I'd use a lock file just to be safe. Depending on how
"restart-daemon" works you might end up with a race condition
inside there, resulting in no daemon getting run until the next
pass.
The easiest way would be
lock="/var/run/mylock"
if [ -f $lock ]; then exit 1; else touch $lock; fi
#do your magic
rm $lock
There are other utilities like flock and lockfile if you are
really concerned about re-entrancy, and depending on the user
you run this script as, you may want to put $lock out of a
normal user's reach. But to protect something running from cron,
this will be more than enough.
Sean
On Thu, Jul 12, 2012 at 7:59 PM, Adam
Thompson
<athompso@dmts.biz>
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@dmts.biz
(204) 291-7950 - direct
(204) 489-6515 - fax
_______________________________________________
Roundtable mailing list
Roundtable@muug.mb.ca
http://www.muug.mb.ca/mailman/listinfo/roundtable
--
Sean Walberg <
sean@ertw.com>
http://ertw.com/
_______________________________________________
Roundtable mailing list
Roundtable@muug.mb.ca
http://www.muug.mb.ca/mailman/listinfo/roundtable