chmod g+ Equivalent

Steve Holden steve at holdenweb.com
Wed Aug 15 01:30:01 CEST 2007


milan_sanremo wrote:
> On Aug 13, 8:06 pm, Steve Holden <st... at holdenweb.com> wrote:
>> milan_sanremo wrote:
>>> I've read the documentation on os.chmod() and can implement all the
>>> standard commands, but what is the syntax for the equivalent of chmod g
>>> + to set the group id?
>> I assume when you say "to set the group id" you actually mean "to assert
>> the setgid bit"? I further presume that when you say "chmod g+" you
>> actually mean "chmod g+s".
> 
> The g+s was an omission on my part.  I can see how it would confuse
> the issue.
> 
> I'm not sure if I mean "to assert the setgid bit".  My SUN docs refer
> to it being 'on'.
> http://docs.sun.com/app/docs/doc/819-3321/6n5i4b767?l=en&a=view&q=setgid+bit
> 
>> You can't have read the documentation very thoroughly. It says right at
>> the top:
>>
>> S_ISUID
>> S_ISGID
> 
> I did see this in the documentation:
> 
> Change the mode of path to the numeric mode. mode may take one of the
> following values (as defined in the stat module) or bitwise or-ed
> combinations of them:
> 
>     * S_ISUID
>     * S_ISGID
> 
> Which refers to:
> http://docs.python.org/lib/module-stat.html
> 
> After which it was still unclear.
> 
> My question is in the command os.chmod(myDirectory, ?) what is the
> value for ? to turn on the setgid bit.
> 
> Contrary to your presumption, I did read the documentation
> thoroughly.  It is inability to understand the concept which prompted
> me to post the question here.
> 
Well, you don't tell us what (if anything) you have tried so far. Python 
has an interpreter that's very easy to use interactively. Why don't you try

     os.chmod(my_directory, os.S_ISGID)

and see if it does what you want? You can often save time by trying such 
things for yourself. Though it needn't be a substitute for asking 
questions on this list, it can make your questions better-informed.

In this particular case, now I understand your needs a little better, 
since you want to *add* a bit setting you will likely have to use 
something like

     current_permissions = os.fstat(my_directory).ST_MODE

to read the directory's current permission bits. Then you will need to 
execute

     os.chmod(my_directory, current_permissions | stat.S_ISGID)

Please don't take this as gospel, though, as I am currently on the road 
with only a Windows computer available, but I think it should get you 
closer to where you want to be.

regards
  Steve
-- 
Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC/Ltd           http://www.holdenweb.com
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