Re: OT: bash vs. ksh subprocess counts
- From: Jared Still <jkstill@xxxxxxxxx>
- To: Dave.Herring@xxxxxxxxxx
- Date: Fri, 20 Apr 2012 09:55:25 -0700
On Sun, Apr 15, 2012 at 10:45 AM, Herring Dave - dherri <
Dave.Herring@xxxxxxxxxx> wrote:
> I realize this is way off topic (probably should be titled "WOT:...") for
> Oracle but #1, I don't currently belong to any good linux/redhat forums and
> #2, the issue found was from an Oracle maint. script :-)
>
WOT = Wide Open Throttle
Sometimes applies to Oracle I guess.
> Anyway, I'm on a RHEL 4.6 server (2.6.9-67.0.22.ELlargesmp) and noticed a
> given DBA maint script wasn't running. It turns out that the only
> difference between when it last ran and now is someone changed the shell to
> be "bash" -> #!/bin/bash vs. #!/bin/ksh. The script has a little if-test
> to start with, used as a way to determine if a previous iteration of the
> job is still running:
>
> if [ `ps -ef|grep -cw $0` -gt 3 ]; then
> echo "$0 is already running"
> exit 2
> fi
>
>
There are better methods for doing this.
Following is a function that creates a PID file and uses it for locking.
Stale locks are handled.
a possible issues with this - not useful as is on cluster, as other
nodes could run the script.
Anyway, it may be of some use.
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
Oracle Blog: http://jkstill.blogspot.com
Home Page: http://jaredstill.com
==== script =====
9:49-poirot:ts20:jkstill-22 > expand -t3 locktest.sh
:
LOCKFILE=/tmp/testlock.lock
function script_lock {
typeset MY_LOCKFILE
MY_LOCKFILE=$1
# remove stale lockfile
[ -r "$MY_LOCKFILE" ] && {
PID=$(cat $MY_LOCKFILE)
ACTIVE=$(ps --no-headers -p $PID)
if [ -z "$ACTIVE" ]; then
rm -f $MY_LOCKFILE
fi
}
# set lock
if (set -o noclobber; echo "$$" > "$MY_LOCKFILE") 2> /dev/null; then
trap 'rm -f "$MY_LOCKFILE"; exit $?' INT TERM EXIT
return 0
else
echo "Failed to acquire $LOCKFILE. Held by $(cat $LOCKFILE)"
exit 1
fi
}
function script_unlock {
rm -f "$LOCKFILE"
trap - INT TERM EXIT
}
script_lock $LOCKFILE
echo press '<ENTER>...'
read dummy
script_unlock
--
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