Shell Programming and Scripting

Unix OS : Linux 2.6x
Shell type : Korn

Hi all ,

This is a requirement to incorporate parallel processing of a Unix code .
I have two pieces of unix code , one of which will act as a parent process .
This script will invoke multiple ( say four ) instances of the second script at one go ,and each of these instances will run parallely , exclusive of the status of the other process.

How will I implement this logic ? What aspects must I consider while designing this kind of relationship ?
Please guide me on this .


Thanks
Kumarjit

You can use a for loop and put the same job with different parameter to background

No , loops would make the execution sequential, because unless the process within a SINGLE loop ietration completes , the control cannot be passed back to the shell prompt for the next iteration processing to commence.

What I want is :
Start instance 1 , immediately start instance 2 and do not wait for the exit status of instance 1 .
SIMULTANEOUS PROCESSING . Not sequential .
Similar to the "tee" command , process input and write to a file at one go.

Thanks
Kumarjit.

Is this a homework assignment? If not, please explain why you need to do this.

If you're going to ignore our suggestions without understanding what was said, we'll quickly decide to spend our time working with people who will pay attention to our suggestions.

Starting a process in the background (AKA starting a process asynchronously) in a loop will allow you to run x instances simultaneously if you go through the loop x times.

best place to start is 'man fork' if background process does not suit your need

Does any of the wordings in my original post give you the feeling that I am seeking help for a HOMEWORK ASSIGNMENT ? It soley a need out of my profession , and if I had even the most basic idea about how to set up asynchronous processing feature (processing at the background or even where to start my search from) , I wouldnt even have taken the pain scribbing a single word for this issue here in this forum .

@rajamadhavan : Thanks for the lead , will take it here-on .

Regards
Kumarjit.

First of all have some sensible logic.

It is not possible to launch many programs SIMULTANEOUSLY from a single Terminal!

However with VERY small increments in time one can launch as many copies of similar or differing scripts and hope that the OS multi(tasking/threading) takes care of the rest.

Starter example:-

Code:

#!/bin/bash
xterm -e /full/path/to/somescript.sh &
xterm -e /full/path/to/some_other_script.sh &
# NOTE the "&" character! Google is your friend here.
x=0
while true
do
        echo "Doing a loop number, $x here..."
        x=$[ ( $x + 1 ) ]
done

This will launch "somescript.sh" in a separate terminal window and "some_other_script.sh" in another terminal window whilst carrying on with its own work!

There is a caveat to this method but I suspect you'll never come across it...