Re: SECONDS=0 does not reset SECONDS, or I'm missing something

[Chet Ramey]

On 6/4/20 6:01 PM, Andreas Kusalananda Kähäri wrote:

>> Yes, SECONDS is in seconds granularity, whether that is seconds since the
>> epoch or seconds since an assignment to it, as you quoted below. There's
>> no expectation of subsecond granularity -- it's just whatever the system
>> tells the shell the current number of seconds is.
>>
>> The next version will use the number of seconds returned from gettimeofday,
>> but there's still nothing in there that attempts to round it up or down
>> depending on tv_usec.
> 
> Oh, I'm not expecting subsecond granularity!  I'm expecting that
> 
>       SECONDS=0; sleep 0.5; echo $SECONDS
> 
> always outputs a zero, which it does not do now if the system's clock
> rolls over to a new full second during the 0.5 seconds of sleep.

I understand; that's why I said the shell uses whatever the system tells
it the number of seconds since the epoch is.


> It's just a bit odd to have the SECONDS parameter tick with the system
> time, which IMHO is not implied by the words "number of seconds since
> the assignment", that's all.

It looks like the problem is mismatched expectations. That's pretty common.

So we have several options: update the documentation to specify that the
system clock is used to determine the number of seconds; get a patch to
the devel branch to change the behavior; or use one of the other available
variables, like EPOCHREALTIME or EPOCHSECONDS.

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/