GNU bug report logs - #45258
mkdir man page unclear in describing -m flag

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From: Pádraig Brady <P <at> draigBrady.com>
To: Bernhard Voelker <mail <at> bernhard-voelker.de>, 45258 <at> debbugs.gnu.org, eggert <at> cs.ucla.edu, chris <at> colohan.com
Subject: bug#45258: mkdir man page unclear in describing -m flag
Date: Wed, 16 Dec 2020 13:34:38 +0000

On 16/12/2020 08:28, Bernhard Voelker wrote:
> On 12/15/20 9:00 PM, Paul Eggert wrote:
>> Thanks for your bug report. I installed the attached patch; although it
>> doesn't use the exact wording you proposed, I hope it works well enough.
> 
> Thanks for clarifying.
> 
>> +If the @option{-m} option is also given, it does not affect
>> +file permission bits of any newly-created parent directories.
>> +To control these bits, set the
>>   umask before invoking @command{mkdir}. [...]
> 
> Some further thoughts on this - maybe just for my reference:
> 
> One aspect of using -p is that the user doesn't want to get an error if
> the target or any of its parent directories already exists.
> 
> If changing the umask before invoking mkdir is not that easy - maybe
> because not called via a shell -, then an alternative to the above
> umask method is to reference each of the target directories separately,
> e.g.:
>    $ mkdir -pm 0700  dir1  dir1/dir2  dir1/dir2/dir3
> 
> But it is important to know that 'mkdir' does not adjust the permission
> bits of any of those already existing directories.
> 
> Therefore, if one does not want to get a failure for already existing
> intermediate directories, and still wants their permission bits to get
> adjusted, then one can use 'install' instead of 'mkdir' (still passing
> each directory level as separate argument!):
> 
>    $ install -dm 0700  dir1  dir1/dir2  dir1/dir2/dir3

Insightful comments. I've updated the gotchas note with them:
https://www.pixelbeat.org/docs/coreutils-gotchas.html#mkdir

cheers,
Pádraig

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