Run script in parallel in while loop

Shell Programming and Scripting
1

Hi
I am running a loop which actually runs same script for different argument value passed to it.

while read repID
do
echo "Starting for $repID";
date;
perl process_report.pl $repID 
done<${FILE_TO_READ}

However this runs in sequence.
I want the loop to not to wait for perl to complete before moving to next record.
So basically , it should call the perl script and move to next line of while loop. I want to run multiple instances of perl via while loop.
Is adding "&" will work fine ?

Thanks in advance
--Raj

2

Hi dashing201

Yes this (&) should work.
Also, you could embrace it in brackets (perl process_report.pl $repID) .

This behaves the same (in this situation, there's a diffrence between the two i cannot explain), as long you dont want to fetch variables, but from the read, i'd guess you're writing the reports of that specific id...

Hope this helps

3

Hello,

You can run the scripts in background, like following is an example for sleep process run in background.

Lets say a file in which number of mins/seconds have been given.(Input file).

cat file23
60
50
80
20
10
100

Now lets say we have a shell script same like your perl script. which needs to be executed in while loop.

cat test2.ksh
Q=$1
echo "starting sleep for" $Q "mins."
sleep $Q

Here is the example of While loop for same.

while read line
do
echo "Executing for" $line
./test2.ksh $line &
done < "file23"
Executing for 60
[1] 20921
Executing for 50
[2] 20922
Executing for 80
[3] 20923
Executing for 20
starting sleep for 60 mins.
[4] 20924
Executing for 10
starting sleep for 50 mins.
[5] 20931
starting sleep for 80 mins.
Executing for 100
[6] 20934

Hope following example may help you, similarly you can too put all proccesses in background while calling your perl script use at last
perl process_report.pl $repID & .

Thanks,
R. Singh

4

Hi Ravinder/Sea

Thanks for the quick reply.
However if I have to implement a check to confirm if all the process have been completed then how can I do it ?
It is required to make sure that all parallel instances are completed before I change status to complete.

Thanks
Raj