How to run command or code in parallel in bash shell under Linux or Unix

To run multiple commands or blocks of code in parallel in a bash shell on a Linux or Unix system, you can use the & operator to run the commands in the background.

Here is an example of how to run two commands in parallel in a bash shell:

command1 &
command2 &

This will run command1 and command2 in the background, allowing them to run concurrently.

You can also use the & operator to run a block of code in the background. For example:

{
    code1
    code2
} &

This will run the code block in the background, allowing the code to run concurrently with other commands or code blocks.

Keep in mind that running commands or code blocks in the background can affect the performance of the system and may interfere with other processes. It is important to carefully consider the implications of running commands or code blocks in parallel before doing so.

You can also use the parallel command to run multiple commands in parallel. For example:

parallel command1 command2 command3 ...

This will run the specified commands in parallel, using as many processes as there are available CPU cores. The parallel command can be useful for running a large number of independent commands concurrently, but it may not be necessary for running a small number of commands in parallel.