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I have one bash script which calls the same perl script in a serial way. The bash script is used to collect the overall results, while the perl script collects the results of my simulations for the given attributes.

The bash script looks as follows: 

mkdir ./results/csv     && \
../perlscripts/v2csv.pl -v -F reach results/Heterogeneous*.vec > ./results/csv/reach.csv
../perlscripts/v2csv.pl -v -F roundTrip results/Heterogeneous*.vec > ./results/csv/RT.csv
../perlscripts/v2csv.pl -v -F downlink results/Heterogeneous*.vec > ./results/csv/DL.csv
../perlscripts/v2csv.pl -v -F clusters results/Heterogeneous*.vec > ./results/csv/clusters.csv

Collecting the results by calling one perl script at a time is really long; I am looking for a way which would allow me to call the different variations of the perl script within the bash script in parallel. Is there a way to achieve this in bash?

Just to clarify, I don't want the commands which call the perl script to be dependent on each other in any way. I want all of them to start at the same point in time, as if I had 4 separate bash-terminals each executing one of these commands.

Similar: https://stackoverflow.com/questions/15644991/running-several-scripts-in-parallel-bash-script

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5

If you have gnu parallel installed, you could make a script with just the commands, e.g.:

../perlscripts/v2csv.pl -v -F reach results/Heterogeneous*.vec > ./results/csv/reach.csv
../perlscripts/v2csv.pl -v -F roundTrip results/Heterogeneous*.vec > ./results/csv/RT.csv
../perlscripts/v2csv.pl -v -F downlink results/Heterogeneous*.vec > ./results/csv/DL.csv
../perlscripts/v2csv.pl -v -F clusters results/Heterogeneous*.vec > ./results/csv/clusters.csv

and then run them in parallel:

mkdir ./results/csv && parallel :::: myscript.sh

Alternatively, invoking the command and using {} - the default replacement string:

mkdir ./results/csv && parallel ../perlscripts/v2csv.pl -v -F {} \
results/Heterogeneous*.vec '>' ./results/csv/{}.csv ::: reach roundTrip downlink clusters

would run the following commands in parallel:

../perlscripts/v2csv.pl -v -F reach results/Heterogeneous*.vec > ./results/csv/reach.csv
../perlscripts/v2csv.pl -v -F roundTrip results/Heterogeneous*.vec > ./results/csv/roundTrip.csv
../perlscripts/v2csv.pl -v -F downlink results/Heterogeneous*.vec > ./results/csv/downlink.csv
../perlscripts/v2csv.pl -v -F clusters results/Heterogeneous*.vec > ./results/csv/clusters.csv
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2
../_Cscripts/v2csv.pl -v -F reach results/Heterogeneous*.vec > ./results/csv/reach.csv &
../_Cscripts/v2csv.pl -v -F roundTrip results/Heterogeneous*.vec > ./results/csv/RT.csv &
../_Cscripts/v2csv.pl -v -F downlink results/Heterogeneous*.vec > ./results/csv/DL.csv &
../_Cscripts/v2csv.pl -v -F clusters results/Heterogeneous*.vec > ./results/csv/clusters.csv &
wait

The & puts the program in background. wait waits for them to stop if you care.

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  • what would happen if there was no wait? – cross Mar 17 '15 at 19:51
  • @Cross without the wait, the script wouldn't wait for all the scripts to finish before it itself ended. – roaima Mar 17 '15 at 19:53
  • I'm not sure. I think the script would just end and the processes would just be running in the background. If that is what you want, precede each command with nohup and be sure. – Robert Jacobs Mar 17 '15 at 19:54
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You can try the following syntax:

mkdir ./results/csv && (script0 & script1 &)

This will run the scripts in the background, not waiting for them to finish. The parentheses introduce a subshell group (so that no script will be run if the mkdir command fails) and the & requests background execution (returning control to the outer shell right away).

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  • how does is differ from the solution given by Robert Jacobs? asking just for understanding purposes – cross Mar 17 '15 at 19:50
  • It's hardly different from the other answer... there was no answer posted when I started typing mine. – dhag Mar 17 '15 at 19:51
  • but you don't have the wait and he does not use paratheses – cross Mar 17 '15 at 20:13
  • That's right; the parentheses are for grouping, so that none of the scripts get run if mkdir fails (one could avoid spawning a sub-shell here, though it's unlikely to be a performance killer if your scripts take long enough to run that you care about running them in parallel), and, without the call to wait, this script will return almost instantly, letting the scripts run in the background. This is a matter of subjective preference; if you want to be blocked until all jobs have completed, then use wait. Otherwise you can use jobs to see if your script is still running. – dhag Mar 17 '15 at 20:44

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