Re: Accessing Date and Time information

[Andrew Johnson <anj@aps.anl.gov>]

Hi Ralph,

Ralph Lange wrote:
> As the VxWorks strftime() does not support "%s" (seconds since the 
> epoch), is there another reasonable way to get this number from the 
> timestamp of a record into the value field of the same (or another) record?

Interesting question; I can't think of any _reasonable_ ways that don't 
involve writing some C code -- there is an unreasonable way to do it 
without coding, but it would be quite a sight to see!

The simplest way is to use a subroutine record, the TSEL link of the 
record should point to the TIME field of the record whose timestamp you 
want to know.  The subroutine code is just:

void timeSubroutine(subRecord *prec) {
    recGblGetTimeStamp(prec);
    prec->val = prec->time.secPastEpoch;
}

If you want the full nanosecond accuracy, or need to adjust the epoch 
you could use some variant of this code:

void timeSubroutine(subRecord *prec) {
    epicsTimeStamp epoch = {0, 0};	/* Jeff won't like this! */
    recGblGetTimeStamp(prec);
    prec->val = epicsTimeDiffInSeconds(&prec->time, &epoch);
}

Of course you could also do this within an ai device support instead, 
but the subroutine record code can be used in as many record instances 
as you need.

- Andrew
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