[RndTbl] race conditions?

[Mike Pfaiffer]

On 12-07-12 07:59 PM, Adam Thompson wrote:
> I just wrote the following snippet to quickly rotate some log files.
> I know this runs without bound, that's acceptable and desirable in
> this case.  What I'm worried about is creating race conditions if
> this gets run from cron every minute...
>
> ###check if daemon has died### if daemon-is-dead; then
> L=mydaemon.log shopt -u failglob for i in $( ls -1r ${L}.[0-9]*
> 2>/dev/null ); do N=${i#$L.} M=$(( ${N} + 1 )) mv -n $i "${L}.${M}"
> done if [ -f ${L} ] ; then mv -n ${L} ${L}.1; fi restart-daemon fi
>
> Am I shooting myself in the foot here?  The obvious race condition is
> if two copies run simultaneously, but this is only for temporary
> debugging purposes.  If necessary, I'll change the cron job from
> every minute to every five minutes.  Even then, the '-n' option to
> GNU mv should protect me...? Does anyone have a safer way to do this
> sort of thing manually?  I don't want this logfile managed by
> logrotate(8).
>
> -Adam Thompson DMTS (Contractor) athompso at dmts.biz (204) 291-7950 -
> direct (204) 489-6515 - fax
>
>
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	Going to sound like a dumb answer... Why not check the ps list to see 
if there is more than one instance running. If not then you are good to 
go. Otherwise shut it down.

				Later
				Mike