Threads in bash?

Question

Is it possible to use threads in bash scripts. I have a driver class in java that i'm trying to run multiple instances of at the same time. The only way i know to do this is make threads in bash, but i'm not sure if thats even possible. Any help would be appreciated

Answer 1

Bash doesn't support threading per se, but you could launch multiple java processes in the background, like:

java myprog & java myprog & java myprog & 

Anything more than that you might look into Python or Ruby, which have thread management utilities, you could wait for each one to finish and collect output/exit status, etc.

Edit: Borrowing the suggestion from @CédricJulien to use wait, here's a more thorough example. Given this MyProg.java program:

public class MyProg {     public static void main(String[] args) {         System.exit(Integer.parseInt(args[0]));     } } 

you could write the following bash-threads.sh script to launch multiple instances of it in parallel:

#!/bin/bash set -o errexit  java MyProg 1 & pid1=$! java MyProg 0 & pid2=$! java MyProg 2 & pid3=$!  wait $pid1 && echo "pid1 exited normally" || echo "pid1 exited abnormally with status $?" wait $pid2 && echo "pid2 exited normally" || echo "pid2 exited abnormally with status $?" wait $pid3 && echo "pid3 exited normally" || echo "pid3 exited abnormally with status $?" 

Its output is:

pid1 exited abnormally with status 1 pid2 exited normally pid3 exited abnormally with status 2