RE: [PATCH v2 3/3] t: add tests for safe.directory when running with sudo

From: rsbecker@nexbridge.com <rsbecker@nexbridge.com>
Date: Apr 28, 2022, 22:45 UTC
Message-ID: <001901d85b51$b5333420$1f999c60$@nexbridge.com>
In-Reply-To: <xmqqczh0etmt.fsf@gitster.g>

On April 28, 2022 6:22 PM, Junio C Hamano wrote:

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><rsbecker@nexbridge.com> writes:
>
>>>is_root() {
>>>  id -u >u
>>>  id -u root >r
>>>  cmp u r
>>>}
>>
>> This is about as portable as I can find and works even in ksh. It could

be

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>optimized.
>>
>> is_root() {
>>   id -u >u
>>   id -u root >r
>>   cmp -s u r
>>   if [ $? -ne 0 ]; then
>>     echo 0
>>   else
>>     echo 1
>>   fi
>> }
>>
>> if [ `is_root` -ne 0 ]; then
>>         echo root
>> else
>>         echo Not root
>> fi
>
>The above looks very roundabout way.  With the first three in is_root that

ends

>with "cmp", we already know from its exit status if "id -u" output for

ourselves

>matches that for root, i.e. if we are root then cmp would have exited with

0.

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>
>So with the first one I quoted from your quote, the caller can say
>
>	if is_root
>	then
>		echo root
>	else
>		echo not root
>	fi
>
>without turning the exit status into string "0" or "1" and comparing that

string with

>"[ `cmd` -ne 0 ]".  And the first one is just as portable.  I agree that

running cmp

>with "-s" is probably a good idea.
>
>What I used to often use in my previous life (in previous century) is

technically

>incorrect, but is a lot more succinct and works well in practice on any

sanely

>installed systems.  Just see if the root directory is writable.  No sane

system makes

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>it writable by anybody but root.
>
>I.e.
>
>	if test -w /
>	then
>		... we are running as root ...
>	else
>		... we are not running as root ...
>	fi

I agree. I think my ksh is rather broken. But we use bash for git testing and can never go back to ksh, so no worries on that score. Thanks.