When you do commands like `docker rm $(docker ps -aq)`, how do you call the `$( . . .

Docker
#1

LordSilver:
When you do commands like docker rm $(docker ps -aq), how do you call the $( ) part?

#2

Alistair Mackay:
$() creates a sub-shell to run the command in the brackets, and captures the output such that you can feed that output to another command. It is a very powerful technique in bash and other similar shells.
docker rm $(docker ps -aq) - will be interpreted like so

  1. Execute docker ps -aq
  2. Execute docker rm using the output of #1 as the argument - i.e. the container(s) to remove