如何在Python中使用os.umask() [英] How to use os.umask() in Python

问题描述

我正在尝试使用os模块设置umask.请注意，我在〜/.profile中设置的普通umask是umask 0027.

I'm trying to set a umask using the os module. Please note my normal umask set in my ~/.profile is umask 0027.

在bash外壳中，

umask 0022

将允许使用权限创建文件

will allow a file to be created with permissions

-rw-r--r--

但是，当我们导入os模块并执行以下操作时:

However, when us import the os module and do this:

os.umask(0022)
[do some other code here that creates a file]

我获得了

----------

首先，如何在外壳中使os.umask(mask)表现得像umask?

First, how do I make os.umask(mask) behave like umask in the shell?

第二，两者之间的区别是什么逻辑?

Second, what is the logic between the difference of the two?

注意:我尝试将0022转换为十进制，以防出现以下情况:

Note: I tried converting the 0022 to decimal in case it is expecting a decimal by doing:

os.umask(18)

但它授予了权限

-----w--w-

还请注意，我尝试过

os.umask(00022)

和

os.mask(0o0022)

哪一个也不起作用.

推荐答案

对umask的误解. umask设置默认的拒绝，而不是默认的权限. 所以

Misunderstanding of umask, I think. The umask sets the default denials, not the default permissions. So

import os
oldmask = os.umask (0o22)
fh1 = os.open ("qq1.junk", os.O_CREAT, 0o777)
fh2 = os.open ("qq2.junk", os.O_CREAT, 0o022)
os.umask (oldmask)
os.close (fh1)
os.close (fh2)

确实应该产生如下文件:

should indeed produce files as follows:

-rwxr-xr-x 1 pax pax 0 Apr 24 11:11 qq1.junk
---------- 1 pax pax 0 Apr 24 11:11 qq2.junk

umask 022删除组和其他组的写访问权限，这正是我们在此处看到的行为. 我发现回到八进制数字表示的二进制文件会有所帮助:

The umask 022 removes write access for group and others, which is exactly the behaviour we see there. I find it helps to go back to the binary that the octal numbers represent:

 usr grp others 
-rwx rwx rwx is represented in octal as 0777, requested for qq1.junk
-000 010 010 umask of 022 removes any permission where there is a 1
-rwx r-x r-x is the result achieved requesting 0777 with umask of 022

---- -w- -w- is represented in octal as 0022, requested for qq2.junk
-000 010 010 umask of 022 removes any permission where there is a 1
---- --- --- is the result achieved requesting 0022 with umask of 022

该程序的行为符合您的要求，不一定符合您的预期.常见的情况是，使用计算机:-)

The program is behaving as you asked it to, not necessarily as you thought it should. Common situation, that, with computers :-)

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