How to Execute Parallel and Concurrent Commands in Bash

As a reminder:

Parallelism is doing a lot of things at once. Concurrency can be used to run things in parallel, but concurrency is about structuring things.

Rob Pike

Using & and wait

This is for concurrent execution.

Using & after a command will put it in the background, and wait will wait for all background processes to finish.

Example

#!/bin/bash

echo "Starting"

command1 &
command2 &
wait

echo "Finished"

Using GNU Parallel

Example

#!/bin/bash

echo "Starting"

parallel ::: "command1" "command2"

echo "Finished"

Example Using pipe

#!/bin/bash

echo "Starting"

echo "command1" > commands.txt
echo "command2" >> commands.txt

cat commands.txt | parallel