How to execute the next command in pipe only if previous have at least one result?

Question

So, I have the following command

$(docker container ls -a -q) | docker container stop

to stop all my docker containers, which works great! Except when I've just wiped clean all of them:

"docker container stop" requires at least 1 argument.
See 'docker container stop --help'.

Usage:  docker container stop [OPTIONS] CONTAINER [CONTAINER...]

Stop one or more running containers

Is there any way I can prevent this error message from showing up using a single line command?

Note: my original command was actually docker container stop $(docker container ls -a -q), which gives the same error message, but I tought it would be easier to describe my problem using pipe/chain one command to the other. Answers for both commands are OK, but I'll prefer to use docker container stop $(docker container ls -a -q)

Answer 1

Since the N-ary stop operation of Docker is silly with regard to zero containers, what you can do is treat docker stop container as as a unary operation which requires exactly one argument, and do your own distribution of a list of terms over that unary operation. Of course, such a way that your logic handles the empty sequence of terms:

for x in $(docker container ls -a -q); do docker container stop $x; done

If $(docker ...) produces nothing, the loop doesn't execute.

Answer 2

You can silence shell output using redirects, see this post for more details: https://stackoverflow.com/questions/2292847/how-to-silence-output-in-a-bash-script

I might use something more like this to handle the response so I still get output.

docker container stop $(docker container ls -a -q) >/dev/null 2>&1 || echo "Nothing to stop."