[mythtv-users] stagger start times for simultaneous recordings?

Mark J. Small msmall at eastlink.ca
Mon Oct 24 15:05:53 UTC 2011


On October 23, 2011, Mike Holden wrote:
> Ronald Frazier wrote:
> >> Were it me, I'd try and implement some crude form of "locking"
> >> inside the channel-change script(s), so that one instance would
> >> loop and sleep/wait until the other has finished its thing.
> > 
> > A while back I had a channel change script with some very basic
> > locking code in it. It doesn't handle race conditions, but should
> > work
> > pretty good (might fail once in a million times or something).
> > Here's
> > a copy:
> > 
> > while [ -f $LOCKFILE ]
> > do
> > #echo "Waiting for lock..."
> > 
> >   sleep .1
> > 
> > done
> > 
> > touch $LOCKFILE
> 
> I suggest you have a look at "flock" (man flock has a good simple
> overview). This provides a simple but foolproof locking mechanism
> using a file locked in exclusive mode.
> 
> (
>     flock -s 200
>     # ... commands executed under lock ...
> ) 200>/path/to/mylockfile

Thanks, Mike, Ronald.

Your posts helped me fix my change channel scripts.  Hopefully I'll have even 
fewer channel change problems.

Mark 
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