Shell Programming and Scripting

Hi Everyone ,

I am facing a strange problem
i have made the follwing script to watch a appending log file (abc.log) but its not moving after the line tail -f ,
any suggestions

=====================================
#!/bin/bash
while true
do
tail -f abc.log | grep "exceptions"
echo hi
done
===================================

but the script keeps on giving the exceptions output as follows:

exception.TaxStrategyException: Error during port.getTax
exception.InterfaceException: Error MNP duplicate found
exception.CardPaymentException: Payment gateway rejected

and i want the out put to be as follows :------
exception.TaxStrategyException: Error during port.getTax
hi
exception.InterfaceException: Error MNP duplicate found
hi
exception.CardPaymentException: Payment gateway rejected
hi
================================================

the basic problem i have seen is that tail -f keeps on checking the appending log file due to which it doesnot ends up and the second command
echo hi never gets executed.

Please help me if there is any other way of doing this

Thanks

tail -f command ends only when killed.
The following script will give you the expected result :

Code:

#!/bin/bash
tail -f abc.log | grep "exceptions" |
while read line
do
   echo $line
   echo hi
done

But i'm not sure that it's what you really want to do.

Aigles,

would below program work as well? I guess not the samething.. plus wastes the resource by going through the whole log everytime.. huh

string=exceptions

while [ -z "$string" ]
do
grep $string abc.log
sleep 2
done
echo hi

Thanks Aigles
There seems that you have given me the solution to my problem;
however i have to go my office to try this technique .
i hope that your trick will solve my problem .
Thanks for the reply

sorry to say that

the trick didnt work

because when i am using


is there any other way of doing this

thanx in advance

It's a buffering problem. If you remove the grep command, all the lines will be processed inside the while loop.

The solution is to filter lines inside the while loop :

Code:

#!/bin/bash
tail -f abc.log | 
while read -r line
do
   [[ "$line" != *exceptions* ]] && continue
   echo $line
   echo hi
done

Many thanks to you My friend

You are really a man in the unix world

This time it worked

I really appreciate your help

Thankyou very much