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another scripting question

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Bryan D. Quinn
Respected Contributor

another scripting question

I have a bit of a scripting dilemma that I need some help with. I need to come up with, if possible, a way to monitor a log file for a certain line of text. This exact line is written to the script multiple times during our nightly backup, but for each instance I need to capture it as it is written to the file. When this happens I will be triggering another event. I have racking my brain trying to come up with a solution. Basically I need something that would act like tail -f, but from a script.
Anybody with any ideas?
I don't need specific code, just some help with a way to approach the problem.

Thanks,
-Bryan
4 REPLIES
Bryan D. Quinn
Respected Contributor

Re: another scripting question

Oops! Sorry, that should not have been databases for the category.

-Bryan
A. Clay Stephenson
Acclaimed Contributor
Solution

Re: another scripting question

Actually you were rather close:

#!/usr/bin/sh

INFILE=myfile

tail -f ${INFILE} | while read X
do
echo "${X}"
done



Create a file "myfile" and start the above script. Now do something like echo "XXX" >> myfile and you will magically see the new line of onput appear. Your processing goes where the current echo "${X}" is.

If it ain't broke, I can fix that.
Kent Ostby
Honored Contributor

Re: another scripting question

Well depending on your time tolerance, you could do something like copy the log file to a temp log file.

Compare that to the copy you made 5 minutes ago and then grep for the line you are looking for and react if you find it.

You can put this all inside a loop with a sleep.

Loop around Something like:

sleep 300
cp logfile ms.newlogfile
diff ms.oldlogfile ms.newlogfile > ms.useme
grep "yourstring" ms.useme > ms.useme2
if [ -s ms.useme2 ]
do your other stuff
fi

Then close the loop

The sleep 300 is your 5 minute delay.
"Well, actually, she is a rocket scientist" -- Steve Martin in "Roxanne"
Bryan D. Quinn
Respected Contributor

Re: another scripting question

Thanks Clay!

So simple, yet so far away! Thanks for clearing up the water for me.

-Bryan