How can I run a script in multiple instances in Ubuntu server?

For example, I have a long running script named scanner.sh placed in /usr/bin/, which I wish to run the script in 10 parallel instances. How can I start the parallel tasks (and pass different flags / options / parameters to them)?

and how can I stop the instances?

# Script to async run scanner.sh
# USAGE: $> bash parallel_scanner.sh "FLAGS FOR INSTANCE 1" ... "FLAGS FOR INSTANCES 10"
$1=`echo $1 | sed 's/"//g'`
$2=`echo $1 | sed 's/"//g'`
$3=`echo $1 | sed 's/"//g'`
$4=`echo $1 | sed 's/"//g'`
$5=`echo $1 | sed 's/"//g'`
$6=`echo $1 | sed 's/"//g'`
$7=`echo $1 | sed 's/"//g'`
$8=`echo $1 | sed 's/"//g'`
$9=`echo $1 | sed 's/"//g'`
$10=`echo $1 | sed 's/"//g'`

bash scanner& $1 2>&1
bash scanner& $2 2>&1
bash scanner& $3 2>&1
bash scanner& $4 2>&1 
bash scanner& $5 2>&1
bash scanner& $6 2>&1
bash scanner& $7 2>&1
bash scanner& $8 2>&1
bash scanner& $9 2>&1
bash scanner& $10 2>&1

& places task in background. 2>&1 redirects STDOUT to STDERR.

To end the processes, type:

$> ps aux | grep scanner
$> kill $PIDS
  • Thanks. But how to stop specific instance? Also, the lines below should be: bash scanner.sh $1 2>&1, right ? – Raptor Oct 3 '14 at 15:00

Using GNU Parallel it looks like this:

parallel scanner {} ::: "--flags --for --instance 1" "--for 2" "--for 3"

It will spawn one job per CPU. To stop simply press CTRL-C.

GNU Parallel is a general parallelizer and makes is easy to run jobs in parallel on the same machine or on multiple machines you have ssh access to. It can often replace a for loop.

If you have 32 different jobs you want to run on 4 CPUs, a straight forward way to parallelize is to run 8 jobs on each CPU:

Simple scheduling

GNU Parallel instead spawns a new process when one finishes - keeping the CPUs active and thus saving time:

GNU Parallel scheduling


If GNU Parallel is not packaged for your distribution, you can do a personal installation, which does not require root access. It can be done in 10 seconds by doing this:

(wget -O - pi.dk/3 || curl pi.dk/3/ || fetch -o - http://pi.dk/3) | bash

For other installation options see http://git.savannah.gnu.org/cgit/parallel.git/tree/README

Learn more

See more examples: http://www.gnu.org/software/parallel/man.html

Watch the intro videos: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1

Walk through the tutorial: http://www.gnu.org/software/parallel/parallel_tutorial.html

Sign up for the email list to get support: https://lists.gnu.org/mailman/listinfo/parallel


I'd like to propose you start using configuration management system like, preferrably Ansible.

It's written on Python, really easy-to-use for everyone, for newbies also.

Follow the docs http://docs.ansible.com/ and get started!


Besides the suggested answer, I use the following command:

nohup ./scanner.py -flag1 flag1value -flag2 flag2value &

to create a new instance. To view all running scanner.py instance, I use:

ps aux | grep scanner.py

To kill a specific instance, I use:

kill -9 {PID}

where {PID} is obtained from the ps aux command, e.g. kill -9 1234

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