On April 28, 2022 6:22 PM, Junio C Hamano wrote:
><rsbecker@xxxxxxxxxxxxx> 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
>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.
>
>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
>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.
