topic Re: Scripting Question in Operating System - Linux

Scripting Question

Malcolm Neo_1 — Wed, 12 Oct 2005 20:31:50 GMT

Below is the code fragment:
if [ $BINDIR/schedule $nodename = "A" ]
then
echo "Message 1"
exit 1
fi
if [ $BINDIR/schedule $nodename = "B" ]
then
echo "Message 2"
exit 0
fi
if [ $BINDIR/schedule $nodename = "C" ]
then
echo "Message 3"
exit 1
fi
sendsms "Message 4" "TT0001" "MYServer"

"schedule" is another script called to check a textfile for values.

Based on the code fragment, lets assuming that "schedule $nodename" is suppose to return "A". Is there any chance that the "sendsms" is run before the "schedule" could return the value? (esp in the scenario that the main script is triggered many times simultaneously)

Re: Scripting Question

Hein van den Heuvel — Wed, 12 Oct 2005 20:37:45 GMT

No. If schedule returns A then the script will exit before executing sendsms.

It would appear that 'schedule' returned something other then A, B, or C under those high contention situation. Maybe it failed outright?.

I would capture the return value in a variable and include that in the senssms text, as well as the nodename that triggered it.

fwiw,
Hein.

Re: Scripting Question

Malcolm Neo_1 — Wed, 12 Oct 2005 21:03:52 GMT

On the script,

echo "Message #" is written to a test file.

i.e. echo "Message #" >> script.log

and for the last part of the script where the sendsms is run, I have something like this:

echo "sendsms Message 4 TT0001 MYServer" >> script.log

The funny thing is when I look back at the log.

I found the follow text in the follow order:
sendsms Message 4 TT0001 MYServer
Message #

In the normal situation, "Message #" should be returned and the script should end and "sendsms Message 4 TT0001 MYServer" should not appear.

Re: Scripting Question

Mel Burslan — Wed, 12 Oct 2005 21:40:11 GMT

your second message tells me that when you run your script, you are redirecting the output to this script.log or something you are telling is inconsistent.

if you can tell what you are really after, i.e., what you want this script to do, maybe the help gets better.

Re: Scripting Question

Mel Burslan — Wed, 12 Oct 2005 21:48:01 GMT

if [ $BINDIR/schedule $nodename = "A" ]
then
echo "Message 1"
exitFLAG=1
fi

if [ $BINDIR/schedule $nodename = "B" ]
then
echo "Message 2"
exitFLAG=0
fi

if [ $BINDIR/schedule $nodename = "C" ]
then
echo "Message 3"
exitFLAG=1
fi

sendsms "Message 4" "TT0001" "MYServer"
exit $exitFLAG

Re: Scripting Question

Bill Hassell — Wed, 12 Oct 2005 22:37:27 GMT

Your code really needs to use the case statement rather than if/else/fi. It's a lot easier to read and the last test catches all text not found in the previous tests:

RESULT=$($BINDIR/schedule $nodename)

case $RESULT in
A) echo "Message 1"
exit 1

B) echo "Message 2"
exit 0

C) echo "Message 3"
exit 1

*) sendsms "Message 4" "TT0001" "MYServer"

The case statement is doing the comparison and allows for multiple choices, longer strings, use of regular expressions like *, and so on.

Re: Scripting Question

Malcolm Neo_1 — Wed, 12 Oct 2005 22:39:26 GMT

Sorry for the confusion. This is what it should look like:

if [ $BINDIR/schedule $nodename = "A" ]
then
echo "Message 1" >> script.log
exit 1
fi
if [ $BINDIR/schedule $nodename = "B" ]
then
echo "Message 2" >> script.log
exit 0
fi
if [ $BINDIR/schedule $nodename = "C" ]
then
echo "Message 3" >> script.log
exit 1
fi
sendsms "Message 4" "TT0001" "MYServer"
echo "sendsms Message 4 TT0001 MYServer" >> script.log

The "if" conditions above is to check if there is a scheduled downtime. If yes, depending of what type of downtime, it will write it to the log file and then exit.

In the case where there is no downtime recorded, all conditions should be invalid and a sms would be sent out and the message will be recorded in the same log file.

However, this is what is seen on the script.log:
sendsms Message 4 TT0001 MYServer
Message 2

Re: Scripting Question

Muthukumar_5 — Thu, 13 Oct 2005 02:57:56 GMT

You can try as,

downtime_type=$($BINDIR/schedule $nodename)

if [ "${downtime_type}" = "A" ]
then
echo "Message 1" >> script.log
exit 1
elif [ "${downtime_type}" = "B" ]
then
echo "Message 2" >> script.log
exit 0
elif [ "${downtime_type}" = "C" ]
then
echo "Message 3" >> script.log
exit 1
else
sendsms "Message 4" "TT0001" "MYServer"
echo "sendsms Message 4 TT0001 MYServer" >> script.log
fi

More than this, use Bill's case method. It is neat.

hth.

Re: Scripting Question

Hein van den Heuvel — Thu, 13 Oct 2005 06:29:30 GMT

Bill'ds case statement solution reminded me of an onder remark I forgot to make explicit...

What if the $BINDIR/schedule result changes exactly between two steps. That is, while it was testing for A is was C, and when it tested for B is had already become A, but neither triggered a match.

So in a concurrent environment you HAVE to first grab the result into a variable, then test it. It is not only the more efficient way to go about business, it is the only right way to do the job.

Regards,
Hein.

Re: Scripting Question

Howard Marshall — Thu, 13 Oct 2005 08:42:48 GMT

Are there any date codes or "begin â ¦end" statements written to the script.log file?

Could it be that what you are seeing is yesterdays run of the script which sent the sms message and todays which generated message 2

I also agree that your best bet is to put it into a case statement.

H

Re: Scripting Question

Rodney Hills — Thu, 13 Oct 2005 08:57:58 GMT

I would recommend putting a

exec >>script.log 2>&1

at the front of the script, so that all output gets redirected to script.log.

HTH

-- Rod Hills

Re: Scripting Question

Bill Hassell — Thu, 13 Oct 2005 09:26:49 GMT

You can also use the logger command to add entries to syslog, something like this:

logger -p local5.warn "Message 2"

Re: Scripting Question

Malcolm Neo_1 — Fri, 14 Oct 2005 03:51:10 GMT

Hi all,
thx for the reply. I have implemented the case statement and would try to test it out to see if it works. Thx for the help.

Re: Scripting Question

Muthukumar_5 — Fri, 14 Oct 2005 04:06:55 GMT

You can also use if-elif-else with date also.

#!/bin/ksh
downtime_type=$($BINDIR/schedule $nodename)
if [ "${downtime_type}" = "A" ]
then
echo "`date +'%b %d %X'` Message 1" >> script.log
exit 1
elif [ "${downtime_type}" = "B" ]
then
echo "`date +'%b %d %X'` Message 2" >> script.log
exit 0
elif [ "${downtime_type}" = "C" ]
then
echo "`date +'%b %d %X'` Message 3" >> script.log
exit 1
else
sendsms "Message 4" "TT0001" "MYServer"
echo "`date +'%b %d %X'` sendsms Message 4 TT0001 MYServer" >> script.log
fi

# END
exit 0

hth.