UNIX for Dummies Questions & Answers

Hi all

I have been doing basic admin on a Sun OS 5.6 system for some time and am just trying to learn about shell scripts to help perform some dull things i do every day.

Im trying to automate a task of trawling through multiple logfiles on clustered boxes for high severity alarms and writing the details to a single logfile that i can review later.

So far i have coded:

b="1"
val="severity.9"
while [ $b -le 9 ]
do
rsh vps-is$b grep -i $val /opt/vps/common/log/alarm.vps.*.log >> /opt/home/peri/gareth/alarms.log
echo "vps-is$b complete"
b=`expr $b + 1`
done

Which works great, it connects to each of my 9 boxes in turn, checks the logs and writes back lines that have "Severity 9" in them apending the data to my central logfile

HOWEVER,

I actually also need to 2 lines beneath the line with "Severity 9" on it to tell me all the detail i need.

Is there any way of asking grep to also return the next 2 lines as well as the line that it finds the string on...???

Many Thanks

Gareth

Try GNU grep.

http://whoopis.com/howtos/man.php?qu...pe=2&section=1

The -A option is probably what you want.

Excellent, Im at home at the moment but will try this as soon as i hit the office in the morning.

Can i use it in conjunction with the -i option as the string sometimes isnt capitalised...???

I don't see why not.

That worked like a charm thanks.

Another quickie if its ok...

Is it possible to test the return that grep gives and perform aditional tasks if it meets a criteria.

By this is mean that if i grep -c a file for a string and the return value is greater than 0 (because its found my string in the file), i want to then change the value of a variable.

The line of code i have so far is:

rsh vps-is1 vsh -Cvps.1 tappman -v1 -l1 status | grep -c "Down"

Is it possible to perform an 'if' test on the grep -c result??

Absolutely. Infact you dont need a grep -c to know whether the grep has been successful or not.

The exit status of grep maintains that information.

Quoting verbatim from man grep

Code:

       Normally, exit status is 0 if selected lines are found and 1 otherwise.
       But the exit status is 2 if an error occurred, unless the -q or --quiet
       or --silent option is used and a selected line is found.

$? holds the exit status of grep.

Code:

rsh vps-is1 vsh -Cvps.1 tappman -v1 -l1 status | grep "Down"

if [[ $? == 0 ]] ; then
echo "We found Down.. Where do you want to go today ?
else
echo "Down not found. What do I do ?
fi ;

You could try this as well. But be careful.

Code:

(($?)) && { commands to be executed when grep did not find anything ; } || { set of commands to be executed after grep found Down ; }

Wow, thank you so much.

Thanks for giving such a comprehensive reply, its really appreciated