmask for the file type bitfields S_IFSOCK    0140000 socket S_IFLNK 0120000 symbolic link S_IFREG 0100000 regular file S_IFBLK 0060000 block device S_IFDIR 0040000 directory S_IFCHR 0020000 character device S_IFIFO 0010000 FIFO S_ISUID 0004000 set UID bit S_ISGID 0002000 set-group-ID bit (see below) S_ISVTX 0001000 sticky bit (see below) 

Answer 2

I think this is the clearest way of getting a file's the permission bits:

stat.S_IMODE(os.lstat("file").st_mode) 

The os.lstat function, will in case the file is a symlink, give you the mode of the link itself, whereas os.stat dereferences the link. Therefore I find os.lstat the most generally useful.

Here's an example case, given regular file "testfile" and symlink to the latter, "testlink":

import stat import os  print oct(stat.S_IMODE(os.lstat("testlink").st_mode)) print oct(stat.S_IMODE(os.stat("testlink").st_mode)) 

This script outputs the following for me:

0777 0666