topic Re: shell script in Operating System - Linux

shell script

Shivkumar — Thu, 06 Oct 2005 13:14:56 GMT

Dear Sirs;

I need a script for the following situation.

Want to run nslookup xx.xx.xx.xx ( this is a virtual ip address )
if it returns
12.16.91.93
Then no problem and output should go to a file for recording
if it returns
14.16.17.22
then it should say "problem" and send the email alert to xxyy.zz@abc.com
(sendmail is already running on the box)
The message should also get recorded in the above mentioned file

check for the size of this file if size is say more than 2mb; it should delete the file and record in a new file

this script should be running after every 25 seconds.

I don't want to run this script as a cron job.

Please suggest.

Thanks
Shiv

Re: shell script

Devender Khatana — Thu, 06 Oct 2005 13:25:43 GMT

Hi,

Scripting part is seperate but I do not think it would be possible to schedule it without cron. Also the frequency is also very less as minimum for the cron to work is 1 minute.

Just curious to see some responses for the same.

Regards,
Devender

Re: shell script

Pete Randall — Thu, 06 Oct 2005 13:34:45 GMT

The scheduling can be done with at, but not at 25 second intervals. Like cron, the smallest interval at deals with is minutes.

echo "script_name" | at now + 1 minute

Pete

Re: shell script

Leif Halvarsson_2 — Thu, 06 Oct 2005 13:36:21 GMT

Hi,
I remember a similar problem for some time ago. A possible solution is to run the script from inittab. Put a sleep 25 statment at the end of the script and use the respawn option in inittab (see /etc/inittab for examples).

Re: shell script

cilene Peterson — Thu, 06 Oct 2005 14:14:40 GMT

I would create a perl script using exec or eval to execute your script, sleep for 25 seconds and execute again...

Good luck!

Re: shell script

cilene Peterson — Thu, 06 Oct 2005 14:17:27 GMT

I would create a perl script using exec or eval to execute your script, sleep for 25 seconds and execute again...

Of course this would be a loop forever program...

Good luck!

Re: shell script

Shivkumar — Thu, 06 Oct 2005 14:37:28 GMT

Can someone please suggest the shell script code ?

Thanks and regards,
Shiv

Re: shell script

Mel Burslan — Thu, 06 Oct 2005 14:37:56 GMT

while true
do #start of forever loop
IPADR=`nslookup | grep Address | awk {'print $2'}`
if [ "$IPADR" = "12.16.91.93" ]
then
(printf "Everything is fine at ";date) >> /tmp/mylogfile
else
if [ "$IPADR" = "14.16.17.22" ]
then
echo problem | sendmail xxyy.zz@abc.com
(echo "PROBLEM ENCOUNTERED at ";date) >> /tmp/mylogfile
else
(echo "UNKNOWN IP RETURNED at ";date) >> /tmp/mylogfile
fi
fi
sleep 25

LOGSIZE=`ll /tmp/mylogfile | awk {'print $5'}`
if [ $LOGSIZE -ge 2000000 ]
then
cat /dev/null > /tmp/mylogfile # zero it out
fi

done # repeat forever

if I were you I would move the logfile to .old extension for future examination and then zero it out, but this is only my opinion

hope this helps

Re: shell script

Tom Danzig — Thu, 06 Oct 2005 15:08:17 GMT

Just a thought ... Mel's script will keep sending an email out every 25 seconds until the issue is corrected. You may want to tailor the code to do otherwise.

Re: shell script

Howard Marshall — Thu, 06 Oct 2005 15:27:55 GMT

This is not a super challenging script but to write it you need to specify a few more things

I assume you are just testing your DNS server or servers and actually fixing that would be the real solution but till then lets get on with it.

First you want a script that is going to loop every 25 seconds or so but you probably don't want it to loop for ever and ever till the end of time. That can be done with a stop file in the /tmp directory

#!ksh

while [ ! -f /tmp/mystopfile ]
do

#do some stuff

sleep 25
done

now all you have to do is touch /tmp/mystop and the loop will drop out and stop the script

next, the business end doing the nslookup and deciding based on the results what to do

I don't know what nslookup version you are using or what switches so I will leave up to you to filter down to just the IP address

IPTRACKERLOG=/tmp/iptrackerlog
If [ wc -l $IPTRACKERLOG > 1000 ]
then
echo "log restart `date` " > $IPTRACKERLOG
fi

IPADDR=`nslookup xx.xx.xx.xx | grep Address | cut c11-`

If [ $IPADDR = "12.16.91.93" ]
Then
Echo "all is well with IP $IPADDR `date`" >> $IPTRACKERLOG

#I assume anything but this response is cause for concern so
else
echo "ERROR >>> tracker found IP $IPADDR `date`" >> $IPTRACKERLOG

#you may want to put a stop file here too and have it set its own otherwise you will get a message every 25 seconds till the script stops or the problem is fixed.
echo "your ip tracker thing on the hpux server got an error" | mailx -s "your ip check script" usr@address.com
fi

legal notice: I don't guarantee any of these commands to work the way they are listed they are here for novelty purposes only and should never actually be used till you have tested and modified them to suit your needs and even then, if it all goes bad, its still not my fault.

Re: shell script

Muthukumar_5 — Fri, 07 Oct 2005 00:55:28 GMT

You can try as,

#!/usr/bin/ksh
stime=25

# User input
ipaddress=""
logfile=/tmp/iplookup.log
mailID="xxyy.zz@abc.com"

while [ 1 ]
do

nslookup $ipaddress | grep -qE '12.16.91.93'
if [ $? -eq 0 ]
then
echo "Lookup Success @ $(date)" >> $logfile
fi

nslookup $ipaddress | grep -qE '14.16.17.22'
if [ $? -eq 0 ]
then
echo "Lookup Failed @ $(date)" >> $logfile
echo "Lookup Problem @ $(date)" | mailx -s"Problem" ${mailID}
fi

ret=$(ls -l $logfile | awk '{ size=$5/1048576; if ( size > 2 ) { print "1"; } else { print "2";}}')

if [ $ret -eq 1 ]
then
cat $logfile >> $logfile.old
fi

sleep $stime

done

# END
exit 0

hth.

Re: shell script

Shivkumar — Tue, 18 Oct 2005 01:15:26 GMT

Muthukumar; i used your script.
i got the output as :
Lookup Success @ Mon Oct 17 23:11:25 PDT 2005
Lookup Success @ Mon Oct 17 23:11:50 PDT 2005

now suppose i want to show ip address also against success and failure in the log file then how to modify this script ?

Thanks,
Shiv

Re: shell script

Muthukumar_5 — Tue, 18 Oct 2005 01:19:52 GMT

do you want to store success results in one file and failure results in one file so that you can keep track?

Without this, you can grep like,

grep 'Success' /tmp/iplookup.log
grep 'Failed' /tmp/iplookup.log

to get results.

If it is not your requirement then revert here.

thx.

Re: shell script

Arunvijai_4 — Tue, 18 Oct 2005 01:33:40 GMT

nslookup $ipaddress | grep -qE '12.16.91.93'
if [ $? -eq 0 ]
then
echo "Lookup Success for $ipaddress @ $(date)" >> $logfile
fi

nslookup $ipaddress | grep -qE '14.16.17.22'
if [ $? -eq 0 ]
then
echo "Lookup Failed for $ipaddress @ $(date)" >> $logfile
echo "Lookup Problem for $ipaddress @ $(date)" | mailx -s"Problem" ${mailID}
fi

Re: shell script

Muthukumar_5 — Tue, 18 Oct 2005 01:49:07 GMT

great arun ;)

Just change script echo statements with ${ipaddress} to get your desired output with IP-Address.

hth.

Re: shell script

rmueller58 — Fri, 04 Nov 2005 09:48:05 GMT

Shiv,

I use a process to page me in the event our primary DNS server fails..

if the NS lookup fails to return xxx.xxx.xxx.xxx then I have the system send me a page via my email pager.. Works great.

#!/bin/bash
ns=`nslookup -sil www.yourwebserver.xxx |head -1 |awk '{print $2}'`
if [ "$ns" != "xxx.xxx.xxx.xxx" ]
then
echo "Lookup failed" > lookup.txt
mail -v -s "xxx.xxx.xxx.xxx failed `date +%Y%m%d:%H%M`" name@email.xxx < lookup.txt
fi