[CentOS] the at command

Robert Moskowitz rgm at htt-consult.com
Tue Jan 22 14:57:03 UTC 2013

On 01/21/2013 10:17 PM, Jerry Geis wrote:
>> Why do you think you need to do that and make sure they run at exactly
>> the same second?  It seems like instead it would be better to make your
>> command more robust to small deviations in the time at which they are
>> run.
> keith - Thanks for your reply.
> I do need to run the commands at exactly the same time.
> It has nothing to do with making my command more "robust".
> It has "everything" to do with "visual" presentation that someone
> viewing the 10 boxes will see. if the 10 boxes are not in sync
> it will be completely obvious and crappy.

you have bigger problems than startring your programs at the same time.  
You need very tight progamatic syncing.  audio variations of more than 
10ms will mess up listening.  I think visual is a bit looser around 
20-30ms; the eyes have more processing power?

The systems I am familiar with have realtime syncing which can't run 
over traditional ethernet.  There ARE 802.1 standards that will meet the 
10ms requirement for audio.  The music people (and manufacturing 
automation) got that added and it works up to 2 bridge hops, but your 
switches/bridges/routers/APs have to support this.

Try using an digital drum to wireless headphones with more than a 10ms 
delay.  It is impossible to drum if this occurs.

> So if cron/at does not support it - I'll find another way.
> Thanks everyone!
> Jerry
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